Optical filtering system and integrated chip integrated with two-photon quantum light source

Abstract

The invention provides an optical filtering system and an integrated chip integrated with a two-photon quantum light source, and the optical filtering system comprises a narrow-band band-stop filter, a periodic narrow-band band-pass filter, and two narrow-band band-pass filters without a free spectrum region, an entangled photon pair formed by pumping laser is processed by a narrow-band band-stop filter, a periodic narrow-band band-pass filter and two free-spectrum-region-free narrow-band band-pass filters in sequence, and then signal photons and idler-frequency photons which are matched with each other are output respectively; or an entangled photon pair formed by the pumping laser is sequentially processed by the periodic narrow-band band-pass filter, the narrow-band band-stop filter and the two narrow-band band-pass filters without the free spectrum regions, and then signal photons and idler frequency photons which are matched with each other are respectively output and obtained. The device can be integrated on a chip, and signal photons and idler frequency photons can be efficiently and accurately output separately.

Description

Technical Field

[0001] The present invention relates to the field of optical quantum information technology, and in particular to an optical filtering system and an integrated chip integrating a two-photon quantum light source. Background Art

[0002] As optical quantum information technology develops towards practical applications, chip-integrated two-photon quantum light sources that use waveguides or resonant cavities on photonic chips as nonlinear optical media have gained widespread attention.

[0003] However, in the current chip-integrated two-photon quantum light source solutions, discrete off-chip filter devices are often used to cascade to filter out the pump light, and it is impossible to efficiently and accurately separate the output of signal photons and idler photons.

[0004] Therefore, finding an optical filtering system that can be integrated on a chip and can efficiently and accurately separate and output signal photons and idler photons has become a current research hotspot. Summary of the invention

[0005] The present invention provides an optical filtering system and an integrated chip of an integrated two-photon quantum light source, which can be integrated on a chip and can efficiently and accurately separate and output signal photons and idler photons.

[0006] The present invention provides an optical filtering system, which comprises a narrowband rejection filter, a periodic narrowband bandpass filter, and two narrowband bandpass filters without free spectral regions, wherein an entangled photon pair formed by a pump laser is processed by the narrowband rejection filter, the periodic narrowband bandpass filter, and the two narrowband bandpass filters without free spectral regions in sequence, and then signal photons and idler photons matching each other are outputted respectively; or an entangled photon pair formed by a pump laser is processed by the periodic narrowband bandpass filter, the narrowband rejection filter, and the two narrowband bandpass filters without free spectral regions in sequence, and then signal photons and idler photons matching each other are outputted respectively, wherein the narrowband rejection filter is used to filter out the pump laser; the periodic narrowband bandpass filter is used to perform periodic narrowband filtering on the generated wide-spectrum signal photons and wide-spectrum idler photons to obtain signal photons and idler photons matching each other; and the two narrowband bandpass filters without free spectral regions are used to distinguish signal photons and idler photons matching each other.

[0007] According to an optical filtering system provided by the present invention, the stopband bandwidth of the narrowband stop filter is greater than or equal to 50 GHz and less than or equal to 1 THz.

[0008] According to an optical filtering system provided by the present invention, the extinction ratio of the narrow-band stop filter is greater than or equal to 80 dB.

[0009] According to an optical filtering system provided by the present invention, the narrowband band-stop filter includes any one or more of a single waveguide Bragg grating band-stop filter, a cascaded waveguide Bragg grating band-stop filter, a single microring filter, a cascaded microring filter, a single unbalanced Mach-Zehnder interferometer, and a cascaded unbalanced Mach-Zehnder interferometer.

[0010] According to an optical filtering system provided by the present invention, the filtering spectrum of the periodic narrowband bandpass filter includes a plurality of narrowband filtering passbands with equally spaced center frequencies, and each of the narrowband filtering passbands has the same symmetrical spectrum, wherein the narrowband filtering passbands include at least a narrowband filtering passband with a first center frequency and a narrowband filtering passband with a second center frequency, and do not have a narrowband filtering passband with a third center frequency, wherein the first center frequency matches the center frequency of the signal photon, the second center frequency matches the center frequency of the idler photon, and the third center frequency matches the center frequency of the pump laser.

