A detection system for locking the shift of the resonance center position of a silicon-based micro-ring resonator

Abstract

The application discloses a detection system of a silicon-based micro-ring resonator, in particular a detection system for locking the shift resonant center position of a silicon-based micro-ring resonator, which comprises a micro-ring resonator device and a detection circuit; the micro-ring resonator device comprises a beam splitter, a phase shifter, a silicon-based micro-ring resonator and a beam combiner; the detection circuit comprises a photodetector, a transimpedance amplifier, a multiplier, a low-pass filter, an adder, a direct current signal generator and a dither signal generator. The monitoring light generated by the micro-ring resonator device is transmitted to the detection circuit part, and the detection circuit part generates a detection signal; according to the size of the detection signal, the working state of the silicon-based micro-ring resonator is judged, the position of the silicon-based micro-ring resonator deviating from the resonant center is locked, and the silicon-based micro-ring resonator is not sensitive to the change of input light power.

Description

Technical Field

[0001] This invention relates to a detection system for silicon-based microring resonators, and more particularly to a detection system for locking the position of the offset resonant center of a silicon-based microring resonator. Background Technology

[0002] With the continuous increase in network traffic and people's growing needs, traditional communication methods are gradually becoming insufficient to meet people's needs. Optical communication technology has begun to flourish. Optical communication technology includes optical interconnect technology. On-chip optical interconnect technology based on silicon-on-insulator (SOI) has advantages such as low latency, large bandwidth, and low loss, providing a solution to the problems caused by the current increase in network traffic.

[0003] A microring resonator (MRR) is an optical device composed of waveguides. Its small radius and high integration density make it a key component in optical interconnect technology. It possesses wavelength selectivity, allowing it to select specific wavelengths of light, playing a crucial role in dense wavelength division multiplexing (DWDM) systems. It is commonly used as a filter, switch, and modulator. However, silicon-based microring resonators have a relatively large thermo-optic coefficient, making them susceptible to temperature variations. This can cause the resonant wavelength to shift, potentially resulting in the microring resonator not operating at its optimal state. Furthermore, the small radius of the microring resonator necessitates stringent manufacturing processes, making manufacturing errors difficult to avoid. The resonant wavelength of each manufactured microring resonator may not be the designed resonant wavelength, leading to suboptimal operation. Therefore, wavelength locking and wavelength shift detection are essential for microring resonators. The maximum value detection method is a commonly used method for wavelength locking of microring resonators. This method uses components such as photodetectors to detect the magnitude of the output photocurrent of the microring resonator. In the resonant state, the output light intensity of the microring resonator is at its maximum, indicating that the microring resonator is in a resonant state. This method uses the photodetector to detect the magnitude of this photocurrent to determine the operating state of the microring resonator. The balanced zero-difference detection method is another commonly used method for detecting the operating wavelength of a microring resonator. This method splits the input light into two parts. One part of the light is combined with the light output from the lower end of the microring resonator using a Mach-Zehnder interferometer (MZI). The phase on one arm of the Mach-Zehnder interferometer is changed, and the intensity of the combined light is detected. When the intensity is zero, the wavelength of this light is the resonant wavelength of the microring resonator, thus detecting whether the microring resonator is operating in a resonant state. Both of these methods lock the position of the resonant center of the microring resonator. Without locking the position of the microring resonator from the resonant center, the locking result is easily affected by the input light power. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art by providing a detection system that uses coherent detection to lock the position of a silicon-based microring resonator off-center from the resonance center and is insensitive to input optical power.

[0005] To achieve the above objectives, the present invention provides a detection system for locking the offset resonant center position of a microring resonator, comprising:

[0006] A microring resonator device includes an up-and-down silicon-based microring resonator, a beam splitter, a phase shifter, and a beam combiner.

[0007] The resonance formula for the silicon-based microring resonator is:

[0008] 2πRN eff =mλ0,m=0,1,2,…

[0009] Where R is the radius of the silicon-based microring resonator, and N eff The effective refractive index is λ0, and the resonant wavelength is λ0.

