Patent Description:
Technologies for obtaining information by reflecting electromagnetic waves at an object or a terrain within a detection distance and measuring a distance, a location, and a shape by using the information have been developed, and a light detection and ranging (LiDAR) system is receiving attention as one of the technologies.

The LiDAR system includes a light steering apparatus for steering light to a desired location and a light detecting device for detecting light reflected from an object after being emitted from the light steering apparatus. To steer the light, a method of mechanically rotating a light irradiation part and a method of using interference of light emitted from a plurality of unit cells or a plurality of waveguides by using an optical phased array (OPA) method are used.

United States Patent Application Number <CIT> presents an actively tunable polar-dielectric optical device.

Chinese Patent Application Number <CIT> presents an optical phase modulator and light beam scanning ware.

Chinese Patent Application Number <CIT> presents a graphene electro-optical modulator based on planar hybridized waveguide.

United States Patent Application Number <CIT> presents an antenna-assisted photovoltaic graphene detector.

United States Patent Application Number <CIT> presents a beam steering device and system including the same.

European Patent Application Number <CIT> presents a beam steering apparatus, method of driving the beam steering apparatus and LiDAR system including the beam steering apparatus.

One or more example embodiments provide a light detecting device and an optical system including the same.

Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the example embodiments of the disclosure.

According to an aspect of an example embodiment, there is provided a light detecting device according to claim <NUM>.

The at least one graphene layer may be provided on the plurality of waveguides.

The light detecting device may further include an intermediate layer provided between the at least one graphene layer and the plurality of waveguides, the intermediate layer including a material having a refractive index that is less than a refractive index of each of the plurality of waveguides.

The at least one graphene layer may be provided on at least one of a top surface and a side surface of the plurality of waveguides.

The at least one graphene layer may include a graphene layer corresponding to all of the plurality of waveguides.

The at least one graphene layer may include a plurality of graphene layers respectively corresponding to some of the plurality of waveguides.

The plurality of waveguides may be integrated into one waveguide at one end of each of the plurality of waveguides, and the at least one graphene layer may include a graphene layer provided on the integrated waveguide.

The light detecting device may further include a gate insulating layer provided on the at least one graphene layer and a gate electrode provided on the gate insulating layer.

The light input device may include an antenna array provided at an end portion of the plurality of waveguides and configured to receive light from an outside of the light detecting device.

The plurality of waveguides may include at least one of a Group IV semiconductor material, a Group III-V semiconductor material, a Group II-VI semiconductor material, an oxide, and a nitride.

The plurality of modulators may be configured to modulate the phase based on applying an electric signal or heat to each of the plurality of waveguides.

The light input device, the plurality of waveguides, the plurality of modulators, the at least one graphene layer, and the at least one first electrode and the at least one second electrode may be provided on a same substrate.

According to another aspect of an example embodiment, there is provided an optical system including a light steering apparatus configured to steer light, and a light detecting device configured to detect the light steered by the light steering apparatus, wherein the light detecting device includes a light input device, a plurality of waveguides extending from the light input device and configured to transmit portions of light input to the light input device, respectively, a plurality of modulators provided on the plurality of waveguides and configured to modulate phases of the portions of the light transmitted in the plurality of waveguides, respectively, at least one graphene layer configured to absorb the portions of the light transmitted in the plurality of waveguides, and at least one first electrode and at least one second electrode electrically connected to the at least one graphene layer.

The light steering apparatus may include a laser light source and a steering device configured to steer the portions of the light emitted from the laser light source.

The light input device may further include an antenna array provided at an end portion of the plurality of waveguides and configured to receive the light steered by the light steering apparatus.

The light input device may further include an intermediate layer provided between the at least one graphene layer and the plurality of waveguides, the intermediate layer including a material having a refractive index that is than a refractive index of the plurality of waveguides.

The plurality of waveguides may be integrated into one waveguide at an end portion of the plurality of waveguides, and the at least one graphene layer may include a graphene layer provided on the integrated waveguide.

The light steering apparatus and the light detecting device may be provided on a same substrate.

The at least one first electrode and at least one second electrode may be directly provided on the at least one graphene layer.

The at least one first electrode and at least one second electrode may be connected to the at least one graphene layer by conductive wires.

Each of the plurality of graphene layers may correspond to each of the plurality of waveguides, respectively, and each of the plurality of graphene layers may be spaced apart from each other.

