Micro resonant cavity system and photon maximum generation rate control method thereof

Abstract

The present application provides a kind of micro resonant cavity system and its photon maximum generation rate control method, system includes: input channel, micro resonant cavity and output channel;The input channel is used to input pump light to micro resonant cavity;The output channel is used to export the photon pair corresponding to the signal light and idler light generated in the micro resonant cavity;One side of the micro resonant cavity is critically coupled with the input channel at pump light resonance peak;The other side of the micro resonant cavity is over-coupled with the output channel at signal light resonance peak and idler light resonance peak, and the greater the coupling coefficient, the higher the single-photon maximum generation rate allowed by micro resonant cavity.The present application improves the maximum photon flow rate allowed by microcavity at signal light frequency and idler light frequency while ensuring high power efficiency of pump light.For the improvement of the maximum allowed photon flow rate, it is derived from the shortening of photon lifetime brought by over-coupling condition, and the widening of signal light and idler light resonance peak.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of quantum optics, and more particularly, relates to a micro resonator system and a method for controlling the maximum generation rate of photons. BACKGROUND

[0002] The photon generation method based on the spontaneous nonlinear effect of micro resonators is an important resource for integrated quantum light sources. This type of photon generation method is used as an announcement single photon source or an entangled photon source due to its unique mechanism of generating pairs of photons, and has many applications in quantum computing, quantum secure communication, and other applications. The resonant effect of the micro resonator can effectively enhance the intensity of the optical field in the cavity, thereby enhancing the interaction between light and matter and improving the strength of the nonlinear effect. Based on this, the single photon source based on the spontaneous nonlinear effect of the micro resonator can achieve efficient generation of entangled photon pairs or be used for announcement single photon sources.

[0003] However, there is a contradiction in the principle of photon generation of the single photon source based on the micro resonator. Since the generated photons are affected by the quality factor of the microcavity, the maximum photon generation rate allowed by the quality factor will decrease as the quality factor increases. Specifically, for a single micro ring resonator with low loss, high quality factor and critical coupling, its high quality factor will increase the lifetime of the generated photons in the time domain, resulting in the inability to allow high repetition frequency of photon outflow, otherwise it will cause the overlap of single photon wave packets in the time domain. On the other hand, since the resonance peak linewidth of the high quality factor microcavity is further narrowed, the Fourier transform of the photon flow pulse must be limited within the bandwidth of the resonance peak, so the micro ring with higher quality factor cannot pass through the high repetition frequency of the photon flow, which further limits the application of high-speed single photon sources.

[0004] In order to get rid of the upper limit of the photon generation rate of the single photon source based on the microcavity, the method of overcoupling can better broaden the resonance peak, while sacrificing a certain quality factor to shorten the lifetime of the photon, thereby allowing a larger repetition frequency of the photon outflow and improving the upper limit of the allowed rate. However, overcoupling will seriously damage the field enhancement factor of the micro ring, and thus cause a very serious decline in efficiency. Therefore, it is necessary to regulate the resonance peak separately to ensure the efficiency of the spontaneous nonlinear effect.

[0005] Even though the photon generation method based on the spontaneous nonlinear effect of the microcavity is still very low in efficiency, with the progress of material science and the further improvement of manufacturing processes, such a single photon source will eventually reach the upper limit of the photon generation rate. Therefore, it is necessary to find a special alternative method to replace the overcoupling scheme without sacrificing the efficiency of the spontaneous nonlinear process as much as possible. SUMMARY

[0006] In view of the defects of the prior art, the purpose of the present application is to provide a micro resonant cavity system and a maximum photon generation rate control method thereof, aiming to solve the problem that the prior art cannot improve the upper limit of the photon generation rate while ensuring the spontaneous nonlinear efficiency of the micro resonant cavity.

[0007] To achieve the above-mentioned purpose, in a first aspect, the present application provides a micro resonant cavity system, comprising: an input channel, a micro resonant cavity and an output channel;

[0008] The input channel is used for inputting pump light into the micro resonant cavity.

[0009] The output channel is used for outputting the photon pairs corresponding to the signal light and idler light generated in the micro resonant cavity.

[0010] One side of the micro resonant cavity is critically coupled with the input channel at the pump light resonance peak.

[0011] The other side of the micro resonant cavity is over-coupled with the output channel at the signal light resonance peak and the idler light resonance peak, and the greater the coupling coefficient, the higher the maximum single-photon generation rate allowed by the micro resonant cavity.

