Middle-infrared band single photon efficient detection system based on room temperature condition

Abstract

The embodiment of the invention discloses an intermediate infrared band single photon efficient detection system based on room temperature conditions. A specific embodiment of the system comprises a pump light source which outputs a wavelength in a preset range and supports a pulse mode and a continuous light mode; the sum frequency module is used for performing sum frequency processing on the intermediate infrared signal light and the pump light to generate near-infrared light, and the sum frequency module comprises a polarization control module, a lens group, a light path beam combining module, a nonlinear crystal, a temperature control device and an adjustable delay line; the filtering system is used for filtering residual pump light and spurious noise, and the filtering system comprises a filtering dichroic mirror, a short-pass filter, a long-pass filter and a band-pass filter; and the detection module converts the optical signal into an electric signal and outputs the electric signal. According to the embodiment, a mid-infrared light signal is converted into visible light by using a nonlinear frequency up-conversion technology, and the detection efficiency and the signal-to-noise ratio are greatly improved by combining a high-performance silicon-based single-photon detector.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the field of single-photon detection in the infrared band, and specifically to a high-efficiency single-photon detection system in the mid-infrared band based on room temperature conditions. Background Art

[0002] The mid-infrared band covers multiple low-loss atmospheric windows and can be used to identify characteristic absorption peaks of gas molecules in trace gas detection, as well as to detect the thermal radiation spectrum of room-temperature objects during thermal imaging. It also has unique advantages in free-space optical communications, significantly reducing the impact of atmospheric absorption and scattering effects on signal transmission. Furthermore, under daylight conditions, solar radiation noise is greatly reduced compared to visible light and near-infrared, making it suitable for long-distance, high-bandwidth space communications, and especially for the noise-sensitive field of quantum communications.

[0003] However, at present, the development of single-photon detectors is concentrated in the near-infrared and visible light bands, and it is difficult to detect single-photon-level signals in the mid-infrared band. Due to the low energy of mid-infrared photons, the band gap of traditional semiconductors is too wide to be directly absorbed and thus detected. At the same time, the thermal excitation noise of the material is significant at room temperature, which can easily mask the single-photon signal. Even with the most advanced superconducting single-photon detectors, there are still problems such as the mismatch between the mid-infrared wavelength and the size of the nanowire structure, resulting in mode mismatch, and the photogenerated carriers are easily captured or recombined by defects in narrow-bandgap materials. Nanowire structures based on materials such as NbN and NbTiN currently achieve detection in the 3-5μm band, and through complex optical cavity coupling and nanowire structure design, the detection efficiency in the 4μm band can reach up to 30%. However, such solutions rely on ultra-low temperature refrigeration or noise shielding technology, and the system is complex, costly, and bulky, which cannot meet the needs of large-scale deployment. Summary of the Invention

[0004] The content of this disclosure is used to briefly introduce concepts that will be described in detail in the detailed description section below. The content of this disclosure is not intended to identify key features or essential features of the claimed technical solution, nor is it intended to limit the scope of the claimed technical solution.

[0005] Some embodiments of the present disclosure propose a high-efficiency single-photon detection system in the mid-infrared band based on room temperature conditions to solve the technical problems mentioned in the above background technology section.

[0006] In a first aspect, some embodiments of the present disclosure provide a mid-infrared band single-photon high-efficiency detection system based on room temperature conditions, the system comprising: a pump light source, which outputs a wavelength in a preset range and supports pulse mode and continuous light mode; a sum frequency module, which is used for sum frequency processing of mid-infrared signal light and pump light to generate near-infrared light, wherein the above-mentioned sum frequency module comprises: a polarization control module, a lens group, an optical path combining module, a nonlinear crystal, a temperature control device, and an adjustable delay line; a filtering system, which is used to filter out residual pump light and stray noise, wherein the above-mentioned filtering system comprises: a filtering dichroic mirror, a short-pass filter, a long-pass filter, and a band-pass filter; a detection module, which converts the optical signal into an electrical signal and outputs it.