Hereinafter, what is described to be "above" or "on" may indicate not only one directly above and in contact, but also one above without contact. In addition, when a part "includes" a certain component, the part may further include another component instead of excluding the other component, unless otherwise stated.

The use of term "the" and similar terms may correspond to both singular and plural.

In the following description, terms such as "unit" and "module" indicate a unit for processing at least one function or operation, wherein the unit and the block may be embodied as hardware or software or embodied by combining hardware and software.

Furthermore, the connecting lines, or connectors shown in the various figures presented are intended to represent exemplary 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 all examples or exemplary terms is merely for describing the technical ideas in detail and such examples and exemplary terms do not limit the scope of the present disclosure unless defined in the claims.

<FIG> illustrates a light detecting device <NUM> according to an example embodiment. In <FIG>, the light detecting device <NUM> for detecting portion of light, for example, portion of light input after being reflected at an object, input from the outside by using an optical phased array (OPA) method is shown.

Referring to <FIG>, the light detecting device <NUM> includes a plurality of waveguides <NUM>, a light input device <NUM>, a plurality of modulators <NUM>, and a graphene layer <NUM>. Here, elements forming the light detecting device <NUM> may be provided on a same substrate <NUM>. However, embodiments are not limited thereto. The plurality of waveguides <NUM> may be arranged in an array form. For example, the plurality of waveguides <NUM> may be arranged in a <NUM>-dimensional (1D) array on the substrate <NUM> in one direction, for example, a y-axis direction of <FIG>. In <FIG>, sixteen waveguides <NUM> are provided on the substrate <NUM>, but the number of waveguides <NUM> may vary.

<FIG> is a cross-sectional view of the plurality of waveguides <NUM>, taken along line A-A' of <FIG>. As an example, four waveguides <NUM> are shown in <FIG> and the following drawings.

Referring to <FIG>, the plurality of waveguides <NUM> are provided on the substrate <NUM>. Here, the substrate <NUM> may include a material having an insulating surface. For example, the substrate <NUM> may include a base substrate <NUM> and an insulating layer <NUM> provided on a top surface of the base substrate <NUM>. The base substrate <NUM> may include, for example, a semiconductor substrate such as a silicon substrate, but is not limited thereto. For example, the base substrate <NUM> may include other various materials. The insulating layer <NUM> may include, for example, a silicon oxide, but is not limited thereto, and the insulating layer <NUM> may include other various materials. Also, an insulating substrate may be used as the substrate <NUM>.

The plurality of waveguides <NUM> are spaced apart from each other on the top surface of the substrate <NUM>. The plurality of waveguides <NUM> are provided such that portion of light L input to the light input device <NUM> from the outside proceed therein. The waveguide <NUM> may include at least one of a semiconductor material, an oxide, and a nitride. Here, the semiconductor material may include, for example, a Group IV semiconductor material such as silicon (Si) or germanium (Ge), a Group III-V semiconductor material, or a Group II-VI semiconductor material. However, the semiconductor material is not limited thereto.

Extending portions <NUM> extending respectively from the plurality of waveguides <NUM> may be provided on the substrate <NUM> with a certain thickness. In <FIG>, the extending portions <NUM> are spaced apart from each other between the waveguides <NUM> adjacent to each other. However, embodiments are not limited thereto. For example, the extending portions <NUM> may be connected to each other between the waveguides <NUM> adjacent to each other.

<FIG> illustrates an example of the plurality of waveguides <NUM> of <FIG> according to another example embodiment. Referring to <FIG>, a plurality of waveguides <NUM>' are spaced apart from each other on the top surface of the substrate <NUM>. Here, the extending portion <NUM> of <FIG> described above is not provided between the plurality of waveguides <NUM>'.

Referring to <FIG>, the light input device <NUM> into which the portion of light L are input from the outside is provided at one end portion of the plurality of waveguides <NUM>. The light input device <NUM> may include an antenna array in which a plurality of antennas <NUM> are arranged in an array form. The plurality of antennas <NUM> may extend respectively from end portions of the plurality of waveguides <NUM>. Here, the plurality of antennas <NUM> may include the same material as the plurality of waveguides <NUM>, but embodiments are not limited thereto.

