Metamaterial-based photon detector

Abstract

Various embodiments are described herein for metamaterial-based photodetector where the metamaterial consists of an array of subwavelength structures. The metamaterial includes a base layer, a first semiconductor layer overlays the base layer, and a second semiconductor layer overlays the first layer. When the first layer and second layer are doped, an active layer or region of semiconductor material between the first layer and the second layer is formed. The subwavelength structures can be reverse biased to act as a photodetector or sensor to detect light down to the single photon regime. When acting as a sensor, the active region can be responsible for absorption, charge, and multiplication. The subwavelength structures can also be forward biased to act as a light emitting diode (LED).

Description

METAMATERIAL-BASED PHOTON DETECTOR INCORPORATION BY REFERENCE

[0001] This application claims priority from U.S. Provisional Patent Application No.63 / 746,461 filed Jan. 17, 2025; the entire contents of which is hereby incorporated herein by reference in its entirety.FIELD

[0002] The various embodiments described herein generally relate to sensors for detecting light, specifically single particles of light (photons), and methods of fabricating thereof.BACKGROUND

[0003] Quantum sensors can detect light at the fundamental limit of nature, down to single particles of light (photons) with high sensitivity, speed and timing accuracy. The ability to detect single photons is advantageous for low-light-level applications such as biological imaging, dose monitoring for cancer treatment, deep-space communication and LiDAR. Additionally, single-photon detection is required for quantum technologies, including quantum sensing, communication and computing. However, commercially available, portable single-photon detectors without cryogenic cooling suffer from limited efficiencies below 25% and poor timing accuracy (-300 ps) in the short-wave infrared region.

[0004] FIG. 1 provides various commercially available single-photon detectors. For example, the leading commercially available single-photon detector on the market is based on superconducting nanowires. These superconducting, single-photon detectors are available with system detection efficiencies exceeding 90% with unparalleled timing resolution below 15 ps. However, superconducting nanowire based single photon detectors require cryogenic cooling, and are not desirable for portable applications such as in defense, health, space and biological imaging.

[0005] An alternative to superconducting nanowire based single-photon detectors are semiconductor-based single-photon detectors. Semiconductor-based single-photon detectors overcome the need for cryogenic cooling and are portable, but come at the costof decreased efficiency and poorer timing resolution by an order of magnitude (-200 - 500 ps). The timing resolution of semiconductor-based single-photon detectors can be improved to below 50 ps by thinning down the active region of the detector, but the efficiency drops significantly to achieve this. Additionally, semiconductor-based singlephoton detectors that operate in the short-wave infrared (SWIR) from 900 nm to 1600 nm use InGaAs or Ge and typically have limited efficiency below 25%, and the efficiency drops rapidly below 1200 nm.

[0006] Silicon-based single-photon detectors have also been developed and are ideal for the visible wavelength range; however, they have limited efficiency in the nearinfrared from 850 nm to 1100 nm. In this region, the efficiency drastically drops above 850 nm with typical efficiencies of -40% at 900 nm and 10% at 1000 nm. The region between 850 nm to 1100 nm is known as the “valley of death” because this is typically where semiconductor-based single-photon detectors are not operable or have very low detection efficiencies below 10%.

[0007] Improved systems are needed.SUMMARY OF VARIOUS EMBODIMENTS

[0008] In one aspect, in at least one embodiment described herein, there is provided a metamaterial comprising: a base layer; a first layer of semiconductor material overlaying the base layer; a second layer of semiconductor material overlaying the first layer; and an active layer of semiconductor material between the first layer and the second layer. The active layer and second layer can form an array of subwavelength structures.

[0009] In at least one embodiment, the first layer of the semiconductor material can be negatively doped. In at least one embodiment, wherein the second layer of the semiconductor material can be positively doped. In some embodiments, the first and second semiconductor layers are oppositely doped, meaning that one layer is doped with acceptor impurities to form a p-type region, while the other layer is doped with donor impurities to form an n-type region. This configuration establishes a p-n junction or, in certain implementations, a p-i-n junction when an intrinsic or lightly doped active layer is positioned between the two layers.

