Optical modulator and electronic apparatus including the same

Provided is an optical modulator including a substrate, and a plurality of meta units provided on the substrate and spaced apart from each other, wherein at least one of the plurality of meta units includes a metal layer provided on the substrate, a dielectric layer provided an upper surface and side surfaces of the metal layer, and an antenna provided on an upper surface of the dielectric layer, the antenna including phase change material, wherein a refractive index of the phase change material changes based on a voltage applied to the metal layer to modulate incident light.

BACKGROUND

Example embodiments of the present disclosure relate to an optical modulator and an electronic apparatus including the same.

2. Description of Related Art

Meta materials include artificial meta structures patterned in random sizes and shapes smaller than wavelengths of the phenomena they influence. Each meta structure included in meta materials shows certain attributes in response to an electromagnetic wave or a sound wave applied to the meta materials.

Recently, there has been attempts to utilize nanostructures using surface plasmon resonance from incident light in optical elements. Such meta materials may be used as an optical modulator. When used as an optical modulator, meta materials may compensate for the weakness of slow operation response time of several microseconds or more due to characteristics of a driving method such as liquid crystal having optical anisotropy used as an optical modulator in the related art, or a microelectromechanical system (MEMS) structure using micro-mechanical movement of light-interrupting/reflecting components.

In the related art, as an optical modulator using meta materials, transparent conducting oxides (TCOs) have been arranged on the periphery of an optical antenna to adjust resonance characteristics. That is, an active layer composed of TCOs is placed at the bottom of the optical antenna, allowing changes in a refractive index according to an external voltage, and accordingly, the resonance conditions change, which leads to phase modulation of a reflective wave. However, the change in refractive index of the TCOs occurs only at an extremely thin boundary surface of the active layer, having a thickness of 1 nm to 2 nm, and thus the modulation efficiency is low.

SUMMARY

One or more example embodiments provide optical modulators which modulate light in a non-mechanical manner and operate as light modulation elements having high performance.

One or more example embodiments also provide optical modulators which achieve a high modulation efficiency by allowing a layer where a refractive index changes to have a thickness of tens to hundreds of nanometers.

One or more example embodiments also provide optical modulators having an antenna width which allows Fabry-Perot resonance to occur in relation to an operating wavelength.

One or more example embodiments also provide optical modulators having a high phase modulation capability with not low reflectance in an infrared region. Provided are electronic apparatuses which utilize optical modulators.

According to an aspect of an example embodiment, there is provided an optical modulator including a substrate, and a plurality of meta units provided on the substrate and spaced apart from each other, wherein at least one of the plurality of meta units includes a metal layer provided on the substrate, a dielectric layer provided an upper surface and side surfaces of the metal layer, and an antenna provided on an upper surface of the dielectric layer, the antenna including phase change material, wherein a refractive index of the phase change material changes based on a voltage applied to the metal layer to modulate incident light.

The plurality of meta units may include a first meta unit and a second meta unit provided adjacent to each other, wherein a metal layer and an antenna included in the first meta unit are provided spaced apart from a metal layer and an antenna included in the second meta unit, respectively, and wherein a dielectric layer included in the first meta unit and a dielectric layer included in the second meta unit are connected to each other.

A difference between a real part of a refractive index of the phase change material in a crystalline state and a real part of a refractive index of the phase change material in an amorphous state may be greater than or equal to 1.

An imaginary part of a refractive index of the phase change material in an infrared wavelength region may be less than or equal to 3.

The phase change material may include at least one of germanium (Ge), antimony (Sb), and tellurium (Te).

The phase change material may include at least one of Ge2Sb2Te5and Ge3Sb2Te6.

The incident light on the meta units may form surface plasmon resonance (SPR) between the antenna and the metal layer.

The antenna may have a width corresponding to Fabry-Perot resonance of incident light.

A width of the antenna may be less than a wavelength of the incident light.

A temperature of the metal layer may change based on a voltage applied to the metal layer, and a temperature of the antenna may change based on the temperature change of the metal layer.

The antenna may have the thickness such that a difference between a maximum temperature and a minimum temperature in an entire area of the antenna is less than 100° C.

A thickness of the antenna may range from 10 nm to 200 nm.

The antenna may have the thickness such that a difference between an average temperature of an area of the antenna and an average temperature of an area of the metal layer is less than 100° C.

The dielectric layer may have a thickness such that a difference between a maximum temperature and a minimum temperature in an entire area of the antenna is less than 100° C.

A thickness of the dielectric layer may range from 3 nm to 80 nm.

The voltage may be applied to each of the plurality of meta units such that light reflected from the optical modulator forms a wavefront and is steered to a specific point.

A steering direction of light reflected from the optical modulator may change based on modulation periods of the plurality of meta units.

The plurality of meta units may be provided one-dimensionally or two-dimensionally.

An electronic apparatus may include the optical modulator.

The electronic apparatus may include at least one of a light detection and ranging (LiDAR) device, a three-dimensional image acquisition device, a holographic display device, a structured light generation device, a portable terminal, and augmented reality or virtual reality glasses.

DETAILED DESCRIPTION

Reference will now be made in detail to example embodiments of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the example embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the example embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, the expression, “at least one of a, b, and c,” should be understood as including only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments are simply provided as an example, and thus, may be embodied in many different forms. Like reference numerals in the drawings denote like elements, and sizes of components in the drawings may be exaggerated for convenience of explanation.

It will be understood that when a component is referred to as being “on” another component or on “upper part” of another component, the component can be directly on the other component or over the other component in a non-contact manner.

As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Throughout the specification, when a portion “includes” an element, another element may be further included, rather than excluding the existence of the other element, unless otherwise described.

Moreover, the terms “part,” “module,” etc. refer to a unit processing at least one function or operation, and may be implemented by a hardware, a software, or a combination thereof.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing embodiments (especially in the context of the following claims) are to be construed to cover both the singular and the plural.

The use of any and all exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate technical ideas and does not pose a limitation on the scope of embodiments unless otherwise claimed.

FIG.1Ais a perspective view showing an optical modulator10according to an example embodiment, andFIG.1Bis a cross-sectional diagram illustrating a meta unit100of the optical modulator10(i.e., the AA′ section ofFIG.1A).FIG.2is a graph showing a refractive index according to a phase of GeSbTe (GST).

With reference toFIGS.1A and1B, the optical modulator10according to an example embodiment may modulate a reflection phase or a transmission phase of light when reflecting or transmitting incident light, and include a substrate20and a plurality of meta units100arranged side by side in a line on the substrate20. At least one of the plurality of meta units100may include a metal layer110arranged on the substrate, a dielectric layer120covering an upper surface and side surfaces of the metal layer110, and an antenna130arranged on an upper surface of the dielectric layer120and including phase change materials. A refractive index of the phase change materials included in the antenna130may change according to a voltage applied to the metal layer110, thereby modulating incident light. At this time, an electrode connected to each metal layer110may apply a voltage140to the metal layer110. The optical modulator10is configured to modulate a phase of incident light, and may be applied to a beam scan device, which is not engaged in mechanical movements, by having different phase distributions for each meta unit100.

