Optical modulating device and apparatus using the same

Abstract

An optical modulation device and an optical device including the same are disclosed. The disclosed optical modulation device comprises an optical modulation element that changes the propagation direction of incident light having a fixed angle of incidence by utilizing the apparent displacement of a meta-grating formed by a driving signal applied to a plurality of nano-antennas. The steered light is emitted by an emission optical system. The emission optical system emits first-order diffracted light by the meta-grating.

Description

Technology Field

[0001] The disclosed embodiments relate to a light modulation device and an optical device equipped with the same. Background Technology

[0002] Optical modulators, which alter the transmission, reflection, and scattering characteristics, phase, amplitude, polarization, intensity, and path of light, are utilized in various optical devices. To control the properties of light in a desired manner within optical systems, optical modulators with diverse structures have been proposed. For instance, liquid crystals exhibiting optical anisotropy or microelectromechanical systems (MEMS) structures utilizing the micro-mechanical movements of light-blocking and reflecting elements are commonly used in optical modulators. However, these devices have limitations in their response time due to the characteristics of their driving mechanisms. In the case of MEMS structures, it is necessary to compensate for the nonlinearity of voltage-displacement characteristics, and an optimized driving voltage profile must be secured to compensate for the effects of vibrations in the kinematic system.

[0003] Recently, there have been attempts to utilize metastructures that use surface plasmon resonance phenomena for incident light in optical modulation devices. The problem to be solved

[0004] A light modulation device capable of reducing photometric light is provided.

[0005] A light modulation device capable of high-speed operation and with small dispersion of responsiveness is provided. means of solving the problem

[0006] An optical modulation device according to one aspect comprises: an incident optical system; a plurality of nano-antennas that form a meta-grating by a driving signal, and an optical modulation element that changes the direction of propagation of incident light incident from the incident optical system at a fixed angle of incidence by using the apparent displacement of the meta-grating according to the driving signal; and an output optical system that emits light steered from the optical modulation element, wherein the output optical system emits first-order diffracted light by the meta-grating.

[0007] The central axis of the above-mentioned emission optical system may be parallel to the optical axis of the first-order diffracted light when the displacement of the above-mentioned meta-grating is 0.

[0008] The central axis of the above-mentioned emission optical system may coincide with the optical axis of the first-order diffracted light when the displacement of the above-mentioned meta-grating is 0.

[0009] The angle of incidence of the incident light with respect to the surface normal vector of the optical modulator and the angle of the central axis of the emission optical system are respectively θ in , θ out Let , and let the wavelength of the incident light be λ0 and the period of the meta-grating be Λ, then

[0010]

[0011] It can satisfy.

[0012] The optical modulation element comprises a plurality of pixels, and each of the plurality of pixels may comprise a plurality of nano-antennas. Each of the plurality of pixels includes one or more antenna groups, and the one or more antenna groups include a plurality of nano-antennas, and the period of the meta-grating may be the same as the period of the antenna group. Each of the plurality of pixels includes two or more antenna groups, and a driving signal of the same pattern may be applied to two or more antenna groups within the same pixel. Let L be the number of the plurality of pixels, M be the number of antenna groups for each of the plurality of pixels, and N be the number of nano-antennas for each antenna group, and let A be the l-th pixel, the m-th antenna group, and the n-th nano-antenna. lmn Let it be denoted as such, and the optical intensity of Almn is R lmn When saying,

[0013]

[0014] It can be. Here, d=1, 2,..., N, and C is any one from 1 to N-1.

[0015] The above plurality of pixels may have a one-dimensional array structure.

[0016] The above plurality of pixels may have a two-dimensional array structure.

[0017] The optical modulation element may include: a reflector; and an active layer positioned between the reflector and the plurality of nano-antennas, the optical properties of which change according to the driving signal. The plurality of nano-antennas may be metal antennas. The plurality of nano-antennas may be dielectric antennas.

[0018] Each of the above plurality of nano antennas may have a Febry-Perot resonant structure comprising a first reflective structure, a cavity layer provided on the first reflective structure, and a second reflective structure provided on the cavity layer.

[0019] An optical modulation device according to one aspect comprises: an incident optical system; an optical modulation element having a plurality of pixels each comprising a plurality of nano antennas, wherein the optical intensity of the plurality of nano antennas changes as a periodic and discrete driving signal is applied to the plurality of nano antennas, thereby changing the propagation direction of incident light incident from the incident optical system at a fixed incident angle; and an output optical system from which light steered from the optical modulation element is emitted; wherein the incident angle of the incident light with respect to the surface normal vector of the optical modulation element and the angle of the central axis of the output optical system are each θ in , θ out Let be denoted as such, and let the wavelength of the incident light be λ0 and the period of the driving signal be Λ, then

[0020]

[0021] Satisfies.

[0022] Each of the plurality of pixels includes one or more antenna groups, and the antenna groups include a plurality of nano-antennas, and the period of the driving signal may be the same as the period of the antenna groups. The same pattern of the driving signal may be applied to two or more antenna groups within the same pixel.

[0023] Let L be the number of the plurality of pixels, M be the number of antenna groups for each of the plurality of pixels, and N be the number of nano-antennas for each antenna group, and let A be the l-th pixel, the m-th antenna group, and the n-th nano-antenna. lmn Let it be denoted as such, and the optical intensity of Almn is R lmn When saying,

[0024]

[0025] It can be. Here, d=1, 2,..., N, and C is an optical modulator that is any one of 1 to N-1.

[0026] An optical device according to one aspect includes the aforementioned light modulation device. The optical device may include at least one of a LiDAR device, a three-dimensional image acquisition device, a holographic display device, and a structured light generating device. Effects of the invention

[0027] According to the embodiments of the optical modulation device described above, an optical modulation device capable of reducing photometric photometry can be implemented. Additionally, an optical modulation device capable of high-speed operation and having small dispersion of responsiveness can be implemented.

[0028] According to the embodiments of the light modulation device described above, excellent steered light with a low ratio of side lobes can be obtained by steering the first-order diffracted light. In addition, since it operates in a so-called all-solid-state without mechanical movement, high-speed operation is possible, and uniform response characteristics can be obtained by reducing the dispersion of responsiveness caused by errors in the manufacturing process. Brief explanation of the drawing