[0010] In at least one embodiment, at least the first, second and active layers form the array of subwavelength structures.

[0011] In at least one embodiment, the array of subwavelength structures are pillared structures.

[0012] In at least one embodiment, a p-i-n junction can be formed by the first, second and active layers.

[0013] In at least one embodiment, the p-i-n junction can be a homojunction. In at least one embodiment, the p-i-n junction can be a heterojunction. In at least one embodiment, the p-i-n junction is selected from at least one of a homojunction, and a heterojunction.

[0014] In at least one embodiment, the active layer comprises an absorption region, a charge region, and a multiplication region. In at least one embodiment, the absorption region, the charge region, and the multiplication region are homojunctions.

[0015] In at least one embodiment, the absorption region, the charge region, and the multiplication region are heterojunctions.

[0016] In at least one embodiment, at least one of the homojunctions or heterojunctions can be in the base layer.

[0017] In at least one embodiment, at least one of the homojunctions or heterojunctions can be in the subwavelength structures.

[0018] In at least one embodiment, the subwavelength structures are tapered. In at least one embodiment, the subwavelength structures are cylindrical. In at least one embodiment, the subwavelength structures have varying diameters. In at least one embodiment, the subwavelength structures are connected to one another through at least one narrow channel. In at least one embodiment, the subwavelength structures are rectangular crosses. In at least one embodiment, wherein the subwavelength structures within one metamaterial array vary in shape. In at least one embodiment, a shape of the subwavelength structures is selected from at least one of the following: tapered, cylindrical, rectangular crosses, and any combination thereof; wherein the subwavelengthstructures have varying diameters; and wherein the subwavelength structures are connected to one another through at least one narrow channel.

[0019] In at least one embodiment, the subwavelength structures have a height ranging between 10 nm to 20000 nm.

[0020] In at least one embodiment, the base layer comprises the multiplication region. In at least one embodiment, the subwavelength structures comprise the absorption region.

[0021] In at least one embodiment, the base layer can be chosen from the list consisting of: InP, Si or any other substrate that can be lattice matched to the first layer. In at least one embodiment, the first layer can be chosen from the list consisting of: type IV semiconductors including but not limited to Si, Ge and type lll-V semiconductors including but not limited to InAIAs, InP, InGaAs, AllnAsSb, InGaAs, InGaAIAs, AIGaAsSb, GaAs, InAs, and InGaAsP. In at least one embodiment, in the active layer can be chosen from the list consisting of: type IV semiconductors including but not limited to Si, Ge and type lll-V semiconductors including but not limited to InAIAs, InP, InGaAs, AllnAsSb, InGaAs, InGaAIAs, AIGaAsSb, GaAs, InAs, and InGaAsP. In at least one embodiment, the second material layer can be chosen from the list consisting of: type IV semiconductors including but not limited to Si, Ge and type lll-V semiconductors including but not limited to InAIAs, InP, InGaAs, AllnAsSb, InGaAs, InGaAIAs, AIGaAsSb, GaAs, InAs, and InGaAsP.

[0022] In at least one embodiment, the subwavelength structures that individually constitute a diode are forward biased to act as a light emitting diode (LED). In at least one embodiment, the subwavelength structures are reverse biased to act as a photodetector. In at least one embodiment, a combination of LED regions and SPAD (single-photon avalanche diode) regions can be created on the metamaterial array.

[0023] In at least one embodiment, each of the LED regions and SPAD regions are addressed electrically separately, to make a compact light source-photodetector, which emits light through the LED regions and detects the scattered light, from the surrounding environment, by the photodetector regions.

[0024] In at least one embodiment, the subwavelength structures are light sources and / or detectors depending on how they are electrically biased. In at least one embodiment, the metamaterial can be adapted for any one or more of: LiDAR, sensing, quantum computing, and imaging. In at least one embodiment, optical interconnects are used to connect a high bandwidth memory (HBM) to the CPU and GPU to reduce the thermal budget imposed by the system, compared to conventional approaches in which copper wires are used. This schematic requires light sources, such as .LEDs, and photodetectors.

