A multi-stage low-loss optical storage and computing unit with adjustable levels

Abstract

The present invention discloses a multi-stage low-loss optical storage and computing unit with adjustable levels, which involves on-chip integrated optical components. This solution is proposed to solve the problem of insufficient control accuracy in the prior art. Two phase change components are symmetrically arranged on the two transmission arms of the Mach-Zehnder interferometer waveguide structure. The phase state on one arm is fixed, and then the phase state on the other arm is controlled in k-level steps, so that the optical signal obtains k*k transmission effects at the output end, thereby realizing a refined optical signal modulation function. The advantage is that the symmetrical distribution of each component can completely make up for the phase difference caused by the introduction of the phase change material, and reduce the difficulty of controlling the modulation accuracy. On the other hand, the first phase change component and the second phase change component can adjust the k-level changes respectively. Since the minimum modulation step length of the first phase change component is greater than the total modulation amount of the second phase change component, a step jump occurs in each level of phase state regulation of the first phase change component, thereby ensuring the modulation accuracy.

Description

Technical Field

[0001] The present invention relates to an on-chip integrated optical storage computing unit, and in particular to a multi-stage low-loss optical storage computing unit with adjustable stages. Background Art

[0002] With the rapid development of information technology, the demand for data storage and processing capabilities in various applications is increasing. Traditional electronic computing faces bottlenecks in energy consumption and speed. Optical storage computing technology uses photons to replace electrons and uses optical components for data storage and processing. It has the advantages of high speed and low energy consumption and has become a research hotspot. Applications such as on-chip photonic computing and optical in-memory computing require active adjustment of the optical phase to achieve accurate data processing and calculation. Different from traditional phase shifting methods such as thermo-optics, electro-optics, and stress-optics, the use of non-volatile, low-power phase change materials to control the phase of optical signals can solve the problems of high power consumption and signal crosstalk in traditional phase shifting methods, while ensuring the persistence of data and the stability of the system. However, the modulation level of the non-volatile phase shift unit still needs to be improved.

[0003] For example, CN 109004985 A proposes an all-optical PAM regenerator with a reflective MZI structure, which can obtain a relatively flat input-output power transfer function by designing the coupling coefficient of the optical coupler and the high nonlinear fiber parameters in the MZI structural unit and appropriately adjusting the gain of the bidirectional optical amplifier. However, in order to obtain the flat effect, it can only abandon the precision control capability of phase regulation, so it still cannot meet the requirements of more sophisticated and more integrated in-memory computing needs. Summary of the invention

[0004] The purpose of the present invention is to provide a multi-stage low-loss optical storage and computing unit with adjustable levels to solve the problems existing in the above-mentioned prior art.

[0005] The multi-stage low-loss optical storage and computing unit with adjustable number of stages described in the present invention comprises a substrate, and a first transmission arm and a second transmission arm arranged on the upper end surface of the substrate; one end of the first transmission arm is the input end of the multi-stage low-loss optical storage and computing unit, and the other end is the output end of the multi-stage low-loss optical storage and computing unit;

[0006] The first transmission arm and the second transmission arm are symmetrically arranged and extend in the same direction, and are close to each other at a position close to the input end to form a first directional coupler, and are close to each other at a position close to the output end to form a second directional coupler, thereby forming a Mach-Zehnder interferometer waveguide structure;

[0007] Between the first directional coupler and the second directional coupler, a first phase change component is provided at a position close to the first directional coupler on the upper end surface of the first transmission arm, and a second phase change component is provided at a position close to the second directional coupler; the first phase change component and the second phase change component are used to modulate the phase of the light beam in the first transmission arm in a step-variable manner;

[0008] Between the first directional coupler and the second directional coupler, a third phase change component is provided at a position close to the first directional coupler on the upper end surface of the second transmission arm, and a fourth phase change component is provided at a position close to the second directional coupler; the third phase change component and the fourth phase change component maintain a preset phase state to compensate for the introduced phase difference between the first phase change component and the second phase change component;

[0009] The first phase change component and the third phase change component have the same size and are at the same distance from the first directional coupler; the second phase change component and the fourth phase change component have the same size and are at the same distance from the second directional coupler; the four phase change components are all reciprocal optical phase shifters;