[0029] FIG. 1 is a schematic diagram showing an optical modulation device according to one embodiment. Figure 2 shows an example of the displacement of a meta-grating when the optical intensity of multiple nano-antennas changes periodically and discretely. Figure 3 shows a simulation environment for explaining the change in the geometric phase of first-order diffracted light due to the displacement of the meta-grating. Figure 4 is a graph showing the simulation results based on the simulation environment of Figure 3, showing the change in the geometric phase of the first-order diffracted light according to the ratio of displacement to the period. Figure 5 is a graph showing the simulation results based on the simulation environment of Figure 3, showing the change in amplitude of the first-order diffracted light according to the ratio of displacement to the period. FIG. 6 is a schematic cross-sectional view of one embodiment of an optical modulation element. Figure 7 shows examples of planar shapes of nanoantennas. FIG. 8 shows various embodiments of a nanoantenna having a Fabry-Perot resonant structure. FIG. 9 is a schematic diagram of one embodiment of an optical modulation element. Figure 10 shows the results of simulating the reflectance spectrum of a nano antenna according to one embodiment of the optical modulation element shown in Figure 9. Figure 11 shows the results of simulating the wavelength-dependent phase according to the discrete displacement of a meta-grating according to one embodiment of the optical modulation element shown in Figure 9. FIG. 12 shows the results of simulating the intensity of the incident light of the first-order diffracted light according to the discrete displacement of the meta-grating according to one embodiment of the optical modulation element shown in FIG. 9. FIGS. 13 and FIGS. 14 are schematic diagrams of an embodiment of an optical modulation element, where FIG. 13 shows a case where there is no relative phase difference between a plurality of pixels, and FIG. 14 shows a case where the beam is steered by the relative phase difference between a plurality of pixels. FIG. 15 shows the formation of first-order diffracted light according to one embodiment of the optical modulation element illustrated in FIG. 13. FIG. 16 shows the formation of first-order diffracted light according to one embodiment of the optical modulation element illustrated in FIG. 14. Figure 17 shows an example of a structure in which multiple pixels are arranged two-dimensionally in a Cartesian coordinate system. Figure 18 shows examples of various tuttibi of a meta-lattice. FIG. 19 is a conceptual diagram illustrating a beam steering device as an example of an optical modulation device. FIG. 20 is a conceptual diagram illustrating a beam steering device as an example of an optical modulation device. FIG. 21 is a block diagram of an example of an optical device employing a light modulation device. FIGS. 22 and FIGS. 23 are conceptual diagrams showing a case in which a LiDAR device including a light modulation device according to one embodiment is applied to a vehicle, where FIG. 22 is a side view and FIG. 23 is a top view. Specific details for implementing the invention

[0030] Hereinafter, an optical modulation device according to embodiments and an optical device including the same will be described in detail with reference to the attached drawings. The widths and thicknesses of the layers or regions depicted in the attached drawings may be slightly exaggerated for the clarity of the specification and convenience of description. Throughout the detailed description, the same reference numerals indicate the same components.

[0031] FIG. 1 is a schematic diagram showing an optical modulation device (1) according to one embodiment. FIG. 2 shows an example of displacement of a meta-grating (MG) when the optical intensity of a plurality of nano-antennas (NA) changes periodically and discretely.

[0032] Referring to FIGS. 1 and 2, one embodiment of an optical modulation device (1) comprises an incident optical system (10) and a plurality of nano antennas (NA) that form a meta-grating (MG) (or effective grating) by a driving signal, and a fixed incident angle (θ) from the incident optical system (10) using the apparent displacement of the meta-grating (MG) according to the driving signal applied to the plurality of nano antennas (NA). in It may include an optical modulation element (20) that changes the propagation direction of incident light (L1) incident on it, and an emission optical system (30) from which light (L2) steered from the optical modulation element (20) is emitted. The emission optical system (30) may emit first-order diffracted light of the incident light (L1) by the meta-grating (MG). Reference numeral 40 indicates a driving signal application unit that applies a driving signal to a plurality of nano-antennas (NA).

[0033] The incident optical system (10) may include a light source. The incident optical system (10) may include one or more optical elements, such as lenses, that shape light irradiated from the light source into an incident light (L1) of a desired shape.

[0034] At least one of the length, width, thickness, and spacing of the plurality of nano antennas (NA) is smaller than the wavelength of the incident light (L1). By applying a driving signal, such as a voltage, to each nano antenna (NA), the optical intensity of each nano antenna (NA), such as the intensity of reflection / transmission / scattering, can be individually controlled. By doing so, an effect such as causing displacement of the meta lattice (MG) can be obtained. By applying periodic and discrete driving signals to the plurality of nano antennas (NA), periodic displacement of the meta lattice (MG) can be induced, thereby allowing the higher-order diffraction components of the light incident on the plurality of nano antennas (NA) to have a geometric phase proportional to the displacement of the meta lattice (MG).

[0035] As an example, the optical modulation element (20) may have a plurality of pixels (MP). Each of the plurality of pixels (MP) may have a plurality of nano antennas (NA). As a periodic and discrete driving signal is applied to the plurality of nano antennas (NA) of each of the plurality of pixels (MP), the optical intensity of the plurality of nano antennas (NA) changes, so that the direction of propagation of incident light (L1) from the incident optical system (10) can be changed and emitted. The pattern of the driving signal may be periodic for each pixel (MP). Each of the plurality of pixels (MP) may include one or more antenna groups (AG). Each antenna group (AG) may include a plurality of nano antennas (NA). In this case, the driving signal may be periodic for each antenna group (AG). That is, the period of the driving signal pattern may be the same as the period of the antenna group (AG). If each pixel (MP) has two or more antenna groups (AG), the same pattern of driving signal may be applied to the two or more antenna groups (AG).

[0036] The number of nano-antennas (NA) in each pixel (MP) can be appropriately determined according to the range and stage of the geometric phase to be expressed. The greater the number of antenna groups (AG) in each pixel (MP), the higher the precision of beam steering can be. Therefore, ideally, the number of antenna groups (AG) in each pixel (MP) should be infinite, but the number of antenna groups (AG) can be appropriately determined according to the required precision of beam steering. For example, each pixel (MP) may include 2 to 3 antenna groups (AG).

[0037] Multiple pixels (MP) may have a one-dimensional array structure. One-dimensional beam steering is possible by appropriately arranging the geometric phases of multiple pixels (MP). Multiple pixels (MP) may have a two-dimensional array structure. Two-dimensional beam steering is possible by appropriately arranging the geometric phases of multiple pixels (MP) arranged in a two-dimensional array. The light may be a plane wave, a spherical wave, a Gaussian beam, etc.

[0038] Reflected light may include a main lobe and a side lobe. When steering the zero-order diffracted light, unwanted side lobes may occur, which may lower the signal-to-noise ratio (SNR). In the optical modulation device (1) of the present embodiment, the first-order diffracted light of the light reflected from the optical modulation element (20) is emitted. Specular reflection light (L3) is the zero-order diffracted light of the incident light (L1) when the geometric phase displacement of a plurality of pixels (MP) is zero. When steering the first-order diffracted light, the ratio of side lobes is lower compared to the zero-order light. Therefore, a good signal-to-noise ratio can be obtained. To this end, the optical modulation device (1) of the present embodiment is equipped with an emission optical system (30) that emits the first-order diffracted light of the incident light (L1) by a meta-grating (MG). The output optical system (30) may include one or more optical elements, such as lenses, for shaping and outputting the first-order diffracted light into a desired shape. In one embodiment, the central axis (31) of the output optical system (30) may be parallel to the optical axis of the first-order diffracted light (L3) when the displacement of the meta-grating (MG) is zero. In one embodiment, as shown in FIG. 1, the central axis (31) of the output optical system (30) may coincide with the optical axis of the first-order diffracted light (L3) when the displacement of the meta-grating (MG) is zero. That is, the angle of incidence of the incident light (L1) with respect to the surface normal vector of the optical modulation element (20) and the angle of the central axis (31) of the output optical system (30) are respectively θ in , θ outLet be denoted as such, and let λ0 be the wavelength of the incident light (L1) and Λ be the period of the meta-grating (MG).

[0039]

[0040] It satisfies the following. The driving signal is patterned, and the period of the meta-grating (MG) is the same as the period of the driving signal pattern applied to a plurality of nano-antennas (NA).

[0041] In the following, the geometric phase of a meta-grating (MG) by a periodic and discrete driving signal applied to a plurality of nano-antennas (NA) is described.