<FIG> illustrates a cross-sectional view of the antenna <NUM> of the light input device <NUM> of <FIG>. In <FIG>, illustrates a cross-section in which one of the antennas <NUM> included in the light input device <NUM> is cut in a length direction, for example, an x-axis direction of <FIG>, of the antenna <NUM>.

Referring to <FIG>, the antenna <NUM> may have a grating structure in which a plurality of grooves 121a are formed at certain intervals. When the portion of light L, for example, portions of laser lights, are input from the outside to the light input device <NUM> including the antenna array, the portion of light L may proceed inside the plurality of waveguides <NUM> while phases thereof are modulated by the plurality of modulators <NUM> described below, and then may be extracted by the graphene layer <NUM>.

Referring to <FIG>, the plurality of modulators <NUM> are provided on the plurality of waveguides <NUM>. The plurality of modulators <NUM> modulate the phases of the portion of light L proceeding inside the plurality of waveguides <NUM>. The plurality of modulators <NUM> may form a certain phase profile by independently modulating the phases of the portion of light L proceeding inside the plurality of waveguides <NUM>. The phase profile formed as such may depend on angles at which the external portion of light L are incident on the light input device <NUM>. Accordingly, when the plurality of modulators <NUM> control the phase profile of the portion of light L proceeding inside the plurality of waveguides <NUM>, light-receiving efficiency of portion of light emitted from an object located in a specific direction may be improved and a location of the object may be determined.

<FIG> illustrates a cross-sectional view of the plurality of modulators <NUM> taken along line B-B' of <FIG>.

Referring to <FIG>, the plurality of modulators <NUM> each include a pair of a first electrodes <NUM> and a second electrode <NUM> provided around the waveguide <NUM>. Here, when a certain electric signal is applied between the first electrode <NUM> and the second electrodes <NUM>, a refractive index of the waveguide <NUM> provided between the first electrode <NUM> and the second electrodes <NUM> is changed by the electric signal. Also, a phase of a light proceeding inside the waveguide <NUM> may be modulated by the change in the refractive index of the waveguide <NUM>. As such, by applying a certain electric signal between the first electrode <NUM> and the second electrodes <NUM> of the modulator <NUM> provided corresponding to each of the plurality of waveguides <NUM>, a certain phase profile may be formed by independently modulating phases of portion of light proceeding inside the plurality of waveguides <NUM>.

<FIG> illustrates another example of the plurality of modulators <NUM> according to an example embodiment.

Referring to <FIG>, each of a plurality of modulators includes a heating element <NUM> provided around the waveguide <NUM>. Here, an intermediate insulating layer <NUM> for preventing a contact between the heating element <NUM> and the waveguide <NUM> may be provided between the waveguide <NUM> and the heating element <NUM>. When heat is applied to the waveguide <NUM> through the certain heating element <NUM>, the refractive index of the waveguide <NUM> is changed. Also, a phase of light proceeding inside the waveguide <NUM> may be modulated by the change in the refractive index of the waveguide <NUM>. As such, when the heating element <NUM> provided according to each of the plurality of waveguides <NUM> applies heat to the waveguide <NUM>, phases of portion of light proceeding inside the plurality of waveguides <NUM> are independently modulated, thereby forming a certain phase profile.

Moreover, a method of applying an electric signal to the waveguide <NUM> or applying heat to the waveguide <NUM> has been described above as a method of changing the refractive index of the waveguide <NUM>. However, this is only an example and another method may be used to change the refractive index of the waveguide <NUM>. For example, a piezoelectric device may be provided around the waveguide <NUM> and the waveguide <NUM> may be modified via the piezoelectric device to change the refractive index of the waveguide <NUM>.

Referring to <FIG>, the graphene layer <NUM> is provided on the plurality of waveguides <NUM> that pass through the plurality of modulators <NUM>. Here, the graphene layer <NUM> may absorb most of the portion of light L proceeding inside the plurality of waveguides <NUM>. The first electrode <NUM> and the second electrode <NUM> are electrically and respectively connected to both end portions of the graphene layer <NUM>.

The graphene layer <NUM> may have a single layer structure or a multilayer structure. For example, the graphene layer <NUM> may include one to ten graphenes , but is not limited thereto. Graphene is a material having a hexagonal honeycomb structure in which carbon atoms are connected two-dimensionally, and has a thin atomic thickness.