[0010] One input of the beam splitter is connected to one end of a transmission waveguide 1, and its two outputs are respectively connected to one end of a transmission waveguide 2 and one end of a transmission waveguide 3. The phase shifter is disposed on the transmission waveguide 3. One input of the beam combiner is connected to the other end of the transmission waveguide 3, and its other input is connected to a transmission waveguide 4. One output is connected to one end of a transmission waveguide 5. A coupling region 1 is formed between the silicon-based micro-ring damper and the transmission waveguide 2, and a coupling region 2 is formed between the silicon-based micro-ring damper and the transmission waveguide 4. The coupling region 1 and the coupling region 2 have the same structure. The other end of the transmission waveguide 1 is the optical input of the micro-ring resonator device, the other end of the transmission waveguide 2 is the optical output of the silicon-based micro-ring resonator, one end of the beam combiner on the transmission waveguide 4 is the optical output of the silicon-based micro-ring resonator, and the other end of the transmission waveguide 5 is the monitoring optical output of the micro-ring resonator device.

[0011] The electric field component expression of the beam splitter is:

[0012]

[0013] Wherein, Ein is the input light in transmission waveguide one, Eo1 = Eo2, Eo1 is the light in transmission waveguide two, β1 is the transmission constant of transmission waveguide two, L1 is the length of transmission waveguide two, Eo2 is the light in transmission waveguide three, β2 is the transmission constant of transmission waveguide three, and L2 is the length of transmission waveguide three.

[0014] The transfer function of the silicon-based microring resonator download terminal is:

[0015]

[0016] Among them, E drop Let t1 and t2 be the light in the lower end of the silicon-based microring resonator, k1 and k2 be the coupling coefficients of the two coupling regions one and two of the silicon-based microring resonator, respectively, t1 and t2 be the transmission coefficients of the two coupling regions one and two of the silicon-based microring resonator, α be the loss, and θ be the phase change of the light in the silicon-based microring resonator.

[0017] The transfer function of the beam combiner is:

[0018]

[0019] Where Eo is the combined light, Eo 11 With Eo 12 These are the two inputs to the beam combiner structure;

[0020] The optical E in the download terminal of the silicon-based microring resonator drop The beam that is combined with the light Eo2 in waveguide 3 via the beam combiner is:

[0021]

[0022] Here, Eo represents the monitoring light;

[0023] A detection circuit includes a photodetector, a transimpedance amplifier, a multiplier, a low-pass filter, an adder, a DC signal generator, and a jitter signal generator.

[0024] One input terminal of the adder is connected to one output terminal of the DC signal generator, and its other input terminal is connected to one output terminal of the jitter signal generator; one output terminal of the photodetector is connected to one input terminal of the transimpedance amplifier, one output terminal of the transimpedance amplifier is connected to one input terminal of the multiplier, the other output terminal of the jitter signal generator is connected to another input terminal of the multiplier, one output terminal of the multiplier is connected to one input terminal of the low-pass filter, and one output terminal of the low-pass filter is the detection signal output terminal of the detection circuit;

[0025] The demodulation equation of the multiplier is:

[0026]

[0027] Where A and B represent the voltage amplitude of the transimpedance amplifier output and the voltage amplitude of the jitter signal, respectively, where A contains the slope information of the monitoring light and ω is the frequency of the jitter signal.

[0028] In this circuit, one output terminal of the adder is connected to the heating resistor of the silicon-based microring resonator, and the monitoring light output terminal of the microring resonator device is connected to one input terminal of the photodetector in the detection circuit.

