CN113093334A - Based on TM0Mode-absorption superconducting nanowire single photon detector and detection method - Google Patents

Abstract

The invention provides a method based on TM₀A superconducting nanowire single photon detector with mode absorption and a detection method thereof comprise the following steps: directional coupler for implementing TE₀Mode to TE₁Switching modes; a polarization rotator connected with the directional coupler for implementing TE₁Mode to TM₀Switching modes; a nanowire single photon detector connected with the polarization rotator and used for realizing TM alignment₀Absorption and detection of the pattern. The invention is based on TM₀Mode-absorbing superconducting nanowire single photon detector junctionSimple structure, and realizes TE on the basis of SOI structure₀Mode to TM₀The high-efficiency conversion of the mode is realized, and the nanowire single photon detector can rapidly absorb and detect the nanowire single photon detector, so that the required length of the nanowire is greatly shortened, the process conditions required by nanowire manufacturing are reduced, the device is protected from being damaged by an etchant, and the working performance of the device is stable.

Description

Based on TM0Mode-absorption superconducting nanowire single photon detector and detection method

Technical Field

The invention belongs to the field of integrated quantum chips, and relates to a quantum chip based on TM₀A superconducting nanowire single photon detector with mode absorption and a detection method.

Background

The single photon detector with high detection efficiency has important application in the field of light quantum, especially some applications based on detection, such as light quantum calculation, quantum key distribution, quantum glass color sampling, lopore-free bell experiment, and the like. In 1550nm communication band, InGaAs near infrared avalanche diode detector is the current mainstream detector, but the dark count of the detector is large, and the detection efficiency is usually lower than 30%. In addition, the detector is an independent structure outside the chip, and does not meet the development trend of miniaturization and integration.

The Superconducting Nanowire Single Photon Detector (SNSPD) is a single photon detector which is developed rapidly in recent years, is a high-sensitivity photon detector for detecting photons by utilizing a superconducting nano film wire, has the advantages of high efficiency, high counting rate, small dark count, small time jitter and the like, and has the auxiliary resonant cavity, reflector and other structures, the single photon detection efficiency can reach over 90 percent at 1550nm waveband, and the dark count is less than 100 Hz. However, the conventional SNSPD adopts a mode of optical fiber vertical incidence, so that the requirement of on-chip integration is not met, and in addition, the bandwidth is limited by structures such as a resonant cavity and the like.

At present, a waveguide traveling wave coupling SNSPD is a better scheme, and a waveguide evanescent wave coupling absorption mode is adopted, wherein the absorption mode is transferred from the outside of a chip to the chip, and the high absorption efficiency can be realized without a resonant cavity structure, so that the defect of the vertical incidence SNSPD can be well solved. SNSPD based on waveguide traveling wave coupling has been implemented on various material systems, such as SOI, SiN, GaAs, etc., and has been applied to some important devices, such as detectors that can distinguish photon numbers, two-photon interference experiments, etc. However, in general, these SNSPDs are used in a quasi-transverse electric mode (TE) absorption manner, and due to the problem of the direction of the TE mode electric field, NbN nanowires with a length of several tens of microns are usually needed to complete nearly 100% absorption, and these structures need to directly grow an NbN thin film on top of a waveguide, which puts higher requirements on the fabrication process of the NbN nanowires, and firstly, the NbN thin film has a thickness of only a few nanometers and a longer structure, which results in a low yield; secondly, the etching process of NbN needs to be accurately controlled, otherwise, the upper surface of the waveguide is damaged by over-etching, and scattering loss is caused.

Disclosure of Invention

In view of the above-mentioned disadvantages of the prior art, it is an object of the present invention to provide a TM-based solution₀A superconducting nanowire single photon detector and a detection method based on mode absorption are used for solving the problems that the superconducting nanowire single photon detector in the prior art is complex in structure, high in required process condition and low in yield.

To achieve the foregoing and other related objects, the present invention provides a TM-based solution₀A mode-absorbing superconducting nanowire single photon detector, comprising:

directional coupler for implementing TE₀Mode to TE₁Switching modes;

a polarization rotator connected with the directional coupler for implementing TE₁Mode to TM₀Switching modes;

a nanowire single photon detector connected with the polarization rotator and used for realizing TM alignment₀Absorption and detection of the pattern.

