CN111694170A - Controllable light beam steering gear based on phase-change material - Google Patents

Abstract

A controllable beam diverter based on phase change material, the device comprises a lower electrode arranged laterally, an upper electrode arranged longitudinally, a phase change material layer is formed in the area where the upper electrode and the lower electrode intersect, and a sandwich structure is formed up and down. The light beam is incident from the bottom surface, and after passing through the device, it is output from the surface, and the deflection angle of the output transmitted light beam is controlled by controlling the state of the phase change material. The invention utilizes the upper and lower electrodes of the phase change material to apply electric pulses to the phase change unit, and the electric pulses generate Joule heat through the phase change material to increase the temperature of the phase change region, so that the phase change material can be in a crystalline state, an amorphous state or a mixed state. It can change the output phase of the transmitted light and realize the function of beam steering. The two-dimensional phase change array of the present invention can be flexibly programmed to obtain any output phase distribution, thereby realizing flexible adjustment of the beam deflection angle. Phase-change materials only consume energy when switching states, so the device has no static power dissipation.

Description

Controllable beam diverter based on phase change material

technical field

The present invention is a controllable beam diverter based on phase change material, belonging to the field of integrated optoelectronics.

Background technique

With the development of integrated optoelectronic technology, various optoelectronic devices have been extensively studied. Among them, an important technology is the ability to effectively manipulate light beams. Especially in the fields of space optical communication, holographic image generation, and lidar technology, miniaturized and high-resolution beam steering technology is urgently needed. For the field of integrated optoelectronics, the realization of dynamic control of the characteristic parameters of light at the micro- and nano-scale leads to many challenges.

Traditional beam steering structures are mainly divided into two categories: mechanical and non-mechanical. The beam steering structure based on MEMS technology is a typical representative of the micromechanical steering structure, which has a low manufacturing cost and can provide a faster steering speed than the traditional mechanical motor. However, it also has many problems. On the one hand, the structure uses material deformation to change the relative position between adjacent unit structures to achieve beam deflection, and the driving voltage is high; on the other hand, the structure is sensitive to changes in the environment and susceptible to vibration. , which brings stability problems. The more popular non-mechanical beam steering structure is realized by a sandwich structure in which the active layer is introduced between the upper and lower electrodes. The materials of the active layer are mainly liquid crystal, electro-optic crystal and quantum dot materials; The refractive index can be adjusted to realize the adjustment of the incident beam; however, the adjustment speed of this technology is slow, the power consumption is high, and the resolution is not high.

In the past few years, metamaterials have shown great promise in realizing the effective control of light beams. In the subwavelength-scale microstructure array fabricated by metamaterials, each unit can manipulate the phase, amplitude or polarization characteristics of the incident electromagnetic wave, so as to realize the control of the wavefront of the emitted or transmitted electromagnetic wave. The metasurface beam steering structures reported so far using metamaterials often use passive structures. Once the device is fabricated, its function is fixed, and it is impossible to dynamically adjust the beam. Caltech reported in 2019 a multi-quantum well metasurface prepared from III-V group materials, which uses a multi-quantum well structure of III-V compound semiconductor materials as a resonant unit by applying a DC voltage to the sub-wavelength unit structure. , which can realize continuous adjustment of the amplitude and phase of the metasurface reflected beam. In the experiment, 270% of the relative reflection mode adjustment can be achieved, and the phase adjustment can be from 0° to 70°. However, this structure needs to grow a specific thickness of III-V group materials on the GaAs substrate for many times to form a Bragg reflector layer, and the preparation process is relatively complicated and the cost is high.

Phase change materials have been extensively studied as optical disk storage materials and electrical memory cells. Phase-change materials usually have crystalline and amorphous states, which have distinct electrical and optical properties such as resistivity and refractive index; by applying appropriate thermal, optical, and electrical stimuli, this can be achieved on the ns scale. The mutual conversion of the two states, and even the intermediate states between these two states, and these states can exist stably at room temperature; therefore, phase change materials can be used in the realization of ultrafast, non-volatile and reconfigurable photonic devices. Has a lot of potential. In 2018, C.D.Wright et al. reported a nonvolatile reconfigurable beam-steering device based on phase-change materials, which used simple metal-insulator-metal building blocks to form metasurfaces; the phase-change material was fully protected To prevent oxidation, the metal on the surface is processed into strip antennas of different widths; the phase change material is induced to convert between crystalline and amorphous states by means of laser irradiation. The device operates at a wavelength of 1530–1570 nm and achieves a beam reflectance of 40%. However, the phase change material layer area of the device is large, and it is difficult to achieve a large-area uniform phase change using laser irradiation; in addition, the surface uses an aluminum strip antenna, the device is sensitive to polarization, and the phase change material is amorphized due to excessively high Temperature may cause aluminum to melt.