[0029] The present invention provides a detection system for locking the position of a silicon-based microring resonator off-center, which can lock the position of the silicon-based microring resonator off-center and is insensitive to the input optical power. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the silicon-based microring resonator with upper and lower paths in this invention;

[0031] Figure 2 These are the simulated transmission spectrum curves of the silicon-based microring resonator with up-and-down paths in this invention;

[0032] Figure 3 This is a schematic diagram of the micro-ring resonator device in this invention;

[0033] Figure 4 This is a schematic diagram of the detection system in this invention;

[0034] Figure 5 These are simulation curves of the transimpedance amplifier output for different input optical powers in this invention;

[0035] Figure 6 These are simulation curves of the detection signal under different input optical powers in this invention;

[0036] Figure 7 This is a simulation curve showing the difference between the detection signal and the output of the transimpedance amplifier for different input optical powers in this invention.

[0037] In the figure: beam splitter 1, phase shifter 2, beam combiner 3, transmission waveguide 3 4, silicon-based microring resonator 5, transmission waveguide 2 6, transmission waveguide 4 7, coupling region 1 8, coupling region 2 9, transmission waveguide 1 10, transmission waveguide 5 11. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0039] Figure 1 This is a structural diagram of a silicon-based microring resonator with a drop-through configuration, including the input terminal, drop terminal, and through terminal. The microring resonator exhibits wavelength selectivity, and its resonance formula is:

[0040] 2πRN eff =mλ0,m=0,1,2,…

[0041] Where R is the radius of the micro-ring resonator, and N eff For the effective refractive index, the wavelength λ0 that satisfies this equation is the resonant wavelength. Light that satisfies the microring resonator's resonance formula will be output from the download end; light that does not satisfy it will be output from the through end, such as... Figure 2 As shown, the transmission spectrum at the download end is a Lorentz curve, reaching its maximum value at the resonant wavelength. This means the light intensity is highest at the resonant wavelength at the download end, while the light intensity is relatively weaker at other wavelengths. Conversely, the light intensity is lowest at the resonant wavelength at the through end, while the light intensity is relatively stronger at other wavelengths. Therefore, the silicon-based microring resonator exhibits wavelength selectivity.

[0042] Figure 3 The diagram shows the microring resonator device of the present invention. One end of the beam splitter 1 is the input end, connected to transmission waveguide 10, and the other end is the output end, connected to transmission waveguide 6 and transmission waveguide 4 respectively. Transmission waveguide 6 is a straight waveguide, and transmission waveguide 4 is a combination of a straight waveguide and a curved waveguide. The phase shifter 2 is located on transmission waveguide 4. A portion of the silicon-based microring resonator 5 and a portion of transmission waveguide 6 form coupling region 8, and a portion of transmission waveguide 7 and a portion of silicon-based microring resonator 5 form coupling region 9. Coupling region 8 and coupling region 9 have the same structure, including the same waveguide structure, the same spacing between the straight waveguide and the silicon-based microring resonator, the same transmission coefficient, and the same transmission coefficient. Transmission waveguide 4 and transmission waveguide 7 are respectively connected to the two input ends of the beam combiner 3. The other end of the beam combiner is connected to transmission waveguide 11 as the monitoring light output end, and the other end of transmission waveguide 6 is the light output end.

[0043] The light input to waveguide one is split into two beams with the same amplitude and phase by a beam splitter, and then transmitted to waveguide two and waveguide three, respectively. The expression for their electric field components is:

[0044]

[0045] Where Ein is the input light in input waveguide one, Eo1 and Eo2 are the beams split by the beam splitter, Eo1 is the light in transmission waveguide two, Eo2 is the light in transmission waveguide three, β is the transmission constant, and L is the length of the transmission waveguide. To make the amplitude and phase of the two beams equal after splitting, the phase shifter is adjusted to compensate for the additional phase difference, so that β1L1=β2L2, therefore Eo1=Eo2. The light Eo1 in transmission waveguide two is coupled into the silicon-based microring resonator through coupling region one, and continuously circulates within the silicon-based microring resonator. The light satisfying the resonance condition of the silicon-based microring resonator is coupled into the download end transmission waveguide four through coupling region two. The transmission function of the download end is obtained according to the transmission matrix method:

[0046]

[0047] Among them, E drop Let t1 and t2 be the light at the input end of the silicon-based microring resonator, k1 and k2 be the coupling coefficients of the two coupling regions one and two of the silicon-based microring resonator, respectively, t1 and t2 be the transmission coefficients of the two coupling regions one and two of the silicon-based microring resonator, α be the loss, and θ be the phase change of the light in the silicon-based microring resonator.

