Phase modulation device and electronic apparatus including same

Abstract

A phase modulation device includes: an upper reflective layer on which incident light is incident; a lower reflective layer disposed on a lower portion of the upper reflective layer; an active layer disposed between the upper reflective layer and the lower reflective layer; a first electrode connected to an upper surface of the active layer; and a second electrode connected to a lower surface of the active layer, in which the lower reflective layer may include a first distributed Bragg reflector (DBR) layer including at least one first low refractive material layer having a first refractive index and at least one first high refractive material layer alternately stacked, the at least one first low refractive material layer having a second refractive index, and the at least one first high refractive material layer having a second refractive index. And the at least one first high refractive index material layer has a second refractive index greater than the first refractive index, and the active layer may include a material having a third refractive index greater than the first refractive index of the at least one first low refractive index material layer.

Description

[0001] This application is based on and claims the benefit of priority from Korean Patent Application No. 10-2023-0078204 filed on June 19, 2023, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0002] The present disclosure relates to a phase modulation device and an electronic device including the phase modulation device. Background Art

[0003] In order to steer the laser beam to a desired position, a method of mechanically rotating the laser emitting component and a method of using an optical phased array (OPA) can be used. The method of using the OPA steers the laser beam by modulating the phase of the laser beam incident on the phase modulation device and emitting the laser beam, and this method has recently attracted attention. The beam steering device using the OPA can be applied to various fields, such as a light detection and ranging (LiDAR) device and a three-dimensional (3D) depth camera that obtains distance information in various directions. Summary of the invention

[0004] Provided are a phase modulation device and an electronic device including the phase modulation device.

[0005] 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 embodiments presented in the disclosure.

[0006] According to one aspect of the present disclosure, a phase modulation device includes: an upper reflection layer, on which incident light is incident; a lower reflection layer, which is arranged on the lower part of the upper reflection layer; an active layer, which is arranged between the upper reflection layer and the lower reflection layer; a first electrode, which is connected to the upper surface of the active layer; and a second electrode, which is connected to the lower surface of the active layer, wherein the lower reflection layer may include a first distributed Bragg reflector (DBR) layer, the first DBR layer includes at least one first low-refractive material layer and at least one first high-refractive material layer alternately stacked, the at least one first low-refractive material layer has a first refractive index, and the at least one first high-refractive material layer has a second refractive index greater than the first refractive index, and the active layer may include a material having a third refractive index, and the third refractive index is greater than the first refractive index of the at least one first low-refractive material layer.

[0007] The active layer may include a material having a first thermo-optic coefficient greater than a second thermo-optic coefficient of the at least one first low-refractive material layer.

[0008] The phase modulation device may be configured to change a refractive index of the active layer based on a current injected into the active layer through the first electrode and the second electrode.

[0009] The active layer may include Si or Ge.

[0010] The thickness of the active layer may be greater than the thickness of the at least one first high-refractive material layer.

[0011] The upper reflection layer may include a high contrast grating (HCG) layer.

[0012] The upper reflection layer may include a second DBR layer, the second DBR layer may include at least one second low-refractive material layer and at least one second high-refractive material layer alternately stacked, and the at least one second low-refractive material layer may have a fourth refractive index, and the at least one second high-refractive material layer may have a fifth refractive index greater than the fourth refractive index.

[0013] The number of alternately stacked layers in the second DBR layer may be smaller than the number of alternately stacked layers in the first DBR layer.

[0014] The phase modulation device may further include a protection layer disposed between the upper reflection layer and the active layer.

[0015] The protective layer may include at least one of silicon oxide, silicon nitride, aluminum oxide, hafnium oxide, and titanium oxide.

[0016] The thickness of the protective layer may be in the range of about 20 nm to about 200 nm.

[0017] The wavelength of the incident light may be in the range of about 900 nm to about 1,000 nm.

[0018] According to one aspect of the present disclosure, a phase modulation device includes: a first distributed Bragg reflector (DBR) layer, including at least one first layer and at least one second layer alternately stacked, at least one first layer including a first low refractive index material having a first refractive index, at least one second layer including a first high refractive index material, the first high refractive index material having a second refractive index greater than the first refractive index; a third layer, disposed on the first DBR layer, the third layer having a third refractive index greater than the first refractive index and having a thickness greater than that of the at least one second layer; a first electrode, connected to the upper surface of the third layer; and a second electrode, connected to the lower surface of the third layer.

[0019] The third layer may have a first thermo-optic coefficient that is greater than a second thermo-optic coefficient of the first low refractive index material of the at least one first layer.

[0020] The third layer may include Si or Ge.

[0021] The phase modulation device may further include a protection layer disposed on the third layer.

[0022] The phase modulation device may further include a high contrast grating (HCG) layer disposed on the third layer.

[0023] The phase modulation device may further include a second DBR layer disposed on the third layer, the second DBR layer may include at least one fourth layer and at least one fifth layer alternately stacked, at least one fourth layer may include a second low refractive index material having a fourth refractive index, and at least one fifth layer may include a second high refractive index material having a fifth refractive index greater than the fourth refractive index.

[0024] According to one aspect of the present disclosure, an electronic device includes: a laser light source configured to emit light of a predetermined wavelength; and a phase modulation device configured to modulate the phase of light of a predetermined wavelength incident thereon from the laser light source, wherein the phase modulation device includes: an upper reflection layer, on which light of a predetermined wavelength is incident; a lower reflection layer disposed on a lower portion of the upper reflection layer; an active layer disposed between the upper reflection layer and the lower reflection layer; a first electrode connected to an upper surface of the active layer; and a second electrode connected to a lower surface of the active layer, wherein the lower reflection layer may include a first distributed Bragg reflector (DBR) layer, the first DBR layer including at least one first low-refractive material layer and at least one first high-refractive material layer alternately stacked, the at least one first low-refractive material layer having a first refractive index, and the at least one first high-refractive material layer having a second refractive index greater than the first refractive index, and the active layer may include a material having a third refractive index greater than the first refractive index of the at least one first low-refractive material layer.

