Patent Description:
An advanced driving assistance system (ADAS) having various functions has been commercialized. For example, there are an increasing number of vehicles equipped with various functions such as adaptive cruise control (ACC), an autonomous emergency braking (AEB) system, and the like. The ACC may enable the vehicle to reduce the speed when there is a risk of collision and to drive the vehicle within a set speed range when there is no risk of collision, by recognizing the position and speed of other vehicles. The AEB system may recognize another vehicle ahead of a host vehicle, and may prevent a collision by automatically applying braking when there is a risk of collision but the driver does not respond or a response method is inappropriate, and the like. Furthermore, it is expected that vehicles capable of autonomous driving will be commercialized in the near future.

Accordingly, interest in optical measurement devices capable of providing information about the vehicle's surroundings is growing. For example, a light detection and ranging (LiDAR) apparatus for vehicles may provide information on a distance, a relative speed, an azimuth angle, and the like with respect to an object in the vicinity of the vehicle by radiating a laser to a selected region in the vicinity of the vehicle and detecting the reflected laser. To this end, the LiDAR apparatus for vehicles needs a beam steering technology to steer light to a desired region.

A beam steering method may largely include a mechanical method and a non-mechanical method. For example, a mechanical beam steering method may include a method of rotating a light source itself, a method of rotating a mirror that reflects light, a method of moving a spherical lens in a direction perpendicular to the optical axis, etc. Furthermore, a non-mechanical beam steering method may include a method using a semiconductor device and a method of electrically controlling the angle of reflected light by using a reflective phase array.

<CIT> describes a spatial light modulator and a beam steering apparatus including the same. The spatial light modulator may include a distributed Bragg reflector provided on a substrate, and a cavity.

<CIT> describes a beam scanning device and a system including the beam scanning device. The beam scanning device includes a spatial light modulator configured to modulate a phase of a light for a corresponding pixel.

<CIT> describes an optical modulating device and a system including the optical modulating device. The optical modulating device includes a substrate and a phase modulator.

One or more example embodiments provide a spatial light modulator with high reliability, a structure of a light detection and ranging (LiDAR) apparatus including the spatial light modulator, a method of manufacturing the spatial light modulator, and a LiDAR apparatus including the spatial light modulator.

According to an aspect of the disclosure, there is provided a spatial light modulator according to claim <NUM>.

The filling layer may include a vacuum layer.

Furthermore, the filling layer may include a layer filled with a fluid.

Furthermore, the filling layer may be in contact with both of an upper surface and a side surface of at least one grating structure of the plurality of grating structures.

Furthermore, the filling layer may is be in contact with a portion of the upper surface of the resonance layer located between the grating structures of the first group and the grating structures of the second group.

The spatial light modulator may further include a dielectric layer provided between neighboring grating structures of the grating structures of the first group and having a heat transfer coefficient exceeding about <NUM> mW/mK.

Furthermore, the dielectric layer may include at least one of a silicon oxide or a silicon nitride.

The spatial light modulator may further include a cover layer provided on the filling layer and spaced apart from the second reflective layer in a direction in which the first reflective layer, the resonance layer, and the second reflective layer are stacked.

Furthermore, the spatial light modulator may further include a spacer layer including two opposing ends, wherein the two opposing ends include a first end having one end in contact with the resonance layer and a second end in contact with the cover layer.

At least one of the plurality of grating structures may be any one of a PIN structure in which the intrinsic semiconductor layer is provided between a p-type semiconductor layer and an N-type semiconductor layer, a NIN structure in which the intrinsic semiconductor layer is provided between two n-type semiconductor layers, and a PIP structure in which the intrinsic semiconductor layer is provided between two p-type semiconductor layers.

Furthermore, the pitch of the grating structure may be less than the wavelength of light modulated by the spatial light modulator.

The reflectivity of the second reflective layer may be less than that of the first reflective layer.

Furthermore, the first reflective layer may include a distributed Bragg reflective layer.

The spatial light modulator may further include an etching stop layer provided between the resonance layer and the filling layer.

Furthermore, the side mode suppression ratio (SMSR) of the spatial light modulator may be about <NUM> dB or more.

According to another aspect of the disclosure, there is provided a light detection and ranging (LiDAR) apparatus according to claim <NUM>.