SUMMARY OF THE INVENTION

Aiming at some deficiencies of the existing beam steering technology, the present invention proposes a controllable beam steering device based on a phase change material. The device uses the upper and lower electrodes of the phase change material to apply electric pulses to the phase change unit, so that the phase change material can It can switch between state, amorphous state and intermediate mixed state, thereby changing the phase of transmitted light and realizing the function of beam steering. The biggest feature of the device is that it can achieve independent access to each phase change unit, freely change the phase distribution of the transmitted light, and realize flexible control of the beam deflection angle. Since phase-change materials are non-volatile in their states, energy is only consumed when states are switched, so the device has no static power consumption.

The technical solution of the present invention is as follows:

A controllable beam diverter based on phase-change material, which is characterized in that a multi-channel horizontally parallel arranged lower electrode and a longitudinally parallel upper electrode are formed on the upper surface of the substrate, and the upper electrode and the lower electrode pass through The isolation layer is isolated, and the phase-change material is filled only in the intersection area to form a phase-change unit, forming a sandwich structure. The light beam is input from the bottom surface of the device and output from the surface after passing through the device. The upper electrode and the lower electrode are used to apply electric pulses to the phase change unit, and Joule heat is generated through the phase change material, which increases the temperature of the phase change material, and realizes the phase change material between the crystalline state, the amorphous state and the intermediate mixed state. The two-dimensional unit array structure of the device can realize independent access to each phase change unit, flexibly control the transmission phase of the beam, and realize the free manipulation of the beam.

The insulating material between the substrate and the upper and lower electrodes may be, but not limited to, silicon dioxide, silicon nitride and other dielectric materials that are transparent to the target wavelength band.

The upper and lower electrode materials can be, but are not limited to, indium tin oxide, graphene and other low-resistance conductive materials that are transparent to the target wavelength band.

The phase-change material of the device can exhibit states of different refractive indices when different electrical pulses are applied, and the phase-change material includes, but is not limited to, transition metal-sulfur compound materials such as GeSbTe, GeTe, GeSe, and SbS.

The technical effect of the present invention is as follows:

The invention uses the upper and lower electrodes of the phase change material to apply electric pulses to the phase change unit, and the electric pulses generate Joule heat through the phase change material to increase the temperature of the phase change area, so that the phase change material can be in a crystalline state, an amorphous state or a mixed state. It can change the output phase of the transmitted light and realize the function of beam steering. The two-dimensional phase change array of the present invention can be flexibly programmed to obtain any output phase distribution, thereby realizing flexible adjustment of the beam deflection angle. Phase-change materials only consume energy when switching states, so the device has no static power dissipation.

Description of drawings

FIG. 1 is a schematic diagram of the controllable beam diverter based on the phase change material of the present invention.

FIG. 2 is a working principle diagram of the controllable beam diverter based on the phase change material of the present invention.

FIG. 3 is the working mechanism of the electric pulse phase change of the controllable beam diverter based on the phase change material of the present invention.

FIG. 4 is the temperature response of the controllable beam diverter based on the phase change material of the present invention under the simulated electric pulse heating of a single phase change unit.

Detailed ways

The embodiments of the present invention are described in detail below: This embodiment is implemented on the premise of the technical solution of the present invention, and provides detailed implementation modes and specific operation processes. It should be pointed out that for those skilled in the art, without departing from the concept of the present invention, several modifications and improvements can be made, which all belong to the protection scope of the present invention.

Please refer to FIG. 1 . FIG. 1 is a schematic structural diagram of a phase-change material-based controllable beam redirector of the present invention. As shown in the figure, a phase-change material-based controllable beam redirector is formed on the upper surface of the substrate 4 The lower electrodes 2 arranged in parallel in the horizontal direction and the upper electrodes 1 arranged in parallel in the vertical direction are separated by the isolation layer 5 between the upper electrodes 1 and the lower electrodes 2, and the phase change unit 3 is formed only by filling the phase change material in the intersection area, A sandwich structure is formed, and the light beam is input from the bottom surface of the device and output from the surface after passing through the device. The upper electrode 1 and the lower electrode 2 are used to apply electric pulses to the phase change unit 3, through the phase change material, Joule heat is generated, the temperature of the phase change material is increased, and the phase change material in the crystalline state, the amorphous state and the intermediate state is realized. The conversion between the mixed states changes the output phase of the transmitted light. The two-dimensional cell array structure of the device can realize independent access to each phase change cell, flexibly control the transmission phase of the beam, and realize the free manipulation of the beam.

Example:

Using silicon dioxide as the substrate, it is mainly composed of three parts: the lower electrode arranged in parallel in the horizontal direction, the phase change material layer in the cross area, and the upper electrode layer arranged in the vertical direction. The upper and lower electrodes are separated by silicon dioxide. First, a layer of ITO is deposited on the silicon dioxide substrate, and electron beam exposure and etching processes are used to form the lower electrodes arranged laterally; then the silicon dioxide layer is deposited and etched to form the through holes of the phase change material; then the phase change material is deposited , the surface is planarized; a layer of ITO is deposited on the surface, and a longitudinally arranged upper electrode is formed by electron beam exposure and etching.

