CN104678676B - A kind of reciprocal optical logical device based on micro-ring resonator - Google Patents

Abstract

The invention provides a reversible optical XOR logic device based on a microring resonator, which is composed of two microring resonators and a Y branch coupler. The reversible optical logic device has two electrical pulse sequence inputs to be calculated, The output is the optical pulse sequence after XOR calculation, and the input and output are in one-to-one correspondence. The manufacturing process of the reversible optical logic device of the present invention is fully compatible with the CMOS process, which makes the device small in size, fast in speed, low in power consumption and easy to integrate, and is expected to play an important role in photonic computers.

Description

A Reversible Optical Logic Device Based on Microring Resonator

technical field

The invention belongs to the field of optical logic computing, and relates to a reversible optical logic device based on a microring resonator, in particular to a reversible XOR optical logic device based on a microring resonator suitable for the fields of optical communication and optical computing.

Background technique

With the continuous development of semiconductor technology, the integration of chips or integrated circuits is getting higher and higher, and the size of integrated components is further reduced. The leakage and heat dissipation problems of traditional electrical devices cannot be well solved. There are more and more signs that optical information processing and optical computing have very bright prospects as a solution to replace traditional electrical information processing. The parallelism of optical signal transmission makes the optical system have a wider information channel than the electrical system; the integrated optical path composed of optical fiber and various optical components can greatly improve the ability of data calculation, transmission and storage, and optical logic devices are optical computing In addition, the energy consumption of photonic devices is extremely low, so photonic devices have attracted the attention of more and more researchers.

Computer operations are binary number calculations, and the existing traditional calculation methods are based on non-reversible logic devices. One bit of information will be lost. According to the Landauer principle, every operation of irreversible calculation will cause the loss of bits, and every bit of information lost will have kTln2 heat energy dissipated. The main feature of the reversible logic device is that after the two-digit binary number is input, the calculation result is a two-digit binary number output, and the input and output are in a one-to-one correspondence, so the input information will not lose information after the operation, because there is no bit After combining the characteristics of low power consumption of optical computing, it can greatly reduce the energy consumption of the computer when it is working, and solve the bottleneck of the huge heat generation of traditional computers.

Contents of the invention

The purpose of the present invention is to provide a reversible optical logic device based on a microring resonator, which does not need to use a strong laser as pump light and is easy to operate.

The present invention is specifically realized through the following technical solutions:

A reversible optical logic device based on microring resonators consists of two microring resonators MRR and a Y-branch coupler made of semiconductor-on-insulator material.

The two microring resonators MRR are the first microring resonator and the second microring resonator, and the first microring resonator includes a first silicon-based nanowire microring, a first input optical waveguide, a first straight Through the optical waveguide and the first download optical waveguide, the first microring resonator has a silicon-based electro-optic modulator or a silicon-based thermo-optic modulator; the second microring resonator includes a second silicon-based nanowire microring, a second input The optical waveguide, the second straight-through optical waveguide, the third input optical waveguide and the second output optical waveguide, the second input optical waveguide is connected with the Y branch straight-through optical waveguide, the third input optical waveguide is connected with the first download optical waveguide; the second micro Ring resonators with silicon-based electro-optic modulators or silicon-based thermo-optic modulators.

The Y branch coupler is that the first Y branch coupler includes a fourth input optical waveguide, a first output optical waveguide and a Y branch straight-through optical waveguide; the fourth input optical waveguide is located on the main straight waveguide of the Y branch coupler, and The first output optical waveguide and the Y branch through optical waveguide are respectively located on the two branch straight waveguides of the first Y branch coupler.

The first input optical waveguide, the first straight-through optical waveguide and the fourth input optical waveguide are sequentially located on the same horizontally arranged straight first waveguide, and one end of the first waveguide is connected to the main straight waveguide of the Y branch coupler. connected; the first download optical waveguide and the third input optical waveguide are located on the U-shaped second waveguide arranged horizontally, the first download optical waveguide is located below the first silicon-based nanowire microring, and the end of the segment is the second A light unloading port T1; the segment below the second silicon-based nanowire microring in the second waveguide is provided with a third input optical waveguide and a second output optical waveguide in sequence; one end of the U-shaped third waveguide is directly connected to the Y branch The optical waveguides are connected, and a second input optical waveguide and a second output optical waveguide are sequentially arranged on the section above the second silicon-based nanowire microring adjacent to the third waveguide, and the end of the section is a second light unloading port.

