Multi-layer Film Filter for SNSPD Extrinsic Dark Count Reduction
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Solution Overview
Problem
Current superconducting nanowire single photon detectors face significant challenges in reducing extrinsic dark counts, which degrade detection efficiency and signal-to-noise ratio, particularly in long-distance fiber quantum communication, due to the lack of effective methods for filtering out optical fiber blackbody radiance and stray light.
Innovation Solution
Integration of a multi-layer film filter with band-pass filtering function on the superconducting nanowire single photon detector, comprising alternately stacked silicon dioxide and silicon layers, to selectively filter out non-signal radiation while maintaining signal radiation and optical coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an optical fiber filter is introduced at low temperature to reduce extrinsic dark count, then the extrinsic dark count is reduced, but signal light is significantly attenuated (about 3dB), which directly affects detection efficiency
Solution Approach 1:
The patent introduces a multi-layer film filter as an intermediary component positioned between the optical fiber and the SNSPD detector. This filter serves as a mediator that selectively transmits signal wavelengths while blocking extraneous radiation, thereby reducing dark counts without significantly attenuating the desired signal light
Solution Approach 2:
The patent optimizes the optical parameters of the multi-layer film filter, including layer thickness, refractive indices, and wavelength selectivity, to achieve a balance between dark count reduction and signal transmission. By carefully tuning these parameters, the filter achieves high rejection of extrinsic radiation while maintaining high transmission at the signal wavelength
2Object-affected harmful factors
If the bias current of the SNSPD is reduced to lower intrinsic dark count, then the intrinsic dark count decreases, but the detection efficiency and signal-to-noise ratio are adversely affected
Solution Approach 1:
The patent converts the harmful effect of extrinsic dark counts into a beneficial filtering opportunity by designing a multi-layer film filter that specifically targets and blocks the wavelength range of extraneous radiation. This approach transforms the problem of dark count noise into an opportunity to enhance signal quality through selective optical filtering
Solution Approach 2:
The patent segments the optical detection function into two distinct components: the multi-layer film filter responsible for wavelength selection and dark count reduction, and the SNSPD detector responsible for photon detection. This segmentation allows each component to be optimized independently, with the filter handling the dark count issue and the detector maintaining high detection efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The multi-layer film filter effectively reduces extrinsic dark counts, enhancing detection efficiency and maintaining signal integrity, thereby improving the overall performance of the superconducting nanowire single photon detector.
Implementation Method 1
the multi-layer film filter is a device implemented by a multi-layer dielectric film and having a band-pass filtering function
Implementation Method 2
A superconducting nanowire single photon detector (SNSPD) is an important photodetector, which may achieve single photon detection
Data Source
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AI summary
Provided are a method and device for reducing the extrinsic dark count of a superconducting nanowire single photon detector (SNSPD), comprising the steps of: integrating a multi-layer film filter on the superconducting nanowire single photon detector; wherein, the multi-layer film filter is a device implemented by a multi-layer dielectric film and having a band-pass filtering function. The extrinsic dark count is the dark count triggered by optical fiber blackbody radiance and external stray light. The superconducting nanowire single photon detector comprises: a substrate having an upper surface integrated with an upper anti-reflection layer and a lower surface integrated with a lower anti-reflection layer; an optical cavity structure; a superconducting nanowire; and a reflector. The present invention is easy to operate, and only needs to integrate the multi-layer film filter on the substrate of the SNSPD to filter non-signal radiation. The method effectively reduces the extrinsic dark count while ensuring the signal radiation and the optical coupling efficiency of a device, thereby improving the detection efficiency of the device in dark count specific conditions.