In the current embodiment, by arranging the graphene layer <NUM> on the plurality of waveguides <NUM>, most of the portion of light L proceeding inside the plurality of waveguides <NUM> may be absorbed by the graphene layer <NUM>, and accordingly, the light detecting device <NUM> having high light-receiving efficiency may be realized.

<FIG> illustrates a cross-sectional view of the graphene layer <NUM>, taken along a line C-C' of <FIG>.

Referring to <FIG>, the graphene layer <NUM> is provided on the plurality of waveguides <NUM>. Here, the graphene layer <NUM> is provided to contact top and side surfaces of each of the plurality of waveguides <NUM>. In this case, portion of light proceeding inside the plurality of waveguides <NUM> may be absorbed by the graphene layer <NUM> via the top and side surfaces of each of the plurality of waveguides <NUM>. The graphene layer <NUM> may be formed by growing at least one graphene on the plurality of waveguides <NUM> or by transferring at least one graphene on the plurality of waveguides <NUM>. Moreover, a reflective film or a non-reflective film may be coated on the other end portions of the waveguides <NUM> that pass through the graphene layer <NUM>.

The first electrode <NUM> and the second electrode <NUM> may be electrically connected to both end portions of the graphene layer <NUM>. Here, the first electrode <NUM> and the second electrode <NUM> may include a material having excellent conductivity. The first electrode <NUM> and the second electrode <NUM> may be provided on a top surface of the substrate <NUM>.

The portion of light proceeding inside the plurality of waveguides <NUM> while a certain voltage is applied between the first electrode <NUM> and the second electrode <NUM> may be mostly absorbed by the graphene layer <NUM>, and at this time, electrons may be generated inside the graphene layer <NUM> and move between the first electrode <NUM> and the second electrode <NUM> to generate a light-receiving current. Such a light-receiving current is measured via the first electrode <NUM> and the second electrode <NUM> to detect the portion of light proceeding inside the plurality of waveguides <NUM>. Here, the voltage applied between the first electrode <NUM> and the second electrode <NUM> may be adjusted to control the light-receiving current and the light-receiving efficiency.

<FIG> illustrates an example of the first electrode <NUM> and the second electrode <NUM> of <FIG>. Referring to <FIG>, the first electrode <NUM> and the second electrode <NUM> may be electrically connected to both ends of the graphene layer <NUM> via the first wire <NUM> and the second wire <NUM>, respectively. Here, the first electrode <NUM> and the second electrode <NUM> may be spaced apart from the substrate <NUM>. However, this is only an example and the first electrode <NUM> and the second electrode <NUM> may be provided on the top surface of the substrate <NUM>.

In the light detecting device <NUM> having such a structure, when external portion of light, for example, portion of light reflected from an object are input to the light input device <NUM>, the portion of light proceed along the plurality of waveguides <NUM>. Also, phases of the portion of light proceeding inside the plurality of waveguides <NUM> are modulated by the plurality of modulators <NUM>, and the portion of light are absorbed by the graphene layer <NUM> provided on the plurality of waveguides <NUM> to be detected through the first electrode <NUM> and the second electrode <NUM>.

In the example embodiment, because the graphene layer <NUM> absorbs most of the portion of light proceeding inside the plurality of waveguides <NUM>, the light detecting device <NUM> having a relatively high light-receiving efficiency may be realized. Also, when the plurality of modulators <NUM> control a phase profile by independently modulating the phases of the portion of light proceeding inside the plurality of waveguides <NUM>, the light-receiving efficiency may be further improved and locations at which the external portion of light are incident may be determined.

As such, because the light detecting device <NUM> is configured to receive light in a specific direction with high efficiency, for example, a light detection and ranging (LiDAR) system for long distances may be more easily implemented. Also, because the LiDAR system may reduce the intensity of output light of a light-emitting device, eye safety may be improved, and miniaturization and low costs of a system may be realized.

<FIG> illustrates a light detecting device according to another example embodiment.

Referring to <FIG>, a graphene layer <NUM> may be provided to contact a top surface of each of the plurality of waveguides <NUM>. In this case, portion of light proceeding inside the plurality of waveguides <NUM> may be absorbed by the graphene layer <NUM> via the top surface of each of the waveguides <NUM>. Cross-sectional shapes of the portion of light proceeding inside the plurality of waveguides <NUM> may vary depending on an optical mode. When the portion of light proceeding inside the plurality of waveguides <NUM> have a cross-section of an oval shape relatively long in an up-and-down direction, the graphene layer <NUM> may be provided to contact the top surface of the waveguides <NUM> as shown in <FIG> such as to effectively absorb the portion of light proceeding inside the waveguides <NUM>.