[0007] In a second aspect, some embodiments of the present disclosure provide an electronic device comprising: one or more processors; a storage device on which one or more programs are stored, and when the one or more programs are executed by one or more processors, the one or more processors implement the system described in any implementation method of the above-mentioned first aspect.

[0008] In a third aspect, some embodiments of the present disclosure provide a computer-readable medium having a computer program stored thereon, wherein when the program is executed by a processor, the system described in any implementation of the first aspect is implemented.

[0009] The aforementioned embodiments of the present disclosure have the following beneficial effects: The room-temperature, high-efficiency, mid-infrared single-photon detection system, based on some embodiments of the present disclosure, utilizes nonlinear frequency up-conversion technology to convert mid-infrared optical signals into visible light. Combined with high-performance silicon-based single-photon detectors, this significantly improves detection efficiency and signal-to-noise ratio. The system operates stably at room temperature. Through optimized optical path and phase matching, it effectively suppresses ambient thermal noise and supports continuous tuning of the 3-5μm low-loss atmospheric window, meeting the long-distance transmission requirements of free-space optical communications. The pulsed pump light source exhibits temporal filtering properties, reducing noise photon accumulation. Combined with a multi-layer optical filtering design, pure single-photon signal extraction is achieved. This system transforms the challenges of mid-infrared detection into mature visible light detection, significantly reducing system complexity and cost. The detection system operates stably at room temperature, eliminating the need for deep refrigeration equipment. It provides an efficient and reliable solution for mid-infrared entangled photon detection in quantum communications, trace gas analysis in environmental monitoring, and medical thermal imaging, overcoming the limitations of traditional infrared detectors in sensitivity, response speed, and applicable scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The above and other features, advantages, and aspects of the various embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. Throughout the drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and that components and elements are not necessarily drawn to scale.

[0011] Figure 1 This is an example flow chart of some embodiments of the mid-infrared band single-photon high-efficiency detection system based on room temperature conditions according to some embodiments of the present disclosure; Figure 2 This is a schematic diagram of a 3.3-micron upconversion single-photon detection module of a mid-infrared band single-photon high-efficiency detection system based on room temperature conditions in some embodiments of the present disclosure; Figure 3 It is a structural diagram of an electronic device suitable for implementing some embodiments of the present disclosure. DETAILED DESCRIPTION

[0012] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as being limited to the embodiments described herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are for illustrative purposes only and are not intended to limit the scope of protection of the present disclosure.

[0013] It should also be noted that, for ease of description, only the parts related to the invention are shown in the drawings. In the absence of conflict, the embodiments and features in the embodiments of the present disclosure may be combined with each other.

[0014] It should be noted that the concepts of "first" and "second" mentioned in this disclosure are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0015] It should be noted that the modifications of "one" and "multiple" mentioned in the present disclosure are illustrative rather than restrictive, and those skilled in the art should understand that unless otherwise clearly indicated in the context, they should be understood as "one or more".

[0016] The names of the messages or information exchanged between multiple devices in the embodiments of the present disclosure are only used for illustrative purposes and are not used to limit the scope of these messages or information.

[0017] The present disclosure will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0018] Figure 1 This is an example flow chart of some embodiments of the present disclosure of a mid-infrared band single-photon high-efficiency detection system based on room temperature conditions. The mid-infrared band single-photon high-efficiency detection system based on room temperature conditions includes: a pump light source, a sum frequency module, a filtering system, and a detection module.

[0019] In some embodiments, the pump light source outputs a wavelength within a preset range and supports both pulsed and continuous light modes. Pump light source: Output wavelength range is approximately 1064 nm, supporting both pulsed and continuous light modes. (Specifications in this embodiment include: pulse width ≤ 1 ns, repetition rate ≥ 10 MHz, and time synchronization with the mid-infrared signal light (synchronization error ≤ 1 ps) achieved via an adjustable delay line. For example, a 1064 nm high-power pulsed laser (pulse width ≤ 100 ps, ​​repetition rate 100 MHz) is used.