实现对光束的转向。FIG. 2 is a schematic diagram of the working principle of the device structure of the present invention. The beam is incident from below the silicon dioxide substrate, passes through the device, and exits the surface of the device. When the phase change material 3 is in the initial state, the light beam is incident vertically and exits vertically. The upper electrode 1 and the lower electrode 2 apply electrical pulses to the different phase change units one by one, the current passes through the phase change material 3 to generate Joule heat, which increases the temperature of the phase change material 3 and changes the state of the different phase change units, thereby changing the different The refractive index profile of the regional phase change material, so that the output phase of the transmitted light differs between adjacent cells

Realize the steering of the beam.

FIG. 3 is a schematic diagram of the electrical pulse phase transition of the device structure of the present invention. An electrical pulse is applied to the phase change unit of the device, and the current flows through the phase change material layer to generate Joule heat, which increases the temperature of the phase change material. When an electric pulse with a narrow width and a high amplitude is applied to make the maximum temperature of the phase change material exceed the melting temperature, and then rapidly cooled to undergo rapid melting and quenching processes, the phase change material can be transformed from a crystalline state to an amorphous state . In the amorphous state, the phase change material has a low refractive index. When an electrical pulse with a wider width and a lower amplitude is applied, the phase change material can obtain a lower heating temperature. When the temperature of the phase change material exceeds the crystallization threshold temperature and is lower than the melting temperature, the The transition of a phase change material from an amorphous state to a crystalline state. In the crystalline state, phase change materials have a higher refractive index. By controlling the amplitude and number of applied electrical pulses, a mixed state between amorphous and crystalline states can be obtained.

Figure 4 uses Ge ₂ Sb ₂ Te ₅ (GST) as the phase change material, and simulates the temperature response of the phase change structural unit in GST under the action of amorphization and crystallization electric pulses, respectively. It can be seen that when a 9V, 10ns amorphization pulse is applied to the upper and lower electrodes, the maximum temperature of the GST region can exceed the amorphization threshold temperature, realizing the transition of GST from crystalline to amorphous; when 7V is applied to the upper and lower electrodes, When the 150ns crystallization pulse is used, the maximum temperature of the GST region is between the crystallization threshold temperature and the amorphization threshold temperature, which can realize the transition of GST from amorphous state to crystalline state.

Experiments show that the invention uses the upper and lower electrodes of the phase change material to apply electric pulses to the phase change unit, and the electric pulses pass through the phase change material to generate Joule heat to increase the temperature of the phase change area, and realize the phase change material in the crystalline state and the amorphous state. Or the transformation between the mixed states, so as to change the output phase of the transmitted light and realize the function of beam steering. The two-dimensional phase change array of the present invention can be flexibly programmed to obtain any output phase distribution, thereby realizing flexible adjustment of the beam deflection angle. Phase change materials only consume energy when switching states, so the device has no static power dissipation.

The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited to this, any person familiar with the technology can easily think of transformation or replacement within the technical scope disclosed by the present invention, All should be included within the scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (5)

1. A controllable beam diverter based on a phase-change material, characterized in that a lower electrode (2) arranged in parallel in a multi-path transverse direction and an upper electrode (1) arranged in parallel in a longitudinal direction are formed on the upper surface of the substrate (4), The upper electrode (1) and the lower electrode (2) are separated by an isolation layer (5), and the intersection region of the upper electrode (1) and the lower electrode (2) is filled with a phase change material to form a phase change unit (3), forming a sandwich structure; An electric pulse is applied to the phase change unit (3) through the upper electrode (1) and the lower electrode (2), and Joule heat is generated through the phase change material, so that the temperature of the phase change material is increased, so that the phase change material in the crystalline state is realized. , amorphous and intermediate mixed states, thereby changing the output phase of the transmitted light. 2. The controllable beam diverter based on phase change material according to claim 1, wherein the material of the silicon substrate (4) and the isolation layer (5) is silicon, silicon dioxide, nitride Silicon, silicon carbide and other dielectric materials that are transparent to the target wavelength band. 3. The controllable beam diverter based on a phase change material according to claim 1, wherein the material of the upper electrode (1) and the lower electrode (2) is indium tin oxide, graphene, etc. Band transparent low resistance conductive material. 4. The controllable beam diverter based on a phase-change material according to claim 1, wherein the phase-change material can exhibit different refractive index states under the application of different electrical pulses, and the phase-change material is GeSbTe, GeTe , GeSe, SbS and other transition metal sulfur compounds. 5 . The controllable beam diverter based on phase change material according to claim 1 , wherein the light beam is input from the bottom surface of the device, and is output from the surface after passing through the device. The two-dimensional cell array of the device The structure can realize independent access to each phase change unit, flexibly control the transmission phase of the beam, and realize the free manipulation of the beam.

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