The reversible optical logic device of the present invention has the following advantages:

1) The reversible optical logic device realized by utilizing the natural characteristics of light replaces the traditional electrical logic device, without the electromagnetic effect of traditional electrical devices and the influence of parasitic resistance and capacitance, so that high-speed and large-capacity information processing can be realized.

2) The reversible optical logic device realized by utilizing the natural characteristics of light replaces the traditional logic device, the operation output results correspond to the input results one by one, and there is no heat dissipation caused by the bit loss of the traditional logic device, which can greatly reduce the energy consumption of the computer .

3) The silicon material SOI on the insulating substrate is used, which means that a layer of single crystal silicon film with a certain thickness is grown on the _SiO2 insulating layer, and the silicon waveguide made of SOI material is used, and its core layer is Si (refractive index 3.45), the cladding layer is SiO ₂ (refractive index 1.45), so the refractive index difference between the cladding layer and the core layer is very large, so the waveguide has a strong ability to confine the optical field so that its bending radius can be small, which is beneficial to Integration at scale.

4) It is only composed of two microring resonators, one Y branch coupler, two straight waveguides, and two curved waveguides, and there is no intersection among them, so the overall device loss is small.

5) The current CMOS process is used to make the device small in size, low in power consumption, good in scalability, and easy to integrate with other components.

Description of drawings

Fig. 1 is a schematic structural diagram of an optical reversible logic device of the present invention;

Fig. 2 is a structural schematic diagram of the first microring resonator in the optical reversible logic device of the present invention;

Fig. 3 is the structural representation of the second microring resonator in the optical reversible logic device of the present invention;

Fig. 4 is a structural schematic diagram of a Y branch coupler in an optical reversible logic device of the present invention;

Fig. 5 is a schematic structural view of the electrodes of the microring resonator MRR with a silicon-based thermo-optic modulator in the optical reversible logic device of the present invention;

Fig. 6 is the structural representation of the electrode of the microring resonator MRR with silicon-based electro-optic modulator in the optical reversible logic device of the present invention;

Marking description in the drawings: 1. The first microring resonator, 2. The second microring resonator, 3. Y branch coupler, 4. Si substrate, 5. SiO ₂ layer, 6. Heating electrode, 7. Silicon-based optical waveguide, 10. The first silicon-based nanowire microring, 11. The first input optical waveguide, 12. The first straight-through optical waveguide, 13. The first download optical waveguide, 20. The second silicon-based nanowire microring Ring, 21, second input optical waveguide, 22, second straight-through optical waveguide, 23, third input optical waveguide, 24, second output optical waveguide, 31, fourth input optical waveguide, 32, first output optical waveguide, 33. The Y branch is directly connected to the optical waveguide.

detailed description

The optical reversible logic device of the present invention will be further explained below in conjunction with the drawings and embodiments.

As shown in Fig. 1, the optical reversible XOR logic device of the present invention includes a first microring resonator and a second microring resonator, and the Y branch coupler is the first Y branch coupler (3).

As shown in Figure 2, the first microring resonator 1 comprises a first silicon-based nanowire microring 10, a first input optical waveguide 11, a first straight-through optical waveguide 12 and a first downloading optical waveguide 13, the first microring Resonator 1 has a silicon-based electro-optic modulator or a silicon-based thermo-optic modulator.

As shown in Figure 3, the second microring resonator 2 includes a second silicon-based nanowire microring 20, a second input optical waveguide 21, a second output optical waveguide 22, a third input optical waveguide 23, a second through optical waveguide 24. The second input optical waveguide 21 is connected to the Y branch straight-through optical waveguide, the third input optical waveguide 23 is connected to the first download optical waveguide 13 of the first microring resonator 1; the second microring resonator 2 has a silicon-based electro-optic modulator or silicon-based thermo-optic modulator.

As shown in Figure 4, Y branch coupler 3, Y branch coupler 3 comprises the 4th input optical waveguide 31, the first output optical waveguide 32 and Y branch through optical waveguide 33; The 4th input optical waveguide 31 is positioned at Y branch coupler 3 and connected to the first straight waveguide 12, the first output optical waveguide 32 and the Y branch straight waveguide 33 are respectively located on the two branch straight waveguides of the Y branch coupler 3.

