CN115167011A - Phase amplitude decoupling modulator for complex amplitude modulation - Google Patents
Phase amplitude decoupling modulator for complex amplitude modulation Download PDFInfo
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
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- G—PHYSICS
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
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Abstract
The invention discloses a phase amplitude decoupling modulator for complex amplitude modulation, which at least comprises a first modulation layer, a second modulation layer and a phase amplitude decoupling modulator, wherein the phase amplitude decoupling modulator comprises a controller, a first excitation module and a second excitation module; the first excitation module inputs independent excitation signals to the first modulation pixel unit; the second excitation module inputs independent excitation signals to the second modulation pixel unit. The invention breaks through the advantages of low amplitude and phase modulation level, mutual constraint of phase amplitude modulation effect, complex preparation process and the like, and can respectively realize independent and multi-level amplitude modulation and complex amplitude complete information reconstruction of phase modulation, thereby improving the performances of resolution, amplitude distribution uniformity, precision, signal-to-noise ratio and the like, and completing the dynamic switching of images and the improvement of reconstructed image quality.
Description
Technical Field
The invention relates to the technical field of optics, in particular to a phase amplitude decoupling modulator for complex amplitude modulation.
Background
The complex amplitude modulation technology records and reconstructs all wave information of a certain target and an object by modulating the complex amplitude information of light waves, has important application prospect in the fields of holographic technology, spatial light modulator and the like, and is widely applied to 3D display, interferometry, military reconnaissance monitoring, information storage, medical detection and other defense military and real life.
The static complex amplitude modulation technology is a common complex amplitude modulation technology in the prior art, the modulation effect of the static complex amplitude modulation technology is fixed when a modulation device structure is generated, the modulation effect cannot be adjusted, and only a determined reconstructed image can be generated. The dynamic complex amplitude modulation can dynamically adjust the light wave information and output a dynamically changed sequence image on the premise of not changing the structure of the device. In the prior art, dynamic complex amplitude modulation is based on signal excitation on a modulation unit structure, so that the optical properties of the modulation unit structure are changed, and thus, the amplitude value and the phase value of an optical wave are modulated.
Due to the fact that the effects of amplitude modulation and phase modulation are mutually limited, a dynamic complex amplitude modulation unit (single-factor dynamic modulation) excited and modulated by one signal cannot obtain the required amplitude and phase combination, namely, cannot obtain the required complex amplitude value.
Optimizing the modulation unit structure to achieve dynamic modulation is a major research direction of researchers at present. For example, by increasing the size of the dynamic complex amplitude modulation unit, pure amplitude dynamic modulation (the amplitude modulation amount changes with the intensity of the excitation signal while the phase shift amount remains unchanged) or pure phase dynamic modulation (the phase modulation amount changes with the intensity of the excitation signal while the amplitude attenuation amount remains unchanged) can be realized to some extent, and the multi-order amplitude and phase change of the unit structure can be realized, so that the complex amplitude value of the optical wave can be modulated more finely. However, the increase of the cell size leads to the reduction of the resolution of the whole device, which is contrary to the trend of high resolution and high precision of the complex amplitude modulation technology.
After the first modulation layer carries out pixelization modulation on the light wave phase, the transmission direction of light waves modulated by different units is changed, and the problem of light information crosstalk between two-level modulation layers is inevitably generated. In order to solve the problem, in the prior art, incident light is limited to be parallel light, and primary modulation is pure amplitude modulation, only the intensity of light is changed, and the phase of the light is not changed, that is, the transmission direction of the light beam after the pure amplitude modulation is unchanged, and emergent light is still the modulation effect of the parallel light after the modulation of an amplitude modulator. However, the pure amplitude modulation unit has complex design, large unit size and high manufacturing cost, and the feasibility of the scheme is greatly reduced.
Disclosure of Invention
The invention aims to provide a phase amplitude decoupling modulator for complex amplitude modulation, which does not lean on the dynamic modulation effect of a modulation unit, adopts two modulation units, combines two independent signal excitations which are easy to control, and greatly improves the controllability of complex amplitude modulation through second-order dynamic regulation.