The plurality of meta units100may include adjoining first meta unit and second meta unit, Each of a metal layer and an antenna of the first meta unit is arranged spaced apart from a metal layer and an antenna of the second meta unit, respectively, and a dielectric layer of the first meta unit and a dielectric layer of the second meta unit are connected to each other.

The plurality of meta units100may be placed at certain intervals.FIG.1Aillustrates exemplary meta units100, and such meta units100may be arranged in regularly. The metal layer110included in the meta unit100is not in contact with the antenna130included in the meta unit100by the dielectric layer120covering an upper surface and side surfaces of the metal layer110, and is electrically separated. A distance between the plurality of meta units100may change.

The antenna130may include phase change materials whose phase may change according to temperature, pressure, etc. When the temperature of the phase change materials increases or decreases, the phase of the phase change materials may change. The phase change materials may have an amorphous state, a crystalline state, and an intermediate state therebetween. Each phase of the phase change materials may have a different refractive index. When the phase change materials go through a phase change from an amorphous state to a crystalline state or from a crystalline state to an amorphous state, an intermediate state may have a refractive index ranging between a refractive index in the amorphous state and a refractive index in the crystalline state. Incident light on the meta unit100including the phase change materials and the metal layer110may be strongly focused between the phase change materials and the metal layer110causing plasmonic resonance. Resonance conditions may be changed according to a refractive index of phase change materials.

For example, when a temperature increases or decreases according to a voltage applied to the metal layer110, a phase change may occur in phase change materials, which leads to a change in a refractive index n caused by the phase change. In addition, the phase change materials may be materials having weak light absorption characteristics in an infrared light region, a visible light region, and/or an ultraviolet light region. The phase change materials may be materials having weak light absorption characteristics in an infrared light region. For example, an imaginary part of a refractive index Im(n) of the phase change materials in an operating infrared wavelength region may be less than or equal to 3. Meanwhile, the phase change materials may include germanium (Ge), antimony (Sb) and tellurium (Te). For example, the phase change materials may include at least one of Ge2Sb2Te5and Ge3Sb2Te6.

To implement a high quality optical modulator10, the optical modulator10may satisfy the following two conditions. First, the intensity of modulated light may remain constant regardless of a modulated phase. When the intensity fails to remain constant, despite light steering, an intensity of light may vary, generating a mottled pattern. Second, a range of a phase shift value of light through modulation may be close to 360°. When a range of a phaseshift is limited, a light steering direction may be limited as well.

The following two characteristics of the optical modulator10are considered for a range of a phase shift of light to reach 360° through modulation. First, a change value of a real part of a refractive index Re(n) of materials of the optical modulator10may be sufficiently large. In such case, a phase shift of light modulated by the optical modulator10may vary according to a wavelength of the light. At this time, when a refractive index of materials of the optical modulator10is changed, a phase shift profile according to a wavelength of light of the optical modulator10may move parallel to a wavelength axis. A possible range of a phase shift of light modulation may be determined by a phase shift before a refractive index change of the materials and a phase shift after a refractive index change of the materials in an operating wavelength. When a change value of a real part of a refractive index of the materials is small, the aforementioned parallel movement of the profile may be small, which leads to a small possible range of a phase shift of the light. When a change value of a real part of a refractive index of the materials is sufficiently large, the aforementioned parallel movement of the profile may be large, which leads to a relatively large possible range of a phase shift of the light that is up to 360°, at the greatest.

Secondly, the materials of the optical modulator10may have a low light absorption rate, and the optical modulator10may be structured to absorb less light. A resonator may have two channels for the reflection characteristics which include the direct reflection, and a reflection through a resonator. When the amplitude of reflection through a resonator is larger than that of the direct reflection, a resonator is referred to be in the over-coupling regime, and in this case, a phase shift profile may gradually increase up to 360°. When the amplitude of direct reflection is larger than that of reflection through a resonator, a resonator is referred to be in the under-coupling regime and in such case a phase shift profile may not reach 360°, and fluctuate similar to waves. In the under-coupling regime, the maximum phase shift may be about 180°. The materials of the optical modulator10may have a low light absorption rate for resonator being in the over-coupling regime. That is, an imaginary part of refractive index of the materials may be small. In the case of large imaginary part of a refractive index, light absorption occurs prior to resonance of the light, causing a weaker reflection through a resonator, which is likely to lead resonator to be in the under-coupling regime.

Accordingly, when a light absorption rate or an imaginary part of a refractive index of materials of the optical modulator10has a small value, a percentage of absorbed light decreases, thereby increasing a modulation efficiency, which leads resonator to be in the over-coupling regime. Then, a maximum threshold value of possible range of phase shift of light may increase. Also, when a difference in a real part of a refractive index of the materials of the optical modulator10before and after phase of the materials changes is large, a maximum value of possible range of a phase shift of the light may increase. With followed characteristics, a quality optical modulator10may be improved.

The antenna130may include germanium (Ge), antimony (Sb), tellurium (Te) and alloys thereof. For example, the antenna130may include at least one of GSTs including Ge2Sb2Te5or Ge3Sb2Te6, which are phase change materials (PCM). GST may have a crystallization temperature of 100° C. to 150° C., and a melting point is about 600° C. When GST is heated at a crystallization temperature for relatively long time, the GST may become in a crystalline state, which is referred to as a SET. When GST is heated to reach a melting point, and then quickly cooled, the GST may become and remain in an amorphous state. This is referred to as a RESET. According toFIG.2, in an amorphous state, a real part of a refractive index in an infrared light region may be between about 3.9 to 4.0, and about 5 in a crystalline state. Further, in an amorphous state, an imaginary part of a refractive index may be about 0.1, and between about 0.5 to 2.0 in a crystalline state. As an imaginary part of a refractive index of GST is small, light absorption may be small, which improves adjustment of phase shift in the over-coupling regime. For example, according to the above, a maximum range of a phase shift may exceed 180°. In addition, a real part of a refractive index of GST may vary significantly over 1 according to a phase, and accordingly, a maximum range of a phase shift of light may reach about 270°, allowing a high modulation efficiency, which leads to a relatively high reflectance. At this time, a value of between the range of the phase shift of 0° to 270° may be represented by an intermediate phase.

A meta unit100may include a single or a plurality of antenna(s)130.FIGS.1A and1Billustrate that a single antenna130is arranged in one meta unit100; however, embodiments are not limited thereto. The plurality of antennas130of one meta unit100may have the same width and thickness. However, embodiments are not limited thereto.

The antenna130may be a rectangular structure. For example, as illustrated inFIGS.1A and1B, the antenna may be arranged in a rectangular shape. However, embodiments are not limited thereto, and may be a structure in various shapes. For example, a shape of its cross section may vary from a rectangle, a triangle, a polygon, a cross, a circle to an oval, etc. The size or shape of the antenna130may vary according to an incident wavelength.