[0011] According to an optical filtering system provided by the present invention, the extinction ratio of the periodic narrow-band pass filter is greater than or equal to 20 dB.

[0012] According to an optical filtering system provided by the present invention, the periodic narrow-band bandpass filter includes any one or more of a microring filter, an unbalanced Mach-Zehnder interferometer, and a waveguide integrated Fabry-Perot filter.

[0013] According to an optical filtering system provided by the present invention, the two narrow-band bandpass filters without free spectral region include a first narrow-band bandpass filter without free spectral region and a second narrow-band bandpass filter without free spectral region, wherein the center frequency of the first narrow-band bandpass filter without free spectral region matches the center frequency of the signal photons, and the center frequency of the second narrow-band bandpass filter without free spectral region matches the center frequency of the idler photons.

[0014] According to an optical filtering system provided by the present invention, the passband bandwidth of the first narrowband bandpass filter without free spectral region is greater than the bandwidth of each narrowband filter passband in the periodic narrowband bandpass filter, and is smaller than the frequency interval between adjacent narrowband filter passbands in the periodic narrowband bandpass filter.

[0015] According to an optical filtering system provided by the present invention, the passband bandwidth of the second narrowband bandpass filter without free spectral region is greater than the bandwidth of each narrowband filter passband in the periodic narrowband bandpass filter, and is smaller than the frequency interval between adjacent narrowband filter passbands in the periodic narrowband bandpass filter.

[0016] According to an optical filtering system provided by the present invention, the extinction ratio of the first narrow-band bandpass filter without free spectral region is greater than or equal to 20 dB.

[0017] According to an optical filtering system provided by the present invention, the extinction ratio of the second narrow-band bandpass filter without free spectral region is greater than or equal to 20 dB.

[0018] According to an optical filtering system provided by the present invention, the first narrow-band bandpass filter without free spectral region includes any one or more of a grating-assisted reverse coupler, a grating-assisted co-directional coupler, and a grating-assisted waveguide integrated Fabry-Perot filter.

[0019] According to an optical filtering system provided by the present invention, the second narrow-band bandpass filter without free spectral region includes any one or more of a grating-assisted reverse coupler, a grating-assisted co-directional coupler, and a grating-assisted waveguide integrated Fabry-Perot filter.

[0020] The present invention also provides an integrated chip integrating a two-photon quantum light source, the integrated chip integrating a two-photon quantum light source comprising a substrate, an optical waveguide, and an optical filtering system, wherein the optical waveguide is arranged on the substrate, wherein a pump laser excites the optical waveguide so that the optical waveguide generates entangled photon pairs based on spontaneous four-wave mixing or generates entangled photon pairs based on spontaneous parametric down-conversion; the optical filtering system is integrated with the optical waveguide and connected to the optical waveguide; the substrate is provided with two ports so that signal photons and idler photons that match each other obtained through filtering processing by the optical filtering system are output along the two ports respectively.

[0021] According to an integrated chip of an integrated two-photon quantum light source provided by the present invention, the optical waveguide includes any one or more of a single-mode silicon waveguide, a single-mode silicon nitride waveguide, a single-mode quartz waveguide, and a periodically poled lithium niobate waveguide.