[0025] The predetermined wavelength may be in the range of about 900 nm to about 1,000 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and other aspects, features and advantages of some embodiments of the present disclosure will become more apparent from the following description in conjunction with the accompanying drawings, in which:

[0027] Figure 1 is a perspective view showing a phase modulation device according to an embodiment;

[0028] Figure 2A is a diagram showing a method according to an embodiment of the present invention. Figure 1 A perspective view of a pixel of a phase modulation device is shown;

[0029] Figure 2B According to the embodiment Figure 2A A cross-sectional view taken along line II';

[0030] Figure 3A is a perspective view showing a phase modulation device according to an embodiment;

[0031] Figure 3B According to the embodiment Figure 3A A cross-sectional view taken along line II-II';

[0032] Figure 4A A phase modulation device according to a first comparative example is shown;

[0033] Figure 4B A phase modulation device according to a second comparative example is shown;

[0034] Figure 5A A phase modulation device according to a second comparative example is shown;

[0035] Figure 5B is a graph showing a reflection spectrum according to a change in an incident angle of an incident light beam incident to a phase modulation device according to a second comparative example;

[0036] Fig. 6A A phase modulation device according to an embodiment is shown;

[0037] Figure 6B is a graph showing a reflection spectrum according to a change in an incident angle of an incident light beam incident to a phase modulation device according to an embodiment;

[0038] Fig. 7A is a diagram showing a region where the refractive index greatly changes due to heating in a phase modulation device according to a first comparative example;

[0039] Figure 7B is a diagram showing a region where the refractive index greatly changes due to heating in the phase modulation device according to the embodiment;

[0040] Fig. 8A FIG. 1 is a diagram showing the SiO2 phase modulation device according to the first comparative example according to the applied voltage. 2 A graph showing simulation results of reflectivity of an active layer;

[0041] Figure 8B is a graph showing simulation results regarding reflectivity of a Si active layer according to an applied voltage in a phase modulation device according to an embodiment;

[0042] Fig.9A FIG. 1 is a diagram showing the SiO2 phase modulation device according to the first comparative example according to the applied voltage. 2 A graph showing simulation results of the reflection phase of the active layer;

[0043] Fig. 9B is a graph showing simulation results regarding a reflection phase of a Si active layer according to an applied voltage in a phase modulation device according to an embodiment;

[0044] Fig. 10A FIG. 1 is a diagram showing the SiO2 phase modulation device according to the first comparative example according to the applied voltage. 2A graph showing simulation results of reflection phase variation of an active layer;

[0045] Fig. 10B is a graph showing simulation results regarding a change in reflection phase of a Si active layer according to an applied voltage in a phase modulation device according to an embodiment;

[0046] Fig.11A is a graph showing a simulation result of a temperature distribution at each grating element position of a high contrast grating (HCG) layer in a phase modulation device according to a first comparative example;

[0047] Fig. 11B is a graph showing simulation results of temperature distribution at each grating element position of the HCG layer in the phase modulation device according to the embodiment;

[0048] Fig.12 is a graph showing SiO2 of the phase modulation device according to the first comparative example. 2 A graph of experimental results comparing the resonant wavelength shift according to applied voltage between an active layer and a Si active layer of a phase modulation device according to an embodiment;

[0049] Fig.13 is a graph showing experimental results regarding a phase spectrum and a reflection spectrum of a phase modulation device according to an embodiment;

[0050] Fig.14 is a graph showing far field distribution measured by beam steering in a phase modulation device according to an embodiment;

[0051] Fig.15 is a cross-sectional view showing a phase modulation device according to an embodiment;

[0052] Fig.16 is a cross-sectional view showing a phase modulation device according to an embodiment; and

[0053] Fig.17 is a diagram illustrating a beam steering system according to an embodiment. DETAILED DESCRIPTION

[0054] Reference is now made in detail to embodiments, examples of which are shown in the accompanying drawings, wherein similar reference numerals throughout the drawings represent similar elements. In this regard, the embodiments presented may have different forms and should not be construed as being limited to the description set forth herein. Therefore, the embodiments are described below only by reference to the drawings to explain various aspects.

[0055] 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 rather than modifying the individual elements in the list. For example, the expression "at least one of a, b, and c" should be understood to include 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.

[0056] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Like reference numerals in the accompanying drawings represent like elements, and the size of each element in the accompanying drawings may be exaggerated for the sake of clarity and convenience of description. The embodiments described below are only examples, and various modifications may be made to these embodiments.

[0057] The "above" or "upper" described below may include upper, lower, left, and right in contact, as well as upper, lower, left, and right in non-contact. Unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, when a part "includes" any element, unless otherwise specified, it means that the part may also include other elements, rather than excluding other elements.

[0058] The term "the" and similar indicative terms may be used in singular and plural forms. If the order of steps constituting a method is not explicitly described or there is no description to the contrary, the steps may be performed in an appropriate order and are not limited to the order described.

[0059] In addition, the terms “unit”, “module” and the like described herein mean a unit that processes at least one function or operation, and may be implemented as hardware or software, or as a combination of hardware and software.

[0060] The connections of lines or connecting members between elements shown in the drawings are examples of functional connections and / or physical or circuit connections and may be replaced in actual devices or may be represented as other various functional connections, physical connections or circuit connections.

[0061] All examples or exemplary terms are used only to describe the technical concept in detail, and the scope thereof is not limited by these examples or exemplary terms unless limited by the claims.

[0062] Figure 1 is a perspective view showing a phase modulation device according to the embodiment.

[0063] refer to Figure 1, the phase modulation device 100 may include a plurality of pixels P arranged in a specific shape or pattern. The plurality of pixels P may be arranged in a two-dimensional or one-dimensional shape or pattern. Each pixel P may independently modulate the phase of the incident light (laser beam) by a change in the refractive index according to the applied voltage. Therefore, the pixels P constituting the phase modulation device 100 may form a phase profile and control the phase profile, thereby emitting and steering the light incident on the phase modulation device 100 in a desired direction. The light incident on the phase modulation device 100 may have a wavelength of, for example, about 900 nm to about 1,000 nm. Figure 1 A case where the phase modulation device 100 is a reflective phase modulation device is shown, but the embodiment is not limited thereto, and the phase modulation device 100 may also be a transmissive phase modulation device.

[0064] Figure 2A is a diagram showing a method according to an embodiment of the present invention. Figure 1 A perspective view of a pixel P of the phase modulation device 100 is shown. Figure 2B According to the embodiment Figure 2A A cross-sectional view taken along line II'.