The first input optical waveguide 11, the first straight-through optical waveguide 12, and the fourth input optical waveguide 31 are successively located on the same straight first waveguide arranged horizontally, and one end of the first waveguide is connected to the main straight waveguide of the Y branch coupler 3. The waveguides are connected; the first downloading optical waveguide 13 and the third input optical waveguide 23 are located on the horizontally arranged "U" shaped second waveguide, and the first downloading optical waveguide 13 is located below the first silicon-based nanowire microring 10, The end of this segment is the first light unloading port T1; the segment below the second silicon-based nanowire microring 20 in the second waveguide is provided with a third input optical waveguide 23 and a second output optical waveguide in sequence; " One end of the U"-shaped third waveguide is connected to the Y branch straight-through optical waveguide 33, and the second input optical waveguide 21 and the second output light are sequentially arranged on the segment above the second silicon-based nanowire microring 20 of the third waveguide. The end of the waveguide 22 is the second optical unloading port T2.

The electrode of the microring resonator MRR of the silicon-based thermo-optic modulator, as shown in Figure 5, has a SiO ₂ layer 5 on the Si substrate 4, a silicon-based optical waveguide 7 on the SiO ₂ layer 5, and a silicon-based optical waveguide 7 on the Si substrate 4. A layer of heating electrodes 6 is laid on the top. Apply a voltage to the leads of the heating electrode 6, and a current will flow through the electrode, which will generate heat and change the temperature of the silicon-based optical waveguide 7 through thermal radiation, thereby changing the effective refractive index Neff of the ring waveguide, and then changing the resonance of the MRR wavelength for dynamic filtering.

It can be seen that the modulation principle of the silicon-based thermo-optic modulator is different from that of the silicon-based electro-optic modulator shown in Figure 6. The silicon-based thermo-optic modulator relies on changing the temperature of the silicon-based optical waveguide to change the effective refractive index of the waveguide . Silicon-based electro-optic modulators change the refractive index of the waveguide by changing the carrier concentration in the track optical waveguide; the speed of thermal radiation is much slower than the speed of carrier annihilation. Therefore, the speed of electro-optic modulation is much faster than that of thermo-optic modulation, but because of the doping of the waveguide, the structure of the electro-optic modulator is more complicated than that of the thermo-optic modulator, and the manufacturing process is simpler. Therefore, silicon-based electro-optic modulation is generally used when high speed is required, while silicon-based thermo-optic modulation is used when the response speed of the device is not high.

The structural parameters of the first silicon-based nanowire microring 10 are exactly the same as the structural parameters of the second silicon-based nanowire microring 20. When the incident optical signal satisfies the resonance condition (m×λ= _Neff ×2π×r), The optical signal will be coupled from the waveguide into the microring through the evanescent field coupling. At this time, if there is an optical waveguide other than the incident one, the optical signal in the microring will also be coupled into the waveguide from the microring through the evanescent field coupling; In the resonance condition (m×λ=N _eff ×2π×r), m represents the resonance order of the microring, its value is a positive integer, λ is the resonance wavelength, Neff is the effective refractive index of the waveguide, and r is the radius of the microring.

By analyzing the optical transmission process of the optical signal in the microring resonator shown in Figure 2 and Figure 3 and the Y branch coupler shown in Figure 4, the working principle of the reversible optical XOR logic device of the present invention is briefly explained:

For the first microring resonator 1 shown in Figure 2, assume that the optical signal is input by the first input optical waveguide 11, when the optical signal passes through the coupling region (the distance between the first input optical waveguide 11 and the first silicon-based nanowire microring 10 In the nearest range), the optical signal enters the first silicon-based nanowire microring 10 through the evanescent field coupling, and the optical signal in the first silicon-based nanowire microring 10 also couples into the first silicon-based nanowire microring 10 through the evanescent field coupling. The first download is in the optical waveguide 13 . For an optical signal satisfying the resonance condition (m×λ= _Neff ×2π×r), when the microring is coupled to the first straight-through optical waveguide 12, due to the destructive interference caused by the phase difference π of the two optical signals, The light extinction phenomenon will occur in the first straight-through optical waveguide 12; the light that does not satisfy the resonance condition cannot satisfy the destructive interference condition due to the phase difference, so the optical signal that does not satisfy the resonance condition can be regarded as passing through the coupling region without any influence output from the first straight-through optical waveguide 12.