Further, the two-stage regulation and control effects of complex amplitude inevitably affect each other, and in the initial scheme of the present invention, high-precision modulation cannot be realized through conventional pure phase modulation after pure amplitude modulation or pure amplitude modulation after pure phase modulation. Through intensive research of a team, the inventor finds that the modulation amount of the pure amplitude dynamic modulation unit to the phase is changed under the excitation of different signal intensities, and similarly, the modulation amount of the pure phase dynamic modulation unit to the amplitude is changed under the excitation of different signal intensities, and the mutual containment between the amplitude modulation and the phase modulation is an important factor causing the imperfect initial scheme of the invention. To date, none of the prior art discloses or relates the above factors and related factors to complex amplitude modulation.
Specifically, the invention adopts the following technical scheme: the method comprises the following steps:
a spatial light modulator comprising at least a first modulation layer and a second modulation layer; the first modulation layer comprises one or more first modulation pixel units, and the second modulation layer comprises one or more second modulation pixel units; the light beam modulated by the first modulation pixel unit is projected to a unique second modulation pixel unit for secondary modulation;
and, a phase amplitude decoupling modulator comprising a controller, a first excitation module and a second excitation module; the first excitation module inputs an excitation signal to the first modulation pixel unit to change the optical property of the first modulation pixel unit; the second excitation module inputs an excitation signal to the second modulation pixel unit to change the optical property of the second modulation pixel unit; the controller controls excitation signals of the first excitation module and the second excitation module, and the control method specifically comprises the following steps:
according to the complex amplitude information A of the target light wave in the nth pixel unit n (t, lambda) and P n (t, λ), and initial complex amplitude information of the input light wave at the nth pixel cell
And
obtaining the phase modulation variable quantity and the amplitude modulation variable quantity of the nth pixel unit, and decoupling to obtain the amplitude attenuation ratio and the phase offset of the nth first modulation pixel unit and the nth second modulation pixel unit, so as to obtain the excitation signals applied to the nth first modulation pixel unit and the nth second modulation pixel unit; where t represents time t and λ represents the wavelength of the incident light.
It should be noted that: the optical properties of the modulation pixel unit refer to various properties of the modulation pixel unit when the modulation pixel unit absorbs, reflects, refracts, scatters and diffracts light, the optical properties of the modulation pixel unit change when the modulation pixel unit is excited by an excitation signal (for example, the phase-change material is excited by an electric signal), the various properties of the modulation pixel unit when the modulation pixel unit absorbs, reflects, refracts, scatters and diffracts light change, and the corresponding amplitude attenuation ratio and phase offset amount also change. That is, after an excitation signal, the optical properties of a modulation pixel unit, such as refractive index and extinction coefficient, change, and the corresponding amplitude attenuation ratio and phase shift amount also change (see fig. 4). The optical modulation can be achieved by a person skilled in the art by back-deriving the required excitation signal from the required amplitude attenuation ratio and phase shift. Therefore, materials that enable the modulation of optical properties, such as phase change materials, liquid crystal materials, etc., can be used as the modulating pixel cells of the present application.
The phase change material may be: geSbTe, geSeSbTe, VO 2 。
The liquid crystal material may be: biphenyl liquid crystal, phenylcyclohexane liquid crystal and ester liquid crystal.
In some preferred embodiments, the first modulation pixel unit directly adopts an amplitude modulation unit, and the second modulation unit directly adopts a phase modulation unit; or the first modulation pixel unit directly adopts a phase modulation unit, and the second modulation unit directly adopts an amplitude modulation unit. The amplitude modulation unit is a pixel modulation unit for emphasizing amplitude regulation, and the phase modulation unit is a pixel modulation unit for emphasizing phase regulation. For example, the amplitude modulation unit used is: under the control of electric excitation, the modulation of the optical wave amplitude is uniformly and multi-step changed within the range of 0-1, and the change amount of the optical wave phase is within +/-pi/5; the phase modulation unit is as follows: under the control of electric excitation, the modulation of optical wave phase is uniformly and multi-step changed in the range of 0-2 pi, and the change quantity of optical wave amplitude is stable, and the fluctuation value is within 10%.