[0042] Let L be the number of pixels (MP) (L is a positive integer), M be the number of antenna groups (NA) within each pixel (MP) (M is a positive integer), and N be the number of nano-antennas (NA) within each antenna group (NA) (N is a positive integer). Let A be the n-th (n=1, 2, ..., N)-th nano-antenna (NA) of the m-th (m=1, 2, ..., M)-th antenna group (NA) of the l-th (l=1, 2, ..., L)-th pixel (MP). lmn It is called, and A lmn R is the intensity of transmission / reflection / scattering lmn It is called. At this time, R lmn It can be determined as shown in the equation (1) below.

[0043] ...Equation (1)

[0044] Here, d=1, 2, ..., N, and mod is the modulo operator, so a mod b is the remainder of a divided by b.

[0045] At each pixel (MP), two different antenna groups (AG) have the same intensity distribution of reflection / transmission / scattering. That is,

[0046] ...Essence(2)

[0047] am.

[0048] In this case, the apparent displacement (effective diaplacement) x of the l-th pixel (MP) l It is equal to the equation (3) below. The phase φ of the l-th pixel (MP) l It is as shown in the equation (4) below.

[0049] ...Essence(3)

[0050] ...Essence(4)

[0051] Therefore, the phase of each pixel (MP) can be controlled by adjusting d, and the smallest phase that can be expressed in each pixel (MP) is 0 degrees when d=1, and the largest phase is as in Equation (5).

[0052] ...Essence(5)

[0053] Referring again to Fig. 2, we examine the apparent displacement of the meta-grating (MG) caused by periodic and discrete driving signals. In Fig. 2, L=1, M=2, and N=4. The nano-antenna (NA) is schematically illustrated. The solid pattern nano-antenna (NA) has strong optical intensity, so R lmn This represents the case where 1 is used, and since the plain nano-antenna (NA) has strong optical intensity, R lmn This indicates the case where it is 0.

[0054] (A) in FIG. 2 is the case where d=1. In Equation (1), R 1,1,1 Calculating (1), nd=1-1=0 and 0 mod 4 = 0 < 4 / 2 = 2. Therefore, R 1,1,1 (1)=1. R in the same way 1,1,2 (1), R 1,1,3 (1), R 1,1,4 If we find (1), R 1,1,2 (1)=1, R 1,1,3 (1)=0, R 1,1,4 (1)=0. Since the optical intensity distribution of the same antenna group (AG) is identical, R 1,2,1 (1)=1, R 1,2,2 (1)=1, R1,2,3 (1)=0, R 1,2,4 (1)=0. Summarizing this result, for the case where d=1, [R 1,1,1 , R 1,1,2 , R 1,1,3 , R 1,1,4 , R 1,2,1 , R 1,2,2 , R 1,2,3 , R 1,2,4 ]=[1,1,0,0,1,1,0,0]. When the optical intensity of the nano-antenna (NA) is periodically strong and weak, it appears as if a grating exists. This is called a meta-grating (MG) or apparent grating, and the period (Λ) of the meta-grating (MG) is equal to the period of the antenna group (AG). As shown in (A) of Figure 2, the displacement of (Λ) is defined as 0 based on the fact that among the four nano-antennas (NA) inside the meta-grating (MG), the two on the left have strong optical intensity and the two on the right have weak optical intensity.

[0055] Figure 2 (B) is the case where d=2. Using Equation (1), [R 1,1,1 , R 1,1,2 , R 1,1,3 , R 1,1,4 , R 1,2,1 , R 1,2,2 , R 1,2,3 , R 1,2,4 ]=[0,1,1,0,0,1,1,0]. Therefore, the effect of the meta-lattice (MG) being displaced by Λ / 4 is realized. (C) in FIG. 2 is the case where d=3. Using Equation (1), [R 1,1,1 , R 1,1,2 , R 1,1,3 , R 1,1,4 , R 1,2,1 , R 1,2,2 , R 1,2,3 , R 1,2,4 ]=[0,0,1,1,0,0,1,1], showing the effect of the meta-lattice (MG) being shifted by Λ / 2. (D) in FIG. 2 is the case where d=4. Using Equation (1), [R 1,1,1 , R1,1,2 , R 1,1,3 , R 1,1,4 , R 1,2,1 , R 1,2,2 , R 1,2,3 , R 1,2,4 ]=[1,0,0,1,1,0,0,1], so the meta-grating (MG) shows the effect of being shifted by 3Λ / 4. Therefore, by applying a driving signal that discretely and periodically changes the optical intensity of a plurality of nano-antennas (NA) to a plurality of nano-antennas (NA), the phase displacement of the meta-grating (MG) defined by Equation (3) can be realized.

[0056] In order to increase the range of expressible phases and to express multiple phase steps, it is necessary to increase the number of nano-antennas (NA) within each pixel (MP), that is, to increase N. Increasing N requires placing more nano-antennas (NA) in each pixel (MP) and more wiring structures to apply driving signals, which increases the complexity of the system. Therefore, an appropriate value for N can be selected depending on the required phase range and the number of phase steps.

[0057] Next, the phase change of diffracted light due to the displacement of the meta-grating (MG) is explained. The plane where the nano-antennae (NA) exist is defined as the plane where Z=0. θ on the XZ plane i Assume that a light wave is incident on a nano-antenna (NA) at an angle of incidence. Assume that there is no change along the y-axis within the pixel (MP). In this case, the wavefunction U of the light wave i (x,y,z) is

[0058]

[0059] .... Here, k is the wavenumber, where k = 2π / λ0, λ0 is the wavelength of the light wave in free space, and A is the amplitude of the incident wave. The wavefunction U in the plane Z=0 i (x,y,z=0) is,

[0060]

[0061] ... The effective grating has a period Λ. If the wave function derived from the effective grating is expressed as a Fourier series,

[0062]

[0063] is. Here, C p is the p-th order Fourier coefficient, and is given as follows.

[0064] ...Essence (6)

[0065] Also, the p-th order diffraction efficiency, η p ne │C p │ 2 is. The value of the light wave transmitted or reflected by the meta-grating (MG) at the grating plane is

[0066]

[0067] is. Here, θ p is the diffraction angle,

[0068]

[0069] is. The coefficient U of the p-order diffraction component 0,p Is

[0070] ...Essence (7)

[0071] It becomes.

[0072] The meta-lattice (MG) is x l p-order diffraction component U in the case of displacement by . ' 0,p Calculate the p-th Fourier coefficient C when there is displacement. ' p Is,

[0073]

[0074]

[0075] ...Essence(8)

[0076] is. Here, Variable substitution was applied. The integration interval of the above expression is divided into two as follows.

[0077]

[0078] The second term on the right-hand side of the above equation again If you apply variable substitution,

[0079]

[0080] ...Essence(9)

[0081] It becomes.

[0082] Meanwhile, since the lattice function g(x) is a periodic function with period Λ,

[0083] is,

[0084] By Euler's formula

[0085] am.

[0086] Therefore, Equation (9) is

[0087]

[0088]

[0089]

[0090]

[0091] ...Essence(10)

[0092] It becomes. If we substitute Equation (7) and Equation (10) into Equation (8),

[0093]

[0094] Gets.

[0095] Therefore, from Equation (7), the coefficient of the p-th order diffraction component when there is a displacement of d is

[0096]

[0097] It is given as follows. For the first-order diffracted light, i.e., the case where p=1 With that much of a term attached,

[0098]

[0099] become x l Phase change φ proportional to / Λ l ...is obtained. By this, equation (4) is proven.