[0065] refer to Figure 2A and Figure 2B The phase modulation device 100 includes an upper reflection layer 101 on which light is incident, a lower reflection layer 102 disposed on a lower portion of the upper reflection layer 101, an active layer 130 disposed between the upper reflection layer 101 and the lower reflection layer 102, and a pair of electrodes 141 and 142 disposed in upper and lower surfaces of the active layer 130.

[0066] A substrate may be provided on the lower portion of the low reflection layer 102, and a semiconductor substrate (e.g., a silicon substrate) may be used as the substrate. However, the present disclosure is not limited thereto. The thickness of the substrate may be determined in consideration of various factors, such as a form factor and / or heat dissipation when the phase modulation device 100 is applied to a product.

[0067] The lower reflection layer 102 may include a distributed Bragg reflector (DBR) layer 110, in which at least one low-refractive material layer 110a and at least one high-refractive material layer 110b are alternately stacked. The material, thickness, etc. of each of the low-refractive material layer 110a and the high-refractive material layer 110b can be adjusted in various ways according to the reflectivity design conditions of the DBR layer 110. Figure 2A and Figure 2B The case where the low-refractive material layer 110a and the high-refractive material layer 110b are alternately stacked three times is shown. However, the present disclosure is not limited thereto, and the number of times the low-refractive material layer 110a and the high-refractive material layer 110b are alternately and repeatedly stacked may be modified in various ways.

[0068] The high refractive material layer 110b may include a material having a refractive index greater than that of the low refractive material layer 110a. For example, the low refractive material layer 110a may include silicon oxide, but is not limited thereto. The high refractive material layer 110b may include silicon (Si). However, the high refractive material layer 110b is not limited thereto, and may include, for example, Ge, GaP, or InP. The thickness of the high refractive material layer 110b may be less than the thickness of the low refractive material layer 110a. For example, the thickness of the high refractive material layer 110b may be from about 60nm to about 90nm. However, the present disclosure is not limited thereto.

[0069] The active layer 130 is disposed on the DBR layer 110. The active layer 130 may be configured to resonate and amplify incident light between the lower reflection layer 102 and the upper reflection layer 101. The active layer 130 may include a single layer. The active layer 130 may include a material having a refractive index greater than that of the low refractive material layer 110a of the DBR layer 110. The active layer 130 may include a material having a thermo-optic coefficient greater than that of the low refractive material layer 110a of the DBR layer 110. The thermo-optic coefficient refers to a change in the refractive index of a material according to a change in its temperature.

[0070] The active layer 130 may include, for example, a material having a refractive index and a thermo-optic coefficient greater than those of silicon oxide. For example, the active layer 130 may include silicon. However, the active layer 130 is not limited thereto and may include, for example, Ge.

[0071] The thickness of the active layer 130 may vary according to the wavelength of the incident light. The thickness of the active layer 130 may be greater than the thickness of the high refractive material layer 110b of the DBR layer 110. For example, when the thickness of the high refractive material layer 110b of the DBR layer 110 is about 60nm to about 90nm, the thickness of the active layer 130 may be greater than 90nm.

[0072] The first electrode 141 and the second electrode 142 are respectively disposed in the upper and lower surfaces of the active layer 130. The first electrode 141 and the second electrode 142 are respectively electrically connected to the upper and lower surfaces of the active layer 130. The first electrode 141 and the second electrode 142 are disposed to directly contact the upper and lower surfaces of the active layer 130, respectively.

[0073] The pair of first electrode 141 and second electrode 142 can generate Joule heat by injecting current into active layer 130, and thus, the refractive index of the material (e.g., Si, Ge, etc.) constituting active layer 130 can be changed, and thus the phase of incident light can be controlled. The first electrode 141 and the second electrode 142 can each include, for example, a doped semiconductor material. As an example, when active layer 130 includes Si, the first electrode 141 and the second electrode 142 can each include n-doped Si. However, the present disclosure is not limited thereto.

[0074] The upper reflection layer 101 is disposed on the upper portion of the active layer 130. The upper reflection layer 101 may include a high contrast grating (HCG) layer 120 constituting an active meta surface. The HCG layer 120 may have a structure in which a plurality of grating elements 120a are periodically arranged on the upper surface of the active layer 130. The plurality of grating elements 120a may have substantially the same shape and size. The width and height of each grating element 120a may be less than the wavelength of the incident light. The height of each grating element 120a may be designed to have a predetermined reflectivity for the incident light. For example, the height of each grating element 120a may be designed to have a reflectivity of 70% or more. The plurality of grating elements 120a may be arranged in one dimension. The arrangement period of the plurality of grating elements 120a may be less than the wavelength of the incident light. Each grating element 120a constituting the HCG layer 120 may include a high refractive index material (e.g., silicon).

[0075] In each pixel P of the phase modulation device 100 according to the embodiment, when a predetermined current is injected into the active layer 130 through the first electrode 141 and the second electrode 142 to generate Joule heat, the temperature of the active layer 130 changes, and the refractive index of the active layer 130 changes according to the temperature change of the active layer 130, so that the phase of the incident light can be modulated.

[0076] According to an embodiment, the active layer 130 disposed between the upper reflection layer 101 and the lower reflection layer 102 includes a material having a high refractive index and a high thermo-optical coefficient (e.g., Si or Ge), which can increase the refractive index of the active layer 130 according to the change of the external electrical signal, and therefore, a large phase change can be obtained with low power consumption, thereby improving efficiency.

[0077] Figure 3A is a perspective view showing a phase modulation device according to the embodiment. Figure 3B According to the embodiment Figure 3A For convenience, Figure 3A and Figure 3B Only one pixel P of the pixels P constituting the phase modulation device 100 is shown, and the same applies to the subsequent drawings. Hereinafter, differences from the above-described embodiment are mainly described.

[0078] refer to Figure 3A and Figure 3B The phase modulation device 200 includes an upper reflection layer 201 on which light is incident, a lower reflection layer 202 disposed on a lower portion of the upper reflection layer 201, an active layer 230 disposed between the upper reflection layer 201 and the lower reflection layer 202, and a pair of electrodes 241 and 242 disposed in the upper and lower surfaces of the active layer 230.

[0079] The low reflection layer 202 may include a first DBR layer 210 in which at least one first low-refractive material layer 210a and at least one first high-refractive material layer 210b are alternately stacked. Figure 3A and Figure 3B The case where the first low-refractive material layer 210a and the first high-refractive material layer 210b are alternately stacked three times is shown. However, the present disclosure is not limited thereto, and the number of times the first low-refractive material layer 210a and the first high-refractive material layer 210b are alternately and repeatedly stacked may be modified in various ways according to design conditions.