Furthermore, the filling layer may be a vacuum layer having no fluid, or a fluid layer filled with a fluid.

Furthermore, the LiDAR apparatus may further include a cover layer provided on the filling layer and spaced apart from the second reflective layer in a direction in which the first reflective layer, the resonance layer, and the second reflective layer are stacked; and a spacer layer including two opposing ends, wherein the two opposing ends include a first end in contact with the cover layer and a second end in contact with the resonance layer.

The LiDAR apparatus may further include an etching stop layer provided between the resonance layer and the filling layer.

Hereinafter, spatial light modulators and LiDAR apparatuses including the same according to various embodiments are described in detail with reference to the accompanying drawings. In the accompanying drawings, like reference numerals refer to like elements throughout. The thickness or size of each layer illustrated in the drawings may be exaggerated for convenience of explanation and clarity. Terms such as "first" and "second" are used herein merely to describe a variety of constituent elements, but the constituent elements are not limited by the terms. Such terms are used only for the purpose of distinguishing one constituent element from another constituent element.

It will be further understood that the terms "comprises" and/or "comprising" used herein specify the presence of stated features or components, but do not preclude the presence or addition of one or more other features or components.

Furthermore, the size or thickness of each layer illustrated in the drawings may be exaggerated for convenience of explanation and clarity. Furthermore, when a certain material layer is referred to as being on a substrate or another layer, the material layer may be in direct contact with the substrate or another layer, or a third layer may be therebetween. A material forming each layer in embodiments below is exemplary, and thus other materials may be used therefor.

Furthermore, terms such as "portion," "module," and the like stated in the specification may signify a unit to process at least one function or operation and the unit may be embodied by hardware, software, or a combination of hardware and software.

The particular implementations shown and described herein are illustrative examples of the disclosure and are not intended to otherwise limit the scope of the disclosure in any way. For the sake of brevity, conventional electronics, control systems, software development and other functional aspects of the systems may not be described in detail. Furthermore, the connecting lines, or connectors shown in the various figures presented are intended to represent functional relationships and/or physical or logical couplings between the various elements. It should be noted that many alternative or additional functional relationships, physical connections or logical connections may be present in a practical device.

The use of the term "the" and similar referents in the context of describing the disclosure are to be construed to cover both the singular and the plural.

Also, the steps of all methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. Furthermore, the use of any and all examples, or language (e.g., "such as") provided herein, is intended merely to better illuminate the disclosure and does not pose a limitation on the scope of the disclosure unless otherwise claimed.

<FIG> is a conceptual cross-sectional view of a spatial light modulator <NUM> according to an example embodiment.

Referring to <FIG>, the spatial light modulator <NUM> may include a first reflective layer <NUM>, a resonance layer <NUM> arranged on the first reflective layer <NUM>, and a second reflective layer <NUM> arranged on the resonance layer <NUM>. The resonance layer <NUM> may be provided between the first reflective layer <NUM> and the second reflective layer <NUM>. A side mode suppression ratio (SMSR) of the spatial light modulator <NUM> according to an example embodiment is about <NUM> dB or more, and thus the directivity of light may be high. The term "SMSR" may refer to an amplitude difference between a main mode (e.g., a main spectral peak, or a center peak longitudinal mode) and a largest side mode (e.g., side peaks, or a nearest higher order mode) in decibels.

The spatial light modulator <NUM> may output light by modulating the phase of incident light Li. The spatial light modulator <NUM> may include a plurality of pixels. The pixels may include, for example, a first pixel PX1 and a second pixel PX2. A pixel may refer to the smallest unit that is independently driven in the spatial light modulator <NUM> or a basic unit that independently modulates the phase of light. A pixel may include one or a plurality of grating structures GS that constitute the second reflective layer <NUM>. <FIG> illustrates an example of a structure including two pixels. The length of one side of each of the first and second pixels PX1 and PX2 may be, for example, about <NUM> to about <NUM>.

The spatial light modulator <NUM> may further include a substrate SUB that supports the first reflective layer <NUM>. The substrate SUB may be a transparent substrate, for example, a silicon substrate or a glass substrate, that transmit light. The substrate SUB is an optional element and may be removed as necessary.