[0010] Between the first directional coupler and the second directional coupler, the phase difference θ between the light beams in the first transmission arm and the second transmission arm is ij for:

[0011] ;

[0012] λ is the wavelength of the input light; L is the length of the first phase change component and the third phase change component; l is the length of the second phase change component and the fourth phase change component; i is the phase change level of the first phase change component, j is the phase change level of the second phase change component, and the phase change level is divided into k levels, where level 1 is amorphous, level k is crystalline, and there are k-2 intermediate phases that change in sequence between level 1 and level k, and k is a positive integer; n i is the refractive index of the first phase change component when the phase state is level i, n j is the refractive index of the second phase change component when the phase state is level j; n a is the refractive index of the third phase change component and the fourth phase change component in a preset phase state.

[0013] The materials of the four phase change components are Sb 2 S 3 .

[0014] The preset phase state is set to be amorphous, a=1.

[0015] The phase change series is divided into 11 levels, k=11.

[0016] The phase modulation step length of the first phase change component is 0.068π to 0.127π; the phase modulation step length of the second phase change component is 0.005π to 0.009π.

[0017] The refractive index of the four phase change components in the crystalline state is 3.3+1.4*10 -5 i, the refractive index in the amorphous state is 2.7+6.0*10 -6 i.

[0018] When the wavelength λ of the input light is between 1500nm and 1600nm, the lengths of the first phase change component and the third phase change component are both 33.6μm, and the lengths of the second phase change component and the fourth phase change component are both 2.4μm; the distance between the first phase change component and the second phase change component and the distance between the third phase change component and the fourth phase change component are the same, both between 6μm and 10μm; the widths of the four phase change components are all 350nm, and the thicknesses are all 20nm.

[0019] The substrate has a length of 140 μm, a width of 70 μm, a thickness of 7 μm, a refractive index of 1.44, and is made of SiO 2 .

[0020] The width of the first transmission arm and the second transmission arm are both 450 nm, and the thickness of the first transmission arm and the second transmission arm are both 220 nm.

[0021] The lengths of the first directional coupler and the second directional coupler are both 7.5 μm, and the coupling intervals are both 100 nm.

[0022] The advantage of the multi-stage low-loss optical storage unit with adjustable levels described in the present invention is that the two transmission arms are symmetrically distributed on the substrate, and the four phase change components respectively arranged on the two transmission arms are also symmetrically distributed, which can completely make up for the phase difference caused by the introduction of the phase change material and reduce the difficulty of controlling the modulation accuracy. On the other hand, the first phase change component and the second phase change component can adjust the k-level change respectively. Since the minimum modulation step of the first phase change component is greater than the total modulation of the second phase change component, a step jump occurs in each phase state regulation of the first phase change component. Between these step levels, the output light transmittance can steadily increase k times, and finally the phase difference of the output light can reach a resolution of k*k, ensuring the modulation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the multi-stage low-loss optical storage and computing unit described in the present invention.

[0024] Figure 2 yes Figure 1 Exploded view of the structure shown.

[0025] Figure 3 It is a schematic diagram of the stacking relationship between the phase change components and the transmission arms of the multi-stage low-loss optical storage and computing unit described in the present invention.

[0026] Figure 4It is a distribution diagram of the electric field intensity of the multi-stage low-loss optical storage and computing unit in the present invention when it is in state one.

[0027] Figure 5 This is the electric field intensity distribution diagram of the multi-stage low-loss optical storage and computing unit in the present invention when it is in state two.

[0028] Figure 6 This is the electric field intensity distribution diagram of the multi-stage low-loss optical storage and computing unit in the present invention when it is in state three.

[0029] Figure 7 This is the electric field intensity distribution diagram of the multi-stage low-loss optical storage and computing unit in the present invention when it is in state four.

[0030] Figure 8 It is a phase shift state distribution diagram of the output end of the multi-stage low-loss optical storage and computing unit described in the present invention when the input optical signal wavelength is 1550nm.

[0031] Fig. 9 It is a 121-level transmittance distribution curve diagram of the output end of the multi-level low-loss optical storage and computing unit described in the present invention when the input optical signal wavelength is 1550nm.