Optionally, the directional coupler comprises a parallel coupled line directional coupler.

Optionally, the directional coupler includes a main waveguide and an auxiliary waveguide which are arranged at an interval, and a width of the main waveguide is smaller than a width of the auxiliary waveguide, wherein the main waveguide includes a first segment, a second segment, and a third segment, which are connected in sequence, and the third segment and the auxiliary waveguide are parallel to each other and coupled.

Optionally, the directional coupler has an input port configured toOne end of the main waveguide for inputting TE to the main waveguide₀Mode, the secondary waveguide is magnetically coupled with the primary waveguide and takes out TE₁Mode(s).

Optionally, the polarization rotator includes a first waveguide, a second waveguide, and a third waveguide connected in sequence, where the first waveguide is connected to the directional coupler.

Optionally, widths of the first waveguide, the second waveguide, and the third waveguide are linearly tapered, respectively.

Optionally, the nanowire single photon detector comprises:

a substrate;

the insulating layer is positioned on the surface of the substrate;

the waveguide is positioned on the surface of the insulating layer;

the covering layer is positioned on the insulating layer and covers the exposed surface of the waveguide;

and the superconducting nanowire is positioned on the surface of the covering layer.

Optionally, the material of the insulating layer includes SiO₂。

Optionally, the material of the covering layer includes SiO₂The distance between the upper surface of the covering layer and the upper surface of the waveguide is not more than 50nm, and the roughness of the covering layer is less than 1 nm.

Optionally, the superconducting nanowire is in a rectangular zigzag square wave shape, and two end portions of the superconducting nanowire are respectively connected with the positive electrode and the negative electrode.

Optionally, the superconducting nanowire is along TM₀The length of the transmission direction is in the range of 5-10 μm.

Optionally, the superconducting nanowire material is selected from one of NbN, NbTiN, TiN, TaN, WSi, Nb, and MoGe.

The invention also provides a TM-based method₀The detection method of the superconducting nanowire single photon detector based on mode absorption comprises the following steps:

inputting TE through input port of directional coupler₀A light wave of a mode;

TE₀modes coupled by main waveguidesTo the secondary waveguide and converted to TE₁A mode;

TE₁mode-oriented TM implementation in polarization converter₀Switching modes;

TM pair realization of nanowire single photon detector through evanescent wave coupling method₀Absorption and detection of the pattern.

As described above, a TM-based aspect of the present invention₀The superconducting nanowire single photon detector with mode absorption has the following beneficial effects:

(1) nanowire single photon detector using TM₀By the mode of mode absorption, the nanowire can complete 100% of optical field absorption only by the length of 5 mu m, and the required length of the nanowire is greatly shortened. Therefore, the process conditions required by the nanowire manufacturing are reduced, the cost can be reduced, the yield can be improved, and the high-efficiency production can be realized;

(2) the nanowire can grow above the covering layer covering the waveguide, so that the covering layer can serve as a barrier layer to prevent the core layer waveguide from being damaged by an etching agent to influence the working performance of the device;

(3) the device has simple integral structure and can realize TE₀Mode to TM₀The high-efficiency conversion of the mode is realized, and the SNSPD can be quickly absorbed and detected, so that the working efficiency is higher.

Drawings

FIG. 1 shows a TM-based scheme provided for the present invention₀And the mode absorption superconducting nanowire single photon detector is in a schematic structural diagram in a top view.

FIG. 2 shows a TM-based scheme provided for the present invention₀And (3) a change law diagram of an effective refractive index imaginary part of a mode in a waveguide in the mode-absorbed superconducting nanowire single photon detector along with the width of the waveguide.

FIG. 3 shows a TM-based scheme provided for the present invention₀And the side-view cross-sectional structure schematic diagram of the superconducting nanowire single photon detector with mode absorption.

FIG. 4 shows a TM-based scheme provided for the present invention₀A flow chart of a detection method of a superconducting nanowire single photon detector based on mode absorption.

Description of the element reference numerals

10 substrate

20 insulating layer

30 cover layer

40 waveguide

401 main waveguide

4011 first stage

4012 second stage

4013 third stage

402 secondary waveguide

403 first waveguide

404 second waveguide

405 third waveguide

50 superconductive nanowire

61 positive electrode

62 negative electrode

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and although the drawings only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation, the form, quantity, position relationship and proportion of the components in actual implementation can be changed freely on the premise of implementing the technical solution of the present invention, and the layout form of the components may be more complicated.