The first reflective layer <NUM> may be a distributed Bragg reflector. For example, the first reflective layer <NUM> may include a first layer <NUM> and a second layer <NUM> having different refractive indexes. The first layer <NUM> and the second layer <NUM> may be alternately and repeatedly stacked. Due to a difference in the refractive index between the first layer <NUM> and the second layer <NUM>, light may be reflected at an interface of each layer and the reflected light may cause interference. The first layer <NUM> or the second layer <NUM> may include silicon (Si), silicon nitride (Si<NUM>N<NUM>), silicon oxide (SiO<NUM>), titanium oxide (TiO<NUM>), and the like. For example, while the first layer <NUM> may include Si, the second layer <NUM> may include SiO<NUM>. The light reflectivity of the first reflective layer <NUM> may be set by adjusting the thickness and/or stack number of the first layer <NUM> and the second layer <NUM>. The light reflectivity of the first reflective layer <NUM> may vary depending on the thickness and/or the number of the first layer <NUM> and the second layer <NUM>.

The first reflective layer <NUM> may include a structure (e.g., a metal reflective layer) other than the distributed Bragg reflector.

<FIG> is a reflection spectrum showing reflectivity when the first reflective layer <NUM> of <FIG> is a distributed Bragg reflector. The reflection spectrum shows reflectivity (in the vertical axis) of the first reflective layer according to wavelength of light (in the horizontal axis).

The spectrum of <FIG> was measured from a distributed Bragg reflector in which the first layer <NUM> has a110 nm thickness and includes Si, the second layer <NUM> has a <NUM> thickness and includes SiO<NUM>, and the first and second layers <NUM> and <NUM> are alternately stacked three times. Referring to <FIG>, the first reflective layer <NUM> shows a high reflectivity close to <NUM> in a range of about <NUM> - about <NUM>.

Referring back to <FIG>, the resonance layer <NUM> is an area where incident light is resonated, and may be arranged between the first reflective layer <NUM> and the second reflective layer <NUM>.

The resonance layer <NUM> may include, for example, SiO<NUM>. A resonance wavelength may be determined according to the thickness of the resonance layer <NUM>. As the thickness of the resonance layer <NUM> increases, the resonance wavelength of light may increase, whereas as the thickness of the resonance layer <NUM> decreases, the resonance wavelength of light may decrease.

The second reflective layer <NUM> may has a structure that enables a reflection function of reflecting light of a specific wavelength and a phase modulation function of modulating the phase of output light.

The second reflective layer <NUM> may include the grating structures GS that are arranged apart from each other at certain intervals. The thickness, width, and pitch of the grating structures GS may be less than the wavelength of light that is modulated by the spatial light modulator <NUM>. The reflectivity of light that is modulated may be increased by adjusting the thickness, width, pitch, and the like of the grating structures GS. The reflectively of the second reflective layer <NUM> may be different from that of the first reflective layer <NUM>, and the reflectivity of the second reflective layer <NUM> may be less than that of the first reflective layer <NUM>.

The incident light Li on the spatial light modulator <NUM> may transmit through the second reflective layer <NUM>, and then may propagate to the resonance layer <NUM>, and may be reflected by the first reflective layer <NUM>. Then, the light is trapped and resonated in the resonance layer <NUM> by the first reflective layer <NUM> and the second reflective layer <NUM> and then output through the second reflective layer <NUM>. Output light Lo<NUM> and Lo<NUM> may have a specific phase, and the phase of the output light Lo<NUM> and Lo<NUM> may be controlled by the refractive index of the second reflective layer <NUM>. The traveling direction light may be determined by a relationship of the phase of light output from adjacent pixels. For example, when the phase of the output light Lo<NUM> of the first pixel PX1 and the phase of the output light Lo<NUM> of the second pixel PX2 are different from each other, the traveling direction of light may be determined by the interaction of the output light Lo<NUM> and Lo<NUM>.

<FIG> is a cross-sectional view showing the grating structures GS of the first pixel PX1 of <FIG>. <FIG> is a cross-sectional view of the grating structures GS that are cut in another direction. Referring to <FIG>, the grating structures GS may include a first doped semiconductor layer <NUM>, an intrinsic semiconductor layer <NUM>, and a second doped semiconductor layer <NUM>. For example, the first doped semiconductor layer <NUM> may be an n-type semiconductor layer, the second doped semiconductor layer <NUM> may be a p-type semiconductor layer, and the grating structures GS may be a PIN diode.