[0022] The present invention provides an optical filtering system and an integrated chip of an integrated two-photon quantum light source, wherein the optical filtering system comprises a narrowband rejection filter, a periodic narrowband bandpass filter, and two narrowband bandpass filters without free spectral regions, wherein an entangled photon pair formed by a pump laser is processed by the narrowband rejection filter, the periodic narrowband bandpass filter, and the two narrowband bandpass filters without free spectral regions in sequence, and then signal photons and idler photons matching each other are outputted respectively; or an entangled photon pair formed by a pump laser is processed by the periodic narrowband bandpass filter, the narrowband rejection filter, and the two narrowband bandpass filters without free spectral regions in sequence, and then signal photons and idler photons matching each other are outputted respectively, wherein the narrowband rejection filter is used to filter out the pump laser; the periodic narrowband bandpass filter is used to perform periodic narrowband filtering on the generated wide-spectrum signal photons and wide-spectrum idler photons to obtain signal photons and idler photons matching each other; and the two narrowband bandpass filters without free spectral regions are used to distinguish signal photons and idler photons matching each other. It has been achieved that the signal photons and idler photons can be separated and output efficiently and accurately on a chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a structural schematic diagram of the optical filtering system provided by the present invention.

[0025] Figure 2 It is a schematic diagram of the structure of an integrated chip of an integrated two-photon quantum light source provided by the present invention.

[0026] Reference numerals: 10: optical filtering system; 110: narrowband rejection filter; 120: periodic narrowband bandpass filter; 130: narrowband bandpass filter without free spectral region; 20: substrate; 30: optical waveguide; 201: port; 100: integrated chip of integrated two-photon quantum light source. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] It is known from the related art that in the use of quantum light sources, a filtering system is required to separate the signal photons and idler photons generated by the nonlinear optical process to different output ports, and at the same time completely filter out the strong pump light. The spectrum center frequency of the signal photons and idler photons after filtering should satisfy the energy conservation relationship of the nonlinear optical process with the pump frequency, and have a consistent spectrum distribution, so as to achieve the matching of the signal photons and idler photons in the spectrum, thereby obtaining high-quality correlated two-photon output. In order to be able to integrate on the chip and to be able to efficiently and accurately separate the signal photons and idler photons for output, the present invention provides an optical filtering system including a narrowband rejection filter, a periodic narrowband bandpass filter, and two narrowband bandpass filters without free spectral regions. The three-stage structure.

[0029] Figure 1 It is a structural schematic diagram of the optical filtering system provided by the present invention.

[0030] The following will be combined Figure 1 The structure of the optical filtering system provided by the present invention is described.

[0031] In an exemplary embodiment of the present invention, Figure 1 It can be known that the optical filtering system 10 may include a narrowband rejection filter 110, a periodic narrowband bandpass filter 120, and two narrowband bandpass filters without free spectral regions 130, and each component will be introduced below.

[0032] In the application process, the entangled photon pair formed by the pump laser can be processed by the narrowband rejection filter 110, the periodic narrowband bandpass filter 120, and the two narrowband bandpass filters without free spectrum region 130 in sequence, and the signal photon and the idler photon matching each other are output respectively, or

[0033] The entangled photon pairs formed by the pump laser can be processed by the periodic narrowband bandpass filter 120, the narrowband band-stop filter 110, and the two narrowband bandpass filters 130 without free spectral regions in sequence, and the signal photons and idler photons that match each other are outputted respectively. In the application process, the narrowband band-stop filter 110, the periodic narrowband bandpass filter 120, and the two narrowband bandpass filters 130 without free spectral regions in the optical filtering system 10 can be directly integrated on an integrated chip of an integrated two-photon quantum light source, for example, by integration with an optical waveguide on the chip.

[0034] In yet another embodiment, a narrowband rejection filter 110 may be used to filter out the pump laser.

[0035] In another embodiment, the periodic narrowband bandpass filter 120 can be used to perform periodic narrowband filtering on the generated wide spectrum signal photons and wide spectrum idler photons to obtain signal photons and idler photons that match each other. The spectrum range of the wide spectrum can be between 350 nanometers (nm) and 1750 nanometers (nm).