Referring to FIG. 1, the present invention provides a TM-based solution₀A mode-absorbing Superconducting nanowire single-photon detector comprises a Directional coupler (DC for short), a Polarization rotator (Polarization rotator) and a nanowire single-photon detector (SNSPD for short), and the mode-absorbing Superconducting nanowire single-photon detector comprises a Directional coupler (DC for short), a Polarization rotator (Polalization rotator) and a nanowire single-photon detector (SNSPD for short), and the mode-absorbing Superconducting nanowire single-photon detector comprises a first substrate, a second substrate, a third substrate, a fourth substrateWherein the directional coupler is used to realize TE₀Mode to TE₁Switching modes; the polarization rotator is connected with the directional coupler and used for realizing TE₁Mode to TM₀Switching modes; the nanowire single photon detector is connected with the polarization rotator and used for realizing TM alignment₀Absorption and detection of the pattern.

As an example, referring to fig. 1, the directional coupler may be a parallel coupled line directional coupler, and the directional coupler includes a main waveguide 401 and a sub-waveguide 402 which are spaced apart from each other. Specifically, the width of the main waveguide 401 is smaller than that of the sub-waveguide 402, wherein the main waveguide 401 is S-shaped and can be divided into three sections, namely a first section 4011, a second section 4012 and a third section 4013, which are connected in sequence. The third segment 4013 and the sub waveguide 402 are parallel and coupled to each other, wherein the third segment 4013 has a length (L)₄) And was 13 μm. In addition, the third segment 4013 of the main waveguide 401 and the sub waveguide 402 are spaced apart from each other by a distance (gap) of 0.15 μm.

It should be noted that, in other embodiments, the lengths and the distances between the main waveguide 401 and the sub-waveguide 402 may be adjusted as required, and the protection scope of the present invention should not be limited excessively herein.

As an example, referring to fig. 1, the directional coupler has an input port (not shown) disposed at one end of the main waveguide 401 to input TE into the main waveguide 401₀Modes, i.e. TE₀The mode is inputted through a port of the first segment 4011, transmitted through the second segment 4012 and the third segment 4013, and converted into TE through a gap between the main waveguide 401 and the sub waveguide 402₁Mode, the sub waveguide 402 electromagnetically couples with the main waveguide 401 and takes out TE₁Mode(s).

It should be noted that, referring to fig. 2, the directional coupler in the whole device is designed according to the mode coupling theory when TE in the main waveguide₀Effective refractive index of mode equal to TE in sub-waveguide₁Effective refractive index of mode, TE in main waveguide₀A mode can be efficiently coupled to an adjacent oneIn the sub-waveguide of (2). The dotted lines indicated in FIG. 2 indicate TE with the same effective refractive index₀Die and TE₁Main waveguide width (W) corresponding to each mode₄)0.41 μm and a sub-waveguide width (W)₃)0.85μm。

As an example, referring to fig. 1, the polarization rotator includes a first waveguide 403, a second waveguide 404, and a third waveguide 405 connected in sequence, and the first waveguide 403 is connected to the directional coupler.

For example, referring to fig. 1, the widths of the first waveguide 403, the second waveguide 404, and the third waveguide 405 are linearly tapered, that is, the cross-sectional shapes of the first waveguide 403, the second waveguide 404, and the third waveguide 405 in the horizontal plane are all trapezoidal, and are along the TE₁The waveguide sections in the transmission direction become narrower gradually.

In particular, the length (L) of the first waveguide 403₃) 10 μm, width (W) of the connection portion with the sub waveguide 402₃) 0.85 μm, width (W) of the connection with the second waveguide 404₂) 0.7 μm; a length (L) of the second waveguide 404₂) 46 μm, width (W) of the connection with the third waveguide 405₁) 0.56 μm; the length (L) of the third waveguide 405₁) 4 μm, width (W) of the connection to the waveguide 40 in the nanowire single photon detector₀) And was 0.5 μm.