[0080] The first high-refractive material layer 210b may include a material with a refractive index greater than that of the first low-refractive material layer 210a. For example, the first low-refractive material layer 210a may include silicon oxide, but is not limited thereto. The first high-refractive material layer 210b may include silicon (Si). However, the first high-refractive material layer 210b is not limited thereto, and may include, for example, Ge, GaP or InP. The thickness of the first high-refractive material layer 210b may be less than the thickness of the first low-refractive material layer 210a. For example, the thickness of the first high-refractive material layer 210b may be from about 60nm to about 90nm, but is not limited thereto.

[0081] The active layer 230 is disposed on the first DBR layer 210. The active layer 230 may include a material having a refractive index greater than that of the first low-refractive material layer 210a of the first DBR layer 210. The active layer 230 may include a material having a thermo-optic coefficient greater than that of the first low-refractive material layer 210a of the first DBR layer 210. The active layer 230 may include, for example, a material having a refractive index and a thermo-optic coefficient greater than that of silicon oxide. For example, the active layer 230 may include Si or Ge.

[0082] The thickness of the active layer 230 may be greater than the thickness of the first high refractive material layer 210b of the first DBR layer 210. For example, when the thickness of the first high refractive material layer 210b of the first DBR layer 210 is about 60nm to about 90nm, the thickness of the active layer 230 may be greater than 90nm.

[0083] The first electrode 241 and the second electrode 242 are respectively disposed in the upper surface and the lower surface of the active layer 230. The first electrode 241 and the second electrode 242 are respectively electrically connected to the upper surface and the lower surface of the active layer 230. The first electrode 241 and the second electrode 242 are disposed to directly contact the upper surface and the lower surface of the active layer 230. The first electrode 241 and the second electrode 242 may include, for example, a doped semiconductor material. As a specific example, when the active layer 230 includes Si, the first electrode 241 and the second electrode 242 may each include n-doped Si. However, the present disclosure is not limited thereto.

[0084] The upper reflection layer 201 is disposed on an upper portion of the active layer 230. The upper reflection layer 201 may include a second DBR layer 220 in which at least one second low-refractive material layer 220a and at least one second high-refractive material layer 220b are alternately stacked. Figure 3A and Figure 3B The case where the second low-refractive material layer 220a and the second high-refractive material layer 220b are alternately stacked twice is shown, but the present disclosure is not limited thereto, and the number of times the second low-refractive material layer 220a and the second high-refractive material layer 220b are alternately and repeatedly stacked can be modified in various ways according to design conditions. For phase control, the number of alternately stacked layers of the second DBR layer 220 can be less than the number of the first DBR layer 210.

[0085] The second high-refractive material layer 220b may include a material having a refractive index greater than that of the second low-refractive material layer 220a. For example, the second low-refractive material layer 220a may include silicon oxide, but is not limited thereto. The second high-refractive material layer 220b may include silicon (Si). However, the second high-refractive material layer 220b is not limited thereto, and may include, for example, Ge, GaP or InP. The thickness of the second high-refractive material layer 220b may be less than the thickness of the second low-refractive material layer 220a.

[0086] In the phase modulation device 200 according to the embodiment, the active layer 230 includes a material having a high refractive index and a high thermo-optical coefficient (for example, Si or Ge), which can increase the refractive index of the active layer 230 according to the change of the external electrical signal, and therefore, a large phase change can be obtained with low power consumption, thereby improving efficiency.

[0087] Figure 4A A phase modulation device 10 according to a first comparative example is shown.

[0088] refer to Figure 4A The phase modulation device 10 includes an upper reflection layer, a lower reflection layer, and an active layer 13 disposed between the upper reflection layer and the lower reflection layer. The lower reflection layer may include a DBR layer 11 in which at least one low refractive material layer 11a and at least one high refractive material layer 11b are alternately stacked.

[0089] The active layer 13 is disposed on the DBR layer 11. The active layer 13 may include silicon oxide. The refractive index and thermo-optic coefficient of silicon oxide may be smaller than those of Si or Ge. The upper reflection layer is disposed on the active layer 13. The upper reflection layer includes a HCG layer 12, in which a plurality of grating elements are periodically arranged. Figure 4A The phase modulation device 10 shown in FIG. 1 can modulate the phase of incident light using a refractive index change due to Joule heat generated by applying an electric signal to the HCG layer 12 or the active layer 13 .

[0090] Figure 4B A phase modulation device 20 according to a second comparative example is shown.

[0091] refer to Figure 4B The phase modulation device 20 includes an upper reflection layer, a lower reflection layer, and an active layer 23 disposed between the upper reflection layer and the lower reflection layer. The lower reflection layer may include a first DBR layer 21 in which at least one first low-refractive material layer 21a and at least one first high-refractive material layer 21b are alternately stacked. Here, the first DBR layer 21 may be Figure 3B The first DBR layer 210 shown in FIG. 1 is the same as that in FIG. 1 , and thus a description thereof is omitted.

[0092] The active layer 23 is disposed on the first DBR layer 21. The active layer 23 may include silicon oxide. The upper reflection layer is disposed on the active layer 23. The upper reflection layer may include a second DBR layer 22 in which at least one second low refractive material layer 22a and at least one second high refractive material layer 22b are alternately stacked. Here, the second DBR layer 22 may be Figure 3B The second DBR layer 220 shown in FIG. 1 is the same as that in FIG. 1 , and thus a description thereof is omitted. Figure 4B The phase modulation device 10 shown in FIG. 1 can modulate the phase of incident light using a refractive index change due to Joule heat generated by applying an electric signal to the active layer 23 .

[0093] In the phase modulation devices 10 and 20 according to the above-mentioned first and second comparative examples, each of the active layers 13 and 23 includes silicon oxide having a refractive index and a thermo-optic coefficient smaller than those of silicon. As described above, when each of the active layers 13 and 23 includes silicon oxide, the phase modulation devices 10 and 20 may have problems in configuration and power consumption of an optical module.

[0094] Figure 5A A phase modulation device according to a second comparative example is shown. Figure 5B is a graph showing a reflection spectrum according to a change in the incident angle of the incident light beam incident on the phase modulation device 20 .