The principle of decoupling is as follows: the phase information of the light wave in the nth pixel unit is simultaneously modulated by the nth first modulation pixel unit and modulated by the nth second modulation pixel unit, and the phase difference between the target light wave and the incident light wave of the nth pixel unit is equal to the sum of the phase modulation amount of the nth first modulation pixel unit and the phase modulation amount of the nth second modulation pixel unit; the amplitude attenuation ratio of the target light wave and the incident light wave of the nth pixel modulation unit is modulated by the nth first modulation pixel unit and the nth second modulation pixel unit at the same time, and the amplitude attenuation ratio of the target light wave and the incident light wave is equal to the product of the amplitude modulation amount of the nth first modulation pixel unit and the amplitude modulation amount of the nth second modulation pixel unit.
Further, the excitation signal is an electrical excitation signal, an optical excitation signal, a stress excitation signal, a thermal excitation signal, or other excitation signals.
Further, the first modulation pixel unit and the second modulation pixel unit are respectively arranged in an array mode to form a first modulation layer and a second modulation layer; the first modulation pixel units and the second modulation pixel units correspond to each other one by one.
Further, the first excitation module and the second excitation module comprise electrode units, and the electrode units are in one-to-one correspondence with the first modulation layer pixel units and the second modulation layer pixel units.
Further, the first modulation layer and the second modulation layer are seamlessly spliced.
The invention has the beneficial effects that: the invention optimizes the front and back two-stage modulation effect by arranging the phase amplitude decoupling modulator. The Two-stage dynamic complex amplitude modulation is an ideal technical path with optimal performance in all aspects and greatly simplified structure, and simultaneously realizes the functions of dynamic modulation, two-stage (Two-stage) independent modulation of phase and amplitude and the like of an image, and can obtain high-quality wavefront reconstruction of a real holographic dynamic image. The method breaks through various limitations of low amplitude and phase modulation level, mutual interference, complex preparation process and the like, and can respectively realize independent and multi-level (multi-level) amplitude modulation and complex amplitude complete information reconstruction of phase modulation, and spatial-temporal separation of the amplitude and phase modulation processes, thereby improving the performances of resolution, amplitude distribution uniformity, precision, signal-to-noise ratio and the like, and completing dynamic switching of images and improvement of reconstructed image quality.
Drawings
FIG. 1 is a first modulation pixel cell of embodiment 1 employing a digital super-surface structure based on phase change materials, different crystalline/amorphous combinations;
FIG. 2 is a graph of complex amplitude modulation of the first modulated pixel cell of FIG. 1 with different equivalent electrical stimulus intensities applied, FIG. 2A showing the amount of adjustment in amplitude with the intensity of the electrical stimulus, and FIG. 2B showing the amount of adjustment in phase with the intensity of the electrical stimulus;
FIG. 3 is a second modulation pixel cell of embodiment 1 employing a digital super-surface structure based on phase change materials, different crystalline/amorphous combinations;
FIG. 4 is a graph of complex amplitude modulation of the second modulated pixel cell of FIG. 3 with different equivalent electrical stimulus intensities, FIG. 4A showing the amount of adjustment in different phases with the intensity of the electrical stimulus, and FIG. 4B showing the amount of adjustment in different amplitudes with the intensity of the electrical stimulus;
fig. 5 is a complex amplitude modulation device structure in which each modulation pixel unit is controlled by an independent excitation module in embodiment 2;
fig. 6 is a cell structure adopted by the first modulation pixel unit and the second modulation pixel unit in embodiment 2;
FIG. 7 is a simulation structure employed in embodiments 2 and 3;
FIG. 8 is a simulation result of two-stage complex amplitude modulation using the decoupling algorithm in example 2, FIG. 8A is an amplitude value distribution diagram of the lightwave output plane, and FIG. 8B is a phase value distribution diagram of the lightwave output plane;
FIG. 9 is a simulation result of two-stage complex amplitude modulation without applying the decoupling algorithm in example 2, FIG. 9A is an amplitude value distribution diagram of the lightwave output plane, and FIG. 9B is a phase value distribution diagram of the lightwave output plane;
FIG. 10 is a cell structure employed in embodiment 3;
FIG. 11 is a simulation result of two-stage complex amplitude modulation using the decoupling algorithm in example 3, FIG. 11A is an amplitude value distribution diagram of a lightwave output plane, and FIG. 11B is a phase value distribution diagram of the lightwave output plane;
FIG. 12 is a simulation result of two-stage complex amplitude modulation without using the decoupling algorithm in example 3, FIG. 12A is an amplitude value distribution diagram of a lightwave output plane, and FIG. 12B is a phase value distribution diagram of the lightwave output plane;
Detailed Description
Example 1
The present embodiment takes two-stage modulation pixel units in front and back as an example, and illustrates the unique advantage of two-stage regulation in improving the complex amplitude dynamic modulation precision.