Please refer to FIG. 1 and FIG. 2, TE₁Mode and TM₀Mode hybridization between modes, waveguide width (W) corresponding to mode hybridization point_co) At 0.65 μm (indicated by the dashed line in FIG. 2), TE could not be distinguished₁Mode and TM₀The mode, and therefore the width of the second waveguide 404 in the designed polarization rotator, is from 0.7 μm (W)₂) Reduced to 0.56 μm (W)₁) Exactly covers the waveguide width corresponding to the mode hybridization point of 0.65 μm, at which time the TE in the waveguide₁The mode can be converted into TM₀And (5) molding. Calculated when L is₂TE at a length of 46 μm₁To TM₀The conversion efficiency of (2) can reach 99%.

It is noted that in other embodiments, the polarization rotator segments are width and lengthThe degree can be adjusted as desired as long as the TE in the waveguide is satisfied₁The mode can be converted into TM with preset conversion efficiency₀The scope of the present invention should not be unduly limited herein.

By way of example, referring to fig. 3, the nanowire single photon detector is designed based on an SOI structure, and includes:

a substrate 10;

an insulating layer 20 positioned on the surface of the substrate 10;

a waveguide 40 positioned on the surface of the insulating layer 20;

a cover layer 30 disposed on the insulating layer 20 and covering an exposed surface of the waveguide 40;

and the superconducting nanowire 50 is positioned on the surface of the covering layer 30.

By way of example, the substrate 10 includes, but is not limited to, a silicon substrate, a magnesium oxide substrate, a germanium substrate, a gallium nitride substrate, a gallium arsenide substrate, or a sapphire substrate. The nanowire single photon detector provided by the invention selects the silicon substrate, because silicon is a common semiconductor material, the nanowire single photon detector has the advantages of low material cost, mature processing technology, high surface flatness, good uniformity and the like. The oxide film can be more easily grown on the silicon substrate, which is beneficial to improving the yield of the nanowire single photon detector.

As an example, the insulating layer 20 may also be a buried oxide layer, which may be SiO₂The material, preferably 2 μm thick.

As an example, the cap layer 30 may be SiO₂The distance between the upper surface of the layer and the upper surface of the waveguide 40 may be 50 nm. Preferably, the capping layer 30 may be thinned by using a Chemical Mechanical Polishing (CMP) technique, so that the distance between the upper surface of the capping layer 30 and the upper surface of the waveguide 40 is less than 50nm, and the roughness of the upper surface is less than 1nm, thereby ensuring that the superconducting nanowire 50 deposited above the capping layer 30 is not affected and the device maintains good working performance.

Please refer to fig. 2 and fig. 3, the nanowire single photon detector is used as a core part of the whole device, and can implement TE₁Mode to TM₀Efficient conversion of modes is based on the principle that when the distance between the upper surface of the cladding layer 30 and the upper surface of the waveguide 40 is thinned to 50nm, the law of variation of the effective refractive index of the modes in the waveguide 40 with the waveguide width occurs, so that TE is converted to a linear TE₁Mode and TM₀Mode hybridization occurs between the modes.

In particular, referring to fig. 3, the nanowire single photon detector has a waveguide width (W) covered by the cladding layer 30₀) 500nm and a thickness of 220 nm.

For example, referring to fig. 1 and fig. 3, the superconducting nanowire 50 is in a rectangular wave shape, a convex end of the rectangular wave is close to a connection between the waveguide of the polarization rotator and the waveguide of the nanowire single photon detector, and two extending ends of the superconducting nanowire 50 are respectively connected to a positive electrode 61 and a negative electrode 62. The superconducting nanowire 50 is along the TM₀The length of the transmission direction is in the range of 5-10 μm. Preferably, the superconducting nanowire 50 is along the TM₀The length of the transmission direction is in the range of 5-6 μm. The superconducting nanowire 50 described in this embodiment is along the TM₀The length in the transport direction was 5 μm. Perpendicular to TM₀The distance between two parallel nanowires in the transmission direction is 80nm, the line width of the superconducting nanowire 50 is 100nm, and the thickness is 7 nm.

As an example, the material of the superconducting nanowire 50 is selected from one of NbN, TiN, TaN, WSi, Nb, and MoGe. Preferably, the present invention uses NbN as the superconducting nanowire material.