The first doped semiconductor layer <NUM> may be a Si layer containing a group <NUM> element, for example, phosphorus (P) or arsenic (As), as impurities. The concentration of impurities included in the first doped semiconductor layer <NUM> may be about <NUM><NUM> to <NUM><NUM> cm-<NUM>. The intrinsic semiconductor layer <NUM> may be a Si layer that does not include impurities. The second doped semiconductor layer <NUM> may be a Si layer containing a group <NUM> element, for example, boron (B), as impurities. The concentration of impurities included in the second doped semiconductor layer <NUM> may be about <NUM><NUM> to <NUM><NUM> cm-<NUM>.

When a voltage is applied between the first doped semiconductor layer <NUM> and the second doped semiconductor layer <NUM>, a current flows in a direction from the first doped semiconductor layer <NUM> to the second doped semiconductor layer <NUM>. Heat is generated in the grating structures GS due to the current, and thus the refractive indexes of the grating structures GS may be changed by the heat. When the refractive indexes of the grating structures GS are changed, the phase of light output from the first and second pixels PX1 and PX2 may be changed. Accordingly, the traveling direction of the light output from the spatial light modulator <NUM> may be controlled by adjusting the amount of a voltage V applied to each of the first and second pixels PX1 and PX2.

<FIG> is a cross-sectional view of the grating structures GS in another direction (Y direction). Referring to <FIG>, the spatial light modulator <NUM> may include first and second electrodes <NUM> and <NUM> to apply a voltage to the grating structures GS. The first electrode <NUM> may be in contact with one end of the first doped semiconductor layer <NUM>, and the second electrode <NUM> may be in contact with one end of the second doped semiconductor layer <NUM>. The second electrode <NUM> may be in contact with an end portion arranged in the Y direction opposite to the end portion that is in contact with the first electrode <NUM>. The first electrode <NUM> may be arranged above the resonance layer <NUM>, and may be a common electrode that applies a common voltage to all pixels included in the spatial light modulator <NUM>. The second electrode <NUM> may be a pixel electrode that is configured to apply a different voltage to each pixel.

Although <FIG> and <FIG> illustrate the grating structures GS in a PIN structure, the disclosure is not limited thereto. The grating structures GS may have an NIN structure in which an intrinsic semiconductor layer is provided two n-type semiconductor layers or a PIP structure in which an intrinsic semiconductor layer is provided two p-type semiconductor layers. For example, the first and second doped semiconductor layer <NUM> and <NUM> may be n-type semiconductor layers or p-type semiconductor layers.

The grating structures GS of the spatial light modulator <NUM> according to an example embodiment is based on Si. The refractive index of Si is proportional to a temperature. <FIG> is a graph showing a relationship between a refractive index and temperature of silicon, according to an example embodiment. As illustrated in <FIG>, as a Si's temperature change increases, a Si's refractive index change increases. The Si's refractive index change is in direct proportion to the Si's temperature change, and thus, the refractive index change may be easily controlled by controlling the temperature change. Thus, by controlling an electrical signal applied to Si, the refractive indexes of the grating structures GS may be easily controlled.

As the heat generated in one grating structures GS may be transferred to another grating structures GS adjacent thereto, crosstalk may be increased and also the pixel driving of the spatial light modulator <NUM> may be difficult.

The spatial light modulator <NUM> according to an example embodiment may further include a filling layer <NUM> that surrounds at least one of the grating structures GS and is in contact with an upper surface of the resonance layer <NUM>. The filling layer <NUM> may have a heat transfer coefficient of about <NUM> mW/mK or less. As the heat transfer coefficient of the filling layer <NUM> is about <NUM> mW/mK or less, heat transfer between the grating structures GS may be reduced.

The filling layer <NUM> may be a vacuum layer. The heat transfer coefficient of the vacuum layer may be about <NUM> mW/mK.

Alternatively, the filling layer <NUM> may be a layer filled with a fluid. For example, the filling layer <NUM> may be a layer filled with air. The heat transfer coefficient of air is about <NUM> mW/mK.