A width w1of the antenna130may be less than a wavelength of incident light. A thickness t1of the antenna130may be less than a wavelength of incident light. A thickness t1of the antenna130may be a few nanometers to hundreds of nanometers. At this time, a thickness of the antenna130may be formed to be greater than tens of nanometers to increase a volume under which a refractive index is changed. As the volume allowing a refractive index change increases, a modulation efficiency of the optical modulator10may be enhanced.

The metal layer110may be arranged under the antenna130placing the dielectric layer120therebetween and serve as a plasmonic substrate. Further, the metal layer110may be connected with electrodes and thus, when a voltage is applied to the metal layer110, it may be serve as a heater. For example, when a voltage is applied to the metal layer110, temperatures of the metal layer110and the adjacent antenna130may increase to a predetermined temperature, and when a voltage is no longer applied, the temperatures of the metal layer110and the adjacent antenna130may decrease to an original temperature. At this time, the temperature of the antenna130may increase and decrease uniformly without a difference between a high and low temperature region. For this, the thickness t1of the antenna130and the thickness t3of the dielectric layer120may be formed accordingly. A detailed description thereon will be provided later with reference toFIG.4B. In addition, a plurality of voltages may be independently connected to each meta unit100and accordingly, different voltages may be applied to each meta unit100. Thus, each meta unit100may experience a temperature increase or decrease independently. The metal layer110may be formed of, for example, gold (Au), aluminum (Al), silver (Ag), copper (Cu), tungsten (W), etc. At this time, the metal layer110may be formed of a metal of low light absorption, for example, Au, which has a low light absorption characteristic.

The metal layer110may have a width greater than the width w1of the antenna130. The width w2of the metal layer110may be less than a wavelength of incident light. The thickness t2of the metal layer110may be less than a wavelength of incident light.

The dielectric layer120may serve as an optical spacer between the antenna130and the metal layer110. In addition, the dielectric layer120may electrically separate the antenna130and the metal layer110. The dielectric layer120may be formed of metallic oxides, for example, various oxides and nitrides, including aluminum oxide (Al2O3), silicon oxide (SiO2), hafnium oxide (HfO2), silicon nitride (Si3N4), etc. At this time, the dielectric layer120may be formed of oxides and nitrides, which may be easily adhered between the antenna130and the metal layer110, for example, Al2O3which has an advantage in adhesion. The thickness t3of the dielectric layer120may be smaller than a wavelength of incident light.

The dielectric layer120may cover an upper surface as well as a side surfaces of the metal layer110, and by extending toward one direction on the substrate, the dielectric layer120of each different meta unit100may be connected to each other. The dielectric layer120in contact with the upper surface of the substrate between meta units100may have the same thickness t3as the dielectric layer120of the meta unit100, or may have a thickness t2+t3, to provide an even distance between the upper surface of the dielectric layer120and the substrate. However, embodiments are not limited thereto, and the dielectric layer120may not be extended to the parts of the substrate with no meta unit100.

A plurality of voltages may be independently connected to each metal layer110. For example, each metal layer110may receive an independent voltage, and each meta unit100may have an independent temperature. As a result, each meta unit100may independently modulate a phase of incident light. Further, by inputting different modulation periods to the plurality of meta units100, light may be steered in various directions. For example, a voltage may be applied to four meta units100from the plurality of meta units100as one period. For example, a voltage may be applied to the four meta units100in order for a phase shift of each meta unit to be 0°, 90°, 180°, and 270°. Further, a voltage may be applied to eight meta units100as one period. For example, a voltage may be applied to the eight meta units100in order for a phase shift of each meta unit to be 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°. As such, when a modulation period of the meta units100changes, a degree at which light is steered may also change, which may provide various light steering directions.

Accordingly, in the optical modulator10including the substrate and the plurality of meta units100arranged side by side in a line adjacent to each other, different voltages may be applied to each meta unit100so that light reflected from the optical modulator10may form a predetermined wavefront and be steered to a certain point. In addition, a steering direction of light reflected from the optical modulator10may vary according to modulation periods of the plurality of meta units100.

FIG.3is a graph showing a magnetic field intensity distribution when light is incident on the optical modulator10and resonates in the meta unit100, andFIG.4Ais a graph showing temperature distribution of a cross section of one meta unit100when a voltage is applied thereto.FIG.4Bis a graph showing changes in current flows in the metal layer110and changes in a maximum temperature and a minimum temperature of the antenna130and the metal layer110before and after a voltage is applied to the meta unit100. When the metal layer110is symmetric in z direction, and the effect on edges is negligible, the meta units100may have a corresponding temperature distribution, independently from z direction of the meta units100.

In the example embodiment illustrated inFIG.3, the antenna130is formed of GST, and the metal layer110is formed of Au, and the dielectric layer120is formed of Al2O3. Further, the width w1of the antenna130is set as 500 nm, the width w2of the metal layer110as 750 nm, the thickness t1of the antenna130as 50 nm, the thickness t2of the metal layer110as 60 nm, and the thickness t3of the dielectric layer120as 6 nm. Further, an absolute value of magnetic field amplitude is normalized as a magnetic field amplitude Ho of incident light. Incident light is a transverse magnetic (TM) polarization mode having a magnetic field in z direction, and incidents vertically in −y direction. The meta unit100is arranged on a SiO2layer having a thickness of 300 nm placed on a silicon substrate at an interval of 900 nm.

According toFIG.3, incident light in the meta unit100may be focused between GST and Au and cause surface plasmon resonance. Through the aforementioned surface plasmon resonance, a phase of the light may be modulated, and in the optical modulator10in which the plurality of meta units100are arranged, different voltages may be applied to each of the plurality of meta units100so that the light may form a desired wavefront and be steered to a certain point.

Meanwhile, an operating wavelength of light resonance may vary according to the width w1of the antenna130. This is because surface plasmon resonance and Fabry-Perot resonance may occur between the surfaces of the antenna130and the metal layer110. By the surface plasmon resonance, the light may extend in a surface direction as an electromagnetic surface wave in the form of surface plasmon polaritons, and be reflected on both sides of the antenna. Such reflection of electronic surface wave may cause Fabry-Perot resonance. The occurrence of Fabry-Perot resonance may be determined according to a wavelength of incident light and a width of the antenna130. Further, an operating wavelength to modulate a reflection phase of light to about 270° may be determined by a width of the antenna130. Accordingly, the antenna130may have a width in accordance with conditions of Fabry-Perot resonance in relation to a wavelength of incident light.

Such conditions of Fabry-Perot resonance may be determined by the following [Equation 1].

When the aforementioned Equation 1 is satisfied, Fabry-Perot resonance may occur. At this time, λ represents an operating wavelength, neffrepresents a valid refractive index of GST, wGSTrepresents a width of GST, and φrefrepresents a phase shift of light when the light is reflected from a side surfaces of GST. For a desired operating wavelength λ, an antenna130satisfying wGSTmay be determined.