[0020] like Figure 1 The example shows a 1064nm pump laser, a 3.3µm signal photon, a DM, a sum frequency detector (SFD), and a Si-APD. The 1064nm pump laser is the pump light emitted by the pump source, and the 3.3µm signal photon is mid-infrared. The DM represents the filter system, and the Si-APD represents the detection module.

[0021] In some embodiments, a sum frequency module is used for sum frequency processing of mid-infrared signal light and pump light to generate near-infrared light. The sum frequency module includes a polarization control module, a lens assembly, an optical beam combining module, a nonlinear crystal, a temperature control device, and an adjustable delay line.

[0022] The polarization control module includes a first glass slide, a second glass slide, a third glass slide, and a fourth glass slide, which adjust the polarization state of the mid-infrared signal light and the pump light. The pump light is polarized by the first and second glass slides, and the mid-infrared signal light is polarized by the third and fourth glass slides.

[0023] like Figure 2 In the example shown, the polarization control module includes λ / 2 wave plate 1 (HWP1), λ / 4 wave plate 1 (QWP1), λ / 2 wave plate 2 (HWP2), and λ / 4 wave plate 2 (QWP2). These modules adjust the polarization states of the two beams. The laser beam undergoes polarization adjustment via HWP1 and QWP1, while the mid-infrared signal beam undergoes polarization adjustment via HWP2 and QWP2, ensuring consistent polarization when the beams are combined. λ / 2 wave plate 1 (HWP1) represents the first beam; λ / 4 wave plate 1 (QWP1) represents the second beam; λ / 2 wave plate 2 (HWP2) represents the third beam; and λ / 4 wave plate 2 (QWP2) represents the fourth beam.

[0024] The above-mentioned lens group includes: a first straight lens, a second straight lens and a third straight lens. The beam is combined with the pump light through the first dichroic mirror after being reduced by the lens and focused at the center of the crystal to enhance the energy density. The third straight lens works at both wavelengths to convert the sum frequency light and the remaining pump beam into horizontal light.

[0025] like Figure 2In the example shown, the lens system consists of straight lenses (L1, L2). The beam is then combined with the pump light through the first dichroic mirror DM1 and focused at the center of the crystal to enhance energy density. Lens L3 operates at both wavelengths, converting the sum frequency light and the remaining pump beam into horizontal light. L1 represents the first straight lens; L2 represents the second straight lens; and L3 represents the third straight lens.

[0026] The optical beam combining module combines the mid-infrared signal light and the pump light through the first dichroic mirror. The two beams are combined through the dichroic mirror (DM1) and focused to the center of the crystal using a lens group to enhance the energy density.

[0027] like Figure 2 As shown in the example, the nonlinear crystal is selected from periodically poled lithium niobate (PPLN), potassium titanyl phosphate (PPKTP) or lithium tantalate (PPLT), the crystal polarization period is 10μm~50μm, and anti-reflection coating is applied on both sides to reduce interface reflection loss.

[0028] Parameters of the embodiment: PPLN crystal with a polarization period of 23.0 μm and double-sided anti-reflection coating (1064 nm / 3300 nm / 804.6 nm) is selected.

[0029] The temperature control device has a control range of 15°C to 100°C, optimizing phase matching by adjusting the crystal temperature, and is suitable for continuous tuning in the 2.5μm to 5μm mid-infrared band. The temperature control device has a control range of 15°C to 100°C, with a temperature control accuracy of ≤±0.01°C. It optimizes phase matching by adjusting the crystal temperature, and is suitable for continuous tuning in the 2.5μm to 5μm mid-infrared band.

[0030] The adjustable delay line DL adjusts the relative optical path lengths of the mid-infrared signal light and the pump light, ensuring that the two beams arrive at the crystal at the same time and that the pulses coincide in time. It can be a fiber optic device or a reflector, and can be placed on either of the two incident beam paths.