[0036] In another embodiment, two narrow-band bandpass filters without free spectral regions 130 can be used to distinguish signal photons and idler photons that match each other. After the entangled photon pairs are sequentially processed by the narrow-band rejection filter 110 to remove the pump laser, the periodic narrow-band bandpass filter 120 to perform periodic narrow-band filtering on the wide-spectrum signal photons and wide-spectrum idler photons generated in the nonlinear optical waveguide, and the two narrow-band bandpass filters without free spectral regions 130 to perform filtering and distinguishing processing, the signal photons and idler photons that match each other can be output respectively, thereby achieving the technical effect of being able to be integrated on a chip and being able to efficiently and accurately separate and output the signal photons and idler photons.

[0037] The optical filtering system provided by the present invention includes a narrowband rejection filter, a periodic narrowband bandpass filter, and two narrowband bandpass filters without free spectral regions, wherein an entangled photon pair formed by a pump laser is processed by the narrowband rejection filter, the periodic narrowband bandpass filter, and the two narrowband bandpass filters without free spectral regions in sequence, and signal photons and idler photons matching each other are outputted respectively; or an entangled photon pair formed by a pump laser is processed by the periodic narrowband bandpass filter, the narrowband rejection filter, and the two narrowband bandpass filters without free spectral regions in sequence, and signal photons and idler photons matching each other are outputted respectively, wherein the narrowband rejection filter is used to filter out the pump laser; the periodic narrowband bandpass filter is used to perform periodic narrowband filtering on the generated wide-spectrum signal photons and wide-spectrum idler photons to obtain signal photons and idler photons matching each other; and the two narrowband bandpass filters without free spectral regions are used to distinguish signal photons and idler photons matching each other. It has been achieved that the signal photons and idler photons can be separated and output efficiently and accurately on a chip.

[0038] In yet another exemplary embodiment of the present invention, the stopband bandwidth of the narrowband stop filter 110 may be greater than or equal to 50 GHz and less than or equal to 1 THz.

[0039] In the application process, the stopband bandwidth of the narrowband stop filter 110 is set to be greater than or equal to 50 GHz and less than or equal to 1 THz, which can ensure that the stopband range covers the spectrum range of the pump laser, thereby effectively filtering out the pump laser.

[0040] In yet another exemplary embodiment of the present invention, the extinction ratio of the narrowband rejection filter 110 may be greater than or equal to 80 dB.

[0041] In one embodiment, the extinction ratio of the narrowband rejection filter 110 is set to be greater than or equal to 80 dB, which can well implement extinction processing, thereby laying a foundation for accurately separating and outputting signal photons and idler photons.

[0042] In another exemplary embodiment of the present invention, the narrowband rejection filter 110 may include any one or more of a single waveguide Bragg grating rejection filter, a cascade waveguide Bragg grating rejection filter, a single microring filter, a cascade microring filter, a single unbalanced Mach-Zehnder interferometer, and a cascaded unbalanced Mach-Zehnder interferometer. In this embodiment, the specific type of the narrowband rejection filter 110 is not limited.

[0043] In another exemplary embodiment of the present invention, the filtering spectrum of the periodic narrowband bandpass filter 120 may include multiple narrowband filtering passbands with equally spaced center frequencies, and each narrowband filtering passband has the same symmetrical spectrum, wherein the narrowband filtering passband includes at least a narrowband filtering passband with a first center frequency, and a narrowband filtering passband with a second center frequency, and does not have a narrowband filtering passband with a third center frequency, wherein the first center frequency matches the center frequency of the signal photon, the second center frequency matches the center frequency of the idler photon, and the third center frequency matches the center frequency of the pump laser.

[0044] In one embodiment, the function of the periodic narrowband bandpass filter 120 is to perform periodic narrowband filtering on the wide spectrum signal photons and idler photons generated in the nonlinear optical waveguide. The filtering spectrum of the periodic narrowband bandpass filter 120 may include a plurality of narrowband filter passbands with equally spaced center frequencies, each filter passband having the same symmetrical spectrum, wherein the center frequency of a filter passband is the center frequency w of the signal photon to be selected. s , the center frequency of a filter passband is the center frequency w of the idler photon to be selected i Furthermore, the periodic narrowband bandpass filter 120 has no filtering passband corresponding to the center frequency w of the pump laser. p Through this embodiment, the pump laser can be further filtered out, and the signal photons and idler photons can also be screened out.