FIG. 1 shows a first modulation pixel cell of this embodiment, which employs a phase change material based digital super surface cell structure, wherein the substrate is 1600nm × 1600nm Si material, and four 800nm high GSST (Ge 2Sb2Se4 Te) circles of different sizes are disposed thereonA column having a radius d 1 ＝425nm，d 2 ＝220nm，d 3 ＝205nm，d 4 =230nm, with an electrical excitation source under each GSST cylinder, the crystalline/amorphous state of each GSST material can be controlled independently. The tested communication wavelength is 1550nm, and the modulation amounts of the amplitude modulation digital super surface unit (first modulation pixel unit) on the amplitude and the phase of the light wave in the area under the different crystalline/amorphous combinations of four GSST materials are shown in FIGS. 2A and 2B, and the data thereof is shown in Table 1 (the diameter is d by ABCD respectively) 1 、d 2 、d 3 And d 4 GSST cylinder of (a):
table 1: the modulation amounts of the amplitude modulation digital super surface unit (first modulation pixel unit) to the amplitude and phase of the optical wave in embodiment 1
FIG. 3 shows a second modulation pixel unit in this embodiment, which employs a digital super-surface structure based on phase-change materials, wherein the substrate is a 1600nm × 1600nm Si material, and four 800nm high GSST (Ge 2Sb2Se4 Te) cylinders with different sizes and radii D 1 ＝470nm，D 2 ＝435nm，D 3 ＝410nm，D 4 =365nm, and each GSST cylinder has an electrical excitation source below it, so that the crystalline/amorphous state of each GSST material can be controlled independently. The communication wavelength of each test is 1550nm, and the modulation amounts of the phase modulation digital super surface unit (second modulation pixel unit) to the amplitude and the phase of the light wave in the area under different crystalline/amorphous combinations of four GSST materials are shown in FIGS. 4A and 4B, and the data thereof is shown in Table 2 (WXYZ represents the diameter D 1 、D 2 、D 3 And D 4 GSST cylinder of (a):
table 2: embodiment 1 is a phase modulation digital super surface unit (second modulation pixel unit) for modulating the amplitude and phase of an optical wave
The single first modulation pixel unit has eight different amplitude modulation amounts and three different phase modulation amount changes, and eight different complex amplitude values are shared; the individual second modulation pixel units have eight complex amplitude modulation amounts with different amplitude phase changes. After the combination, the range of the complex amplitude modulation which can be modulated is expanded to 8 × 8 types. Assuming that the incident light is a plane wave of a vertical incidence device, the phase is 0, the amplitude is 1, and all amplitude values of the light wave obtained by all different crystalline/amorphous combinations of the first modulation pixel unit and the second modulation pixel unit are shown in table 3:
table 3: all light wave amplitude modulation values obtained by different crystalline/amorphous combination
| Amplitude value | BCD/A | BD/AC | CD/AB | B/ACD | /ABCD | AB/CD | AC/BD | A/BCD |
| XYZ/W | 0.012 | 0.016 | 0.0096 | 0.0088 | 0.0088 | 0.0076 | 0.0008 | 0.0072 |
| WXY/Z | 0.108 | 0.144 | 0.0864 | 0.0792 | 0.0792 | 0.0684 | 0.0072 | 0.0648 |
| WX/YZ | 0.132 | 0.176 | 0.1056 | 0.0968 | 0.0968 | 0.0836 | 0.0088 | 0.0792 |
| W/XYZ | 0.216 | 0.288 | 0.1728 | 0.1584 | 0.1584 | 0.1368 | 0.0144 | 0.1296 |
| /WXYZ | 0.312 | 0.416 | 0.2496 | 0.2288 | 0.2288 | 0.1976 | 0.0208 | 0.1872 |
| Z/WXY | 0.384 | 0.512 | 0.3072 | 0.2816 | 0.2816 | 0.2432 | 0.0256 | 0.2304 |
| Y/WXZ | 0.432 | 0.576 | 0.3456 | 0.3168 | 0.3168 | 0.2736 | 0.0288 | 0.2592 |
| YZ/WX | 0.492 | 0.656 | 0.3936 | 0.3608 | 0.3608 | 0.3116 | 0.0328 | 0.2952 |
All phase values of the optical wave obtained by all different crystalline/amorphous combinations of the amplitude dynamic modulation unit and the phase dynamic modulation unit are shown in table 4 and table 3:
table 4: all optical wave phase modulation values obtained by different crystalline/amorphous combinations
From the above, by changing the excitation modes of the first modulation pixel unit and the second modulation pixel unit and selecting different crystalline/amorphous combinations, the eight amplitude phase combinations of the original one-level modulation can be expanded to obtain 64 amplitude phase modulation combinations, and the precision of the optical wave complex amplitude modulation is greatly improved.
Those skilled in the art should understand that the present embodiment can be equally replaced by other PCM microstructures, and can also achieve the technical effects of the present embodiment with high precision, such as rod-shaped, V-shaped, cross-shaped, C-shaped structures, etc., and the thickness is in the range of 50-600 nm. The PCM microstructures are arranged and combined, and each microstructure is provided with a separate electric excitation source, so that mutual transformation between crystalline states and amorphous states of each microstructure can be realized, the optical properties (such as refractive index, extinction coefficient and the like) of the first modulation pixel unit are changed, and the phase modulation amount and the amplitude modulation amount of the whole digital super-surface unit (modulation pixel unit) are changed. In addition, a plurality of PCM microstructures with different shapes can be respectively placed on a substrate to form a digital super surface unit, each microstructure is electrically excited to generate the change of optical properties under different phase state combinations, so that the change of the amplitude attenuation ratio and the phase offset of the digital super surface unit is realized, each change value is coded, and the near-continuous multi-order phase change in the [0,2 pi ] full range and the near-continuous multi-order amplitude change in the [0,1] full range can be realized.
In the present application, each modulation pixel unit on the first modulation layer and the second modulation layer is regulated and controlled by an independent signal excitation source, and the units do not interfere with each other.
Example 2
As shown in fig. 5, the present embodiment provides a complex amplitude dynamic modulator, which includes a first modulation layer and a second modulation layer, wherein the first modulation layer has first modulation pixel units M1 to M3, and each first modulation pixel unit is applied with an excitation signal by an independent first excitation module; the second modulation layer is provided with second modulation pixel units N1-N3, and each second modulation pixel unit is applied with an excitation signal by an independent second excitation module; the first modulation pixel unit and the second modulation pixel unit form an array respectively, the first modulation layer pixel unit and the second modulation layer pixel unit are spliced seamlessly, and the controller controls the intensity of the excitation signals output by the first excitation module and the second excitation module.
When the local light wave is modulated once by the first modulation pixel unit M1 of the spatial light modulator, the controller controls the first excitation module to provide the excitation signal U input by the first modulation pixel unit M1 M1 To change the optical properties of the first pixel modulation unit; the once modulated light wave is secondarily modulated by the second modulation pixel unit N1, and the controller controls the excitation intensity U applied to the second modulation pixel unit N1 by the second excitation module N1 To change its optical properties; the controller controls the excitation signals output by the first excitation module and the second excitation module, so that the target light wave is subjected to two-stage modulation by the spatial light modulator to obtain a target light wave value.