[0012] In an optional example, the closer the coupling distance between the micro resonant cavity and the output channel, the higher the coupling coefficient.

[0013] In a second aspect, the present application provides a photon maximum generation rate control method for the micro resonant cavity system provided in the first aspect, comprising the following steps:

[0014] The micro resonant cavity is prepared by selecting a predetermined material, so that the intrinsic loss is within a predetermined range, so as to ensure the efficiency of the spontaneous nonlinear effect of the micro resonant cavity.

[0015] The coupling distance between the input channel and the micro resonant cavity is adjusted to regulate the first coupling coefficient between the input channel and the micro resonant cavity, so that the loss caused by the input channel to the micro resonant cavity is equal to the intrinsic loss of the micro resonant cavity, so that when the pump light is input into the micro resonant cavity through the input channel, the micro resonant cavity is critically coupled with the input channel at the pump light resonance peak.

[0016] The coupling distance between the output channel and the micro resonant cavity is adjusted to regulate the second coupling coefficient between the output channel and the micro resonant cavity, so that the loss caused by the output channel to the micro resonant cavity is greater than the intrinsic loss of the micro resonant cavity, so that when the photon pairs are output through the output channel, the micro resonant cavity is over-coupled with the output channel at the signal light resonance peak and the idler light resonance peak.

[0017] The second coupling coefficient is adjusted to change the degree of over-coupling and control the maximum single-photon generation rate allowed by the micro resonant cavity; the greater the second coupling coefficient, the deeper the degree of over-coupling, and the higher the maximum generation rate.

[0018] In an optional example, the maximum photon generation rate is inversely proportional to the total quality factor of the micro resonant cavity at the signal light resonant peak and the idler light resonant peak.

[0019] The reciprocal of the total quality factor is equal to the sum of the reciprocal of the intrinsic quality factor of the micro resonant cavity and the reciprocal of the external quality factor of the micro resonant cavity at the signal light resonant peak and the idler light resonant peak.

[0020] The external quality factor of the micro resonant cavity at the signal light resonant peak and the idler light resonant peak is inversely proportional to the second coupling coefficient.

[0021] In an optional example, the external quality factor of the micro resonant cavity at the signal light resonant peak and the idler light resonant peak is less than the intrinsic quality factor; wherein the quality factor is inversely proportional to the corresponding loss.

[0022] In an optional example, the reciprocal of the total quality factor of the micro resonant cavity at the pump light resonant peak is equal to the sum of the reciprocal of the intrinsic quality factor of the micro resonant cavity and the reciprocal of the external quality factor of the micro resonant cavity at the pump light resonant peak; the external quality factor of the micro resonant cavity at the pump light resonant peak is inversely proportional to the first coupling coefficient.

[0023] Controlling the first coupling coefficient makes the loss brought by the input channel to the micro resonant cavity equal to the intrinsic loss of the micro resonant cavity, so that the external quality factor of the micro resonant cavity at the pump light resonant peak is equal to the intrinsic quality factor, so as to make the pump light input from the input channel completely coupled into the micro resonant cavity.

[0024] Overall, compared with the prior art, the above technical solutions conceived by the present application have the following beneficial effects:

[0025] The present application provides a micro resonant cavity system and a maximum photon generation rate control method thereof, which separates the coupling strength between the micro resonant cavity and the pump light input channel and the photon output channel, so as to achieve the purpose of separately regulating the resonant peak width of the micro resonant cavity at different wavelengths, thereby improving the maximum photon flow rate allowed by the micro cavity at the signal light frequency and the idler light frequency while ensuring high power efficiency of the pump light. The improvement of the maximum allowed photon flow rate is derived from the shortening of the photon lifetime caused by the overcoupling condition and the widening of the signal light and idler light resonant peaks.

[0026] The present application provides a micro resonant cavity system and a maximum photon generation rate control method thereof, which utilizes the spontaneous nonlinear effect of the micro resonant cavity to generate photons, and has very good integration compared with fiber ring or bulk crystal devices (size in centimeter to meter level), and has the advantage of better integration on a chip.

[0027] The present application provides a kind of micro resonant cavity system and its maximum photon generation rate control method, the micro resonant cavity used can be second-order nonlinear material or third-order nonlinear material, both kinds of materials can efficiently generate photon pair, and material loss is relatively low, power consumption is also relatively low.

[0028] The present application provides a kind of micro resonant cavity system and its maximum photon generation rate control method, the micro resonant cavity spontaneous nonlinear effect used can be second-order spontaneous parametric down-conversion effect, also can be third-order spontaneous four-wave mixing effect, and is widely used.