[0095] Figure 5A The first DBR layer 21 includes three pairs of first low refractive material layers SiO 2 and a first high refractive material layer Si, the second DBR layer 22 includes two pairs of second low refractive material layers SiO 2 and a second high refractive material layer Si. The active layer 23 includes SiO with a thickness of 370 nm. 2 .

[0096] Figure 5BIt shows that according to the incident Figure 5A The reflection spectrum of the incident light beam on the phase modulation device 20 is shown as a function of the incident angle θ. The incident angle θ is ±2° and ±4° relative to 45°. Figure 5B , when the incident angle θ changes to 41°, 43°, 45°, 47°, and 49°, the resonant wavelength changes to 959nm, 951nm, 943nm, 936nm, and 927nm, respectively. That is, in the phase modulation device 20 including the active layer 23 including silicon oxide, when the incident angle θ changes from 41° to 49°, the resonant wavelength changes from 959nm to 927nm, which is a change of 32nm. As described above, it can be seen that in the phase modulation device 20 including the active layer 23 including silicon oxide, when the incident angle θ changes, the resonant wavelength changes greatly.

[0097] Generally, in an operation of configuring a beam steering system by assembling a laser light source and a phase modulation device, an incident angle θ of an incident light beam incident from the laser light source may have dispersion or range. In this case, when the resonant wavelength varies greatly according to a change in the incident angle θ, phase modulation may not occur. That is, phase modulation occurs near the resonant wavelength. When the resonant wavelength varies greatly according to a change in the incident angle θ, the resonant wavelength may not match the wavelength of the incident light beam according to the change in the incident angle θ. In this case, phase modulation may not occur.

[0098] In the phase modulation device 20 including the active layer 23 including silicon oxide, power consumption may increase. Compared with silicon, silicon oxide has a very small thermo-optic coefficient of about 5×10 -7 K -1 Therefore, the refractive index change of the active layer 23 according to the external electrical signal is small, and as a result, the phase modulation device 20 using silicon oxide as the active layer 23 requires high power consumption to obtain a desired phase change.

[0099] Fig. 6A A phase modulation device 200 according to an embodiment is shown. Figure 6B : is a graph showing a reflection spectrum according to a change in the incident angle θ of the incident light beam incident to the phase modulation device 200 .

[0100] Fig. 6A The first DBR layer 210 includes three pairs of first low refractive material layers SiO 2 and a first high refractive material layer Si, the second DBR layer 220 includes two pairs of second low refractive material layers SiO 2 and a second high refractive material layer Si. The active layer 230 includes Si with a thickness of 370 nm.

[0101] Figure 6B It shows that according to the incident Fig. 6A The reflection spectrum of the incident light beam on the phase modulation device 200 is shown as a function of the incident angle θ. The incident angle θ is ±2° and ±4° relative to 45°. Figure 6B , when the incident angle θ changes to 41°, 43°, 45°, 47°, and 49°, the resonant wavelength changes to 948.5nm, 945.5nm, 943.5nm, 940.5nm, and 937.5nm, respectively. That is, it can be seen that in the phase modulation device 200 including the active layer 230 including silicon, when the incident angle θ changes from 41° to 49°, the resonant wavelength changes from 948.5nm to 937.5nm, which changes by 11nm. As described above, it can be seen that in the phase modulation device 200 including the active layer 230 including silicon, when the incident angle θ changes, the change in the resonant wavelength is smaller than the change in the resonant wavelength in the phase modulation device 20 including the active layer 23 including silicon oxide. That is, it can be seen that in the phase modulation device 200 including the active layer 230 including silicon, the change in the resonant wavelength is less sensitive or insensitive to the change in the incident angle θ. Therefore, when the phase modulation device 200 including the active layer 230 including silicon is combined with a laser light source to configure a beam steering system, robust characteristics against variations in the incident angle θ of an incident light beam incident from the laser light source may be achieved.

[0102] Compared with silicon oxide, silicon has a very large thermo-optic coefficient of about 1.8×10 at a wavelength of 940 nm and room temperature. -4 K -1 , which exhibits a large refractive index change with temperature. Therefore, the refractive index change of the active layer 230 according to the external electrical signal is large, and thus the phase modulation device 200 using silicon as the active layer 230 can obtain a large phase change even with low power consumption.

[0103] Fig. 7A 1 is a diagram showing a region R1 in which the refractive index greatly changes due to heating in the phase modulation device 10 according to the first comparative example. The HCG layer 12 includes Si, and the active layer 13 includes SiO 2 .

[0104] refer to Fig. 7A When Joule heat is generated by applying a predetermined electrical signal to the HCG layer 12 or the active layer 13, the HCG layer 12 and the active layer 13 are heated, and thus the refractive index thereof changes. As described above, since silicon oxide has a very low thermo-optic coefficient compared to silicon, the active layer 13 including silicon oxide does not undergo a large refractive index change due to heating. Therefore, the region R1 in which the refractive index is greatly changed due to heating can be formed only in the HCG layer 12.

[0105] Figure 7B1 is a diagram showing a region R2 where the refractive index is greatly changed by heating in the phase modulation device 100 according to the embodiment. The HCG layer 120 includes Si, and the active layer 130 includes Si.

[0106] refer to Figure 7B , when Joule heat is generated by injecting a predetermined current into the active layer 130 through a pair of first electrodes 141 and second electrodes 142, the active layer 130 is heated, and the HCG layer 120 on the active layer 130 may also be heated. Since silicon has a large thermo-optic coefficient compared to silicon oxide, the active layer 130 including silicon may generate a large refractive index change due to heating. Therefore, a region R2 in which the refractive index greatly changes due to heating may be formed in the active layer 130 and the HCG layer 120. When the refractive indices of not only the active layer 130 but also the HCG layer 120 are significantly changed due to heating, the phase of the incident light may be more effectively controlled.

[0107] Fig. 8A It shows that according to Fig. 7A In the phase modulation device 10 of the first comparative example shown in FIG. 2 A graph showing simulation results of the reflectivity of the active layer 13 .

[0108] refer to Fig. 8A , when the applied voltage is 0V, the resonant wavelength is about 940nm, the full width at half maximum (FWHM) is 11nm, and the Q factor is 86. As the applied voltage increases, the resonant wavelength red-shifts. Specifically, when the applied voltage increases from 0V to 20V, the resonant wavelength increases from about 940nm to about 950nm, so a red shift of about +10nm may occur.