The electrical excitation U of the first modulation pixel cell M1 will be described below by taking the first pixel cell as an example M1 And the electrical excitation U of the second modulation pixel cell N1 N1 Solution of (2)The coupling process is as follows:
wherein A and P are the amplitude value and phase value of the target light wave, respectively, A 0 And P 0 Amplitude values and phase values of the incident light waves, respectively; a. The M1 And P M1 Represents the modulation of the amplitude of the optical wave and the offset generated by the phase of the optical wave by the first modulation pixel unit M1; a. The N1 And P N1 The modulation of the amplitude of the optical wave and the offset generated by the phase of the optical wave are represented by the second modulation pixel unit N1; satisfies the following conditions:
A M1 ＝f MA (U M1 )
P M1 ＝f MP (U M1 )
P N1 ＝f NP (U N1 )
A N1 ＝f NA (U N1 )
f MA (U M1 ) Represents the first modulation pixel unit M1 at U as an amplitude modulation function of the first modulation pixel unit M1 The amplitude attenuation ratio of the generated light wave is reduced under the electric excitation of (2). f. of NA (U N1 ) Represents the second modulation pixel unit N1 at U as an amplitude modulation function of the second modulation pixel unit N1 The amplitude attenuation ratio of the generated light wave is reduced under the electric excitation of the optical fiber. f. of MP (U M1 ) Is the phase modulation function of the first modulation pixel unit, and indicates that the first modulation pixel unit M1 is in U M1 The phase shift of the generated optical wave is generated under the electric excitation of the optical sensor. f. of NP (U N1 ) Phase modulation function of the second modulation pixel unit, indicating that the second modulation pixel unit N1 is in U N1 The phase shift of the generated light wave is generated under the electric excitation of the optical fiber.
The excitation signal is changed by controlling parameters such as the width and the number of electric pulses, the excitation intensity of the signal is changed, and the electric pulses are respectively input into a first modulation pixel unit and a second modulation pixel unit based on the phase change material, so that the phase change material is subjected to phase state change, the optical property of the device is changed, and the independent dynamic modulation of amplitude and phase information is realized.
In this embodiment, the first modulation pixel unit and the second modulation pixel unit may adopt a structure based on a GST material as shown in fig. 6, the size of the GST material is 600nm × 600nm × 200nm, and the upper and lower sides are transparent electrode material layers. The phase-change material can generate a plurality of intermediate states with different crystallization degrees under the excitation of different electric pulse intensities, and the optical properties are changed in multiple stages, so that the amplitude modulation quantity and the phase modulation quantity in multiple stages are realized.
As shown in fig. 7, the first modulation layer includes a first modulation pixel unit, the second modulation layer includes a second modulation pixel unit, and the two modulation pixel units apply excitation signals through independent excitation modules, and change the excitation intensities of the signals applied to the first modulation pixel unit and the second modulation pixel unit, so as to change the amplitude attenuation ratio and the phase shift amount of the two modulation units, respectively, and further control the amplitude modulation amount and the phase modulation amount of the first modulation pixel unit and the second modulation pixel unit, respectively.
Input light of the present embodiment the input light of this example is
Object light wave
The excitation signals applied to the first modulation pixel unit and the second modulation pixel unit in fig. 7 are optimized by using the decoupling algorithm, and amplitude and phase simulation results are obtained respectively: the amplitude value of the light wave at the center of the output plane is
Deviation from target amplitude is 2%; phase value of the light wave at the center of the output plane
The deviation from the target amplitude was 5%, as shown in fig. 8.
Drawing(s)The first modulating pixel element of 7 is set to pure amplitude modulation and an electrical excitation signal is applied such that the amplitude attenuation ratio is 0.2, and the second modulating pixel element is set to pure phase modulation and an electrical excitation signal is applied such that the phase shift value is-0.20 pi. The amplitude value of the light wave at the center of the output plane is as follows under the condition of not adopting decoupling algorithm to optimize the excitation signal
Deviation from target amplitude is 36%; phase value of the light wave at the center of the output plane
The deviation from the target amplitude is 60%, and it can be seen that the amplitude and phase deviation values are too large, as shown in fig. 9.