[0100] Figure 3 shows a simulation environment for explaining the change in the geometric phase of first-order diffracted light due to the displacement of a meta-grating (MG). The refractive index of the medium (M) is 1.0. The refractive index of the grating (G) is 1.2, and the dielectric constant is 1.44. The grating (G) is a rectangular grating with a width of 500 nm and a height of 1000 nm, and the period is 1000 nm. Simulations are performed for light waves having two polarizations: TM (transverse magnetic) and TE (transverse electric). The incident angle of the light wave with respect to the vector perpendicular to the grating (G) is 65 degrees. The simulations are performed for a total of six cases with wavelengths ranging from 1200 nm to 1700 nm at 100 nm intervals. Figures 3 (A), (B), and (C) represent cases where the displacements are 0, Λ / 3, and 2Λ / 3, respectively.

[0101] Figure 4 is a graph showing the simulation results based on the simulation environment of Figure 3, illustrating the change in the geometric phase of the first-order diffracted light according to the ratio of displacement to the period (Λ). In Figure 4, 'a' on the horizontal axis represents the ratio of displacement to the period (Λ). That is, x l = aΛ. The vertical axis is the geometric phase (φ) of the first-order diffracted light. Referring to Fig. 4, it can be seen that the phase of the first-order diffracted light changes in proportion to the displacement over a wide wavelength range.

[0102] In phase arrays, the range of phases that can be represented by each pixel (MP) must be wide, and the amplitude must be uniform while changing the phase. This is because if the amplitude changes as the phase is adjusted, the generated light wave may produce unwanted side lobes in addition to the main lobe, which can lead to a decrease in the signal-to-noise ratio (SNR).

[0103] Figure 5 is a graph showing the simulation results based on the simulation environment of Figure 3, illustrating the change in amplitude of the first-order diffracted light according to the ratio of displacement to the period (Λ). In Figure 5, 'a' on the horizontal axis represents the ratio of displacement to the period (Λ). That is, x l = aΛ. The vertical axis represents the amplitude of the first-order diffracted light. Referring to Fig. 5, it can be seen that the amplitude of the first-order diffracted light remains constant even when the displacement changes over a wide wavelength band. From this, it can be seen that steering the first-order diffracted light can reduce photometry and thus obtain an excellent signal-to-noise ratio.

[0104] As described above, when a periodic and discrete driving signal is applied to a plurality of nano-antennas (NA) so that the optical intensity, i.e., the intensity of transmission / reflection / scattering, changes periodically, the optical intensity of the plurality of nano-antennas (NA) has the effect of having an apparent periodic structure. This is called a meta-grating or apparent grating. When the positions of the ridges and grooves of the meta-grating are moved, an apparent displacement occurs. The first-order diffracted light has a geometric phase corresponding to 2π times the value obtained by dividing the apparent displacement by the period (Λ) of the meta-grating (MG). Therefore, as the apparent displacement of the meta-grating (MG) is controlled, the phase of the pixel (MP) having the meta-grating (MG) changes. Since the amplitude is maintained constant while the geometric phase of the first-order diffracted light is changed, a light modulation device (1) capable of phase-only-modulation can be realized.

[0105] The optical modulation element (20) may have various structures. FIG. 6 is a schematic cross-sectional view of one embodiment of the optical modulation element (20). Referring to FIG. 6, the optical modulation element (20) may include a reflector (211), an active layer (212) positioned between the reflector (211) and a plurality of nano antennas (NA), and whose optical properties change according to a driving signal. An insulating layer may be disposed between the reflector (211) and the active layer (212), and between the active layer (212) and the plurality of nano antennas (NA). The optical modulation element (20) of the embodiment shown in FIG. 6 has a first insulating layer (213) disposed between the reflector (211) and the active layer (212), and a second insulating layer (214) disposed between the active layer (212) and the plurality of nano antennas (NA).

[0106] The reflector (211) may be a back reflector electrode placed below the active layer (212). That is, the reflector (211) can perform the function of an electrode while simultaneously serving to reflect light. The reflector (211) may be optically coupled with a nano antenna (NA), and light may be reflected by the optical interaction between the nano antenna (NA) and the reflector (211). The reflector (211) may be formed of a certain conductor, such as a metal. For example, the reflector (211) may include at least one metal selected from the group consisting of Cu, Al, Ni, Fe, Co, Zn, Ti, Ru, Rh, Pd, Pt, Os, Ir, Ag, Au, etc., and may also include an alloy having at least one of these. Alternatively, the reflector (100) may include a thin film in which metal nanoparticles such as Ag or Au are dispersed, a carbon nanostructure such as graphene or CNT (carbon nanotube), a conductive polymer such as PEDOT (poly(3,4-ethylenedioxythiophene)), PPy (polypyrrole), or P3HT (poly(3-hexylthiophene)), or a conductive oxide.

[0107] A nano antenna (NA) is a nanostructure antenna for light that captures energy by converting light of a specific wavelength (or frequency) (including incident light, visible and invisible electromagnetic waves) into a form of localized surface plasmon resonance. The nano antenna (NA) may be a conductive pattern (e.g., a metal pattern). The conductive pattern may be in contact with a non-conductive layer (e.g., a dielectric layer). Plasmon resonance may occur at the interface between the conductive pattern and the non-conductive layer (e.g., a dielectric layer). In this case, the non-conductive layer (e.g., a dielectric layer) may be a second insulating layer (214) and may be a layer separate from the second insulating layer (214). For convenience, the conductive pattern itself will be considered as the nano antenna (N10) in the following description. Interfaces where surface plasmon resonance occurs, such as the interface between a conductive layer pattern and a non-conductive layer (e.g., a dielectric layer), can be collectively referred to as "meta-surfaces" or "meta-structures."

[0108] Figure 7 shows examples of planar shapes of nano-antennas (NA). As illustrated in Figure 7, nano-antennas (NA) can have various planar shapes, such as square, rectangular, circular, donut-shaped, or cross-shaped. Nano-antennas (NA) can have sub-wavelength dimensions. Here, sub-wavelength refers to a dimension smaller than the operating wavelength of the nano-antenna (NA). At least one of the dimensions forming the shape of the nano-antenna (NA), such as thickness, width, height, or the spacing between nano-antennas (NA), may have sub-wavelength dimensions. The resonant wavelength may vary depending on the shape or dimensions of the nano-antenna (NA).

[0109] The nano antenna (NA) may be formed from a highly conductive metallic material capable of generating surface plasmon excitation. For example, at least one metal selected from the group consisting of Cu, Al, Ni, Fe, Co, Zn, Ti, Ru, Rh, Pd, Pt, Os, Ir, Ag, Au, etc. may be employed, or it may be made of an alloy containing at least one of these. Alternatively, the nano antenna (NA) may include a thin film in which metal nanoparticles such as Ag or Au are dispersed, carbon nanostructures such as graphene or CNT (carbon nanotube), conductive polymers such as PEDOT (poly(3,4-ethylenedioxythiophene)), PPy (polypyrrole), or P3HT (poly(3-hexylthiophene)), or conductive oxides. The nano antenna (NA) and the reflector (211) may be made of different metals. The nano antenna (NA) may also be a dielectric antenna.