Referring to fig. 1 and 4, the present invention further provides a TM-based apparatus₀The detection method of the superconducting nanowire single photon detector based on mode absorption comprises the following steps:

s1: inputting TE through input port of directional coupler₀A light wave of a mode;

S2：TE₀the mode is coupled from the primary waveguide to the secondary waveguide and converted into TE₁A mode;

s3: TE1 mode for realizing TM in polarization converter₀Switching modes;

s4: method for coupling nanowire single photon detector through evanescent waveRealize to TM₀Absorption and detection of the pattern.

As an example, in step S2, referring to fig. 2, based on the mode coupling theory, when TE is in the main waveguide 401₀The effective index of the mode is equal to the TE in the sub-waveguide 402₁TE in the main waveguide 401 at the effective refractive index of the mode₀The mode can be efficiently coupled into the adjacent secondary waveguide 402. Specifically, in this embodiment, the TE in the main waveguide 401₀Effective refractive index of mode and TE in the sub-waveguide 402₁The effective refractive indices of the modes are equal and all are 2.24, the dominant waveguide width (W)₄)0.41 μm, a sub-waveguide width (W)₃) 0.85 μm, TE₀The mode is coupled from the primary waveguide to the secondary waveguide and converted into TE₁Mode(s).

It is noted that in other embodiments, the TE is in the main waveguide 401₀Effective refractive index of mode and TE in the sub-waveguide 402₁The effective refractive indexes of the modes are equal and can be adjusted according to needs, and the corresponding main waveguide width and the corresponding secondary waveguide width are also adjusted, so that the protection scope of the invention is not limited excessively.

For example, in step S3, please refer to fig. 1 and 2, TE₁Mode and TM₀Mode hybridization between modes, waveguide thickness (W) corresponding to mode hybridization points_co) At 0.65 μm (indicated by the dashed box in FIG. 2), we cannot distinguish between TE₁Mode and TM₀The mode, and therefore the width of the second waveguide 404 in the designed polarization rotator, is from 0.7 μm (W)₂) Reduced to 0.56 μm (W)₁) Exactly covers the waveguide width corresponding to the mode hybridization point of 0.65 μm, at which time the TE in the waveguide₁The mode can be converted into TM₀And (5) molding. Calculated when L is₂TE at a length of 46 μm₁To TM₀The conversion efficiency of (2) can reach 99%.

It should be noted that most silicon-based photonic devices use the TE model, specifically TE₀The mode serves as a fundamental mode in the device because the TM mode has a larger loss than the TE mode, and therefore, the TE mode is used in the waveguide for transmission in the transmission portion of the device. And TE mode if absorbed in the detecting part of the deviceBecause of the problem of the direction of the TE mode electric field, the superconducting nanowire 50 of several tens of microns long is usually needed to complete nearly 100% absorption, and the superconducting nanowire 50 needs to be directly grown above the waveguide 40, which puts high requirements on the nanowire manufacturing process, and firstly, the yield is low due to the fact that the nanowire thin film is only a few nanometers thick and has a long structure; secondly, the etching process of the nanowires needs to be precisely controlled, otherwise, the upper surface of the waveguide 40 is damaged by over-etching, which brings scattering loss. And if TM is used₀In the mode absorption mode, not only the length of the superconducting nanowire 50 can be greatly shortened, but also the superconducting nanowire 50 can be grown above the capping layer 30 of the waveguide 40, so that the capping layer 30 can serve as a barrier layer to prevent the core waveguide from being damaged by the etchant. Therefore, a polarization rotation structure for converting TE mode to TM mode is needed₀And (5) molding.

By way of example, in step S4, the superconducting nanowire 50 in the nanowire single photon detector is positioned along the TM₀The length of the transmission direction is only 5 mu m, and 100 percent of light field absorption can be completed.

By way of example, the TM-based₀The waveguide 40 in the mode-absorbing superconducting nanowire single photon detector is a silicon waveguide.