Similarly, inFIGS.4A and4B, the antenna130is formed of GST, the metal layer110is formed of Au, and the dielectric layer120is formed of Al2O3. Here, wGSTis set as 500 nm, wAuas 750 nm, tGSTas 50 nm, tAUas 60 nm, and tAl2O3as 6 nm. Further, the optical modulator10is arranged on a SiO2layer. According to FIGS.4A and4B, when a voltage is applied to the metal layer110, a maximum temperature and a minimum temperature of Au may increase or decrease in almost equally. In addition, a maximum temperature and a minimum temperature of GST may increase or decrease almost equally. Also, temperatures of GST and Au may increase or decrease almost equally. Such uniform temperature change may become an advantage at the time of phase change of GST to a crystalline state or to an amorphous state, and may allow uniform phase modulation in the entire area of a meta unit100.

According to another example embodiment, when a voltage is applied to the metal layer110in one meta unit100, a maximum temperature and a minimum temperature of GST may increase or decrease with a difference less than 100° C. At this time, when the difference between the maximum temperature and minimum temperature of GST according to time change is less than 100° C., the efficiency achieved therefrom may be close to that under uniform phase modulation.

According toFIG.4B, a voltage is applied when t is 200 ns, and it remains constant for 1000 ns until the voltage is cut off when t is 1200 ns. The voltage is applied so that a current of 15 mA flows in the metal layer110. When a voltage is applied consistently, temperature of GST may increase to 650° C. which is a melting point, and after the voltage application and heat generation are terminated, the temperature may decrease to less than or equal to 160° C. in 100 ns. Accordingly, GST in a crystalline state may go through a phase change (RESET) to be in an amorphous state. When GST is heated at a temperature ranging from 100° C. and 150° C. for relatively long time, GST in an amorphous state may go through a phase change (SET) to be in a crystalline state. According toFIG.4B, as the aforementioned temperature change occurs uniformly in the entire area of GST, the foregoing phase changes (SET and RESET) may also occur uniformly in the entire volume of GST. Accordingly, uniform phase modulation may occur in the entire area of one meta unit100. In addition, as a temperature of Au, which serves as a heater, may not increase excessively at the time of phase change of GST, energy-efficient modulation may also be achievable. For example, a crystallization from an amorphous state to a crystalline state according to a temperature decrease, and an amorphorization from a crystalline state to an amorphous state according to a temperature increase may take place in a stable manner, and such crystallization and amorphorization may occur repeatedly.

According to an example embodiment, when a voltage is applied to the metal layer110in one meta unit100, the antenna130may have a thickness which allows a uniform temperature change, e.g., a temperature increase or decrease, throughout the entire area of the antenna130. For example, when a thickness of the antenna130is too large, a difference between a minimum temperature and a maximum temperature of the antenna130area may be generated in the event of temperature change. Accordingly, the antenna130may have a thickness which allows a uniform temperature change in the entire area of the antenna130. When determining a thickness of the antenna130, thermal conductivities of the metal layer110, the dielectric layer120, and the antenna130may be considered. Further, when a thickness of the antenna130is too small, a region where a refractive index may vary may be reduced, affecting a modulation efficiency. Therefore, the antenna130may have a thermally and optically co-optimal thickness in consideration of the aforementioned temperature conditions and modulation efficiency. For example, the thickness of the antenna130may be 10 nm to 100 nm.

According to another example embodiment, when a voltage is applied to the metal layer110in one meta unit100, a difference between a maximum temperature and a minimum temperature of the antenna130area may remain less than 100° C. In this case, the antenna130may have a thickness which allows temperature to change with temperature difference less than 100° C. in the entire area of the antenna130. In this example, the efficiency may be close to an efficiency achieved when temperature changes in the antenna130occur uniformly in its entire area. Therefore, the antenna130may have a thermally and optically co-optimal thickness in consideration of the aforementioned temperature conditions and modulation efficiency. For example, the thickness of the antenna130may be 10 nm to 200 nm.

According to another example embodiment, when a voltage is applied to the metal layer110in one meta unit100, a difference between an average temperature of the antenna130area and an average temperature of the metal layer110area may remain less than 100° C. In this case, the antenna130may have a thickness which allows temperature to change with temperature difference less than 100° C. between the average temperature of the antenna130area and the average temperature of the metal layer110area.

According to an example embodiment, when a voltage is applied to the metal layer110in one meta unit100, the dielectric layer120may have a thickness which allows a uniform temperature change, e.g., a temperature increase or decrease, throughout the entire area of the antenna130. For example, when a thickness of the dielectric layer120is too thick, a thermal conductivity according to a thermal conduction equation may decrease, which may lead to a difference between a minimum temperature and a maximum temperature of the antenna130area in the event of temperature change. Accordingly, the dielectric layer120may have a thickness which allows a uniform temperature change in the entire area of the antenna130. When determining a thickness of the dielectric layer120, thermal conductivities of the metal layer110, the dielectric layer120, and the antenna130may be considered. For example, the thickness of the dielectric layer120may be 3 nm to 60 nm.

According to another example embodiment, when a voltage is applied to the metal layer110in one meta unit100, a difference between a maximum temperature and a minimum temperature of the antenna130area may remain less than 100° C. In this case, the dielectric layer120may have a thickness which allows temperature to change with temperature difference less than 100° C. in the entire area of the antenna130. In such case, the efficiency may be close to an efficiency achieved under a uniform temperature change in the antenna130. For example, the thickness of the dielectric layer120may be 3 nm to 80 nm.

According to another example embodiment, when a voltage is applied to the metal layer110in one meta unit100, a difference between an average temperature of the antenna130area and an average temperature of the metal layer110area may remain less than 100° C. In this case, the dielectric layer120may have a thickness which allows temperature to change with temperature difference less than 100° C. between the average temperature of the antenna130area and the average temperature of the metal layer110area.

According to an example embodiment, the arrangement interval between the meta units100may be determined not to thermally affect adjacent meta units100. For example, when the interval between the meta units100is too narrow, temperatures of each meta unit100may not be maintained independently due to a thermal crosstalk caused by a heat generated from each meta unit100. Accordingly, the interval between the meta units100may be determined not to cause a thermal crosstalk in the meta units100.

FIG.5is a graph showing a reflectance and a change of reflection phase shift spectrum according a phase change of GST when an antenna130includes GST in whole. The solid line in the graph ofFIG.5represents reflectance of GST in an amorphous state, and the dotted line represents reflectance of GST in a crystalline state. In an infrared light region (e.g. where λ is 1.4 μm), a reflectance in an amorphous state may be about 70%, and a reflectance in a crystalline state may be about 40%, which are considered fairly high. This shows that a high efficiency operation is achievable at the time of beam steering through an optical modulator10according to an example embodiment.