[0048] The transfer function of the beam combiner is:

[0049]

[0050] Where Eo is the combined light, Eo 11 With Eo 12 These are the two input beams of the beam combiner.

[0051] Optical E in the download terminal of silicon-based microring resonator drop The beam that is combined with the light Eo2 in waveguide 3 via the beam combiner is:

[0052]

[0053] Eo is the monitoring light.

[0054] The core layer of a silicon-based microring resonator is made of silicon, and light is confined within the core layer. Silicon has a large thermo-optic coefficient and is easily affected by temperature. When the temperature of silicon changes, the effective refractive index of silicon changes. The effective refractive index is closely related to the wavelength selectivity of the silicon-based microring resonator. When the effective refractive index changes, the characteristics of the silicon-based microring resonator also change.

[0055] like Figure 4As shown, the detection circuit of this invention includes a photodetector, a transimpedance amplifier, a multiplier, a low-pass filter, an adder, a DC signal generator, and a jitter signal generator. The DC signal and the jitter signal are added by the adder and then applied to the heating resistor on the silicon-based microring resonator through port b. The jitter signal is a small-amplitude cosine signal. Based on the thermo-optical characteristics of the silicon core layer in the silicon-based microring resonator, this jitter signal changes the effective refractive index of the silicon-based microring resonator, thereby modulating the light within the silicon-based microring resonator. After passing through the silicon-based microring resonator, the monitoring light is transmitted to the detection circuit through port a. The monitoring light first enters the photodetector, which converts the optical signal into a current signal. The current signal is then converted into a voltage signal V0 by the transimpedance amplifier and multiplied by the original jitter signal in the multiplier for demodulation.

[0056]

[0057] Where A and B represent the voltage amplitude of the transimpedance amplifier output and the voltage amplitude of the original jitter signal, respectively, with A containing the slope information of the monitoring light and ω being the frequency of the jitter signal. After the multiplier's output signal enters the low-pass filter, the higher frequency signal components are filtered out, leaving the DC signal component AB / 2, which is output as the detection signal from port c of the detection circuit.

[0058] Based on the above implementation scheme, the present invention was simulated. Figure 5 The simulation curves show the output voltage V0 of the transimpedance amplifier under different input optical powers. V0 is the smallest at the resonant wavelength, and the voltage is relatively larger at other wavelengths. The waveform is symmetrical from left to right, and the magnitude of V0 is related to the input optical power; the higher the input optical power, the larger the value of V0.

[0059] Figure 6 To simulate the detection signal V1, the slope of V1 is approximated as that of V0. At the resonant wavelength, the detection signal V1 is 0, indicating that the silicon-based microring resonator is operating in resonance. When the detection signal V1 is not equal to 0, it indicates that the silicon-based microring resonator is not operating in resonance. Furthermore, the detection signal V1 corresponds one-to-one with V0; V1 is the feedback signal associated with the resonant wavelength. The value of V1 reflects the operating wavelength of the silicon-based microring resonator at that moment, thus pinpointing the position of the silicon-based microring resonator off-resonant wavelength. The value of the detection signal V1 is also closely related to the input optical power; as the input optical power increases, the value of the detection signal V1 increases accordingly.

[0060] To eliminate the influence of input optical power, the detection signal V1 is divided by V0, and the simulation results are as follows. Figure 7As shown, the simulated curves of V1 / V0 completely overlap under different input optical powers, indicating that the result is not sensitive to input optical power. The variation curve of V1 / V0 is similar to that of V1. When V1 / V0 equals 0, the silicon-based microring resonator is operating in the resonant state, and the value of V1 / V0 corresponds one-to-one with the operating wavelength of the silicon-based microring resonator, which can pinpoint the position of the silicon-based microring resonator off-center from the resonant center.