[0110] The active layer (212) may be a layer whose physical properties change according to its electrical conditions. Depending on the electrical conditions associated with the active layer (212) and its surrounding region, the permittivity or refractive index of the active layer (212) may change. The change in the permittivity of the active layer (212) may be due to a change in the charge concentration (charge density) of the region(s) within the active layer (212). In other words, the permittivity of the active layer (212) may change due to a change in the charge concentration of the region(s) within the active layer (212). The permittivity of the active layer (212) may change depending on the electric field or voltage applied to the active layer (212). The active layer (212) may include, for example, a semiconductor, an oxide, a nitride, or a liquid crystal. The active layer (212) may include a transparent conductive oxide (TCO) such as ITO (indium tin oxide), IZO (indium zinc oxide), AZO (aluminum zinc oxide), GZO (gallium zinc oxide), AGZO (aluminum gallium zinc oxide), or GIZO (gallium indium zinc oxide). The active layer (212) may include a transition metal nitride (TMN) such as TiN, ZrN, HfN, or TaN, a phase transition material, graphene, a transition metal dichalcogenide, or a two-dimensional material. In addition, it may include an electro-optic (EO) material in which the effective dielectric constant changes when an electrical signal is applied. The above electro-optical material may include, for example, crystalline materials such as LiNbO3, LiTaO3, KTN (potassium tantalate niobate), and PZT (lead zirconate titanate), or may include various polymers having electro-optical properties.

[0111] The first insulating layer (213) and the second insulating layer (214) may include an insulating material (dielectric material). At least one of the first and second insulating layers (213)(214) may include at least one of an insulating silicon compound and an insulating metal compound. The insulating silicon compound may include, for example, silicon oxide (SiOx), silicon nitride (SixNy), silicon oxynitride (SiON), etc., and the insulating metal compound may include, for example, aluminum oxide (Al2O3), hafnium oxide (HfO), zirconium oxide (ZrO), hafnium silicon oxide (HfSiO), etc. The first insulating layer (213) and the second insulating layer (214) may be formed of the same material or may have different material compositions.

[0112] The active layer (212) can be electrically insulated from the reflector (211) by the first insulating layer (213), and the active layer (212) can be electrically insulated from the nano antenna (NA) by the second insulating layer (214). Depending on the voltage (driving signal) applied between the reflector (211) and the active layer (212), the charge concentration in the first boundary region of the active layer (212) with the first insulating layer (213) can be changed. Additionally, depending on the voltage (driving signal) applied between the active layer (212) and the nano antenna (NA), the charge concentration in the second boundary region of the active layer (212) with the second insulating layer (214) can be changed.

[0113] Each of the first boundary region and the second boundary region can be divided into a plurality of unit regions corresponding to a plurality of nano antennas (NA), and depending on the voltage, it can become a charge accumulation region or a charge depletion region. If the voltage applied to the nano antenna (NA) is higher than the voltage applied to the active layer (212), a charge accumulation region may be formed on the upper part of the active layer (212). If the voltage applied to the nano antenna (NA) is lower than the voltage applied to the active layer (212), a charge depletion region may be formed on the upper part of the active layer (212). If the voltage applied to the reflector (211) is higher than the voltage applied to the active layer (212), a charge accumulation region may be formed on the lower part of the active layer (212). When the voltage applied to the reflector (211) is lower than the voltage applied to the active layer (212), a charge depletion region may be formed in the lower part of the active layer (212). As a charge accumulation region and / or a charge depletion region are formed in the active layer (212), the reflection characteristics of the optical modulation element (20) can be controlled. Accordingly, the aforementioned meta-grating (MG) can be formed, and by appropriately arranging the geometric phases of a plurality of pixels (MP), the direction of the first-order diffracted light can be controlled to steer the beam.

[0114] In one embodiment, the optical modulation element (20) may be implemented by a plurality of nano antennas (NA) having a Fabry-Perot resonant structure. FIG. 8 shows various embodiments of nano antennas (NA) having a Fabry-Perot resonant structure. Referring to FIG. 8, the nano antenna (NA) may include a first reflective structure (221), a cavity layer (222) provided on the first reflective structure (221), and a second reflective structure (223) provided on the cavity layer (222).

[0115] As an example, as illustrated in (A) and (B) of FIG. 8, the first reflective structure (221) and the second reflective structure (223) may both be distributed Bragg reflectors (DBR) in which materials with different refractive indices are alternately stacked. As an example, as illustrated in (C) of FIG. 8, the first reflective structure (221) may be a distributed Bragg reflector (DBR), and the second reflective structure (223) may be a high contrast grating (HCG) in which a column, disk, or grating structure with a high refractive index is surrounded by a medium with a low refractive index. As an example, as illustrated in (D) of FIG. 8, the first reflective structure (221) may be a high contrast grating (HCG), and the second reflective structure (223) may be a distributed Bragg reflector (DBR). As an example, as shown in (E) of FIG. 8, both the first reflective structure (221) and the second reflective structure (223) may be high contrast grating reflectors (HCG).

[0116] One of the first reflective structure (221), the cavity layer (222), and the second reflective structure (223) may be an active layer in which optical properties, such as refractive index and dielectric flux, are changed by a driving signal. The driving signal may be, for example, a voltage signal, or a heating signal that applies heat to the corresponding component. For example, the cavity layer (222) may be an active layer. In this case, the cavity layer (222) may be formed of the same material as the aforementioned active layer (Fig. 6: 212). At least one of the layers forming the first reflective structure (221) or the second reflective structure (223) may be an active layer in which optical properties are changed by a driving signal. For example, at least one layer of the first reflective structure (221) may be an electro-optical material layer comprising an electro-optical (EO) material in which the effective dielectric flux changes when an electrical signal is applied. Accordingly, when power is applied from an external power source, the refractive index of the electro-optical material layer of the first reflective structure (221) changes, and the phase of the light resonating between the first reflective structure (221) and the second reflective structure (223) changes.

[0117] Depending on the structure / shape and arrangement method of the nano antenna (NA), the resonant wavelength, resonant wavelength width, resonant polarization characteristics, resonant angle, reflection / transmission / scattering characteristics, etc., may vary. Therefore, by controlling the structure / shape and arrangement method of the nano antenna (NA), an optical modulation device (20) having characteristics suitable for the purpose can be manufactured. By using the optical modulation device (20) according to the embodiments, a device for steering a beam in a predetermined direction can be implemented.

[0118] FIG. 9 is a schematic diagram of one embodiment of an optical modulation element (20). The optical modulation element (20) shown in FIG. 9 has the structure shown in FIG. 6, and the lower reflector (211) is formed of Au, the active layer (212) is formed of ITO, the first insulating layer (214) is formed of oxide, and the nano antenna (NA) is formed of Au. The thickness of the active layer (212) may be 10 nm, and the thickness of the lower reflector (211) may be semi-infinite. A driving signal is applied between the active layer (212) and the nano antenna (NA). The active layer (212) is a common electrode, and an individual driving signal is applied to the nano antenna (NA).

[0119] One pixel (MP) has one antenna group (AG), and one antenna group (AG) has six nano-antennas (NA). That is, M=1 and N=6. The period of the nano-antenna (NA) is 400 nm, the width is 200 nm, and the thickness is 20 nm. The period of the antenna group (AG) is 400 nm × 6 = 2400 nm. The period of the pixel (MP) is 2400 nm.