It can be known from the above embodiments that the accuracy of the two-stage complex amplitude modulation can be effectively improved by using the decoupling algorithm.
Example 3
In the embodiment, different pixel modulation unit structures are adopted, so that the accuracy of two-stage complex amplitude modulation can be effectively improved by a decoupling algorithm.
In this embodiment, the first modulation pixel unit and the second modulation pixel unit adopt the super-surface structure based on the phase-change material as shown in fig. 10, and the substrate is SiO with a thickness of 500nm × 500nm × 200nm 2 The material, the center places 200nm radius, height 200nm GST material cylinder, the cylinder by independent excitation module applied excitation signal. The GST material can generate a plurality of intermediate states with different degrees of crystallinity under different electric excitations, and the optical properties of the super-surface unit (pixel modulation unit) are changed in multiple steps under different electric excitations, so that the amplitude modulation amount and the phase modulation amount in multiple steps are realized.
As shown in fig. 7, the simulation structure of this embodiment includes a first modulation layer including a first modulation pixel unit, and a second modulation layer including a second modulation pixel unit, where the two modulation pixel units are applied with excitation signals by independent excitation modules, and the excitation signals applied to the first modulation pixel unit and the second modulation pixel unit are changed, so as to change the amplitude attenuation ratio and the phase shift amount of the two modulation units, respectively, and further control the amplitude modulation amount and the phase modulation amount of the first modulation pixel unit and the second modulation pixel unit, respectively.
Signal stimulus U applied to first modulation pixel unit M1 And signal excitation U on the second modulation pixel unit N1 The decoupling process of (2) is as follows:
wherein A and P are the amplitude value and phase value of the target light wave, respectively, A 0 And P 0 Amplitude values and phase values of the incident light waves, respectively; a. The M1 And P M1 The modulation of the amplitude of the optical wave and the offset generated by the phase of the optical wave by the first modulation pixel unit M1 are shown; a. The N1 And P N1 The modulation of the second modulation pixel unit N1 on the amplitude of the optical wave and the offset generated on the phase of the optical wave are shown; satisfies the following conditions:
A M1 ＝f MA (U M1 )
P M1 ＝f MP (U M1 )
P N1 ＝f NP (U N1 )
A N1 ＝f NA (U N1 )
f MA (U M1 ) Represents the first modulation pixel unit M1 at U as an amplitude modulation function of the first modulation pixel unit M1 The amplitude attenuation ratio of the generated light wave is reduced under the electric excitation of (2). f. of NA (U N1 ) Representing the second modulation pixel unit N1 at U as an amplitude modulation function of the second modulation pixel unit N1 The amplitude attenuation ratio of the generated light wave is reduced under the electric excitation of (2). f. of MP (U M1 ) Is the phase modulation function of the first modulation pixel unit, and indicates that the first modulation pixel unit M1 is in U M1 The phase shift of the generated optical wave is generated under the electric excitation of the optical sensor. f. of NP (U N1 ) Phase modulation function of the second modulation pixel unit, indicating that the second modulation pixel unit N1 is in U N1 The phase shift of the generated optical wave is generated under the electric excitation of the optical sensor.
The excitation signal is changed by controlling parameters such as the width and the number of electric pulses, the excitation intensity of the signal is changed, and the electric pulses are respectively input into a first modulation pixel unit and a second modulation pixel unit based on the phase change material, so that the phase change material is subjected to phase state change, the optical property of the device is changed, and the independent dynamic modulation of amplitude and phase information is realized.
Input light of the present embodiment the input light of this example is
Object light wave
The amplitude and phase simulation results obtained by optimizing the excitation levels applied to the first modulation pixel element and the second modulation pixel element of fig. 7, respectively, according to the above-described method are: the amplitude value of the light wave at the center of the output plane is
Deviation from target amplitude is 5%; the phase value of the light wave at the center of the output plane is
The deviation from the target amplitude was 1.54%, as shown in fig. 11A and 11B.