The broken line in the graph ofFIG.5represents a change of reflection phase shift spectrum of light. For example, the line represents values obtained by subtracting reflection phase shift spectrum in a crystalline state from reflection phase shift spectrum in an amorphous state, and in a region where a wavelength is 1.4 μm to 1.55 μm, a range of phase shift may be possible up to 3π/2 (rad), i.e., about 270°. Such substantial phase shift may occur in a range of tens of or hundreds of nanometers, which is a full thickness of the antenna130. For example, as a refractive index of phase change materials varies in the entire area of the antenna130, a higher efficiency may be achieved compared to that from a layer in the related art having a thickness of several nanometers where a refractive index change occurs. For example, when tGSTis 50 nm as inFIG.4A, a refractive index varies in the entire area of GST, which leads to a higher modulation efficiency compared to an efficiency obtained from using a conventional conducting oxide having a thickness of 1 nm to 2 nm.

FIG.6is a perspective view of an optical modulator10including a plurality of antennas130for each meta unit100. Compared toFIG.1, the plurality of antennas130may be arranged on one meta unit100. A width of the plurality of antennas130may be determined by an operating wavelength. A temperature of the plurality of antennas130arranged on one meta unit100may be adjusted by the same metal layer110. The plurality of antennas130of one meta unit100may have the same width and thickness. As described above, by placing a plurality of antennas130, a beam may be steered in various directions. In this case, by changing a modulation period of the plurality of meta units, the beam may be steered in a corresponding direction.

According to an example embodiment, the meta unit100may be arranged one-dimensionally, and according to another example embodiment, the meta unit100may be arranged two-dimensionally.FIG.7is a cross-sectional view illustrating a meta unit100arranged two-dimensionally. When the meta unit100is arranged one-dimensionally, it is possible to steer a reflected beam in a direction perpendicular to the antenna130. When the meta unit100is arranged two-dimensionally, it is possible to steer a reflected beam in a direction not only perpendicular to but horizontal with the antenna130. In this manner, the optical modulator10may steer a beam two-dimensionally.

FIG.8is a conceptual diagram for explaining a beam steering device1000A including an optical modulator10according to an example embodiment.

With reference toFIG.8, a beam may be steered in a one-dimensional direction by using a beam steering device1000A. For example, the beam may be steered in a first direction DD1toward a predetermined object OBJ. The beam steering device1000A may include a one-dimensional array of a plurality of optical modulators10according to an example embodiment.

FIG.9is a conceptual diagram for explaining a beam steering device1000B including an optical modulator10according to another example embodiment.

With reference toFIG.9, a beam may be steered in a two-dimensional direction by using a beam steering device1000B. For example, the beam may be steered in the first direction DD1toward a predetermined object OBJ and in a second direction DD2perpendicular thereto. The beam steering device1000B may include a two-dimensional array of a plurality of optical modulators10according to an example embodiment. The beam steering devices1000A and1000B described with reference toFIGS.8and9may be a non-mechanical beam scanning apparatus.

FIG.10is a block diagram illustrating an overall system of an electronic apparatus A1including a beam steering device with an optical modulator10according to an example embodiment.

With reference toFIG.10, the electronic apparatus A1may include a beam steering device1000. The beam steering device1000may include an optical modulator10described with reference toFIGS.1A,1B,3,6,7, etc. The electronic apparatus A1may include a light source in the beam steering device1000, or include a light source provided separately from the beam steering device1000. The electronic apparatus A1may include a detector1100configured to detect light reflected by an object of light steered by the beam steering device1000. The detector1100may include a plurality of light detecting elements, and may further include other optical components. The electronic apparatus A1may further include a circuit1200connected to at least one of the beam steering device1000and the detector1100. The circuit1200may include a calculator configured to obtain and calculate data, and further include a driver, a processor, etc. In addition, the circuit1200may further include a power supply, a memory, etc.

FIG.10illustrates that an electronic apparatus A1includes a beam steering device1000and a detector1100included in a single device. However, the beam steering device1000and the detector1100may be provided in each separate device instead of being included in a single device. Further, the circuit1200may not be connected in a wired manner to the beam steering device1000or the detector1100, and may be connected by a wireless communication. The configuration ofFIG.10may be changed in various other ways.

An optical modulator or a beam steering device including the optical modulator according to example embodiments described above may be applied to various electronic apparatuses. For example, the beam steering device may be applied to a light detection and ranging (LiDAR) device. The LiDAR device may be a device adopting a phase-shift method or a time-of-flight (TOF) method. Further, an optical modulator or a beam steering device including the optical modulator according to an example embodiment may be embedded in electronic apparatuses, such as a smartphone, a wearable device (augmented reality, and virtual reality implementation glasses, etc.), Internet of Things (IoT) devices, home appliances, tablet personal computers (PCs), a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation, a drone, a robot, an unmanned vehicle, an autonomous vehicle, an advanced drivers assistance system (ADAS), etc.

FIGS.11and12are conceptual diagrams illustrating application of a LiDAR device including an optical modulator according to an example embodiment to a vehicle.FIG.11is a diagram illustrating a side view of the application, andFIG.12is a diagram illustrating a top view of the application.

With reference toFIG.11, a LiDAR device51may be applied to a vehicle50, and information on an object60may be obtained by using the device. The vehicle50may be an automobile having an autonomous driving function. By using the LiDAR device51, an object or person located in a driving direction of a vehicle50, for example, an object60, may be detected. In addition, by using information on a time difference between transmission signals and detection signals, a distance to the object60may be measured. Moreover, as illustrated inFIG.12, information on a nearby object61and a distant object62within a scanning range may be obtained.

An optical modulator according to various example embodiments may be applied to various electronic apparatuses besides a LiDAR device. For example, by using the optical modulator according to various example embodiments, three-dimensional information on a space or an object may be obtained by means of scanning, and thus, it may be applied to a three-dimensional image acquisition device or a three-dimensional camera, etc. Further, the optical modulator may be applied to a holographic display device and a structured light generation device. Also, the optical modulator may be applied to various optical components/apparatuses such as various beam scanning devices, hologram generating devices, optical coupling devices, variable focus lenses, depth sensors, etc. Moreover, the optical modulator may be applied to various fields where a “metasurface” or “metastructure” is used. Apart from the above, an optical modulator and an electronic apparatus including the same according to an example embodiment may be applied to diverse fields of optics and electronic apparatuses for various purposes.

FIG.13is a block diagram illustrating a schematic configuration of an electronic apparatus according to an example embodiment.

With reference toFIG.13, in a network environment2200, an electronic apparatus2201may communicate with other electronic apparatus2202through a first network2298(a short-distance wireless communication network, etc.), or with another electronic apparatus2204and/or server2208through a second network2299(a long-distance wireless communication network, etc.) The electronic apparatus2201may communicate with the electronic apparatus2204through the server2208. The electronic apparatus2201may include a processor2220, a memory2230, an input device2250, an acoustic output device2255, a display device2260, an audio module2270, a sensor module2210, an interface2277, a haptic module2279, a camera module2280, a power management module2288, a battery2289, a communication module2290, a subscriber identification module2296, and/or an antenna module2297. In the electronic apparatus2201, some of the aforementioned components (e.g., a display device2260, etc.) may be omitted, or other components may be added. Some of the foregoing components may be implemented as a single integrated circuit. For example, a fingerprint sensor2211of the sensor module2210, or an iris sensor, an illumination sensor, etc. may be implemented by being embedded in the display device2260(e.g. a display, etc.)