[0120] FIG. 10 shows the results of simulating the reflectance spectrum of a nano antenna (NA) according to one embodiment of the optical modulation element (20) illustrated in FIG. 9. 0V is applied to the active layer (212) and a positive voltage (V) is applied to the nano antenna (NA). a When ) is applied, the concentration of free electrons increases in the boundary region between the active layer (212) and the second insulating layer (214), resulting in a charge accumulation state (Fig. 9: ACC). As a result, the reflectance becomes blue-shifted, as indicated by BS in Fig. 10. Conversely, when a negative voltage (V) is applied to the nano-antenna (NA), dWhen the active layer (212) and the second insulating layer (214) are applied, the concentration of free electrons decreases in the boundary region between the active layer (212) and the second insulating layer (214), resulting in a charge depletion state (Fig. 9: DEP). As a result, the reflectance becomes red-shifted as indicated by RS in Fig. 10. In Fig. 10, when a light source with a wavelength of 1500 nm is incident on the optical modulation element (20) at an angle of 40 degrees, the reflectance of the nano antenna (NA) is 38% in the charge accumulation state and 22% in the charge depletion state. That is, a contrast of 16%p, which is the difference in reflectance, can be obtained.

[0121] FIG. 11 shows the results of simulating the wavelength-dependent phase (φ) according to the discrete displacement of the meta-grating (MG) according to one embodiment of the optical modulation element (20) illustrated in FIG. 9. The graph in FIG. 11 shows the driving signals (V1, V2, V3, V4, V5, V6) applied to the six nano-antennas (NA) when d=1 = (V a , V a , V a , V d , V d , V d This is the geometric phase (φ) of the first-order diffracted light when the displacement of the apparent grating is discretely increased (d=2, 3, 4, 5, 6) with respect to ). The driving signal applied to the six nano-antennas (NA) is discretely varied as follows. V a is the voltage that forms the charge accumulation region, V d represents the voltage that forms the charge depletion region.

[0122] d=1, (V1, V2, V3, V4, V5, V6)=(V a , V a , V a , V d , V d , V d )

[0123] d=2, (V1, V2, V3, V4, V5, V6)=(V d , V a , V a, V a , V d , V d )

[0124] d=3, (V1, V2, V3, V4, V5, V6)=(V d , V d , V a , V a , V a , V d )

[0125] d=4, (V1, V2, V3, V4, V5, V6)=(V d , V d , V d , V a , V a , V a )

[0126] d=5, (V1, V2, V3, V4, V5, V6)=(V a , V d , V d , V d , V a , V a )

[0127] d=6, (V1, V2, V3, V4, V5, V6)=(V a , V a , V d , V d , V d , V a )

[0128] Referring to FIG. 11, the geometric phase (φ) has values ​​of 0, 60, 120, 180, 240, and 360 degrees depending on the displacement. Such geometric phase (φ) values ​​appear commonly from wavelengths of 1000 nm to 180 nm.

[0129] FIG. 12 shows the results of simulating the intensity of the incident light of the first-order diffracted light according to the discrete displacement of the meta-grating (MG) according to one embodiment of the optical modulation element (20) shown in FIG. 9. Referring to FIG. 12, as the displacement of the meta-grating (MG) is discretely increased, the ratio (%) of the intensity of the first-order diffracted light wave to the intensity of the incident light wave is shown for each wavelength. It shows an efficiency of about 5% near about 1500 nm. It has the advantage that the efficiency does not change when the displacement is changed for a fixed wavelength. The efficiency value may vary depending on the wavelength, because the difference in reflectance (contrast) of the nano-antenna (NA) constituting the meta-grating (MG) shows a difference as shown in FIG. 10.

[0130] FIGS. 13 and FIGS. 14 are schematic diagrams of an embodiment of an optical modulation element (20), FIG. 13 shows a case where there is no relative phase difference between a plurality of pixels (MP), and FIG. 14 shows a case where the beam is steered by a relative phase difference between a plurality of pixels (MP). The optical modulation element (20) shown in FIGS. 13 and FIG. 14 has the structure shown in FIG. 6, and the lower reflector (211) is formed of Au, the active layer (212) is formed of ITO, the first insulating layer (214) is formed of oxide, and the nano antenna (NA) is formed of Au. The thickness of the active layer (212) is 5 nm, and the doping concentration is 5 × 10⁻⁶ 20 / cm 3The thickness of the second insulating layer (214) is 10 nm, and the refractive index is 2.0. The thickness of the lower reflector (211) is semi-infinite. A driving signal is applied between the active layer (212) and the nano antenna (NA). The active layer (212) is a common electrode, and individual driving signals are applied to the nano antenna (NA). Two pixels (MP1) (MP2) are arranged in one dimension. Each of the two pixels (MP1) (MP2) has two antenna groups (AG1) (AG2), and each antenna group (AG1) (AG2) has four nano antennas (NA). That is, L=2, M=2, N=4. The length of the nano antenna (NA) is 210 nm, the thickness is 50 nm, and the period is 330 nm. The period (Λ) of the antenna group (AG) is 330 nm × 4 = 1320 nm. The period of the pixel (MP) is 1320nm × 2 = 2640nm.

[0131] In the case of Fig. 13, an arbitrary nanoantenna A lmn Driving signal V applied to lmn It becomes a relationship that satisfies the following conditional expression.

[0132]

[0133] That is, the driving signal patterns of pixels (MP1) and (MP2) are identical, and the driving signal patterns are as follows.

[0134] (V 111 , V 112 , V 113 , V 114 ) = (V a , V a , V d , V d )

[0135] (V 121 , V 122 , V 123 , V 124 ) = (V a , V a , V d , V d )

[0136] (V 211, V 212 , V 213 , V 214 ) = (V a , V a , V d , V d )

[0137] (V 221 , V 222 , V 223 , V 224 ) = (V a , V a , V d , V d )

[0138] Therefore, the geometric phase according to the displacement of the meta-grating (MG) is the same at pixels (MP1) and (MP2). The emission angle of the first-order diffracted light is

[0139]

[0140] It can be calculated by Λ, which is the period of the driving signal pattern, i.e., the period of the antenna group (AG), 1320 nm. When incident light of wavelength 1550 nm and TM polarization is incident on the optical modulation element (20) at an incident angle of 60 degrees, the exit angle of the first-order diffracted light is -17.8 degrees. FIG. 15 shows the first-order diffracted light formed according to one embodiment of the optical modulation element (20) shown in FIG. 13. As shown in FIG. 15, it can be seen that the first-order diffracted light with very small photometric is formed at an exit angle of about -17.8 degrees.

[0141] In the case of Fig. 14, pixels (MP1) and (MP2) have a geometric phase difference of 180 degrees. For this drive, an arbitrary nano-antenna A lmn Driving signal V applied to lmn It becomes a relationship that satisfies the following conditional expression.

[0142]

[0143] That is, the driving signal pattern of pixels (MP1)(MP2) is as follows.

[0144] (V 111 , V112 , V 113 , V 114 ) = (V a , V a , V d , V d )

[0145] (V 121 , V 122 , V 123 , V 124 ) = (V a , V a , V d , V d )

[0146] (V 211 , V 212 , V 213 , V 214 ) = (V d , V d ,V a , V a )

[0147] (V 221 , V 222 , V 223 , V 224 ) = (V d , V d ,V a , V a )

[0148] Therefore, the geometric phase of pixel (MP1) is 0 degrees, and the geometric phase of pixel (MP2) is 180 degrees. As a result, the two pixels (MP1) and (MP2) with 0 and 180 degrees form a superpixel. The period of the superpixel is twice the period of each pixel (MP1) and (MP2), and since each pixel (MP1) and (MP2) contains two antenna groups (AG1) and (AG2), the period of the superpixel (Λ sp ) becomes four times the period (Λ) of antenna groups (AG1)(AG2). The emission angle of the first-order diffracted light is

[0149]

[0150] It can be calculated by... When incident light of TM polarization with a period of 1320 nm and a wavelength of 1550 nm is incident on the optical modulation element (20) at an incident angle of 60 degrees, the exit angle of the first-order diffracted light is -0.84 degrees. FIG. 16 shows the first-order diffracted light formed according to one embodiment of the optical modulation element (20) shown in FIG. 14. As shown in FIG. 16, it can be seen that first-order diffracted light with very small photometric is formed at an exit angle of about -0.84 degrees.