[0032] Reference numerals:

[0033] 100-substrate;

[0034] 210 - first transmission arm, 211 - input end, 212 - output end;

[0035] 220 - second transmission arm;

[0036] 231 - a first directional coupler, 232 - a second directional coupler;

[0037] 311 - a first phase change component, 312 - a second phase change component, 321 - a third phase change component, 322 - a fourth phase change component. DETAILED DESCRIPTION

[0038] like Figures 1 to 3 As shown, the multi-stage low-loss optical storage and computing unit with adjustable number of stages in the present invention comprises a substrate 100, and a first transmission arm 210 and a second transmission arm 220 arranged on the upper end surface of the substrate 100. One end of the first transmission arm 210 is the input end 211 of the multi-stage low-loss optical storage and computing unit, and the other end is the output end 212 of the multi-stage low-loss optical storage and computing unit.

[0039] The first transmission arm 210 and the second transmission arm 220 are symmetrically arranged and extend in the same direction. They are close to each other near the input end 211 to form a first directional coupler 231 , and close to each other near the output end 212 to form a second directional coupler 232 , thereby forming a Mach-Zehnder interferometer waveguide structure.

[0040] Between the first directional coupler 231 and the second directional coupler 232, a first phase change component 311 is provided at a position close to the first directional coupler 231 on the upper end surface of the first transmission arm 210, and a second phase change component 312 is provided at a position close to the second directional coupler 232. The first phase change component 311 and the second phase change component 312 are used to modulate the phase of the light beam in the first transmission arm 210 in a step-variable manner.

[0041] Between the first directional coupler 231 and the second directional coupler 232, a third phase change component 321 is provided at a position close to the first directional coupler 231 on the upper end surface of the second transmission arm 220, and a fourth phase change component 322 is provided at a position close to the second directional coupler 232. The third phase change component 321 and the fourth phase change component 322 maintain a preset phase state, and are used to compensate for the introduced phase difference between the first phase change component 311 and the second phase change component 312.

[0042] The first phase change component 311 and the third phase change component 321 have the same size and are at the same distance from the first directional coupler 231. The second phase change component 312 and the fourth phase change component 322 have the same size and are at the same distance from the second directional coupler 232. All four phase change components are reciprocal optical phase shifters.

[0043] The material of the four phase change components is preferably Sb 2 S 3 The selection of this material can minimize light absorption and maintain the characteristics of low loss. The refractive index of the four phase change components in the crystalline state is 3.3+1.4*10 -5 i, the refractive index in the amorphous state is 2.7+6.0*10 -6 i.

[0044] Between the first directional coupler 231 and the second directional coupler 232, the phase difference θ between the light beams in the first transmission arm 210 and the second transmission arm 220 is ij for:

[0045] .

[0046] λ is the wavelength of the input light. L is the length of the first phase change component 311 and the third phase change component 321. l is the length of the second phase change component 312 and the fourth phase change component 322. i is the phase change level of the first phase change component 311, j is the phase change level of the second phase change component 312, and the phase change level is divided into k levels, where level 1 is amorphous, level k is crystalline, and there are k-2 intermediate phases that change in sequence between level 1 and level k, and k is a positive integer. i is the refractive index of the first phase change component 311 when the phase state is level i, n jis the refractive index of the second phase change component 312 when the phase state is level j. a is the refractive index of the third phase change component 321 and the fourth phase change component 322 in a preset phase state.

[0047] The phase change series can be divided into multiple levels, 3≤k≤11, and the series can be set according to the modulation requirements, preferably 11 levels, that is, k=11.

[0048] The phase modulation step length of the first phase change component 311 is 0.068π to 0.127π. The phase modulation step length of the second phase change component 312 is 0.005π to 0.009π.

[0049] When the wavelength λ of the input light is between 1500nm and 1600nm, the lengths of the first phase change component 311 and the third phase change component 321 are both 33.6μm, and the lengths of the second phase change component 312 and the fourth phase change component 322 are both 2.4μm. The distance between the first phase change component 311 and the second phase change component 312 and the distance between the third phase change component 321 and the fourth phase change component 322 are the same, both between 6μm and 10μm. The width of the four phase change components is 350nm and the thickness is 20nm.

[0050] The substrate 100 has a length of 140 μm, a width of 70 μm, a thickness of 7 μm, a refractive index of 1.44, and is made of SiO 2 .