The processor2220may control one or more other components (e.g., hardware, software components, etc.) of the electronic apparatus2201connected to the processor2220by executing a software (e.g., a program2240, etc.), and execute various data processing or operations. As a part of data processing or operations, the processor2220may load commands and/or data received from other components (e.g., the sensor module2210, communication module2290, etc.) to a volatile memory2232, process commands and/or data stored in the volatile memory2232, and store the resulting data in a non-volatile memory2234. The processor2220may include a main processor2221(e.g., a central processing unit, application processor, etc.), and a co-processor2223which may operate independently or together with the main processor (e.g., a graphics processing unit, image signal processor, sensor hub processor, communication processor, etc.) The co-processor2223may use less electricity than the main processor2221, and perform a specialized function.

The co-processor2223may control functions and/or states related to some components of the electronic apparatus2201(e.g., a display device2260, sensor module2210, communication module2290, etc.) in place of the main processor2221when the main processor2221is in an inactive state (e.g., in a sleep), and together with the main processor2221when the main processor2221is in an active state (e.g., when an application is being executed). The co-processor2223(e.g., an image signal processor, communication processor, etc.) may be implemented as a part of other functionally related components (e.g., a camera module2280, communication module2290, etc.)

The memory2230may store various data required by components of the electronic apparatus2201(e.g., a processor2220, sensor module2276, etc.) The data may include, for example, a software (e.g., a program2240, etc.) and input data and/or output data regarding relevant commands. The memory2230may include a volatile memory2232and/or non-volatile memory2234.

The program2240may be stored in the memory2230as a software, and may include an operating system2242, a middleware2244, and/or an application2246.

The input device2250may receive commands and/or data to be used to components (e.g., a processor2220. etc.) of the electronic apparatus2201from the outside (e.g., a user, etc.) of the electronic apparatus2201. The input device2250may include a microphone, a mouse, a keyboard, and/or a digital pen (e.g., a stylus pen, etc.)

The acoustic output device2255may output acoustic signals to the outside of the electronic apparatus2201. The acoustic output device2255may include a speaker and/or a receiver. The speaker may be used for general purposes such as multimedia play or playback, and the receiver may be used to receive incoming calls. The receiver may be integrated as a part of the speaker or implemented independently as a separate device.

The display device2260may visually provide information to the outside of the electronic apparatus2201. The display device2260may include a display, a hologram device, a projector, or a control circuit configured to control the said devices. The display device2260may include a touch circuitry configured to sense a touch, and/or a sensor circuit (e.g., a pressure sensor, etc.) configured to measure an intensity of force generated by a touch.

The audio module2270may convert sounds into electric signals, or reversely, electric signals into sounds. The audio module2270may obtain a sound through the input device2250, or output a sound via the acoustic output device2255, and/or speakers and/or headphones of other electronic apparatuses (e.g., an electronic apparatus2102, etc.) directly or wirelessly connected with the electronic apparatus2201.

The sensor module2210may sense an operational state (e.g., power, temperature, etc.) of the electronic apparatus2201or external environmental state (e.g., user state, etc.), and generate electric signals and/or data values corresponding to a sensed state. The sensor module2210may include a fingerprint sensor2211, an acceleration sensor2212, a position sensor2213, a 3D sensor2214, etc., and may further include an iris sensor, a gyro sensor, an atmospheric pressure sensor, a magnetic sensor, a grip sensor, a proximity sensor, a color sensor, an infrared (IR) sensor, a biometric sensor, a temperature sensor, a humidity sensor, and/or an illumination sensor.

The 3D sensor2214configured to irradiate a predetermined light to an object and analyze light reflected from the object to sense its shape, and movement, etc. may include any one of optical modulators according to the aforementioned embodiments.

The interface2277may support one or more designated protocols which may be used to directly or wirelessly connect the electronic apparatus2201with other electronic apparatuses (e.g., the electronic apparatus2102, etc.) The interface2277may include a high definition multimedia interface (HDMI), a universal serial bus (USB) interface, an SD card interface, and/or an audio interface.

A connection terminal2278may include a connector that may physically connect the electronic apparatus2201with other electronic apparatuses (e.g., the electronic apparatus2102, etc.) The connection terminal2278may include a HDMI connector, a USB connector, an SD card connector, and/or an audio connector (e.g., a headphone connector, etc.)

The haptic module2279may convert electric signals into mechanical stimuli (e.g., vibration, motion, etc.) or electric stimuli that a user can perceive through the sense of touch or sense of movement. The haptic module2279may include a motor, a piezoelectric element, and/or an electric stimulator.

The camera module2280may take static images and moving pictures. The camera module2280may include a lens assembly including one or more lenses, image sensors, image signal processors, and/or flashes. The lens assembly included in the camera module2280may collect light emitted from an object, which is subject to an image photographing, and may include any one of optical modulators according to the aforementioned embodiments.

The power management module2288may manage power supplied to the electronic apparatus2201. The power management module2288may be implemented as a part of a power management integrated circuit (PMIC).

The battery2289may supply power to components of the electronic apparatus2201. The battery2289may include a first battery, which is unrechargeable, and a second battery which is rechargeable and/or a fuel cell.

The communication module2290may support establishment of a direct (wired) communication channel and/or wireless communication channel between the electronic apparatus2201and other electronic apparatuses (e.g., the electronic apparatus2102, electronic apparatus2104, server2108, etc.), and performance of communication through established communication channels. The communication module2290may be operated independently from the processor2220(e.g., an application processor, etc.) and may include one or more communication processors that support direct communication and/or wireless communication. The communication module2290may include a wireless communication module2292(e.g., a cellular communication module, short-distance wireless communication module, global navigation satellite system (GNSS) communication module, etc.) and/or a wired communication module2294(e.g., a local area network (LAN) communication module, power line communication module, etc.) Among the aforementioned communication modules, a corresponding communication module may communicate with other electronic apparatuses through a first network2298(e.g., short-distance communication networks, including a bluetooth, WiFi Direct, or infrared data association (IrDA)) and a second network2299(e.g., long-distance communication networks including a cellar network, internet, or computer networks, such as LAN, wide area network (WAN), etc.) Such various types of communication modules may be integrated into one component (e.g., a single chip, etc.), or may be implemented as a plurality of separate components (e.g., multiple chips). The wireless communication module2292may verify and authenticate the electronic apparatus2201in communication networks, such as the first network2298and/or the second network2299by using subscriber information (e.g., international mobile station identity (IMSI), etc.) stored in the subscriber identification module2296.