[0045] In yet another exemplary embodiment of the present invention, the extinction ratio of the periodic narrow-band pass filter 120 may be greater than or equal to 20 dB.

[0046] In one embodiment, the extinction ratio of the periodic narrowband bandpass filter 120 is set to be greater than or equal to 20 dB, which can well implement extinction processing, thereby laying a foundation for accurately separating and outputting signal photons and idler photons.

[0047] In another exemplary embodiment of the present invention, the periodic narrow-band bandpass filter 120 may include any one or more of a micro-ring filter, an unbalanced Mach-Zehnder interferometer, and a waveguide integrated Fabry-Perot filter. In this embodiment, the specific type of the periodic narrow-band bandpass filter 120 is not limited.

[0048] In another exemplary embodiment of the present invention, the two narrow-band bandpass filters without free spectral region 130 may include a first narrow-band bandpass filter without free spectral region and a second narrow-band bandpass filter without free spectral region, wherein the center frequency of the first narrow-band bandpass filter without free spectral region is equal to the center frequency w of the signal photon. s The center frequency of the second narrow-band bandpass filter without free spectrum region matches the center frequency of the idler photon wi In this embodiment, by setting the center frequency of the first narrow-band bandpass filter without free spectrum region to be equal to the center frequency w of the signal photon, s The center frequency of the second narrow-band bandpass filter without free spectrum region is set to match the center frequency of the idler photon w i , the center frequency can be effectively selected as w s The signal photon and the center frequency are w i The idler photons are output from the chip from two different ports.

[0049] In another exemplary embodiment of the present invention, the passband bandwidth of the first free spectral region narrowband pass filter is greater than the bandwidth of each narrowband filter passband in the periodic narrowband pass filter and smaller than the frequency interval between adjacent narrowband filter passbands in the periodic narrowband pass filter.

[0050] In another exemplary embodiment of the present invention, the passband bandwidth of the second free spectral region narrowband pass filter is greater than the bandwidth of each narrowband filter passband in the periodic narrowband pass filter and less than the frequency interval between adjacent narrowband filter passbands in the periodic narrowband pass filter.

[0051] Through the above-mentioned embodiment, the center frequency can be effectively selected as w s The signal photon and the center frequency are w i The idler photons are output from the chip from two different ports.

[0052] In yet another exemplary embodiment of the present invention, the extinction ratio of the first narrow-band bandpass filter without free spectral region may be greater than or equal to 20 dB.

[0053] In yet another exemplary embodiment of the present invention, the extinction ratio of the second narrow-band bandpass filter without a free spectral region may be greater than or equal to 20 dB.

[0054] In the application process, by setting the extinction ratio of two narrow-band bandpass filters 130 without free spectral regions (including a first narrow-band bandpass filter without free spectral regions and a second narrow-band bandpass filter without free spectral regions) to be greater than or equal to 20 dB, the extinction processing can be well achieved, thereby laying the foundation for accurately separating and outputting signal photons and idler photons.

[0055] In another exemplary embodiment of the present invention, the first free spectral region-free narrowband bandpass filter may include any one or more of a grating-assisted reverse coupler, a grating-assisted co-directional coupler, and a grating-assisted waveguide integrated Fabry-Perot filter.

[0056] In another exemplary embodiment of the present invention, the second free spectral region-free narrowband bandpass filter may include any one or more of a grating-assisted reverse coupler, a grating-assisted co-directional coupler, and a grating-assisted waveguide-integrated Fabry-Perot filter.

[0057] In the aforementioned embodiment, the specific types of the first narrow-band bandpass filter without free spectral region and the second narrow-band bandpass filter without free spectral region are not limited.