According to an example embodiment, as the grating structures GS are divided by the filling layer <NUM> having a low heat transfer coefficient, the heat generated from one of the grating structures GS may be prevented from being transferred to the other of the grating structures GS, thereby reducing crosstalk between the grating structures GS.

<FIG> illustrates a spatial light modulator <NUM>' in which the grating structures GS are divided by a Si oxide layer <NUM>, as a comparative example. The heat transfer coefficient of a Si oxide is about <NUM> mW/mK, which is about <NUM> times or more greater than the heat transfer coefficient of the filling layer <NUM> according to an example embodiment.

In the spatial light modulator <NUM> of an example embodiment and the spatial light modulator <NUM>' of the comparative example, the first reflective layer <NUM> is formed by stacking three pairs of layers of Si and SiO<NUM> materials in the thicknesses of about <NUM> and about <NUM>, respectively. The resonance layer <NUM> is formed of SiO<NUM> on the first reflective layer <NUM>, and as a PIN structure of the grating structures GS, an n-type semiconductor layer having a thickness of about <NUM>, the intrinsic semiconductor layer <NUM> having a thickness of about <NUM>, and a p-type semiconductor layer having a thickness of about <NUM> are stacked.

The grating structures GS of the spatial light modulator <NUM> according to an example embodiment are divided by air, and the grating structures GS of the comparative example are divided by SiO<NUM>. <FIG> is a graph showing a result of evaluating the directivity of the spatial light modulator <NUM>' of the comparative example. <FIG> is a graph showing a result of evaluating the directivity of the spatial light modulator <NUM> according to an example embodiment.

A side mode suppression ratio (SMSR) refers to the intensity of the 1st order beam with respect to the intensity of the 0th order beam, and as the SMSR increases, the directivity of light increases. It may be checked that, while the SMSR of the spatial light modulator <NUM> of an example embodiment is about <NUM> dB, the SMSR of the spatial light modulator <NUM> of the comparative example is almost about <NUM> dB. Accordingly, it may be seen that the spatial light modulator <NUM> according to an example embodiment in which the grating structures GS are divided by air has an improved SMSR compared with the spatial light modulator <NUM>' of the comparative example in which the grating structures GS are divided by an Si oxide.

<FIG> are cross-sectional views showing a method of manufacturing the spatial light modulator <NUM>, according to an example embodiment.

Referring to <FIG>, the first reflective layer <NUM> may be formed on the substrate SUB.

The substrate SUB may be a substrate including a transparent material that transmits light, for example, a Si substrate or a glass substrate.

The first reflective layer <NUM> may be a distributed Bragg reflective layer in which the first and second layers <NUM> and <NUM> having different refractive indexes are stacked, and the first layer <NUM> may include, for example, Si of a thickness of about <NUM>, and the second layer <NUM> may include, for example, SiO<NUM> of a thickness of about <NUM>. The first reflective layer <NUM> may include the first and second layers <NUM> and <NUM> that are repeatedly or alternately arranged. The first and second layers <NUM> and <NUM> may be placed on top of each other. The first and second layers <NUM> and <NUM> may be formed, for example, by a chemical vapor deposition (CVD) method.

Referring to <FIG>, the resonance layer <NUM> is provided on the first reflective layer <NUM>. The resonance layer <NUM> may include, for example, SiO<NUM>. The thickness of the resonance layer <NUM> may be about <NUM> to about <NUM>, and may be formed, for example, by the CVD deposition.

Referring to <FIG>, the second reflective layer <NUM> having the grating structures GS may be provided on the resonance layer <NUM>.

Referring to <FIG>, the first doped semiconductor layer <NUM>, the intrinsic semiconductor layer <NUM>, and the second doped semiconductor layer <NUM> are sequentially formed on the resonance layer <NUM>. The first doped semiconductor layer <NUM>, the intrinsic semiconductor layer <NUM>, and the second doped semiconductor layer <NUM> may be formed by the CVD method.

Referring to <FIG>, by patterning the first doped semiconductor layer <NUM>, the intrinsic semiconductor layer <NUM>, and the second doped semiconductor layer <NUM>, the grating structures GS that are arranged apart from each other may be formed. For example, the grating structures GS having a certain width and pitch may be formed through a photolithography process and an etching process.