If the first modulating pixel cell in fig. 7 is set to pure amplitude modulation and the electrical excitation signal is applied such that the amplitude attenuation ratio is 0.20, the second modulating pixel cell is set to pure phase modulation and the electrical excitation signal is applied such that the phase shift value is-0.65 pi. Without decoupling optimization, the amplitude value of the light wave at the center of the output plane is
Deviation from target amplitude was 77.5%; phase value of the light wave at the center of the output plane
Deviation from the target amplitude was 32.9%, and it can be seen thatThe amplitude and phase deviation values are too large.
It can be known from the above embodiments that the accuracy of the two-stage complex amplitude modulation can be effectively improved by using the decoupling algorithm.
It should be noted that the structures of the two layers of modulation pixel units are not necessarily identical. It will be appreciated by those skilled in the art that either the phase change material or the meta-material of the present embodiment can be used as a modulating pixel cell. Therefore, the phase change material cell in the present embodiment may be replaced with a pixel cell made of a super surface material, or the like.
Claims (9)
1. A phase amplitude decoupling modulator for complex amplitude modulation, comprising:
a spatial light modulator including at least a first modulation layer and a second modulation layer; the first modulation layer comprises one or more first modulation pixel units, and the second modulation layer comprises one or more second modulation pixel units; the light beams modulated by the first modulation pixel unit are projected to a unique second modulation pixel unit;
and, a phase amplitude decoupling modulator comprising a controller, a first excitation module and a second excitation module; the first excitation module inputs an excitation signal to the first modulation pixel unit; the second excitation module inputs an excitation signal to the second modulation pixel unit; the controller controls excitation signals of the first excitation module and the second excitation module, and the control method specifically comprises the following steps:
according to the complex amplitude information A of the target light wave in the nth pixel unit n (t, lambda) and P n (t, λ), and initial complex amplitude information of the input light wave at the nth pixel cell
And
obtaining the phase modulation variable quantity and the amplitude modulation variable quantity of the nth pixel unit, and obtaining the nth first modulation pixel unit andthe amplitude attenuation ratio and the phase offset of the nth second modulation pixel unit respectively are obtained, so that the excitation signals applied to the nth first modulation pixel unit and the nth second modulation pixel unit are obtained; where t represents time t and λ represents the wavelength of the incident light.
2. The modulator of claim 1, wherein the excitation signal is an electrical excitation signal, an optical excitation signal, a stress excitation signal, a thermal excitation signal, or other excitation signal.
3. The modulator of claim 1, wherein the first and second modulating pixel cells are phase change material, liquid crystal material, or other material that enables modulation of optical properties.
4. The modulator of claim 3, wherein the phase change material is selected from the group consisting of: geSbTe, geSeSbTe, VO 2 。
5. The modulator of claim 3, wherein said liquid crystal material is selected from the group consisting of: biphenyl liquid crystal, phenylcyclohexane liquid crystal and ester liquid crystal.
6. The modulator according to claim 1, wherein the first modulating pixel unit is an amplitude modulating unit, and the second modulating unit is a phase modulating unit; or the first modulation pixel unit is a phase modulation unit, and the second modulation unit is an amplitude modulation unit.
7. The modulator according to claim 1, wherein the first modulation pixel unit and the second modulation pixel unit are respectively arranged in an array to form the first modulation layer and the second modulation layer; the first modulation pixel units and the second modulation pixel units are in one-to-one correspondence.
8. The modulator according to claim 1, wherein the first and second excitation modules comprise electrode units, and the electrode units are in one-to-one correspondence with the first and second modulation layer pixel units.
9. The modulator of claim 1, wherein the first modulation layer and the second modulation layer are seamlessly spliced.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117742119A (en) * | 2023-12-27 | 2024-03-22 | 华中科技大学 | Holographic display device based on phase change material |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117742119A (en) * | 2023-12-27 | 2024-03-22 | 华中科技大学 | Holographic display device based on phase change material |
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