For the second microring resonator 2 shown in Figure 3, it is assumed that the optical signal is input by the second input optical waveguide 21 (the optical signal input from the first input terminal 11 does not meet the resonance condition of the first silicon-based nanowire microring 10 ), when the optical signal passes through the coupling region (the second input optical waveguide 21 and the second straight-through optical waveguide 22 and the second silicon-based nanowire microring 20 in the shortest range), the resonance condition (m×λ=N _eff ×2π×r) optical signal enters the second silicon-based nanowire microring 20 through evanescent field coupling, and the optical signal in the second silicon-based nanowire microring 20 also couples into the second silicon-based nanowire microring 20 through evanescent field coupling Two output optical waveguides 24, and output through the second output optical waveguide 24; the light that does not meet the resonance condition can be regarded as output from the second straight-through optical waveguide 22 through the coupling region without any influence. When the optical signal is input by the third input optical waveguide 23 (the optical signal input from the first input port satisfies the resonance condition of the first silicon-based nanowire microring 10), the optical signal passes through the coupling region (the third input optical waveguide 23 and When the second silicon-based nanowire microring 20 is the closest range), the optical signal that satisfies the resonance condition (m×λ=N _eff ×2π×r) enters the second silicon-based nanowire microring through evanescent field coupling In 20, the optical signal in the second silicon-based nanowire microring 20 will also be coupled into the second downloading optical waveguide 22 through the evanescent field coupling effect and unloaded from the second optical unloading port T2; the light that does not satisfy the resonance condition can be seen output from the second output optical waveguide 24 through the coupling region without any influence.

For the Y-branch coupler 3 shown in Figure 4, when the optical signal is input from the fourth input optical waveguide 31, the optical signal is divided into two beams by the first Y-branch coupler 3, respectively from the first output optical waveguide 32 and The first Y branch is output directly through the waveguide 33 .

The above analysis is the working characteristics of the static microring resonator. In summary, the microring resonator will fix the signals of certain wavelengths (wavelengths that meet the resonance conditions) to be downloaded, and the signals of certain wavelengths to pass through (not satisfying the resonance conditions). Conditional wavelength); when the device is working, the resonant wavelength of the microring resonator is also required to be dynamically adjustable. From the resonance condition (m×λ=N _eff ×2π×r), changing the radius R and the effective refractive index Neff of the silicon-based nanowire microring will change the resonance wavelength of the silicon-based nanowire microring. Here, the resonant wavelength of the silicon-based nanowire microring is changed by adjusting the effective refractive index Neff of the microring waveguide. The effective refractive index is related to the refractive index of the silicon-based nanowire microring material, and there are two ways to change the material’s refractive index: one is to heat the material, change the temperature of the material, and use the thermo-optic effect to change the material’s refractive index, namely The above-mentioned silicon-based thermo-optic modulator; the second is to use the electro-optic effect to change the refractive index of the material through carrier injection, that is, the above-mentioned silicon-based electro-optic modulator. Since the thermal modulation speed is affected by the thermal convection speed, and the electrical modulation speed depends on the carrier lifetime, the electrical modulation speed is faster, and electrical modulation is used in high-speed systems.

The working process of the reversible XOR optical logic device of the present invention is illustrated below by taking the thermal modulation mechanism as an example:

Firstly, since the process parameters we set are completely consistent, the completely resonant wavelengths of the nanowire microring 10 and the nanowire microring 20 (theoretically identical.

For the reversible optical logic device shown in Figure 1, the continuous signal light (cw) at the working wavelength is input at the optical signal input terminal (input), and then the modulation voltage is applied to the two microrings to heat the microrings to change the microrings The resonant wavelength of the resonant wavelength, and define that when the output port has light output, it is represented by logic "1", and when the output port has no light output, it is represented by logic "0". The reversible optical XOR logic device has four working states.