[0051] The width of the first transmission arm 210 and the thickness of the second transmission arm 220 are both 450 nm and 220 nm respectively.

[0052] The lengths of the first directional coupler 231 and the second directional coupler 232 are both 7.5 μm, and the coupling intervals are both 100 nm.

[0053] When working, the preset phase state is set to a specified phase state, and then the phase states of the first phase change component 311 and the second phase change component 312 are adjusted respectively, so that the input light is coupled to the first transmission arm 210 and the second transmission arm 220 respectively through the first directional coupler 231, and then a phase shift occurs in the subsequent waveguide transmission, so that the light beams of the first transmission arm 210 and the second transmission arm 220 respectively reaching the second directional coupler 232 have the required modulated phase difference, and finally coupled output is performed. Due to the phase difference, the light beam output after coupling by the second directional coupler 232 will have a change in transmittance, thereby realizing the function of the optical storage unit to regulate the optical signal. For the convenience of control, the preset phase state is preferably amorphous, that is, a=1.

[0054] Different phases of phase change materials will cause different refractive indices and losses in the transmission waveguide. The refractive index of the waveguide structure is high. When the refractive index of the phase change material changes, the ability to limit the light beam in the waveguide changes, thereby affecting the phase of the light beam after transmission in the waveguide.

[0055] like Figure 8 As shown, when the two phase change components of the first transmission arm 210 change from the amorphous state to the crystalline state through 9 intermediate phases, the input light can be phase modulated from 0 to π. In this embodiment, taking the input light wavelength λ=1550nm and k=11 as an example:

[0056] In a special case, the four phase change components are all amorphous, and the electric field distribution of the optical path is as follows: Figure 4 The light path does not pass through the output end 212, and the light transmittance of the output end 212 is 0. Fig. 9 The corresponding phase shift is 0.

[0057] In a special case of state 2, the second phase change component 312 is in a crystalline state, and the other three phase change components remain in an amorphous state. The electric field distribution of the optical path is as follows: Figure 5 A small portion of the light signal will be output from the output end 212, and the light transmittance is 0.0104 at this time. Fig. 9 The corresponding phase shift is 0.2121.

[0058] In a special case of state three, the first phase change component 311 is in a crystalline state, and the other three phase change components remain in an amorphous state. The electric field distribution of the optical path is as follows: Figure 6 There will be more light signals output from the output end 212 than in state 2, and the light transmittance is 0.9274, as shown in FIG. Fig. 9 The corresponding phase shift is 2.9294.

[0059] In a special case of state 4, the first phase change component 311 and the second phase change component 312 are both in a crystalline state, and the other two phase change components remain in an amorphous state. The electric field distribution of the optical path is as follows: Figure 7 As shown. The light signal with the least attenuation is output from the output end 212, and the light transmittance is 0.9337. Fig. 9 The corresponding phase shift is 3.1415.

[0060] The above four states are all special cases. Since the phase change material can present multiple phases, there are at least k*k changes. In actual work, the minimum modulation step of the first phase change component 311 will be greater than the total modulation of the second phase change component 312, so that a step jump occurs in each phase state regulation of the first phase change component. Fig. 9As shown in the figure, the first phase change component 311 plays a role of coarse adjustment, while the second phase change component 312 plays a role of fine adjustment. Between these step levels, the light transmittance of the output end 212 increases steadily.