[0031] In some embodiments, a filtering system is used to filter out residual pump light and stray noise. The filtering system includes a filtering dichroic mirror (DM2), a short-pass filter, a long-pass filter, and a band-pass filter (bandwidth ≤ 10 nm) to filter out residual pump light and stray noise.

[0032] The converted horizontal light is separated by a filtering dichroic mirror and separated from the residual pump light. The pump light and stray noise are filtered out by a short-pass filter, a long-pass filter and a band-pass filter, and then coupled to the detection module.

[0033] For example, a dichroic filter (DM2), a short-pass filter (850nm), a long-pass filter (750nm), and a band-pass filter (800nm±5nm). The dichroic filter (DM2) separates the converted 804.6nm light from the residual pump light, and filters out the pump light and stray noise through a combination of filters (short-pass, long-pass, and band-pass), and finally couples it to a silicon single-photon detector (Si-APD). Si-APD represents a detection module. Figure 2 In the example, Filters represents a short-pass filter (850nm), a long-pass filter (750nm), and a band-pass filter (800nm±5nm). The sum-frequency optical path can represent the sum-frequency module and the filter system.

[0034] In some embodiments, the detection module converts the optical signal into an electrical signal and outputs it. This detection module integrates a spectral analysis module and an imaging module to perform real-time spectral analysis or spatial imaging on the converted optical signal. The detection module is a silicon single-photon detector (Si-APD, detection efficiency ≥60% @ 804.6nm, dark counts ≤100cps), which converts the optical signal into an electrical signal and outputs it. The spectral analysis module or imaging module can be optionally integrated to perform real-time spectral analysis or spatial imaging on the converted optical signal.

[0035] In operation, the mid-infrared signal light and the pump light pass through the polarization control modules on their respective optical paths and are combined at the first dichroic mirror after being beam-contracted by a lens. The polarization of the mid-infrared signal light and the pump light are adjusted. After being combined, the mid-infrared signal light and the pump light are incident on the nonlinear crystal to generate a sum frequency effect, generating infrared light. The temperature of the nonlinear crystal is adjusted by a temperature control device to compensate for wavelength drift and maintain conversion. The lens group on the optical path of the mid-infrared signal light and the pump light focuses the parallel light emitted by the light source, and the focus is at the center of the nonlinear crystal. The converted mid-infrared signal light and the remaining pump light are converted into horizontal light by the third straight lens. The third straight lens is confocal with the first straight lens and the second straight lens.

[0036] That is, the workflow of the high-efficiency single-photon detection system in the mid-infrared band based on room temperature conditions is as follows: 1. The mid-infrared signal light and pump light pass through the polarization control modules on their respective optical paths and are combined at DM1 after being beam-contracted by a lens. The polarization of the two is adjusted so that their polarizations are consistent when combined. 2. The mid-infrared signal light is combined with the pump light and injected into the PPLN crystal, generating a sum frequency reaction to generate infrared light. The crystal temperature is precisely regulated by a temperature control device to compensate for wavelength drift and maintain efficient conversion.

[0037] 3. The lens device on the optical path of the mid-infrared signal light and the pump light (operating in their respective operating bands) focuses the parallel light emitted by the light source, and the focus is at the center of the PPLN.

[0038] 4. The converted infrared light (804.6 nm) and the remaining pump light are converted into parallel light through a dual-wavelength lens, which is confocal with L1 and L2.

[0039] 5. The converted infrared light (804.6 nm) is reflected by DM2 and separated from the residual pump light. Background noise is then further filtered through a combination of short-pass, long-pass, and bandpass filters. Finally, the signal light is coupled to a Si-APD detector, enabling single-photon-level sensitive detection.

[0040] 6. The adjustable delay line (DL) precisely matches the arrival time of the pump and signal lights at the crystal to ensure pulse overlap. When the signal light is blocked, the detector noise floor (≤100 cps) is measured and deducted during data processing to improve the signal-to-noise ratio.