Referring to <FIG>, a graphene layer <NUM> may be provided to contact side surfaces of each of the plurality of waveguides <NUM>. Here, portion of light proceeding inside the plurality of waveguides <NUM> may be absorbed by the graphene layer <NUM> via the side surfaces of each of the waveguides <NUM>. Portions of the graphene layer <NUM> excluding a portion contacting the side surfaces of the waveguides <NUM> may be integrally connected to each other.

When the portion of light proceeding inside the plurality of waveguides <NUM> have a cross-section of an oval shape relatively long in a left-and-right direction, the graphene layer <NUM> may be provided to contact the side surfaces of the waveguides <NUM>, as shown in <FIG>, to more effectively absorb the portion of light proceeding inside the waveguides <NUM>.

Referring to <FIG>, an intermediate layer <NUM> is provided between the waveguide <NUM> and the graphene layer <NUM>. Here, the intermediate layer <NUM> may include a material having a lower refractive index than the waveguide <NUM>. By adjusting the material or thickness of the intermediate layer <NUM>, the intermediate layer <NUM> may control the amount of light absorbed by the graphene layer <NUM>.

Referring to <FIG>, a gate insulating layer <NUM> is provided on a top surface of each of the plurality of waveguides <NUM>, and a gate electrode <NUM> is provided on a top surface of the gate insulating layer <NUM>. The first electrode <NUM> and the second electrode <NUM> may respectively include a source electrode and a drain electrode. In this case, a light-receiving characteristic of the light detecting device may be controlled by adjusting voltages applied to the first electrode <NUM> and the second electrode <NUM> and the gate electrode <NUM>.

In the above example embodiments, one graphene layer <NUM> is provided correspondingly to all of the plurality of waveguides <NUM>. However, as described below, a plurality of graphene layers may be provided according to some of a plurality of waveguides. In this case, light detection may be performed by driving all of the graphene layers or by independently driving the graphene layers.

Referring to <FIG>, a plurality of graphene layers <NUM>' are provided on the plurality of waveguides <NUM>. In <FIG>, two graphene layers <NUM>' are provided on four waveguides <NUM>. Here, each graphene layer <NUM>' may correspond to two waveguides <NUM>. Also, the first electrode <NUM>' and the second electrode <NUM>' are electrically connected to each graphene layer <NUM>'.

Referring to <FIG>, a plurality of graphene layers <NUM>" are provided on the plurality of waveguides <NUM> in a one-to-one manner. In <FIG>, four graphene layers <NUM>" are provided on four waveguides <NUM>, respectively. Here, each graphene layer <NUM>" may correspond to each waveguide <NUM>, and the first electrode <NUM>" and the second electrode <NUM>" are electrically connected to each graphene layer <NUM>".

<FIG> illustrates a light detecting device <NUM> according to another example embodiment. The plurality of waveguides <NUM>, the light input device <NUM>, and the plurality of modulators <NUM> of the light detecting device <NUM> of <FIG> have been described above with reference to the light detecting device <NUM> of <FIG>.

Referring to <FIG>, the plurality of waveguides <NUM> that pass through the plurality of modulators <NUM> may be combined with each other to be integrated into one waveguide <NUM>. A graphene layer <NUM> is provided on the waveguide <NUM> and the first electrode <NUM> and the second electrode <NUM> are electrically connected to both end portions of the graphene layer <NUM>.

Portion of light proceeding inside the plurality of waveguides <NUM> are combined with each other in the waveguide <NUM> and the combined portion of light are absorbed by the graphene layer <NUM> to be detected via the first electrode <NUM> and the second electrode <NUM>.

According to the above example embodiments, as a graphene layer absorbs most of portion of light proceeding inside a plurality of waveguides, a light detecting device having a relatively high light-receiving efficiency may be implemented. Also, the light-receiving efficiency may be further improved as a plurality of modulators independently modulate phases of the portion of light proceeding inside the plurality of waveguides to control a phase profile.

Because the light detecting device described above is capable of receiving light in a specific direction with high efficiency, for example, a LiDAR system for long distances may be more easily implemented. Also, because the LiDAR system may reduce the intensity of output light of a light-emitting device, eye safety may be improved, and miniaturization and low costs of a system may be realized.