[0058] It should be noted that the optical filtering system described above can be applied to quantum light source chips of various material systems, including but not limited to silicon quantum light source chips, silicon dioxide quantum light source chips, silicon nitride quantum light source chips, lithium niobate quantum light source chips, etc., thereby realizing the effective integration of multiple chips.

[0059] The optical filtering system 10 provided by the present invention comprises a three-stage structure of a narrowband rejection filter 110, a periodic narrowband bandpass filter 120, and two narrowband bandpass filters 130 without free spectral regions. The filtering system is composed of three different types of on-chip filters to achieve the function of spectroscopic filtering of signal photons and idler photons of specific frequencies. By giving full play to the performance characteristics of various filters, the filtering system achieves the following performance requirements: 1) By designing the filter stopband center frequency of the narrowband stop filter 110, the filter passband interval and the filter passband center frequency of the periodic narrowband bandpass filter 120, and the center frequencies of the two narrowband bandpass filters 130 without free spectrum regions, specific frequency signal photons and idler photons that satisfy the energy conservation relationship with the pump light frequency can be selected and output from the two ports respectively.

[0060] 2) Since the passband filtering bandwidth of the two narrowband bandpass filters 130 without free spectral regions is greater than the bandwidth of the periodic narrowband bandpass filter 120, the spectrum pattern of the selected output signal photons and idler photons is completely determined by the passband filtering spectrum pattern of the periodic narrowband bandpass filter 120. Since each passband of the periodic narrowband bandpass filter 120 has the same symmetrical filtering spectrum pattern, this ensures that the selected signal photons and idler photons are matched in spectrum.

[0061] 3) Through the cascade of the three-stage structure of the narrowband rejection filter 110, the periodic narrowband bandpass filter 120, and the two narrowband bandpass filters without free spectrum region 130, the filtering system provides more than 120dB of pump light extinction for the filtering passband of signal photons and idler photons. Therefore, the filtering system fully realizes the performance requirements of the quantum light source for the on-chip filtering system. The use of this filtering system can realize a quantum light source chip with integrated filtering function and nonlinear optical waveguide, without the need for filtering devices outside the chip to assist the filtering function.

[0062] Based on the same inventive concept, the second aspect of the present invention further provides an integrated chip integrating a two-photon quantum light source. The integrated chip integrating a two-photon quantum light source will be introduced below.

[0063] Figure 2 It is a schematic diagram of the structure of an integrated chip of an integrated two-photon quantum light source provided by the present invention.

[0064] The following will be combined Figure 2 The structure of the integrated chip of the integrated two-photon quantum light source provided by the present invention is described.

[0065] In an exemplary embodiment of the present invention, Figure 2 It can be seen that the integrated chip 100 integrating the two-photon quantum light source may include a substrate 20, an optical waveguide 30, and an optical filtering system 10, wherein the optical filtering system 10 includes a narrowband stop filter 110, a periodic narrowband bandpass filter 120, and two narrowband bandpass filters 130 without a free spectral region.

[0066] In one embodiment, the optical waveguide 30 is disposed on the substrate 20, wherein the pump laser excites the optical waveguide 30 so that the optical waveguide 30 generates entangled photon pairs based on spontaneous four-wave mixing or generates entangled photon pairs based on spontaneous parametric down-conversion.

[0067] In one embodiment, the optical filtering system 10 is integrated with the optical waveguide 30 and connected to the optical waveguide 30, thereby achieving integration with a chip.

[0068] In yet another embodiment, the substrate 20 is provided with two ports 201 , so that the signal photons and idler photons that match each other and are obtained through filtering by the optical filtering system 10 are output along the two ports 201 respectively.

[0069] In yet another embodiment, the optical waveguide 30 may include any one or more of a single-mode silicon waveguide, a single-mode silicon nitride waveguide, a single-mode quartz waveguide, and a periodically poled lithium niobate waveguide.

[0070] Through the above-mentioned embodiments, the integrated chip 100 integrating the two-photon quantum light source is integrated with the optical filtering system 10, and achieves the technical effect of accurately separating and outputting the signal photons and the idler photons.