[0041] 7. Increase the pump light power, obtain the efficiency and noise curve, optimize the pump power, and achieve a balance between signal and noise ratio.

[0042] The embodiment takes 3.3μm mid-infrared signal detection as an example: First, the polarization states of the pump light and signal light (HWP1 / QWP1, HWP2 / QWP2) are adjusted, and the beams are combined and focused onto the PPLN crystal through DM1.

[0043] Second, set the temperature control device to 35~36℃ to optimize the crystal phase matching conditions (such as 3.3μm, 4.0μm, etc.), and the measured conversion efficiency is ≥30%.

[0044] Third, the filtered 804.6 nm light is coupled to the Si-APD via a single-mode fiber, and the signal counts are recorded and the background noise is subtracted.

[0045] Fourth, by adjusting the pump power (100mW~1W), the maximum ratio of dark counts to signal counts is determined to optimize the detection efficiency.

[0046] Reference below Figure 3 , which shows a schematic structural diagram of an electronic device (such as a computing device) suitable for implementing some embodiments of the present disclosure. Figure 3 The electronic device shown is only an example and should not limit the functions and scope of use of the embodiments of the present disclosure. Figure 3As shown, the computer device includes a processor, a memory and a network interface connected via a system bus, wherein the memory may include a non-volatile storage medium and an internal memory. The non-volatile storage medium may store an operating system and a computer program. The computer program includes program instructions, which, when executed, enable the processor to execute any one of the mid-infrared band single-photon high-efficiency detection systems based on room temperature conditions. The processor is used to provide computing and control capabilities to support the operation of the entire computer device. The internal memory provides an environment for the operation of the computer program in the non-volatile storage medium, which, when executed by the processor, enables the processor to execute any one of the mid-infrared band single-photon high-efficiency detection systems based on room temperature conditions. The network interface is used for network communication, such as sending assigned tasks, etc. Those skilled in the art will understand that Figure 3 The structure shown in the figure is merely a block diagram of a portion of the structure related to the solution of the present disclosure, and does not constitute a limitation on the computer device to which the solution of the present disclosure is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0047] It should be understood that the processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc.

[0048] In one embodiment, the processor is configured to execute a computer program stored in a memory to implement the following steps: a pump light source, which outputs a wavelength within a preset range and supports both pulse mode and continuous light mode; a sum frequency module, which performs sum frequency processing on mid-infrared signal light and pump light to generate near-infrared light, wherein the sum frequency module includes a polarization control module, a lens group, an optical path combining module, a nonlinear crystal, a temperature control device, and an adjustable delay line; a filtering system, which is configured to filter out residual pump light and stray noise, wherein the filtering system includes a filtering dichroic mirror, a short-pass filter, a long-pass filter, and a band-pass filter; and a detection module, which converts the optical signal into an electrical signal and outputs the electrical signal.

[0049] An embodiment of the present disclosure also provides a computer-readable storage medium, on which a computer program is stored. The computer program includes program instructions. The system implemented when the program instructions are executed can refer to the various embodiments of the mid-infrared band single-photon high-efficiency detection system based on room temperature conditions disclosed in the present disclosure.

[0050] The computer-readable storage medium may be an internal storage unit of the computer device described in the aforementioned embodiment, such as a hard disk or memory of the computer device. The computer-readable storage medium may also be an external storage device of the computer device, such as a plug-in hard disk, a SmartMedia Card (SMC), a Secure Digital (SD) card, a flash memory card, etc., provided on the computer device.

[0051] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, system, article, or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, system, article, or system. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, system, article, or system comprising the element.

[0052] The above descriptions are merely some preferred embodiments of the present disclosure and illustrate the underlying technical principles. Those skilled in the art should understand that the scope of the invention encompassed by the embodiments of the present disclosure is not limited to technical solutions formed by specific combinations of the aforementioned technical features. It also encompasses other technical solutions formed by any combination of the aforementioned technical features or their equivalents, without departing from the aforementioned inventive concept. For example, a technical solution formed by replacing the aforementioned features with (but not limited to) technical features with similar functions disclosed in the embodiments of the present disclosure.