Referring to <FIG>, a sacrificial layer <NUM> may fill between the grating structures GS. The sacrificial layer <NUM> may include a Si oxide. However, the disclosure is not limited thereto. The sacrificial layer <NUM> may be formed of a material that is distinguished from the grating structures GS and is easily etched.

Thereafter, an additional heat treatment process may be performed. While Si included in the grating structures GS has a polycrystalline structure, the grating structures GS may be heat treated such that the height of partial or entire grain of the polycrystalline structure is the same as the thickness of the grating structures GS. In other words, the crystal size of the grating structures GS is increased through the heat treatment, and thus, the grain may have a column shape. The sacrificial layer <NUM> may prevent the grating structures GS, an electrode, and the like from being oxidized during the heat treatment.

The heat treatment may be a short heat treatment at high temperature, or a long heat treatment at low temperature and then an additional heat treatment at high temperature.

For example, the heat treatment on the grating structures GS may be performed at low temperature for a long time. For example, the grating structures GS may be heated at a temperature of about <NUM> - about <NUM> for about <NUM> hours - about <NUM> hours. Accordingly, the grating structures GS may have a polycrystalline structure having a large crystal size.

After the low-temperature heat treatment, a high-temperature heat treatment for heating at high temperature for a short time may be further included. The high-temperature heat treatment may be performed at about <NUM> or more within about <NUM> minutes. The high-temperature heat treatment may be performed at about <NUM> or less for about <NUM> minute or more. Through the high-temperature heat treatment, defects remaining in the grating structures GS may be removed, and thus, the crystallinity of the grating structures GS may be further improved.

Referring to <FIG>, the sacrificial layer <NUM> may be removed. A space left after the sacrificial layer <NUM> is removed may be filled with air. The above-described air layer may become the filling layer <NUM> according to an example embodiment. In the process of removing the sacrificial layer <NUM>, the material of the sacrificial layer <NUM> may remain above the grating structures GS. In addition to air, the space may be filled with a fluid having a heat transfer coefficient of about <NUM> mW/mK or less. Alternatively, the air and the like may be then removed such that the space between the grating structures GS may be in a vacuum state.

As the space between the grating structures GS is filled with a fluid having a low thermal conductivity or maintained in a vacuum state, the thermal crosstalk between the grating structures GS may be reduced, thereby improving a light steering efficiency.

<FIG> is a cross-sectional view of a spatial light modulator 10a according to another example embodiment. Referring to <FIG>, the grating structures GS may be grouped by a pixel unit, and the grating structures GS that are grouped may be surrounded by a dielectric layer.

The grating structures GS may include a grating structure PX1 of a first group, a grating structure PX2 of a second group, and a grating structure PX3 of a third group. A first electrical signal, for example, a current, may be applied to the grating structure PX1 of the first group, a second electrical signal may be applied to the grating structure PX2 of the second group, and a third electrical signal may be applied to the grating structure PX3 of the third group. Thus, each of the grating structures PX1, PX2, and PX3 of the first to third groups may form a pixel. As the same electrical signal is applied in units of groups in the grating structures GS, the grating structures in the same group may have the same heat distribution. In the grating structure in a group unit, a dielectric layer <NUM> having a high heat transfer coefficient may connect the grouped grating structures. The dielectric layer <NUM> may have a heat transfer coefficient of about <NUM> mW/mK or more. For example, the dielectric layer <NUM> may include at least one of a Si oxide or a Si nitride.

Each of the grating structures PX1, PX2, and PX3 that are grouped may be surrounded by a filling layer 400a having a heat transfer coefficient of <NUM> mW/mK or less. The filling layer 400a may be in contact with the upper surface of the resonance layer <NUM> that is exposed between the grouped grating structures PX1, PX2, and PX3.

<FIG> is a cross-sectional view of a spatial light modulator 10b including a cover layer <NUM> and a spacer layer <NUM>, according to an example embodiment. When comparing <FIG> with <FIG>, the spatial light modulator 10b of <FIG> may further include the cover layer <NUM> arranged on the filling layer <NUM> and spatially apart from the grating structures GS and the spacer layer <NUM> having one end in contact with the resonance layer <NUM> and the other end in contact with the cover layer <NUM>. Both of the cover layer <NUM> and the spacer layer <NUM> may be formed of a light transmissive material. The cover layer <NUM> may prevent the grating structures GS from being exposed to the outside and contaminated. The spacer layer <NUM> may support the cover layer <NUM> to be spatially apart from the grating structures GS. The spacer layer <NUM> may prevent the cover layer <NUM> from being in contact with the grating structures GS, thereby preventing generation of thermal crosstalk between the grating structures GS or pixels. The thickness of the spacer layer <NUM> may be greater than that of each of the grating structures GS.