[0071] In another embodiment, the nonlinear optical waveguide (corresponding optical waveguide) can be fabricated using a silicon on insulator (SOI) substrate using a conventional silicon photonic integrated chip process. The optical waveguide 30 is partially a single-mode silicon waveguide, the narrowband rejection filter 110 uses a cascaded waveguide Bragg grating (WBG) rejection filter, the periodic narrowband bandpass filter 120 uses a micro-ring resonant cavity, and the two free-spectral region-free narrowband bandpass filters 130 with different center frequencies use a grating-assisted reverse coupler.

[0072] Among them, after the optical communication band pump laser is input into the chip through the quartz optical fiber, it first stimulates the spontaneous four-wave mixing effect in the single-mode silicon waveguide to generate entangled photon pairs, and then passes through the cascaded waveguide Bragg grating (WBG) band-stop filter to filter out the pump light. The stopband bandwidth of the WBG band-stop filter is set to 400GHz, and the extinction ratio is greater than 80dB. Then, the wide-spectrum signal photons and idler photons generated in the silicon waveguide are periodically narrow-band filtered through the microring resonator, and the interval between adjacent filter peaks (i.e., FSR) is set to 500GHz, and the passband bandwidth is set to 10GHz. Then, through the first-stage grating-assisted reverse coupler (corresponding to the first free-spectral region narrow-bandpass filter), the frequency w is selected. s The signal photon is output from one port 201 and passes through the second-stage grating-assisted reverse coupler (corresponding to the second narrow-band bandpass filter without free spectrum region) to select the frequency w i The signal photons are output from another port 201. The passband bandwidths of the two grating-assisted reverse couplers are both set to 100 GHz, and the extinction ratio is greater than 20 dB.

[0073] It can be seen from the above description that the integrated chip of the integrated two-photon quantum light source provided by the present invention integrates the optical filtering system 10, and achieves the technical effect of accurately separating and outputting signal photons and idler photons.

[0074] It is further understood that, although the operations are described in a specific order in the accompanying drawings in the embodiments of the present invention, it should not be understood as requiring the operations to be performed in the specific order or serial order shown, or requiring the execution of all the operations shown to obtain the desired results. In certain environments, multitasking and parallel processing may be advantageous.

[0075] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0076] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical filtering system, characterized in that: The optical filtering system includes a narrowband stop filter, a periodic narrowband pass filter, and two narrowband pass filters without free spectral region, wherein: The entangled photon pairs formed by the pump laser are processed by a narrowband rejection filter, a periodic narrowband pass filter, and two narrowband pass filters without free spectrum regions, and the signal photons and idler photons that match each other are output respectively, or The entangled photon pairs formed by the pump laser are processed by a periodic narrowband bandpass filter, a narrowband stop filter, and two narrowband bandpass filters without free spectrum regions, and then the signal photons and idler photons matching each other are output respectively, where: The narrowband rejection filter is used to filter out the pump laser; The periodic narrowband bandpass filter is used to perform periodic narrowband filtering on the generated wide-spectrum signal photons and wide-spectrum idler photons to obtain signal photons and idler photons that match each other; The two narrow-band bandpass filters without free spectral regions are used to distinguish signal photons and idler photons that match each other.

2. The optical filtering system according to claim 1, characterized in that: The stopband bandwidth of the narrowband stop filter is greater than or equal to 50 GHz and less than or equal to 1 THz.

3. The optical filtering system according to claim 1 or 2, characterized in that: The extinction ratio of the narrowband rejection filter is greater than or equal to 80 dB.

4. The optical filtering system according to claim 3, characterized in that: The narrowband rejection filter includes any one or more of a single waveguide Bragg grating rejection filter, a cascaded waveguide Bragg grating rejection filter, a single microring filter, a cascaded microring filter, a single unbalanced Mach-Zehnder interferometer, and a cascaded unbalanced Mach-Zehnder interferometer.