[0109] Figure 8B It shows that according to Figure 7B 2 is a graph showing simulation results of the reflectivity of the Si active layer 130 according to the applied voltage in the phase modulation device 100 of the embodiment shown in FIG.

[0110] refer to Figure 8B , when the applied voltage is 0V, the resonant wavelength is about 940nm, the FWHM is 12nm, and the Q factor is 80. When the applied voltage increases, the resonant wavelength red shift occurs. Specifically, when the applied voltage increases from 0V to 20V, the resonant wavelength increases from about 940nm to about 960nm, so a red shift of about +20nm may occur. As described above, with SiO 2 Compared with the active layer 13, under the same applied voltage, a large red shift can occur in the Si active layer 130, which indicates that the efficiency and directivity of the phase modulation device 100 can be improved. Therefore, the phase modulation device 100 including the Si active layer 130 can achieve the same performance as that including the SiO active layer 130 even with less power consumption.2 The phase modulation device 10 of the active layer 13 has the same efficiency and directivity.

[0111] Fig.9A It shows that according to Fig. 7A In the phase modulation device 10 of the first comparative example shown in FIG. 2 A graph showing simulation results of the reflection phase of the active layer 13 . Fig. 9B It shows that according to Figure 7B 2 is a graph showing simulation results of the reflection phase of the Si active layer 130 according to the applied voltage in the phase modulation device 100 of the embodiment shown in FIG.

[0112] refer to Fig.9A and Fig. 9B , it can be seen that due to the SiO 2 Compared with the Si active layer 13 , the red shift due to the applied voltage in the Si active layer 130 is greatly increased, so more phase changes occur in the Si active layer 130 .

[0113] Fig. 10A It shows that according to Fig. 7A In the phase modulation device 10 of the first comparative example shown in FIG. 2 A graph showing simulation results of the reflection phase change of the active layer 13 . Fig. 10B It shows that according to Figure 7B 2 is a graph showing simulation results of a change in the reflection phase of the Si active layer 130 according to an applied voltage in the phase modulation device 100 of the embodiment shown in FIG. Fig. 10A and Fig. 10B The phase change according to the applied voltage is shown compared with the phase when the applied voltage is 0 V.

[0114] refer to Fig. 10A and Fig. 10B , it can be seen that SiO 2 The active layer 13 has a maximum phase change of about 200°, while the Si active layer 130 has a maximum phase change of about 270°, which is greater than that of SiO 2 The maximum phase change of the active layer 13.

[0115] Fig.11A It shows that according to Fig. 7A FIG. 2 is a graph showing a simulation result of the temperature distribution at each grating element position of the HCG layer 12 in the phase modulation device 10 of the first comparative example. Fig.11A The grating elements constituting the HCG layer 120 are shown in FIG. 1 . When heat is generated by applying a predetermined voltage to the HCG layer 120, Fig. 7A Temperature distribution in the y-axis direction.

[0116] Fig. 11B It shows that according to Figure 7B A graph showing simulation results of temperature distribution at each grating element position of the HCG layer 120 in the phase modulation device 100 of the embodiment is shown. Fig. 11B The grating elements constituting the HCG layer 120 are shown in FIG. 1 . When heat is generated by applying a predetermined voltage to the HCG layer 120, Figure 7B Temperature distribution in the y-axis direction.

[0117] refer to Fig.11A and Fig. 11B , it can be seen that, in the phase modulation device 100 according to the embodiment, the internal temperature of the Si grating element constituting the HCG layer 120 is relatively uniform, compared with the phase modulation device 10 according to the first comparative example.

[0118] Fig.12 It shows that according to Fig. 7A The SiO 2 The active layer 13 and the Figure 7B FIG. 1 is a graph showing experimental results of comparison of the resonant wavelength shift according to the applied voltage between the Si active layers 130 of the phase modulation devices 100 of the embodiment.

[0119] refer to Fig.12 , when the voltage applied to the phase modulation device 10 according to the first comparative example and the phase modulation device 100 according to the embodiment is the same (for example, 10 V), SiO 2 The resonance wavelength shift (red shift) of the active layer 13 was measured to be about 5 nm, and the resonance wavelength shift (red shift) of the Si active layer 130 was measured to be about 7 nm. Therefore, it can be seen that under the same applied voltage of 10 V, the red shift of the Si active layer 130 is greater than that of the SiO 2 The red shift of the active layer 13 is about 40% larger. This shows that compared with the SiO 2 Compared with the phase modulation device 10 including the Si active layer 130 , the phase modulation device 100 including the Si active layer 130 can reduce the power consumption required to achieve the same red shift.

[0120] An active layer including a material (e.g., Si or Ge) having a refractive index and a thermo-optic coefficient greater than those of silicon oxide can have sufficiently excellent resonance characteristics and a high Q factor without significant loss relative to an incident light beam in a wavelength range of about 900 nm to about 1000 nm. Therefore, a phase modulation device including the active layer can be driven in an overcoupling region, wherein the active layer includes a material having a high refractive index and a high thermo-optic coefficient.

[0121] Fig.13 It shows that according to Figure 7BFIG. 1 is a graph showing experimental results of the phase spectrum and reflection spectrum of the phase modulation device 100 of the embodiment shown in FIG. Fig.13 In the figure, “A” represents the phase spectrum and “B” represents the reflection spectrum. Fig.13 , it can be confirmed that the phase spectrum exists in the overcoupling region where the phase changes by more than 300° depending on the wavelength.

[0122] Fig.14 It is shown that according to Figure 7B A graph of far-field distribution measured by beam steering in the phase modulation device 100 of the illustrated embodiment. Fig.14 Shown according to Figure 1 FIG. 1 shows the far field distribution of the position of the pixel P of the phase modulation device 100. Fig.14 It can be seen that the phase modulation device 100 according to the embodiment can achieve beam steering with high directivity by using the Si active layer 130 .

[0123] Fig.15 A cross-sectional view of a phase modulation device 300 according to an embodiment is shown. Fig.15 The phase modulation device 300 shown is Figure 2A and Figure 2B The phase modulation device 100 shown in FIG. 1 is similar to the phase modulation device 100 shown in FIG. 1 , except that the protective layer 340 is formed on the upper surface of the active layer 330. Figure 2A and Figure 2B The differences between the embodiments shown.