[0029] The present application provides a kind of micro resonant cavity system and its maximum photon generation rate control method, the micro resonant cavity used is not limited to structure, can make micro ring resonant cavity, micro disk resonant cavity, microsphere resonant cavity etc., this kind of resonant cavity all has very small volume and very good integration, and low power consumption.

[0030] The present application provides a kind of micro resonant cavity system and its maximum photon generation rate control method, the method for separately controlling the resonant peak of microcavity is, by separating pump light input channel and photon output channel, and separately controlling first coupling coefficient and second coupling coefficient, to independently regulate pump light resonant peak and signal light, idler light resonant peak. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is the schematic diagram of spontaneous parametric down-conversion principle provided by prior art;

[0032] Figure 2 It is the schematic diagram of spontaneous four-wave mixing principle provided by prior art;

[0033] Figure 3 It is the schematic diagram of micro resonant cavity system provided by the embodiment of the present application;

[0034] Figure 4 It is the schematic diagram of resonant peak distribution of micro resonant cavity provided by the embodiment of the present application. DETAILED DESCRIPTION

[0035] For the convenience of understanding, the following first to the English abbreviation and relevant technical terms involved in the embodiment of the present application are explained and described.

[0036] The embodiment of the present application is described below in conjunction with the drawings in the embodiment of the present application.

[0037] The present application provides a kind of micro resonant cavity system and its maximum photon generation rate control method, comprising;Micro resonant cavity;Pump light input channel;Photon output channel;Micro resonant cavity is used for the resonance of pump light, under the action of spontaneous nonlinear effect, signal light and idler light wavelength spontaneously generates photon pair;Micro resonant cavity has high quality factor, and and pump light input channel, photon output channel coupling;At pump light wavelength, micro resonant cavity and pump channel are in critical coupling state, to ensure the high quality factor of pump resonance peak;At signal light and idler light wavelength, micro resonant cavity and photon output channel are in over-coupling state, to improve the maximum photon generation rate allowed by system;The present application balances the effect of allowable maximum photon generation rate and pump efficiency by regulating the resonance peak of quantum light source based on micro resonant cavity.

[0038] To achieve the above object, the present application provides a kind of control micro resonant cavity system photon maximum generation rate method, comprising the following steps:

[0039] Micro resonant cavity is coupled with pump input channel, and is coupled with photon output channel simultaneously;The intrinsic loss of the micro resonant cavity is controlled to control the intrinsic quality factor of micro resonant cavity;The intrinsic quality factor is only related to the intrinsic loss of micro resonant cavity, and is not related to the coupling of the pump input channel or the photon output channel;

[0040] Micro resonant cavity is coupled with pump input channel, and is coupled with photon output channel simultaneously;The intrinsic loss of the micro resonant cavity is controlled to control the intrinsic quality factor of micro resonant cavity;The intrinsic quality factor is only related to the intrinsic loss of micro resonant cavity, and is not related to the coupling of the pump input channel or the photon output channel;

[0041] The coupling coefficient of the micro resonant cavity and pump input channel is controlled, so that the micro resonant cavity is in critical coupling state at pump light resonance peak, so that the pump light input channel input pump light is completely coupled into micro resonant cavity, and resonance is established in micro resonant cavity;The pump light input channel and micro resonant cavity are in critical coupling state, specifically: by adjusting the coupling coefficient of the micro resonant cavity and pump input channel, the loss caused by the pump light input channel to the micro resonant cavity is equal to the intrinsic loss of the micro resonant cavity;

[0042] The coupling coefficient of the micro resonant cavity and photon output channel is controlled, so that the micro resonant cavity is in over-coupling state at signal light resonance peak and idler light resonance peak;The over-coupling state at the signal light resonance peak and idler light resonance peak is adjusted to control the maximum single photon generation rate allowed by micro resonant cavity;

[0043] In an optional example, the coupling coefficient of the micro resonant cavity to the pump light input channel is a first coupling coefficient; the coupling coefficient of the micro resonant cavity to the photon output channel is a second coupling coefficient; the first coupling coefficient only affects the pump light resonance peak, and does not affect the signal light and idler light resonance peaks; the second coupling coefficient only affects the signal light and idler light resonance peaks, and does not affect the pump light resonance peak.

[0044] The first coupling coefficient is controlled to control the external quality factor of the micro resonant cavity at the pump light resonance peak; the second coupling coefficient is controlled to control the external quality factor of the micro resonant cavity at the signal light and idler light resonance peaks.