In summary, the present invention provides a TM-based solution₀A mode-absorbing superconducting nanowire single photon detector, comprising: directional coupler for implementing TE₀Mode to TE₁Switching modes; a polarization rotator connected with the directional coupler for implementing TE₁Mode to TM₀Switching modes; a nanowire single photon detector connected with the polarization rotator and used for realizing TM alignment₀Absorption and detection of the pattern. The invention is based on TM₀The superconducting nanowire single photon detector with mode absorption has the following beneficial effects: (1) nanowire single photon detector by using TM₀By the mode of mode absorption, the nanowire can complete 100% of optical field absorption only by the length of 5 mu m, and the required length of the nanowire is greatly shortened. Therefore, the process conditions required for nanowire fabrication are reduced, the cost can be reduced and the cost can be increasedThe yield is high, and high-efficiency production is realized. (2) The nanowire can be grown above the cladding layer of the cladding waveguide, so that the cladding layer can serve as a barrier layer to prevent the core waveguide from being damaged by an etchant to affect the working performance of the device. (3) The device has simple integral structure and can realize TE₀Mode to TM₀The high-efficiency conversion of the mode is realized, and the SNSPD can be quickly absorbed and detected, so that the working efficiency is higher.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims (13)

1. Based on TM₀A superconducting nanowire single photon detector with mode absorption is characterized by comprising:

directional coupler for implementing TE₀Mode to TE₁Switching modes;

a polarization rotator connected with the directional coupler for implementing TE₁Mode to TM₀Switching modes;

a nanowire single photon detector connected with the polarization rotator and used for realizing TM alignment₀Absorption and detection of the pattern.

2. The TM-based of claim 1₀The superconducting nanowire single photon detector of mode absorption, its characterized in that: the directional coupler comprises a parallel coupled line directional coupler.

3. The TM-based of claim 2₀The superconducting nanowire single photon detector of mode absorption, its characterized in that: the directional coupler comprises a main waveguide and an auxiliary waveguide which are arranged at intervals, the width of the main waveguide is smaller than that of the auxiliary waveguide, and the main waveguideThe waveguide comprises a first section, a second section and a third section which are connected in sequence, and the third section and the auxiliary waveguide are parallel and coupled with each other.

4. The TM-based according to claim 3₀The superconducting nanowire single photon detector of mode absorption, its characterized in that: the directional coupler has an input port arranged at one end of the main waveguide to input TE to the main waveguide₀Mode, the secondary waveguide is magnetically coupled with the primary waveguide and takes out TE₁Mode(s).

5. The TM-based of claim 1₀The superconducting nanowire single photon detector of mode absorption, its characterized in that: the polarization rotator comprises a first waveguide, a second waveguide and a third waveguide which are sequentially connected, and the first waveguide is connected with the directional coupler.

6. The TM-based according to claim 5₀The superconducting nanowire single photon detector of mode absorption, its characterized in that: the widths of the first waveguide, the second waveguide and the third waveguide are linearly gradually changed.

7. The TM-based of claim 1₀The superconducting nanowire single photon detector of mode absorption, its characterized in that: the nanowire single photon detector comprises:

a substrate;

the insulating layer is positioned on the surface of the substrate;

the waveguide is positioned on the surface of the insulating layer;

the covering layer is positioned on the insulating layer and covers the exposed surface of the waveguide;

and the superconducting nanowire is positioned on the surface of the covering layer.

8. The nanowire single photon detector of claim 7 wherein: the insulating layer is made of SiO₂。

9. The nanowire single photon detector of claim 7 wherein: the material of the covering layer comprises SiO₂The distance between the upper surface of the covering layer and the upper surface of the waveguide is not more than 50nm, and the roughness of the covering layer is less than 1 nm.

10. The nanowire single photon detector of claim 7 wherein: the superconducting nanowire is in a rectangular zigzag square wave shape, and two end parts of the superconducting nanowire are respectively connected with the positive electrode and the negative electrode.

11. The nanowire single photon detector of claim 7 wherein: the superconducting nanowire is along TM₀The length of the transmission direction is in the range of 5-10 μm.

12. The nanowire single photon detector of claim 7 wherein: the material of the superconducting nanowire is selected from one of NbN, NbTiN, TiN, TaN, WSi, Nb and MoGe.

13. Based on TM₀The detection method of the superconducting nanowire single photon detector based on mode absorption is characterized by comprising the following steps of:

inputting TE through input port of directional coupler₀A light wave of a mode;

TE₀the mode is coupled from the primary waveguide to the secondary waveguide and converted into TE₁A mode;

TE₁mode-oriented TM implementation in polarization converter₀Switching modes;

TM pair realization of nanowire single photon detector through evanescent wave coupling method₀Absorption and detection of the pattern.

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