Claims

1. A high-efficiency single-photon detection system in the mid-infrared band based on room temperature conditions, characterized in that: include: Pump light source, outputting wavelengths in a preset range, supporting pulse mode and continuous light mode; A sum frequency module is used for sum frequency processing of mid-infrared signal light and pump light to generate near-infrared light, wherein the sum frequency module includes: a polarization control module, a lens group, an optical path beam combining module, a nonlinear crystal, a temperature control device, and an adjustable delay line; A filtering system for filtering out residual pump light and stray noise, wherein the filtering system comprises: a filtering dichroic mirror, a short-pass filter, a long-pass filter, and a band-pass filter; The detection module converts the optical signal into an electrical signal and outputs it.

2. The room temperature mid-infrared band single photon high-efficiency detection system according to claim 1 is characterized in that: The polarization control module includes: a first glass slide, a second glass slide, a third glass slide, and a fourth glass slide, which adjust the polarization state of the mid-infrared signal light and the pump light. The pump light is polarized by the first and second glass slides, and the mid-infrared signal light is polarized by the third and fourth glass slides. The lens group includes: a first straight lens, a second straight lens and a third straight lens. The beam is reduced by the lens and combined with the pump light through the first dichroic mirror and focused at the center of the crystal to enhance the energy density. The third straight lens works at both wavelengths to convert the sum frequency light and the remaining pump light beam into horizontal light. The optical path combining module combines the mid-infrared signal light and the pump light through a first dichroic mirror; The temperature control device has a temperature control range of 15°C to 100°C, and optimizes phase matching by adjusting the crystal temperature, adapting to continuous tuning in the 2.5μm to 5μm mid-infrared band; The adjustable delay line adjusts the relative optical path of the mid-infrared signal light and the pump light so that the two beams of light arrive at the crystal at the same time and the pulses overlap in time domain.

3. The room temperature mid-infrared band single photon high-efficiency detection system according to claim 2, characterized in that: The converted horizontal light is separated by a filtering dichroic mirror and separated from the residual pump light. The pump light and stray noise are filtered out by a short-pass filter, a long-pass filter and a band-pass filter, and then coupled to the detection module.

4. The room temperature mid-infrared band single photon high-efficiency detection system according to claim 3 is characterized in that: The detection module integrates a spectrum analysis module and an imaging module to perform real-time spectrum analysis or spatial imaging on the converted light signal.

5. The room temperature mid-infrared band single photon high-efficiency detection system according to claim 4, characterized in that: In the working state, the mid-infrared signal light and the pump light pass through the polarization control modules on their respective optical paths and are combined at the first dichroic mirror after being beam-reduced by the lens to adjust the polarization of the mid-infrared signal light and the pump light; The mid-infrared signal light and the pump light are combined and incident on the nonlinear crystal to generate infrared light by sum frequency reaction. The temperature of the nonlinear crystal is adjusted by a temperature control device to compensate for wavelength drift and maintain conversion; The lens group on the optical path of the mid-infrared signal light and the pump light focuses the parallel light emitted by the light source, and the focus is at the center of the nonlinear crystal; the converted mid-infrared signal light and the remaining pump light are converted into horizontal light by the third straight lens, and the third straight lens is confocal with the first straight lens and the second straight lens.

6. An electronic device, characterized in that: include: one or more processors; a storage device having one or more programs stored thereon; When the one or more programs are executed by the one or more processors, the one or more processors implement the mid-infrared band single-photon high-efficiency detection system based on room temperature conditions as described in claims 1-4.

7. A computer-readable medium, characterized in that A computer program is stored thereon, wherein when the computer program is executed by a processor, the mid-infrared band single-photon high-efficiency detection system based on room temperature conditions as described in claims 1-4 is implemented.

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