[0045] The reciprocal of the total quality factor of the micro resonant cavity at the pump light resonance peak is equal to the sum of the reciprocal of the intrinsic quality factor of the micro resonant cavity and the reciprocal of the external quality factor of the micro resonant cavity at the pump light resonance peak; the reciprocal of the total quality factor of the micro resonant cavity at the signal light and idler light resonance peaks is equal to the sum of the reciprocal of the intrinsic quality factor of the micro resonant cavity and the reciprocal of the external quality factor of the micro resonant cavity at the signal light and idler light resonance peaks.

[0046] In an optional example, the first coupling coefficient is controlled so that the micro resonant cavity is critically coupled to the pump input channel at the pump light resonance peak, so that the external quality factor of the micro resonant cavity at the pump light resonance peak is the same as the intrinsic quality factor of the micro resonant cavity, and the total quality factor at the pump light resonance peak is equal to half of the intrinsic quality factor.

[0047] In an optional example, the second coupling coefficient is controlled so that the micro resonant cavity is over-coupled to the photon input channel at the signal light and idler light resonance peaks, so that the external quality factor of the micro resonant cavity at the signal light and idler light resonance peaks is less than the intrinsic quality factor of the micro resonant cavity, thereby increasing the width of the signal light and idler light resonance peaks, and increasing the maximum photon generation rate allowed by the micro resonant cavity.

[0048] In an optional example, pump light is input to the pump input channel, the pump light is coupled into the micro resonant cavity through the input channel, and a resonance is established in the micro resonant cavity, so that pairs of signal photons and idler photons are spontaneously generated at the signal light and idler light resonance peaks; the pairs of signal photons and idler photons are coupled out of the micro resonant cavity and into the photon output channel, and are output by the photon output channel.

[0049] Specifically, the micro resonant cavity with a high intrinsic quality factor is selected, and preferably, the micro resonant cavity is a second-order nonlinear material or a third-order nonlinear material.

[0050] The micro resonant cavity and the pump light input channel are coupled, and the coupling coefficient is a first coupling coefficient; the micro resonant cavity and the photon output channel are coupled, and the coupling coefficient is a second coupling coefficient; the first coupling coefficient is adjusted, so that the micro resonant cavity is in a critical coupling state at the pump light resonant peak; the second coupling coefficient is adjusted, so that the micro resonant cavity is in an over-coupling state at the signal light resonant peak and the idler light resonant peak;

[0051] Preferably, the method for obtaining that the micro resonant cavity is in a critical coupling state at the pump light resonant peak and the pump light input channel is as follows:

[0052] The coupling coefficient between the micro resonant cavity and the pump input channel is adjusted, so that the loss caused by the pump light input channel to the micro resonant cavity is equal to the intrinsic loss of the micro resonant cavity;

[0053] The pump light is injected into the pump light input channel, and then enters the micro resonant cavity through coupling and establishes resonance therein; the signal photons and idler photons are spontaneously generated at the signal light resonant peak and the idler light resonant peak, and then enter the photon output channel through coupling and are output;

[0054] The present application separates the coupling strength between the micro resonant cavity and the pump light input channel and the photon output channel, so as to achieve the purpose of separately regulating the resonant peak width of the micro resonant cavity at different wavelengths, thereby improving the maximum photon flow rate allowed by the micro cavity at the signal light frequency and the idler light frequency while ensuring high power efficiency of the pump light.

[0055] The method for separately regulating and controlling coupling described in the present application can be implemented by various device structures, and is not limited to a single structure.

[0056] The method for improving the maximum photon generation rate of the micro cavity single photon source provided by the present application is not limited to a single material platform or micro resonant cavity structure, and can be implemented on various second-order nonlinear or third-order nonlinear material platforms.

[0057] In order to further illustrate the method provided by the present application for improving the generation rate of the maximum photon pair, the present application is compared with the prior art as follows:

[0058] (1) Compared with the high nonlinear optical fiber system, the photon pair generation method provided by the present application has good integration, and the nonlinear coefficient of the integrated micro cavity is high, so that more photon pairs can be generated with lower power compared with the optical fiber system.

[0059] (2) Compared with the waveguide structure, the photon pair generation method provided by the present application utilizes the resonance enhancement effect of the micro resonant cavity, so that the power consumption can be significantly reduced, and the pump light resonant peak is in a critical coupling state, thereby having the maximum nonlinear gain.