5. The optical filtering system according to claim 1, characterized in that: The filtering spectrum of the periodic narrowband bandpass filter includes a plurality of narrowband filtering passbands with equally spaced center frequencies, and each of the narrowband filtering passbands has the same symmetrical spectrum, wherein the narrowband filtering passbands include at least a narrowband filtering passband with a first center frequency and a narrowband filtering passband with a second center frequency, and do not have a narrowband filtering passband with a third center frequency, wherein the first center frequency matches the center frequency of the signal photon, the second center frequency matches the center frequency of the idler photon, and the third center frequency matches the center frequency of the pump laser.

6. The optical filtering system according to claim 5, characterized in that: The extinction ratio of the periodic narrow-band pass filter is greater than or equal to 20 dB.

7. The optical filtering system according to claim 5 or 6, characterized in that: The periodic narrow-band bandpass filter includes any one or more of a micro-ring filter, an unbalanced Mach-Zehnder interferometer, and a waveguide integrated Fabry-Perot filter.

8. The optical filtering system according to claim 1, characterized in that: The two narrow-band bandpass filters without free spectral region include a first narrow-band bandpass filter without free spectral region and a second narrow-band bandpass filter without free spectral region, wherein the center frequency of the first narrow-band bandpass filter without free spectral region matches the center frequency of the signal photons, and the center frequency of the second narrow-band bandpass filter without free spectral region matches the center frequency of the idler photons.

9. The optical filtering system according to claim 8, characterized in that: The passband bandwidth of the first free spectral region narrowband pass filter is greater than the bandwidth of each narrowband filter passband in the periodic narrowband pass filter, and is less than the frequency interval between adjacent narrowband filter passbands in the periodic narrowband pass filter.

10. The optical filtering system according to claim 8, characterized in that: The passband bandwidth of the second narrowband bandpass filter without free spectral region is greater than the bandwidth of each narrowband filter passband in the periodic narrowband bandpass filter, and is less than the frequency interval between adjacent narrowband filter passbands in the periodic narrowband bandpass filter.

11. The optical filtering system according to claim 8, characterized in that: The extinction ratio of the first narrow-band bandpass filter without free spectral region is greater than or equal to 20 dB.

12. The optical filtering system according to claim 8, characterized in that: The extinction ratio of the second narrow-band bandpass filter without free spectral region is greater than or equal to 20 dB.

13. The optical filtering system according to any one of claims 8 to 12, characterized in that: The first free spectral region-free narrowband bandpass filter comprises any one or more of a grating-assisted reverse coupler, a grating-assisted co-directional coupler, and a grating-assisted waveguide integrated Fabry-Perot filter.

14. The optical filtering system according to any one of claims 8 to 12, characterized in that: The second free spectral region-free narrowband bandpass filter includes any one or more of a grating-assisted reverse coupler, a grating-assisted co-directional coupler, and a grating-assisted waveguide integrated Fabry-Perot filter.

15. An integrated chip integrating a two-photon quantum light source, characterized in that: The integrated chip of the integrated two-photon quantum light source comprises a substrate, an optical waveguide, and the optical filtering system according to any one of claims 1 to 14, wherein: The optical waveguide is disposed on the substrate, wherein the pump laser excites the optical waveguide so that the optical waveguide generates entangled photon pairs based on spontaneous four-wave mixing or generates entangled photon pairs based on spontaneous parametric down conversion; The optical filtering system is integrated with the optical waveguide and connected to the optical waveguide; The substrate is provided with two ports, so that the signal photons and idler photons matching each other obtained through filtering by the optical filtering system are output along the two ports respectively.

16. The integrated chip of the integrated two-photon quantum light source according to claim 15, characterized in that: The optical waveguide includes any one or more of a single-mode silicon waveguide, a single-mode silicon nitride waveguide, a single-mode quartz waveguide, and a periodically poled lithium niobate waveguide.

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