[0151] Multiple pixels (MP) may be arranged in two dimensions. FIG. 17 shows an example of a structure in which multiple pixels (MP) are arranged in two dimensions in a Cartesian coordinate system. In FIG. 17, (A) shows a two-dimensional arrangement of multiple pixels (MP). In FIG. 17, (B) shows the phase (φ) of a meta-grid (MG) corresponding to each of the multiple pixels (MP).

[0152] Referring to FIG. 17, each pixel (MP) has two antenna groups (AG), and each antenna group (AG) has four nano-antennas (NA). When a plurality of nano-antennas (NA) of each pixel (MP) apply a periodic and discrete driving signal, an apparent grid is formed at each pixel (MP). In FIG. 17 (A), the nano-antennas (NA) indicated by solid patterns represent a state with strong optical intensity, and the nano-antennas (NA) indicated by plain patterns represent a state with weak optical intensity.

[0153] Incident light (L1) can be incident on multiple pixels (MP) at an incident angle θ with respect to the normal (Ln) within an incident plane (S1) perpendicular to multiple pixels (MP). If the phases of the meta-gratings (MG) of all pixels (MP) are the same, the first-order diffracted light is emitted in the direction of the normal (Ln). If there is a phase gradient between neighboring pixels (MP), two-dimensional beam steering is possible. Therefore, by appropriately arranging the phases of the meta-gratings (MG) of multiple pixels (MP), two-dimensionally steered first-order diffracted light (L2) can be obtained that is emitted along an exit plane (S2) having an angle with respect to the incident plane (S1).

[0154] In this embodiment, a driving signal is applied so that the meta-grids (MG) of the four pixels (MP) belonging to each row (raw) have geometric phase differences of 0, 90, 180, and 360 degrees, respectively, and the meta-grids (MG) of the four pixels (MP) belonging to each column have geometric phase differences of 0, 90, 180, and 360 degrees, respectively. That is, a driving signal is applied so that each pixel (MP) has a phase difference of 90 degrees with respect to its neighboring pixel (MP). By doing so, two-dimensional beam steering is possible.

[0155] In FIG. 17, a plurality of pixels (MP) having a two-dimensional array structure in an orthogonal coordinate system are exemplified, but the plurality of pixels (MP) can be arranged in various coordinate systems such as polar coordinates and hexagonal coordinates.

[0156] The pattern of the driving signal can have various duty cycles. Accordingly, an apparent grating having various duty cycles can be formed. In the case of the embodiment of the optical modulation element (20) shown in FIG. 9, the duty cycle of the meta-greater (MG) is 50%. Various duty cycles can be implemented by generalizing Equation (1) as follows.

[0157] ...Essence(11)

[0158] Here, C is a criterion, which is N / 2 in Equation (1). The generalized C can have values ​​from 1 to N-1. FIG. 18 shows examples of various duty cycles of a meta-grating (MG). Referring to FIG. 18, the distribution of various C values ​​is shown when M=2, N=4, and d=1. Since N=4, C can have values ​​from 1 to 3. FIG. 18 (A) shows the case where C=1, and the duty cycle of the meta-grating (MG) is 25%. FIG. 18 (B) shows the case where C=2, and the duty cycle of the meta-grating (MG) is 50%. FIG. 18 (C) shows the case where C=1, and the duty cycle of the meta-grating (MG) is 75%. The duty cycle can be appropriately determined to increase the proportion of light emitted in the desired direction and decrease the proportion of light emitted in the undesirable direction.

[0159] According to the embodiments of the optical modulation device (1) described above, the optical intensity of the nano antenna (NA), i.e., the intensity of transmission / reflection / scattering, is individually controlled to form an apparent grating or a meta-greasing (MG), and a displacement is induced in the distribution of the optical intensity of the nano antenna (NA) inside the pixel (MP) so that the higher-order diffraction component of the incident light wave has a geometric phase proportional to the displacement. The optical modulation device (1) of this type can easily control the displacement of the meta-greasing (MG) by digitizing and changing the distribution of the optical intensity of the nano antenna (NA). Therefore, the beam can be steered to various desired angles using a digitized control method. In addition, by steering the first-order diffracted light, the amplitude of the emitted light is maintained constant within the steering range. Therefore, excellent steering light with a low ratio of side lobes can be obtained. Furthermore, the wiring structure for applying a driving signal to a plurality of nano antennas (NA) is simple, and linear voltage-phase response characteristics can be obtained. In addition, since it operates in a so-called all-solid-state without mechanical movement, high-speed operation is possible, and uniform response characteristics can be obtained due to the small dispersion of responsiveness caused by errors in the manufacturing process.

[0160] FIG. 19 is a conceptual diagram for explaining a beam steering device (1000A) as an example of an optical modulation device (1). Referring to FIG. 19, a beam can be steered in a one-dimensional direction using the beam steering device (1000A). That is, the beam can be steered in a first direction (D1) toward a predetermined object (OBJ). The beam steering device (1000A) may employ an optical modulation element (20) comprising a plurality of pixels (MP) arranged in a one-dimensional manner.

[0161] FIG. 20 is a conceptual diagram for explaining a beam steering device (1000B) as an example of an optical modulation device (1). Referring to FIG. 20, a beam can be steered in a two-dimensional direction using the beam steering device (1000B). That is, the beam can be steered toward a predetermined object (OBJ) according to a first direction (D1) and a second direction (D2) perpendicular thereto. An optical modulation element (20) including a plurality of pixels (MP) arranged two-dimensionally may be employed in the beam steering device (1000B). The beam steering device (1000A, 1000B) described with reference to FIG. 19 and FIG. 20 may be a non-mechanical ultrafast beam scanning apparatus.

[0162] FIG. 21 is a block diagram of an example of an optical device (2) employing a light modulation device (1). Referring to FIG. 21, the optical device (2) may include a beam steering unit (1000). The beam steering unit (1000) may include the aforementioned light modulation device (1). The optical device (2) may include a detection unit (2000) for detecting light reflected by a subject (not shown) from light steered by the beam steering unit (1000). The detection unit (2000) may include a plurality of light detection elements and may further include other optical members. Additionally, the optical device (2) may further include a circuit unit (3000) connected to at least one of the beam steering unit (1000) and the detection unit (2000). The circuit unit (3000) may include a calculation unit that acquires and calculates data, and may further include a driving unit and a control unit, etc. Additionally, the circuit section (3000) may further include a power supply section and memory, etc. According to the beam steering section (1000) employing the optical modulation device (1) of the present embodiment, the signal-to-noise ratio of the detection section (2000) can be improved because the first-order diffracted light with reduced side lobes is steered. Furthermore, since there is no mechanical movement for beam steering, high-speed operation is possible and the dispersion of responsiveness is small. Therefore, precise high-speed optical detection is possible.