The antenna module2297may transmit signals and/or power to the outside (e.g., other electronic apparatuses, etc.) or receive them from the outside. The antenna may include a radiator consisting of conductive patterns formed on a substrate (e.g., a printed circuit board (PCB), etc.) The antenna module2297may include one or more antennas. When a plurality of antennas are included, it may be selected from the plurality of antennas the antennas suitable for communication methods used in communication networks, such as the first network2298and/or the second network2299. Signals and/or power may be transmitted or received between the communication module2290and other electronic apparatuses via the selected antennas. Other components (e.g., a radio frequency integrated circuit (RFIC), etc.) other than the antenna may be included as a part in the antenna module2297.

Some of the components may be connected and exchange signals (e.g., commands, data, etc.) with each other through communication methods among peripheral devices (e.g., a bus, general purpose input and output (GPIO), serial peripheral interphase (SPI), mobile industry processor interface (MIPI), etc.)

Commands or data may be transmitted or received between the electronic apparatus2201and external electronic apparatus2204via the server2108connected to the second network2299. Other electronic apparatuses2202and2204may be the same or different type of apparatus with the electronic apparatus2201. All or parts of operations executed in the electronic apparatus2201may be executed in one or more other electronic apparatuses2202,2204and2208. For example, when the electronic apparatus2201needs to perform a certain function or service, it may request execution of the function or service in whole or in part from one or more other electronic apparatuses, instead of executing the function or service for itself. One or more other electronic apparatuses which have received the aforementioned request may execute an additional function or service associated with the request, and may transmit the results of the execution to the electronic apparatus2201. To this end, cloud computing, distributed computing, and/or client-server computing technologies may be used.

FIG.14is an exemplary block diagram illustrating a schematic configuration of a camera module provided in an electronic apparatus ofFIG.13.

With reference toFIG.14, the camera module2280may include a lens assembly2310, a flash2320, an image sensor2330, an image stabilizer2340, a memory2350(e.g., a buffer memory, etc.), and/or an image signal processor2360. The lens assembly2310can collect light emitted from an object, which is subject to an image photographing, and may include any one of the aforementioned optical modulators. The lens assembly2310may include one or more refractive lenses and optical modulators. The optical modulator provided therein may have a predetermined phase profile and may be designed as a lens having a compensation structure to reduce phase discontinuity. The lens assembly2310having such optical modulator may implement a desired optical performance and have a short optical total length.

In addition to this, the camera module2280may further include an actuator. The actuator may, for example, operate locations of lens elements constituting the lens assembly2310for zooming and/or autofocus (AF), and adjust a separation distance between the lens elements.

The camera module2280may include a plurality of lens assemblies2310, and in such case, the camera module2280may be a dual camera, a 360-degree camera, or a spherical camera. Some of the plurality of lens assemblies2310may have same lens attributes (e.g., an angle of view, a focal distance, an automatic focus, a F number, an optical zoom, etc.), or different lens attributes. The lens assembly2310may include a wide angle lens or telephoto lens.

The flash2320may emit light which is used to intensify light emitted or reflected from an object. The flash2320may include one or more light emitting diodes (e.g., a red-green-blue (RGB) LED, white LED, infrared LED, ultraviolet LED, etc.), and/or xenon lamp. The image sensor2330may obtain an image corresponding to an object by converting light, which has been emitted or reflected from the object and then transmitted via the lens assembly2310, into electric signals. The image sensor2330may include one or more sensors selected from a RGB sensor, a black and white (BW) sensor, an infrared light (IR) sensor, or an ultraviolet light (UV) sensor, which all have different attributes. Each sensor included in the image sensor2330may be implemented as a charged coupled device (CCD) sensor and/or a complementary metal oxide semiconductor (CMOS) sensor.

The image stabilizer2340may react to movements of the camera module2280or the electronic apparatus2301including the same to move one or more lenses or image sensors2330included in the lens assembly2310in a certain direction, or control operation characteristics (e.g., adjustment of a read-out timing, etc.) of the image sensor2330to compensate for negative effects caused by the movements. The image stabilizer2340may sense movements of the camera module2280or the electronic apparatus2301by using a gyro sensor (not explicitly shown in the drawings) or an acceleration sensor (not explicitly shown in the drawings) arranged inside or outside the camera module2280. The image stabilizer2340may be implemented in an optical manner.

the memory2350may store the entire or parts of data regarding an image obtained through the image sensor2330for next image processing operation. For example, when a plurality of images are obtained at a high speed, the obtained original data (e.g., Bayer-patterned data, high resolution data, etc.) may be stored in the memory2350, and only low resolution images may be displayed. Then, the memory may be used for transmission of the original data of selected images (e.g., images selected by a user, etc.) to the image signal processor2360. The memory2350may be integrated into the memory2230of the electronic apparatus2201, or configured as a separate memory which operates independently.

The image signal processor2360may perform one or more image processing operations regarding image obtained via the image sensor2330or image data stored in the memory2350. One or more image processing operations may include a depth map generation, 3D modeling, panorama generation, feature point extraction, image synthesis, and/or image compensation (e.g., noise reduction, resolution adjustment, brightness adjustment, blurring, blurring, sharpening, softening, etc.) The image signal processor2360may perform a control (e.g., an exposure time control, or read-out timing control, etc.) of components (e.g., an image sensor2330, etc.) included in the camera module2280. The image processed by the image signal processor2360may be stored again in the memory2350for additional processing or provided to external components (e.g., the memory2230, display device2260, electronic apparatus2202, electronic apparatus2204, server2208, etc.) of the camera module2280. The image signal processor2360may be integrated into the processor2220, or be configured as a separate processor which operates independently from the processor2220. When the image signal processor2360is configured as a separate processor distinct from the processor2220, images processed by the image signal processor2360may be displayed via the display device2260after an additional image processing by the image processor2220.

The electronic apparatus2201may include a plurality of camera modules2280each having different attributes or functions. In this case, one of the plurality of camera modules2280may be a wide angle camera, and another may be a telephoto camera. Similarly, one of the plurality of camera modules2280may be a front camera and another may be a rear camera.

FIG.15is a block diagram illustrating a schematic configuration of a 3D sensor provided in the electronic apparatus ofFIG.13.

The 3D sensor2214may sense shapes, movements, etc. of an object by irradiating a predetermined light to the object and then receiving and analyzing light reflected from the object. The 3D sensor2214may include a light source2420, an optical modulator2410, an optical detector2430, a signal processor2440and a memory2450. As the optical modulator2410, any one of optical modulators according to the aforementioned embodiments may be adopted, and a target phase delay profile may be set allowing the optical modulator to function as a beam deflector or a beam shaper.

The light source2420may radiate light to be used for a shape or location analysis of an object. The light source2420may include a light source which generates and irradiates light of a predetermined wavelength. The light source2420may include a light source which generates and irradiates light having a wavelength band suitable for a shape or location analysis of an object, for example, a laser diode (LD), light emitting diode (LED), super luminescent diode (SLD), etc. which generate and irradiate light having an infrared band wavelength. The light source2420may be a tunable laser diode. The light source2420may generate and irradiate lights having each different wavelength bands. The light source2420may generate and irradiate pulse light or continuous light.