The working principle of the reversible optical logic device of the present invention is analyzed in detail below in conjunction with the structural diagram: when the first silicon-based nanowire microring 10 is powered down (logic "0"), the second silicon-based nanowire microring 20 is also powered down When it is flat (logic "0"), the two microrings are in a resonant state, and there is no light output at the light output ports Y1 and Y2 (both logic values are "0"); when the first silicon-based nanowire The microring 10 adds a high level (logic "1"), the second silicon-based nanowire microring 20 adds a low level (logic "0"), the second silicon-based nanowire microring 20 is in a resonant state, and the first silicon-based nanowire microring 20 is in a resonant state. The base nanowire microring 10 is in a non-resonant state, and there are light outputs (logic values are "1") at the output ports Y1 and Y2 of the light; when the first silicon-based nanowire microring 10 adds a low level (logic "0") ”), the second silicon-based nanowire microring 20 adds a high level (logic “1”), at this moment the second silicon-based nanowire microring 20 is in a non-resonant state, and the first silicon-based nanowire microring 10 is in resonance state, there is light output at the light output port Y2 (logic value "1"), and there is no light output at the light output port Y1 (logic value "0"); when the first silicon-based nanowire microring 10 is heightened Level (logic "1"), the second silicon-based nanowire microring 20 also adds a high level (logic "1"), and at this moment the two microrings are all in a non-resonant state, and there is Light output (logic value "1"), no light output at the light output port Y2 (logic value "0"). It can be seen that the input of the optical logic device of the present invention is two binary high and low level electrical signals to be calculated and a continuous laser signal at the working wavelength, and the output is the optical signal after the XOR operation; therefore The optical reversible device can complete the reversible XOR operation of two one-bit binary numbers. The basic unit of each microring resonator MRR is a microring resonator MRR optical switch with a thermal modulation mechanism or an electrical modulation mechanism. The 2-bit electrical signal to be calculated acts on the respective MRR as follows: 20 is the working wavelength at the resonant wavelength without modulation, so when the modulated electrical signal added to the microring 10 or 20 is at a high level, the resonant frequency of the MRR shifts and detunes at the wavelength of the input laser; When the modulation electrical signal on the microring 10 or 20 is at a low level, the MRR resonates at the wavelength of the input laser, and the optical signal is downloaded; a continuous laser with a specific working wavelength is input at an optical port of the reversible optical logic device, to be calculated The 2-bit high and low level electrical signals act on the first silicon-based nanowire microring 10 and the second silicon-based nanowire microring 20 respectively, and the two signal output ports are output in the form of optical logic and 2-bit input electrical signals The reversible XOR calculation result corresponding to the signal completes the function of the reversible optical logic device.

The truth table of the reversible XOR calculation completed by the optical reversible device of the present invention is shown in Table 1:

Table 1 Truth table of optical reversible XOR logic device

A B Y1(A) Y2(XOR)

0 0 0 0 1 0 1 1 0 1 0 1 1 1 1 0

The specific embodiments described above have further described the purpose of the present invention, technical solutions and beneficial effects in detail. It should be understood that the above are only specific embodiments of the present invention, and are not intended to limit the present invention. , within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., should be included within the protection scope of the present invention.

Claims (1)

1. A reversible optical logic device based on a microring resonator, characterized in that it is made of two microring resonators MRR and a Y branch coupler made of semiconductor material on an insulator; The two microring resonators MRR are a first microring resonator (1) and a second microring resonator (2), and the first microring resonator (1) includes a first silicon-based nanowire microring ( 10), the first input optical waveguide (11), the first straight-through optical waveguide (12) and the first download optical waveguide (13), the first microring resonator (1) has a silicon-based electro-optic modulator or a silicon-based Thermo-optic modulator; the second microring resonator (2) includes a second silicon-based nanowire microring (20), a second input optical waveguide (21), a second through optical waveguide (22), a third input optical waveguide (23) and the second output optical waveguide (24), the second input optical waveguide (21) is connected to the Y branch straight-through optical waveguide (33), and the third input optical waveguide (23) is connected to the first download optical waveguide (13) ; The second microring resonator (2) has a silicon-based electro-optic modulator or a silicon-based thermo-optic modulator; The first downloading optical waveguide (13) and the third input optical waveguide (23) are located on the U-shaped second waveguide arranged horizontally, and the first downloading optical waveguide (13) is located on the first silicon-based nanowire microring ( 10) Below, the other end of the straight waveguide of the second waveguide located below the first silicon-based nanowire microring (10) and provided with the first downloading optical waveguide (13) is the first light unloading port (T1); A third input optical waveguide (23) and a second output optical waveguide (24) are sequentially arranged on the section of the second waveguide located below the second silicon-based nanowire microring (20); The Y-branch coupler is a first Y-branch coupler (3), including a fourth input optical waveguide (31), a first output optical waveguide (32) and a Y-branch straight-through optical waveguide (33); the first The four input optical waveguides (31) are located on the main straight waveguide of the first Y-branch coupler (3), and are connected to the second straight-through optical waveguide (22), the first output optical waveguide (32) and the Y-branch straight-through optical waveguide ( 33) respectively located on the two branch straight waveguides of the first Y branch coupler (3); The first input optical waveguide (11), the first straight-through optical waveguide (12) and the fourth input optical waveguide (31) are sequentially located on the same straight first waveguide arranged horizontally, one end of the first waveguide Connect with the main straight waveguide of the Y branch coupler (3); The Y branch straight-through optical waveguide (33) is connected to one end of the U-shaped third waveguide, and the second input optical waveguide ( 21) and the second output optical waveguide (22), the end of the straight waveguide with the second input optical waveguide (21) and the second output optical waveguide (22) in the third waveguide is the second optical unloading port (T2) .