[0163] Although FIG. 21 illustrates a case where the optical device (2) includes a beam steering unit (1000) and a detection unit (2000) within a single device, the beam steering unit (1000) and the detection unit (2000) may not be provided as a single device but may be provided separately in different devices. Additionally, the circuit unit (3000) may not be connected to the beam steering unit (1000) or the detection unit (2000) via a wired connection but may be connected via wireless communication. Furthermore, the configuration of FIG. 21 may be varied in many ways.

[0164] The optical modulation device (1) according to the embodiment described above can be applied to various optical devices. For example, the optical modulation device (1) can be applied to a LiDAR (Light Detection And Ranging) device. The LiDAR device may be a phase-shift type or a TOF (time-of-flight) type device. The LiDAR device can be applied to autonomous vehicles, flying objects such as drones, mobile devices, small walking means (e.g., bicycles, motorcycles, strollers, boards, etc.), robots, assistive means for people / animals (e.g., canes, helmets, jewelry, clothing, watches, bags, etc.), IoT (Internet of Things) devices / systems, security devices / systems, etc.

[0165] FIGS. 22 and FIGS. 23 are conceptual diagrams showing a case where a LiDAR device including a light modulation device (1) according to one embodiment is applied to a vehicle. FIG. 22 is a side view, and FIG. 23 is a top view. Referring to FIG. 22, a LiDAR device (51) can be applied to a vehicle (50), and information about a subject (60) can be obtained using this. The vehicle (50) may be a car with an autonomous driving function. Using the LiDAR device (51), an object or person, i.e., a subject (60), in the direction in which the vehicle (50) is traveling can be detected. In addition, the distance to the subject (60) can be measured using information such as the time difference between a transmitted signal and a detected signal. In addition, as shown in FIG. 23, information about a nearby subject (61) and a distant subject (62) within the scan range can be obtained.

[0166] The optical modulation device according to various embodiments of the present invention can be applied to various optical devices other than LiDAR. For example, since the optical modulation device according to various embodiments allows for the acquisition of three-dimensional information of space and objects through scanning, it can be applied to 3D image acquisition devices or 3D cameras. In addition, the optical modulation device can be applied to holographic display devices and structured light generating devices. Furthermore, the optical modulation device can be applied to various optical devices such as various beam scanning devices, hologram generating devices, optical coupling devices, variable focus lenses, and depth sensors. Additionally, the optical modulation device can be applied to various fields where "meta-surfaces" or "meta-structures" are utilized. Furthermore, the optical modulation device according to the embodiments of the present invention and the optical device including the same can be applied for various purposes in various optical and electronic device fields.

[0167] The optical modulation device and the optical device including the above-described device have been described with reference to the embodiments illustrated in the drawings, but this is merely illustrative and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the rights is defined in the claims, not in the foregoing description, and all variations within the scope of equivalence should be interpreted as being included in the scope of the rights. Explanation of the symbols

[0168] 1...Optical modulator 2...Optical device 10...Incident optical system 20...Optical modulation element 30...Exit optical system 31...Central axis of the exit optical system 40...Drive signal application unit 211...Lower reflector 212...Active layer 213...First insulating layer 214...Second insulating layer 221...First reflective structure 222...Cavity layer 223...Second reflection structure 1000...Beam steering unit 1000A, 1000B...Beam steering device 2000...Detector unit 3000...Circuit unit NA...Nano Antenna AG...Antenna Group MP...Pixel

Claims

Claim 1 An optical modulation device comprising: an incident optical system; a plurality of nano-antennas forming a meta-grating by a driving signal, wherein the direction of propagation of incident light incident from the incident optical system at a fixed incident angle is changed by utilizing the apparent displacement of the meta-grating according to the driving signal; and an output optical system from which light steered from the optical modulation device is emitted, wherein the output optical system emits first-order diffracted light of the incident light by the meta-grating, wherein the optical modulation device has a plurality of pixels, wherein each of the plurality of pixels includes two or more antenna groups, wherein each of the two or more antenna groups includes a plurality of nano-antennas, wherein the period of the meta-grating is the same as the period of the antenna group, and wherein the driving signal of the same pattern is applied to the two or more antenna groups within the same pixel. Claim 2 In claim 1, the central axis of the emission optical system is a light modulation device parallel to the optical axis of the first-order diffracted light when the displacement of the meta-grating is 0. Claim 3 A light modulation device according to claim 1, wherein the central axis of the emission optical system coincides with the optical axis of the first-order diffracted light when the displacement of the meta-grating is 0. Claim 4 In claim 1, the angle of incidence of the incident light with respect to the surface normal vector of the optical modulator and the angle of the central axis of the emission optical system are each θ in , θ out Let , and let the wavelength of the incident light be λ0 and the period of the meta-grating be Λ, then Optical modulation device satisfying [ ]. Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 In claim 1, let L be the number of the plurality of pixels, M be the number of antenna groups for each of the plurality of pixels, and N be the number of nano-antennas for each antenna group, and let A be the l-th pixel, the m-th antenna group, and the n-th nano-antenna. lmn Let it be denoted as such, and the optical intensity of Almn is R lmn When saying, Here, d=1, 2,..., N, and C is an optical modulator that is any one of 1 to N-1. Claim 9 In claim 1, the plurality of pixels is an optical modulation device having a one-dimensional array structure. Claim 10 In claim 1, the plurality of pixels is an optical modulation device having a two-dimensional array structure. Claim 11 In claim 1, the optical modulation device comprises: a reflector; an active layer positioned between the reflector and the plurality of nano antennas, the optical properties of which change according to the driving signal. Claim 12 In claim 11, the plurality of nano antennas are optical modulation devices that are metal antennas. Claim 13 In claim 11, the plurality of nano antennas are optical modulation devices that are dielectric antennas. Claim 14 In claim 1, each of the plurality of nano antennas comprises a first reflective structure, a cavity layer provided on the first reflective structure, and a second reflective structure provided on the cavity layer, forming an optical modulation device having a Fabry-Perot resonant structure. Claim 15 An incident optical system; an optical modulator having a plurality of pixels, each comprising a plurality of nano antennas, wherein the optical intensity of the plurality of nano antennas changes as a periodic and discrete driving signal is applied to the plurality of nano antennas, thereby changing the propagation direction of incident light incident from the incident optical system at a fixed incident angle; and an output optical system from which light steered by the optical modulator is emitted; wherein the incident angle of the incident light with respect to the surface normal vector of the optical modulator and the angle of the central axis of the output optical system are each θ in , θ out Let be denoted as such, and let the wavelength of the incident light be λ0 and the period of the driving signal be Λ, then An optical modulation device satisfying the following, wherein each of the plurality of pixels includes two or more antenna groups, each of the two or more antenna groups includes a plurality of nano-antennas, the period of the driving signal is the same as the period of the antenna group, and the driving signal of the same pattern is applied to the two or more antenna groups within the same pixel. Claim 16 delete Claim 17 delete Claim 18 In paragraph 15, let L be the number of the plurality of pixels, M be the number of antenna groups for each of the plurality of pixels, and N be the number of nano-antennas for each antenna group, and let A be the l-th pixel, the m-th antenna group, and the n-th nano-antenna. lmn Let it be denoted as such, and the optical intensity of Almn is R lmn When saying, Here, d=1, 2,..., N, and C is an optical modulator that is any one of 1 to N-1. Claim 19 An optical device comprising any one of the optical modulation devices of paragraphs 1 through 4, paragraphs 8 through 15, or paragraph 18. Claim 20 In claim 19, the optical device comprises at least one of a LiDAR device, a three-dimensional image acquisition device, a holographic display device, and a structured light generating device.

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