Such a light detecting device may be applied to a field of identifying an object or a terrain or measuring a location, distance, and shape by using light. For example, the light detecting device may be applied to fields of image sensors, distance sensors, environmental sensors, autonomous vehicles, flying objects such as drones, mobile devices, walking tools, and security devices.

<FIG> illustrates an optical system <NUM> according to an example embodiment.

Referring to <FIG>, the optical system <NUM> may include a light steering apparatus <NUM>, a light detecting device <NUM>, and a driving device <NUM>. Here, the driving device <NUM> may include a driving circuit for driving the light steering apparatus <NUM> and the light detecting device <NUM>. Elements forming the optical system <NUM> may be provided on a same substrate <NUM>. However, embodiments are not limited thereto, and some of the elements forming the optical system <NUM> may not be provided in the same substrate <NUM>.

The light steering apparatus <NUM> includes a laser light source <NUM> emitting a laser beam L' and a steering device <NUM> scanning the laser beam L' emitted from the laser light source <NUM>. A laser diode, for example, may be used as the laser light source <NUM>, but embodiments are not limited thereto.

The steering device <NUM> may be configured to scan the laser beam L' by using, for example, an optical phased array (OPA) method. In this case, the steering device <NUM> may scan the laser beam L' by using interference of portion of light of which phases are modulated and emitted from a plurality of device cells having a meta structure or from a plurality of waveguides.

When the steering device <NUM> includes the plurality of waveguides, the laser beam L' may be two-dimensionally scanned via phase modulation and wavelength modulation. Also, when the steering device <NUM> includes the plurality of cells arranged two-dimensionally, the laser beam L' may be scanned two-dimensionally.

Moreover, in addition to the OPA method described above, the steering device <NUM> may use a method of mechanically moving the laser light source <NUM> or a flash method in which laser beams are simultaneously emitted from a plurality of laser light sources.

The laser beam L' reflected from an object <NUM> among the laser beams L' scanned by the light steering apparatus <NUM> may be detected by the light detecting device <NUM>. Here, the light detecting device <NUM> may be one of light detecting devices according to the above-described example embodiments.

The optical system <NUM> described above may be used in, for example, a LiDAR system, a depth sensor, or a 3D sensor. However, this is only an example and the optical system <NUM> may be applied to other various fields.

According to the example embodiments described above, because a graphene layer absorbs most of portion of light proceeding inside a plurality of waveguides, a light detecting device and optical system having a relatively high light-receiving efficiency may be implemented. Also, when a plurality of modulators control a phase profile by independently modulating phases of the portion of light proceeding inside the plurality of waveguides, the light-receiving efficiency may be improved and locations at which external portion of light are incident may be determined. Because the light detecting device is capable of receiving light in a specific direction with high efficiency, for example, a LiDAR system for long distances may be easily implemented. Also, because the LiDAR system may reduce the intensity of output light of a light-emitting device, eye safety may be improved, and miniaturization and low costs of a system may be realized.

It should be understood that example embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each example embodiment should typically be considered as available for other similar features or aspects in other embodiments.

Claim 1:
A light detecting device (<NUM>) comprising:
a light input device (<NUM>) configured to receive light;
a plurality of waveguides (<NUM>) extending from the light input device, the plurality of waveguides being configured to transmit portions of the light received by the light input device (<NUM>), respectively;
a plurality of modulators (<NUM>) provided on the plurality of waveguides (<NUM>) and configured to modulate phases of the portions of light transmitted in the plurality of waveguides (<NUM>), respectively;
at least one graphene layer (<NUM>) configured to absorb the portions of light transmitted in the plurality of waveguides (<NUM>); and
at least one first electrode (<NUM>) and at least one second electrode (<NUM>)
electrically connected to the at least one graphene layer (<NUM>), respectively, and characterized in that the a plurality of modulators (<NUM>) each comprise a first electrode (<NUM>) and a second electrode (<NUM>) and are configured to form a phase profile by independently modulating a phase of each of the portions of light transmitted in the plurality of waveguides (<NUM>) by applying an electric signal between the first electrode (<NUM>) and the second electrodes (<NUM>) of each modulator (<NUM>), so as to improve the light-receiving efficiency of the portions of light in a specific direction.