[0060] (3) Compared with a single critically coupled high-Q resonator, the photon pair generation method provided by the application can improve the maximum photon generation rate allowed, is not limited by the fixed total quality factor of the system, and has a breakthrough in the upper limit of the light source generation rate.

[0061] (4) Compared with a single over-coupled high-Q resonator, the photon pair generation method provided by the application has higher power efficiency, and can generate more photons than the over-coupled micro resonator under the same pump power.

[0062] The photons are generated by using spontaneous parametric down conversion (SPDC), and the principle is as shown in Figure 1 . As shown in Figure 1 , a pump light with a frequency of ω p spontaneously transfers energy to signal light with a frequency of ω s and idler light with a frequency of ω i , the frequencies of the signal light and the idler light are far away from the pump light, and the frequencies of the three lights satisfy ω p = ω s + ω i .

[0063] The photons are generated by using spontaneous four-wave mixing (SPDC), and the principle is as shown in Figure 1 . As shown in Figure 1 , a pump light with a frequency of ω p spontaneously transfers energy to signal light with a frequency of ω s and idler light with a frequency of ω i , the frequencies of the signal light and the idler light are located on both sides of the pump light and are symmetric about the pump light, and the frequencies of the three lights satisfy 2ω p = ω s + ω i .

[0064] As shown in Figure 3 , a micro resonator is coupled with a pump input channel and a photon output channel; the two coupling coefficients are k1 and k2, respectively, referred to as the first coupling coefficient and the second coupling coefficient; the first coupling coefficient only affects the pump light resonance peak, and the second coupling coefficient only affects the signal light resonance peak and the idler light resonance peak; such a structure in which the coupling coefficients independently affect the resonance peaks can be realized by coupling a micro resonator with a non-symmetric Mach-Zehnder interference arm.

[0065] As an embodiment of the application, as shown in Figure 4 , it is a micro resonator in which a pump resonance peak is in a critically coupled state, and a signal light resonance peak and an idler light resonance peak are in an over-coupled state; the quality factor of the pump light resonance peak is Q p , and the quality factors of the signal light and the idler light resonance peaks are both Q s ; the Qp greater than Q s . According to the relationship between the maximum rate of photon generation and the quality factor Q, the maximum photon generation rate is where v is the frequency of the photon; the maximum photon generation rate and Q s are inversely proportional, so the lower Q s value allows a higher maximum photon generation rate.

[0066] The advantages of the method are illustrated below using specific resonance peak distribution and quality factor values.

[0067] First example: for three resonance peaks with Q p = 3 x 10 p , the high-quality factor resonator in the critical coupling state, for example, Q 6 = 3 x 10 p , the maximum photon generation rate will be limited to 100 MHz. As can be seen, if the coupling states of the micro resonator and the input channel and the input channel are not discretely controlled, if the micro resonator and the input channel and the output channel are in the critical coupling state, the total quality factor of the pump resonance peak and the signal resonance peak and the idler resonance peak is Q s , at this time, in the case of ensuring the high power efficiency of the pump light, the maximum photon generation rate will be limited.

[0068] Second example: for three resonance peaks with Q s = 3 x 10 4 , the low-quality factor resonator in the over-coupling state, for example, Q p = 3 x 10 s , the maximum photon generation rate will be increased to 10 GHz. As can be seen, if the coupling states of the micro resonator and the input channel and the input channel are not discretely controlled, if the micro resonator and the input channel and the output channel are in the over-coupling state, since all three resonance peaks are in the over-coupling state, the efficiency of the spontaneous nonlinear process will be greatly reduced, and the system needs more power to obtain more photon generation rate, greatly increasing the pump power consumption.

[0069] For the present application, the method of discretely regulating the resonance peak as shown in Figure 4 , in the case of ensuring the critical coupling state of the pump light resonance peak, at this time the total quality factor at the pump light resonance peak is equal to Q s . The signal light resonance peak and the idler light resonance peak are in the over-coupling state and have a low quality factor, and the total quality factor at the signal light resonance peak and the idler light resonance peak is equal to Q p ., the maximum photon generation rate allowed by the system is 10GHz; and due to the critical coupling of the pump resonance peak, the utilization efficiency of the pump light is maximized, and compared with three resonance peaks of the over-coupled micro resonant cavity, only about one tenth of the pump light power is required to generate the same number of photon generation rate. It can be seen that the present application achieves the purpose of independently regulating the resonance peak width of the micro resonant cavity at different wavelengths, thereby improving the maximum photon flow rate allowed by the micro cavity at the signal light frequency and the idle frequency light frequency while ensuring high power efficiency of the pump light.