[0061] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A multi-stage low-loss optical storage and computing unit with adjustable number of stages, comprising a substrate (100), and a first transmission arm (210) and a second transmission arm (220) arranged on the upper end surface of the substrate (100); one end of the first transmission arm (210) is an input end (211) of the multi-stage low-loss optical storage and computing unit, and the other end is an output end (212) of the multi-stage low-loss optical storage and computing unit; The first transmission arm (210) and the second transmission arm (220) are symmetrically arranged and extend in the same direction, and are close to each other at a position close to the input end (211) to form a first directional coupler (231), and are close to each other at a position close to the output end (212) to form a second directional coupler (232), thereby forming a Mach-Zehnder interferometer waveguide structure; It is characterized in that Between the first directional coupler (231) and the second directional coupler (232), a first phase change component (311) is provided at a position close to the first directional coupler (231) on the upper end surface of the first transmission arm (210), and a second phase change component (312) is provided at a position close to the second directional coupler (232); the first phase change component (311) and the second phase change component (312) are used to modulate the phase of a light beam in the first transmission arm (210) in a step-variable manner; Between the first directional coupler (231) and the second directional coupler (232), a third phase change component (321) is provided at a position close to the first directional coupler (231) on the upper end surface of the second transmission arm (220), and a fourth phase change component (322) is provided at a position close to the second directional coupler (232); the third phase change component (321) and the fourth phase change component (322) maintain a preset phase state, and are used to compensate for the introduced phase difference between the first phase change component (311) and the second phase change component (312); The first phase change component (311) and the third phase change component (321) have the same size and are at the same distance from the first directional coupler (231); the second phase change component (312) and the fourth phase change component (322) have the same size and are at the same distance from the second directional coupler (232); and the four phase change components are all reciprocal optical phase shifters; Between the first directional coupler (231) and the second directional coupler (232), the phase difference θ between the light beams in the first transmission arm (210) and the second transmission arm (220) is ij for: ； λ is the wavelength of the input light; L is the length of the first phase change component (311) and the third phase change component (321); l is the length of the second phase change component (312) and the fourth phase change component (322); i is the phase change series of the first phase change component (311), j is the phase change series of the second phase change component (312), the phase change series is divided into k levels, wherein level 1 is amorphous, level k is crystalline, and between level 1 and level k there are k-2 intermediate phases that change in sequence, and k is a positive integer; n i is the refractive index of the first phase change component (311) when the phase state is level i, n j is the refractive index of the second phase change component (312) when the phase state is level j; a is the refractive index of the third phase change component (321) and the fourth phase change component (322) in a preset phase state; The first phase change component (311) plays a role of coarse adjustment, and the second phase change component (312) plays a role of fine adjustment; and the minimum modulation step of the first phase change component (311) is greater than the total modulation amount of the second phase change component (312), so that a step jump occurs in each level of phase state regulation of the first phase change component (311).

2. According to claim 1, a multi-stage low-loss optical storage and computing unit with adjustable levels, characterized in that: The materials of the four phase change components are all Sb2S3.

3. According to claim 2, a multi-stage low-loss optical storage and computing unit with adjustable levels, characterized in that: The preset phase state is set to be amorphous, a=1.

4. According to claim 2, a multi-stage low-loss optical storage and computing unit with adjustable levels, characterized in that: The phase change series is divided into 11 levels, k=11.

5. According to claim 2, a multi-stage low-loss optical storage and computing unit with adjustable levels, characterized in that: The phase modulation step length of the first phase change component (311) is 0.068π to 0.127π; the phase modulation step length of the second phase change component (312) is 0.005π to 0.009π.

6. According to claim 2, a multi-stage low-loss optical storage and computing unit with adjustable levels, characterized in that: The refractive index of the four phase change components in the crystalline state is 3.3+1.4*10 -5 i, the refractive index in the amorphous state is 2.7+6.0*10 -6 i.

7. The multi-stage low-loss optical storage and computing unit with adjustable levels according to claim 2, characterized in that: When the wavelength λ of the input light is between 1500nm and 1600nm, the lengths of the first phase change component (311) and the third phase change component (321) are both 33.6μm, and the lengths of the second phase change component (312) and the fourth phase change component (322) are both 2.4μm; the distance between the first phase change component (311) and the second phase change component (312) and the distance between the third phase change component (321) and the fourth phase change component (322) are the same, both between 6μm and 10μm; the widths of the four phase change components are all 350nm, and the thicknesses are all 20nm.

8. The multi-stage low-loss optical storage and computing unit with adjustable levels according to claim 1, characterized in that: The substrate (100) has a length of 140 μm, a width of 70 μm, a thickness of 7 μm, a refractive index of 1.44, and is made of SiO2.

9. The multi-stage low-loss optical storage and computing unit with adjustable levels according to claim 1, characterized in that: The width of the first transmission arm (210) and the second transmission arm (220) are both 450 nm, and the thickness is both 220 nm.

10. The multi-stage low-loss optical storage and computing unit with adjustable levels according to claim 9, characterized in that: The lengths of the first directional coupler (231) and the second directional coupler (232) are both 7.5 μm, and the coupling intervals are both 100 nm.

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