<FIG> is a cross-sectional view of a spatial light modulator 10c including an etching stop layer <NUM>, according to an example embodiment. When comparing <FIG> with <FIG>, the spatial light modulator 10c of <FIG> may further include the etching stop layer <NUM> on the upper surface of the resonance layer <NUM>. The etching stop layer <NUM> may prevent the resonance layer <NUM> from being damaged by an etching process during the processes of forming the grating structures GS and removing the sacrificial layer <NUM>. In <FIG>, the etching stop layer <NUM> is illustrated as being arranged on the entire upper surface of the resonance layer <NUM>. However, the disclosure is not limited thereto. The etching stop layer <NUM> may be arranged in a region of the upper surface of the resonance layer <NUM> that is not overlapped with the grating structures GS. The etching stop layer <NUM> may include a material different from the resonance layer <NUM>. For example, the etching stop layer <NUM> may include a Si nitride.

The spatial light modulators <NUM>, 10a, 10b, and 10c described above may be applied to, for example, beam steering devices such as depth sensors used in three-dimensional cameras or three-dimensional sensors such as LiDAR apparatuses, to increase precision. LiDAR apparatuses may be applied to mobile devices such as autonomous vehicles, drones, and the like, small walking means, for example, bicycles, motorcycles, strollers, boards, etc., robots, auxiliary means for people/animals, for example, sticks, helmets, accessories, clothing, watches, bags, etc., Internet of Things (IoT) devices/systems, security devices/systems, and the like.

Furthermore, the spatial light modulators <NUM>, 10a, 10b, and 10c may be applied to various systems other than LiDAR apparatuses. For example, as three-dimensional information of space and an object may be acquired through scanning by using the spatial light modulators <NUM>, 10a, 10b, and 10c, the spatial light modulators <NUM>, 10a, 10b, and 10c may be applied to a three-dimensional image acquisition device, a three-dimensional camera, and the like. Furthermore, the spatial light modulators <NUM>, 10a, 10b, and 10c may be applied to a holographic display device and a structured light generation device. Furthermore, the spatial light modulators <NUM>, 10a, 10b, and 10c may be applied to various optical devices such as hologram generators, optical coupling devices, variable focus lenses, depth sensors, and the like. Furthermore, the spatial light modulators <NUM>, 10a, 10b, and 10c may be applied to various fields in which a meta surface or a meta structure is used. In addition, the spatial light modulators <NUM>, 10a, 10b, and 10c according to embodiments of the disclosure, and a LiDAR apparatus including the same, may be applied to various fields of optical and electronic devices for various uses.

<FIG> is a schematic block diagram showing the structure of a LiDAR apparatus <NUM> according to an example embodiment.

Referring to <FIG>, the LiDAR apparatus <NUM> according to an example embodiment may include a light source <NUM> for radiating light, a spatial light modulator <NUM> for controlling a traveling direction of incident light from the light source <NUM>, a photodetector <NUM> for detecting light emitted from the spatial light modulator <NUM> and reflected from an object, and a controller (e.g., a processor) <NUM> for controlling the spatial light modulator <NUM>.

The light source <NUM> may include, for example, a light source for emitting visible light or a laser diode (LD) or light-emitting diode (LED) for emitting a near infrared ray of about <NUM> to about <NUM> band.

The spatial light modulator <NUM> may include the spatial light modulators <NUM>, 10a, 10b, and 10c of <FIG>, <FIG>, <FIG>, and <FIG>. The spatial light modulator <NUM> may control the traveling direction of light by modulating the phase of light for each pixel. The spatial light modulator <NUM> may scan light with a wide viewing angle.

The controller <NUM> may control the operations of the spatial light modulator <NUM>, the light source <NUM>, and the photodetector <NUM>. For example, the controller <NUM> may control the on/off operation of the light source <NUM> and the photodetector <NUM>, and the beam scanning operation of the spatial light modulator <NUM>. Furthermore, the controller <NUM> may calculate information about the object on the basis of a measurement result of the photodetector <NUM>.