[0124] refer to Fig.15 The phase modulation device 300 includes a lower reflection layer 302, an upper reflection layer 301, an active layer 330 arranged between the lower reflection layer 302 and the upper reflection layer 301, a pair of first electrodes 341 and a second electrode 342 arranged on the upper surface and the lower surface of the active layer 330, and a protective layer 340 arranged between the active layer 330 and the upper reflection layer 301.

[0125] The lower reflection layer 302 may include a DBR layer 310 in which at least one low-refractive material layer and at least one high-refractive material layer are alternately stacked. The upper reflection layer 301 may include a HCG layer 320 having a structure in which a plurality of grating elements are periodically arranged on an upper surface of the active layer 330. The DBR layer 310 and the HCG layer 320 are respectively connected to Figure 2A and Figure 2B The DBR layer 110 and the HCG layer 120 of the illustrated embodiment are the same, and thus a detailed description thereof is omitted.

[0126] The active layer 330 is disposed between the DBR layer 310 and the HCG layer 320. The active layer 330 may include a material having a refractive index greater than that of the low refractive material layer of the DBR layer 310. The active layer 330 may include a material having a thermo-optic coefficient greater than that of the low refractive material layer of the DBR layer 310. The active layer 330 may include, for example, a material having a refractive index and a thermo-optic coefficient greater than that of silicon oxide. For example, the active layer 330 may include Si or Ge. The thickness of the active layer 330 may be greater than that of the high refractive material layer of the DBR layer 310.

[0127] The first electrode 341 and the second electrode 342 are respectively disposed on the upper surface and the lower surface of the active layer 330. The first electrode 341 and the second electrode 342 are respectively electrically connected to the upper surface and the lower surface of the active layer 330. The first electrode 341 and the second electrode 342 may each include, for example, a doped semiconductor material. As a specific example, when the active layer 330 includes Si, the first electrode 341 and the second electrode 342 may include n-doped Si. The first electrode 341 and the second electrode 342 are respectively connected to the upper surface and the lower surface of the active layer 330. Figure 2A and Figure 2B The first electrode 141 and the second electrode 142 of the illustrated embodiment are the same, and thus a detailed description thereof is omitted.

[0128] The protective layer 340 is disposed between the active layer 330 and the HCG layer 320. The protective layer 340 may be used to prevent device peeling during annealing of an active layer material (eg, Si or Ge) to generate Joule heat.

[0129] The protective layer 340 may include, for example, at least one of silicon oxide, silicon nitride, aluminum oxide, hafnium oxide, and titanium oxide. However, the present disclosure is not limited thereto. The thickness of the protective layer 340 may be about 20 nm to about 200 nm, but this is only an example.

[0130] Fig.16 A cross-sectional view of a phase modulation device 400 according to an embodiment is shown. Fig.16 The phase modulation device 400 shown is Figure 3A and Figure 3B The phase modulation device 200 shown in FIG. 1 is similar to the phase modulation device 200 shown in FIG. 1 , except that the protective layer 440 is formed on the upper surface of the active layer 430. Figure 3A and Figure 3B The differences between the embodiments shown.

[0131] refer to Fig.16The phase modulation device 400 includes a lower reflection layer 402, an upper reflection layer 401, an active layer 430 arranged between the lower reflection layer 402 and the upper reflection layer 401, a pair of first electrodes 441 and a second electrode 442 arranged on the upper surface and the lower surface of the active layer 430, and a protective layer 440 arranged between the active layer 430 and the upper reflection layer 401.

[0132] The lower reflection layer 402 may include a first DBR layer 410 in which at least one first low-refractive material layer and at least one first high-refractive material layer are alternately stacked. The upper reflection layer 401 may include a second DBR layer 420 in which at least one second low-refractive material layer and at least one second high-refractive material layer are alternately stacked. The first DBR layer 410 and the second DBR layer 420 are respectively connected to Figure 3A and Figure 3B The first DBR layer 210 and the second DBR layer 220 of the illustrated embodiment are the same, and thus a detailed description thereof is omitted.

[0133] The active layer 430 is disposed between the first DBR layer 410 and the second DBR layer 420. The active layer 430 may include a material having a refractive index greater than that of the low refractive material layer of the first DBR layer 410. The active layer 430 may include a material having a thermo-optic coefficient greater than that of the low refractive material layer of the first DBR layer 410. For example, the active layer 430 may include Si or Ge. The thickness of the active layer 430 may be greater than that of the high refractive material layer of the first DBR layer 410.

[0134] The first electrode 441 and the second electrode 442 are respectively disposed on the upper surface and the lower surface of the active layer 430. The first electrode 441 and the second electrode 442 are respectively electrically connected to the upper surface and the lower surface of the active layer 430. The first electrode 441 and the second electrode 442 may each include, for example, a doped semiconductor material. As a specific example, when the active layer 430 includes Si, the first electrode 441 and the second electrode 442 may each include n-doped Si. The first electrode 441 and the second electrode 442 are respectively connected to the upper surface and the lower surface of the active layer 430. Figure 3A and Figure 3B The first electrode 241 and the second electrode 242 of the illustrated embodiment are the same, and thus a detailed description thereof is omitted.

[0135] The protective layer 440 is disposed between the active layer 430 and the second DBR layer 420. The protective layer 440 may include, for example, at least one of silicon oxide, silicon nitride, aluminum oxide, hafnium oxide, and titanium oxide. However, the present disclosure is not limited thereto. The thickness of the protective layer 440 may be about 20 nm to about 200 nm, but this is only an example.

[0136] The phase modulation devices 100 , 200 , 300 , and 400 according to the above-described embodiments may be applied to a beam steering system for steering an incident laser beam in a desired direction.

[0137] Fig.17 A beam steering system 1000 is shown according to an embodiment. Fig.17 The beam steering system 1000 may include a laser light source 810 that emits a laser beam of a predetermined wavelength, a phase modulation device 800 that steers an incident laser beam, a detector 820 that detects the steered laser beam, and a driver 830. The driver 830 may include a driving circuit that drives the laser light source 810, the phase modulation device 800, and the detector 820.