[0061] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes in shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A detection system for locking the position of the resonant center offset of a microring resonator, characterized in that: include: A microring resonator device includes an up-and-down silicon-based microring resonator, a beam splitter, a phase shifter, and a beam combiner. The resonance formula for the silicon-based microring resonator is: ； in, Let be the radius of the silicon-based microring resonator. For effective refractive index, The resonant wavelength; One input terminal of the beam splitter is connected to one end of a first transmission waveguide, and its two output terminals are respectively connected to one end of a second transmission waveguide and one end of a third transmission waveguide. The phase shifter is mounted on the transmission waveguide three. One input terminal of the beam combiner is connected to the other end of transmission waveguide three, its other input terminal is connected to transmission waveguide four, and its output terminal is connected to one end of transmission waveguide five. A coupling region is formed between the silicon-based microring resonator and the transmission waveguide. A second coupling region is formed between the silicon-based microring resonator and the transmission waveguide. Coupled region one and coupled region two have the same structure. The other end of the transmission waveguide is the optical input terminal of the microring resonator device. The other end of the second transmission waveguide is the optical output terminal of a silicon-based microring resonator. One end of the coupling bundler on the transmission waveguide four is the optical download end of a silicon-based microring resonator. The other end of the transmission waveguide five is the monitoring optical output end of the micro-ring resonator device; The electric field component expression of the beam splitter is: ； in, To transmit the input light in waveguide one, , To transmit light in waveguide two, 1 represents the propagation constant of waveguide 2. 1 represents the length of waveguide 2. To transmit light in waveguide three, 2 represents the transmission constant of waveguide 3. 2 represents the length of waveguide 3; The transfer function of the silicon-based microring resonator download terminal is: ； in, The light source at the lower end of the silicon-based microring resonator. These are the coupling coefficients of two coupling regions, one and two, of the silicon-based microring resonator. Let be the transmission coefficients of the two coupling regions, I and II, of the silicon-based microring resonator. For loss, This refers to the phase change of light in a silicon-based microring resonator. The transfer function of the beam combiner is: ； in, The light after beam combining and These are the two inputs to the beam combiner structure; The light in the download terminal of the silicon-based microring resonator With the light in the transmission waveguide three The light beam combined by the beam combiner is: ； in, That is, monitoring light; A detection circuit includes a photodetector, a transimpedance amplifier, a multiplier, a low-pass filter, an adder, a DC signal generator, and a jitter signal generator. One input terminal of the adder is connected to one output terminal of a DC signal generator, and its other input terminal is connected to one output terminal of a jitter signal generator. One output terminal of the photodetector is connected to one input terminal of the transimpedance amplifier. One output terminal of the transimpedance amplifier is connected to one input terminal of the multiplier. The other output of the jitter signal generator is connected to the other input of the multiplier. One output of the multiplier is connected to one input of a low-pass filter. One output terminal of the low-pass filter is the detection signal output terminal of the detection circuit; The demodulation equation of the multiplier is: ； in, These represent the voltage amplitude at the output of the transimpedance amplifier and the voltage amplitude of the jitter signal, respectively. It contains information about the slope of the monitored light. The frequency of the jitter signal; In the detection circuit, one output terminal of the adder is connected to the heating resistor of the silicon-based microring resonator, and the monitoring light output terminal of the microring resonator device is connected to one input terminal of the photodetector in the detection circuit. The monitoring light first enters the photodetector, which converts the light signal into a current signal. The current signal is then converted into a voltage signal by a transimpedance amplifier. The signal is multiplied by the original jitter signal in the multiplier for demodulation; the output signal of the multiplier enters a low-pass filter, where higher frequency signal components are filtered out, leaving only the DC signal component. As a detection signal The detection signal is output from port C of the detection circuit. Approximately The slope; the detection signal and Divide, The value corresponds one-to-one with the operating wavelength of the silicon-based microring resonator, which can pinpoint the position of the offset resonant center of the silicon-based microring resonator.

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