[0070] It should be understood that expressions such as "include" and "may include" used in the present application indicate the presence of disclosed functions, operations or constituent elements, and do not limit one or more additional functions, operations and constituent elements. In the present application, terms such as "include" and / or "have" can be interpreted to mean that a specific characteristic, number, operation, constituent element, component or combination thereof is present, but cannot be interpreted to exclude the presence or addition of one or more other characteristics, numbers, operations, constituent elements, components or combinations thereof.

[0071] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A microresonant cavity system, characterized in that, include: Input channel, micro resonant cavity, and output channel; The input channel is used to input pump light into the micro-resonant cavity; The output channel is used to output the photon pairs corresponding to the signal light and idler light generated in the micro-resonant cavity; By separating the pump light input channel and the photon output channel, and separately controlling the first coupling coefficient and the second coupling coefficient, the pump light resonance peak and the signal light and idler light resonance peak can be independently tuned. One side of the micro-resonant cavity is critically coupled to the input channel at the pump light resonance peak; The other side of the micro-resonant cavity is overcoupled to the output channel at the signal light resonance peak and the idler light resonance peak. The larger the coupling coefficient, the higher the maximum single photon generation rate allowed by the micro-resonant cavity. The closer the coupling distance between the micro-resonant cavity and the output channel, the higher the coupling coefficient. The coupling coefficient between the micro-resonator and the pump light input channel is the first coupling coefficient; the coupling coefficient between the micro-resonator and the photon output channel is the second coupling coefficient.

2. A method for controlling the maximum photon generation rate of the microresonator system according to claim 1, characterized in that, Includes the following steps: The micro-resonant cavity is prepared using a predetermined material, ensuring that its intrinsic loss is within a predetermined range, so as to guarantee the efficiency of the spontaneous nonlinear effect of the micro-resonant cavity. The coupling distance between the input channel and the micro-resonant cavity is adjusted to regulate the first coupling coefficient between the input channel and the micro-resonant cavity, so that the loss brought by the input channel to the micro-resonant cavity is equal to the intrinsic loss of the micro-resonant cavity, so that when the pump light is input into the micro-resonant cavity through the input channel, the micro-resonant cavity and the input channel are critically coupled at the resonance peak of the pump light. The coupling distance between the output channel and the micro-resonant cavity is adjusted to regulate the second coupling coefficient between the output channel and the micro-resonant cavity, so that the loss of the output channel to the micro-resonant cavity is greater than the intrinsic loss of the micro-resonant cavity, so that when the photon pair is output through the output channel, the micro-resonant cavity and the output channel are overcoupled at the signal light resonance peak and the idler light resonance peak. The second coupling coefficient is adjusted to change the degree of overcoupling and control the maximum single-photon generation rate allowed by the micro-resonator; wherein, the larger the second coupling coefficient is, the deeper the degree of overcoupling and the higher the maximum generation rate.

3. The method according to claim 2, characterized in that, The maximum photon generation rate is inversely proportional to the total quality factor of the micro-resonant cavity at the signal light resonance peak and the idler light resonance peak. The reciprocal of the total quality factor is equal to the sum of the reciprocal of the intrinsic quality factor of the micro-resonator and the reciprocal of the external quality factor of the micro-resonator at the signal light resonance peak and the idler light resonance peak. The external quality factor of the microresonator at the signal light resonance peak and the idler light resonance peak is inversely proportional to the second coupling coefficient.

4. The method according to claim 2 or 3, characterized in that, The external quality factor of the micro-resonant cavity at the signal light resonance peak and the idler light resonance peak is smaller than the intrinsic quality factor; wherein, the quality factor is inversely proportional to the corresponding loss.

5. The method according to claim 2 or 3, characterized in that, The reciprocal of the total quality factor of the micro-resonator at the pump light resonance peak is equal to the sum of the reciprocal of the intrinsic quality factor of the micro-resonator and the reciprocal of the external quality factor of the micro-resonator at the pump light resonance peak; the external quality factor of the micro-resonator at the pump light resonance peak is inversely proportional to the first coupling coefficient. The first coupling coefficient is controlled so that the loss of the micro-resonator caused by the input channel is equal to the intrinsic loss of the micro-resonator, so that the external quality factor of the micro-resonator at the pump light resonance peak is equal to the intrinsic quality factor, so that the pump light input from the input channel is fully coupled into the micro-resonator.

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