The optical modulator2410may modulate light radiated from the light source2420and transmit the modulated light to an object. When the optical modulator2410is a beam deflector, the optical modulator2410may deflect incident light in a predetermined direction toward an object. When the optical modulator2410is a beam shaper, the optical modulator2410may modulate incident light to have a distribution with a predetermined pattern. The optical modulator2410may form structured light suitable for a three-dimensional shape analysis.

As described above, the optical modulator2410may set a phase delay dispersion (∂φ/∂λ) to 0, a positive number, or a negative number, and implement a continuous phase delay profile. Accordingly, it is possible to perform achromatic optical modulation. By increasing a deviation according to a wavelength, a deflection direction may vary for each wavelength, or different beam patterns may be formed for each wavelength for irradiation to an object.

The optical detector2430may receive reflected light of light irradiated to an object via the optical modulator2410. The optical detector2430may include an array of a plurality of sensors configured to sense light, or only a single sensor.

The signal processor2440may analyze shapes, etc. of an object by processing signals sensed by the optical detector2430. The signal processor2440may analyze a three-dimensional shape including a depth position of an object.

For a three-dimensional shape analysis, an operation for measuring a time-of-flight of light may be performed. Various operation methods may be used for measuring the time-of-flight of light For example, in the direct time measurement method, pulse light is irradiated to an object, and a travel time for the light to be reflected from the object and return is measured by a timer for calculation of distance. As for the correlation method, a distance is calculated by irradiating pulse light to an object and measuring brightness of light reflected from the object. In the phase delay measurement method, light having a continuous wave, such as sine wave is irradiated to an object, and a phase shift of light reflected from the object is sensed to be converted into a distance.

When structured light is irradiated to an object, a depth position of the object may be calculated from changes in patterns of the structured light reflected from the object, e.g., the comparison result between the patterns of the reflected structured light and incident structured light. The depth information of the object may be extracted by tracking a pattern change by coordinates of the structured light reflected from the object, and from this, three-dimensional information relating to shapes, movements, etc. of the object may be extracted.

The memory2450may store programs and other data necessary for operations of the signal processor2440.

The operation results of the signal processor2440, e.g., information on shapes, locations, etc. of an object may be transmitted to another unit arranged in the electronic apparatus2200or another electronic apparatus. For example, applications2246stored in the memory2230may use such information. Other electronic apparatuses to which the results are transmitted may be a display device or a printer which outputs the results. In addition to the above, the aforementioned electronic apparatuses may further include, but not limited to, an autonomous device, such as an unmanned vehicle, autonomous vehicle, robot, drone, etc., a smartphone, a smart watch, a mobile phone, a personal digital assistant (PDA), a laptop, a PC, various wearable devices, other mobile or non-mobile computing devices and IoT devices.

FIG.16is a block diagram illustrating a schematic configuration of an electronic apparatus according to another example embodiment.

The electronic apparatus3000ofFIG.16may be a glasses-type augmented reality (AR) device. The electronic apparatus3000may include a display engine3400, a processor3300, an eye tracking sensor3100, an interface3500, and a memory3220.

The processor3300may drive an operating system or application to control overall operations of the augmented reality device including the display engine3400, and may process various data including image data and perform operations. For example, the processor3300may process image data including a left eye virtual image and right eye virtual image which are rendered to have a binocular parallax.

The interface3500, which inputs or outputs external data or operation commands, may include a user interface such as, for example, a user-operable touchpad, a controller, an operation button, etc. The interface3500may include a wired communication module such as a USB module, or a wireless communication module such as a bluetooth, and through these, the interface may receive user operation information or virtual image data transmitted from an interface included in an external device.

The memory3200may include an embedded memory, such as a volatile memory or a non-volatile memory. The memory3200may store various data, programs, or applications, which operate and control an augmented reality device by means of control by the processor3300, input/output signals, or virtual image data.

The display engine3400is configured to receive image data generated by the processor3300and to generate light of virtual images, and may include a left eye optical engine3410and a right eye optical engine3420. Each of the left eye optical engine3410and the right eye optical engine3420may include a light source which outputs light and a display panel which forms a virtual image by using light output from the light source, and have the same function as a small projector. The light source may be implemented, for example, by a LED, and the display panel, for example, by a Liquid Crystal On Silicon (LCoS).

The eye tracking sensor3100may be mounted at a position where pupils of a user wearing an augmented reality device are trackable, and transmit signals corresponding to user's gaze information to the processor3300. Such eye tracking sensor3100may detect gaze information including a user's gaze direction where user's eyes stare, user's pupil position, coordinates of pupil centerpoint, etc. The processor3300may determine a type of eye movements based on the user's gaze information detected by the eye tracking sensor3100. For example, the processor3300may determine various types of eye movements based on the gaze information obtained from the eye tracking sensor, including a fixation (e.g., staring at a certain point), pursuit e.g., following a moving object), saccade (e.g., moving fast from one staring point to another staring point), etc.

FIG.17is a block diagram illustrating a schematic configuration of an eye tracking sensor provided in the electronic apparatus ofFIG.16.

The eye tracking sensor3100may include an illumination optics3110, a detection optics3120, a signal processor3150, and a memory3160. The illumination optics3110may include a light source irradiating light, for example, infrared light to a location of an object (e.g., user's eye). The detection optics3120configured to detect reflected light may include a meta lens3130and a sensor3140. The signal processor3150may calculate user's pupil position, etc., from results of sensing by the detection optics3120.

As the meta lens3130, any one or combinations or modifications of optical modulators according to the aforementioned embodiments may be used. The meta lens3130may concentrate light from an object in the sensor3140. An incident angle of light which is incident on the sensor3140in the eye tracking sensor3100located very close to user's eyes may be greater than or equal to 30° or larger. The meta lens3130may have a structure provided with a compensation region, and an efficiency decrease may be reduced even regarding light having a large incident angle. Accordingly, an accuracy in eye tracking may increase.

As glasses-type devices may also be used not only as an augmented reality (AR) device but as glasses-type virtual reality (VR) device, user's gaze at VR images provided from the device may also be tracked.

Optical modulators which modulate lights in a non-mechanical manner and operate as light modulation elements having high performance are provided.

The optical modulator may increase a modulation efficiency by allowing a thickness of a layer where a refractive index changes to be tens to hundreds of nanometers.

The optical modulator may increase a phase modulation efficiency through high phase modulation capability and reflectance in an infrared light region.

The antenna of the optical modulator may have a width in accordance with conditions of Fabry-Perot resonance relating to incident light.

The optical modulator may be used as a beam scanning device, and for example, as a LiDAR sensor, a depth sensor, variable focus lenses, a hologram, etc., and further, may be employed in production of a phase modulation array or display element using optical modulators, or adopted in various electronic apparatuses.