[0138] The laser light source 810 can emit a laser beam having a wavelength of about 900nm to about 1000nm. As the laser light source 810, a laser diode can be used, for example. However, this is merely an example. The laser beam emitted from the laser light source 810 is incident on the phase modulation device 800. The phase modulation device 800 steers the laser beam in a desired direction by modulating the phase of the incident laser beam and emitting the incident laser beam. The phase modulation device 800 can be any one of the phase modulation devices 100, 200, 300, and 400 according to the above-mentioned embodiments. When the laser beam steered by the phase modulation device 800 is emitted to an object and reflected, the detector 820 can detect the reflected laser beam.

[0139] The above-described beam steering system 1000 may be applied to various electronic devices such as a three-dimensional (3D) depth camera, a depth sensor, a 3D sensor, and light detection and ranging (LiDAR) that obtain distance information in each direction.

[0140] According to an embodiment, the active layer of the phase modulation device includes a material (e.g., Si or Ge) having a refractive index and a thermo-optic coefficient greater than that of silicon oxide, which can increase the refractive index change of the active layer according to an external electrical signal, and thus, a large phase change can be obtained with low power consumption, thereby improving efficiency. Although the embodiment has been described above, this is merely an example, and various modifications may be made to those skilled in the art.

[0141] It should be understood that the embodiments described herein should be considered in a descriptive sense only and not for restrictive purposes. The description of features or aspects in each embodiment should generally be considered as applicable to other similar features or aspects in other embodiments. Although one or more embodiments have been described with reference to the accompanying drawings, it should be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope defined by the appended claims.

Claims

1. A phase modulation device, include: an upper reflection layer on which incident light is incident; A lower reflection layer, disposed on the lower portion of the upper reflection layer; An active layer, disposed between the upper reflection layer and the lower reflection layer; a first electrode connected to the upper surface of the active layer; as well as a second electrode connected to the lower surface of the active layer, The lower reflection layer comprises a first distributed Bragg reflector (DBR) layer, wherein the first DBR layer comprises at least one first low-refractive material layer and at least one first high-refractive material layer alternately stacked. wherein the at least one first low-refractive material layer has a first refractive index, and the at least one first high-refractive material layer has a second refractive index greater than the first refractive index, and The active layer includes a material having a third refractive index, and the third refractive index is greater than the first refractive index of the at least one first low-refractive material layer.

2. The phase modulation device according to claim 1, in, The active layer includes a material having a first thermo-optic coefficient greater than a second thermo-optic coefficient of the at least one first low-refractive material layer.

3. The phase modulation device according to claim 1, in, The phase modulation device is configured to change a refractive index of the active layer based on a current injected into the active layer through the first electrode and the second electrode.

4. The phase modulation device according to claim 1, in, The active layer includes Si or Ge.

5. The phase modulation device according to claim 1, in, The thickness of the active layer is greater than the thickness of the at least one first high-refractive material layer.

6. The phase modulation device according to claim 1, in, The upper reflection layer includes a high contrast grating HCG layer.

7. The phase modulation device according to claim 1, in, The upper reflection layer includes a second DBR layer. The second DBR layer includes at least one second low-refractive material layer and at least one second high-refractive material layer stacked alternately, and The at least one second low-refractive material layer has a fourth refractive index, and the at least one second high-refractive material layer has a fifth refractive index greater than the fourth refractive index.

8. The phase modulation device according to claim 7, in, The number of alternately stacked layers in the second DBR layer is smaller than the number of alternately stacked layers in the first DBR layer. 9 . The phase modulation device according to claim 1 , further comprising a protection layer disposed between the upper reflection layer and the active layer.

10. The phase modulation device according to claim 9, in, The protective layer includes at least one of silicon oxide, silicon nitride, aluminum oxide, hafnium oxide, and titanium oxide.

11. The phase modulation device according to claim 9, in, The thickness of the protective layer is in the range of 20 nm to 200 nm.

12. The phase modulation device according to claim 1, in, The wavelength of the incident light is in the range of 900 nm to 1,000 nm.

13. A phase modulation device, include: A first distributed Bragg reflector (DBR) layer, comprising at least one first layer and at least one second layer alternately stacked, wherein the at least one first layer comprises a first low-refractive-index material having a first refractive index, and the at least one second layer comprises a first high-refractive-index material having a second refractive index greater than the first refractive index; a third layer disposed on the first DBR layer, the third layer having a third refractive index greater than the first refractive index and having a thickness greater than that of the at least one second layer; a first electrode connected to the upper surface of the third layer; as well as The second electrode is connected to the lower surface of the third layer.

14. The phase modulation device according to claim 13, in, The third layer has a first thermo-optic coefficient that is greater than a second thermo-optic coefficient of the first low refractive index material of the at least one first layer.

15. The phase modulation device according to claim 13, in, The third layer includes Si or Ge.

16. The phase modulation device according to claim 13, further comprising a protection layer disposed on the third layer.

17. The phase modulation device according to claim 13, further comprising a high contrast grating (HCG) layer disposed on the third layer.

18. The phase modulation device according to claim 13, further comprising a second DBR layer disposed on the third layer, in, The second DBR layer includes at least one fourth layer and at least one fifth layer which are alternately stacked, wherein the at least one fourth layer comprises a second low refractive index material having a fourth refractive index, and Wherein, the at least one fifth layer comprises a second high refractive index material having a fifth refractive index greater than the fourth refractive index.

19. An electronic device, include: a laser light source configured to emit light of a predetermined wavelength; as well as a phase modulation device configured to modulate the phase of the light of the predetermined wavelength incident on the phase modulation device from the laser light source, Wherein, the phase modulation device comprises: an upper reflection layer, on which the light of the predetermined wavelength is incident; A lower reflection layer, disposed on the lower portion of the upper reflection layer; An active layer, disposed between the upper reflection layer and the lower reflection layer; A first electrode connected to an upper surface of the active layer; and a second electrode connected to the lower surface of the active layer, The lower reflection layer comprises a first distributed Bragg reflector (DBR) layer, wherein the first DBR layer comprises at least one first low-refractive material layer and at least one first high-refractive material layer alternately stacked. wherein the at least one first low-refractive material layer has a first refractive index, and the at least one first high-refractive material layer has a second refractive index greater than the first refractive index, and The active layer includes a material having a third refractive index, and the third refractive index is greater than the first refractive index of the at least one first low-refractive material layer.

20. The electronic device according to claim 19, in, The predetermined wavelength is in the range of 900 nm to 1,000 nm.

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