The LiDAR apparatus <NUM> may periodically radiate light with respect to many regions therearound, by using the spatial light modulator <NUM>, to acquire information about objects therearound at a plurality of locations.

<FIG> is a schematic block diagram showing the structure of a LiDAR apparatus <NUM> according to another example embodiment.

Referring to <FIG>, The LiDAR apparatus <NUM> may include a spatial light modulator <NUM> and a photodetector <NUM> for detecting light that has a traveling direction controlled by the spatial light modulator <NUM> and is reflected by an object. The LiDAR apparatus <NUM> may further include an electric circuit <NUM> connected to the spatial light modulator <NUM> and/or the photodetector <NUM>. The electric circuit <NUM> may include an operating portion for acquiring and operating data, a driving portion, a controller, and the like. Furthermore, the electric circuit <NUM> may further include a power unit, a memory, and the like.

The LiDAR apparatus <NUM> of <FIG> is illustrated as including the spatial light modulator <NUM> and the photodetector <NUM> in one device, the spatial light modulator <NUM> and the photodetector <NUM> may be separately provided in separate devices, not provided in one device. Furthermore, the electric circuit <NUM> may be connected to the spatial light modulator <NUM> or the photodetector <NUM>, not in a wired manner, but in a wireless communication manner.

The above-described LiDAR apparatuses may be a phase-shift type apparatus or a time-of-flight (TOF) type apparatus.

<FIG> and <FIG> are conceptual views showing a case in which a LiDAR apparatus <NUM> is applied to a vehicle <NUM>. <FIG> is a view when viewed from the side of the vehicle, and <FIG> is a view when viewed from the above.

Referring to <FIG>, the LiDAR apparatus <NUM> may be applied to the vehicle <NUM>, and information about an object <NUM> may be acquired by using the LiDAR apparatus <NUM>. The vehicle <NUM> may be a vehicle having an autonomous function. An object or a human, that is, the object <NUM>, located in a direction in which the vehicle <NUM> drives may be detected by suing the LiDAR apparatus <NUM>. Furthermore, a distance to the object <NUM> may be measured by using information such as a time difference between a transmitting signal and a detection signal. Furthermore, as illustrated in <FIG>, information about the object <NUM> located nearby and an object <NUM> located remotely, which are within a scan range, may be acquired.

While not restricted thereto, an example embodiment can be embodied as computer-readable code on a computer-readable recording medium. The computer-readable recording medium is any data storage device that can store data that can be thereafter read by a computer system. Examples of the computer-readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, and optical data storage devices. The computer-readable recording medium can also be distributed over network-coupled computer systems so that the computer-readable code is stored and executed in a distributed fashion. Also, an example embodiment may be written as a computer program transmitted over a computer-readable transmission medium, such as a carrier wave, and received and implemented in general-use or special-purpose digital computers that execute the programs. Moreover, it is understood that in example embodiments, one or more units of the above-described apparatuses and devices can include circuitry, a processor, a microprocessor, etc., and may execute a computer program stored in a computer-readable medium.

As the heat transfer between the grating structures or pixels included in the spatial light modulator and the LiDAR apparatus according to an example embodiment is reduced, a light phase modulation efficiency may be improved.

Claim 1:
A spatial light modulator (<NUM>) comprising:
a first reflective layer (<NUM>);
a second reflective layer (<NUM>) comprising a plurality of grating structures (GS) spaced apart from each other;
a resonance layer (<NUM>) provided between the first reflective layer and the second reflective layer; and further characterized by
a filling layer (<NUM>) having a heat transfer coefficient of <NUM> mW/mK or less, and being in contact with an upper surface of the resonance layer and surrounding at least one grating structure of the plurality of grating structures;
wherein each of the plurality of grating structures comprises a first doped semiconductor layer, an intrinsic conductor layer, and a second doped semiconductor layer; and
wherein the plurality of grating structures comprise:
grating structures of a first group to which a first electrical signal is applied; and
grating structures of a second group to which a second electrical signal is applied, and
wherein the filling layer surrounds at least one of the grating structures of the first group or the grating structures of the second group.