[0025] In one aspect, in at least one embodiment described herein, there is provided a single-photon detector. The detector can comprise the metamaterial; and a readout electronic circuit coupled to the metamaterial for receiving electronic signals generated from the metamaterial.

[0026] In at least one embodiment, the detector can further include a thermoelectric cooler integrated with the single photon detector. In at least one embodiment, the detector can be hermetically packaged.

[0027] In at least one embodiment, the single-photon detector can be integrated with a sensing system; a LIDAR system; a quantum computing system, and / or a communication system.

[0028] In at least one embodiment, the single-photon detector can be integrated with random number generation utilizing noise, signal detection, detection timing, detection location, wavelength, polarization, and phase.

[0029] In at least one embodiment, the single-photon detector can be integrated with an integrated photonic circuit.

[0030] In at least one embodiment, the single-photon detector can be integrated with a quantum computer.

[0031] In at least one embodiment, the single-photon detector can be integrated with a quantum communication system.

[0032] In at least one embodiment, the single-photon detector can be integrated with a quantum repeater nodes.

[0033] In at least one embodiment, the single-photon detector can be integrated with a quantum sensing and imaging system.

[0034] In at least one embodiment, the single-photon detector can be integrated with a quantum LiDAR system.

[0035] In at least one embodiment, the single-photon detector can be integrated with a sensing system used in dose monitoring in cancer treatment.

[0036] In at least one embodiment, the single-photon detector can be integrated with a Raman spectroscopy system for cancer diagnostics.

[0037] In at least one embodiment, the single-photon detector can be integrated with a sensing and detection system in autonomous vehicles.BRIEF DESCRIPTION OF THE DRAWINGS

[0038] For a better understanding of the various embodiments described herein, and to show more clearly how these various embodiments may be carried into effect, reference will be made, by way of example, to the accompanying drawings which show at least one example embodiment, and in which:FIG. 1 is a diagram showing various single-photon detectors that are commercially available.FIG. 2A is a block diagram of the metamaterial, according to at least one embodiment. FIG. 2B is a block diagram of the metamaterial, according to at least one embodiment. FIG. 3 is a block diagram of the metamaterial, according to at least one embodiment. FIG. 4A is a block diagram of the metamaterial, according to at least one embodiment. FIG. 4B is a block diagram of the metamaterial, according to at least one embodiment. FIG. 5 is a block diagram of the metamaterial, according to at least one embodiment. FIG. 6 is a block diagram of the metamaterial, according to at least one embodiment. FIG. 7 is a block diagram of the metamaterial, according to at least one embodiment. FIG. 8 is an SEM (scanning electron microscope) image of the metamaterial, according to at least one embodiment.FIG. 9 is an SEM (scanning electron microscope) image of the metamaterial, according to at least one embodiment.FIG. 10 is an SEM (scanning electron microscope) image of the single-photon sensor, according to at least one embodiment.FIG. 11 is a chart showing the responsivity (A / W) of the sensor at varying voltages.FIG. 12 is a photograph of the sensor, according to at least one embodiment.FIG. 13 is a photograph of the sensor, according to at least one embodiment.FIG. 14 is a photograph of the sensor, according to at least one embodiment.FIG. 15 is a chart showing the electric field (V / cm) distribution of the material layer stack for the metamaterial.FIG. 16 is a chart showing the reverse current-voltage (l-V) characteristic curve of the sensor.FIG. 17 is a chart showing the absorption efficiency of an InP sensor compared to an InGaAs metamaterial.FIG. 18 is a chart showing the dark count pulses of the metamaterial single-photon detector.FIG. 19 is a chart showing a dark count pulse of the metamaterial single-photon detector. FIG. 20 is a schematic diagram of a passive quenching circuit of the single-photon detector, according to at least one embodiment.FIG. 21 is a photograph of the packaged single-photon detector, according to at least one embodiment.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] Various apparatuses or processes will be described below to provide an example of an embodiment of each claimed invention. No embodiment described below limits any claimed invention and any claimed invention may cover processes or apparatuses that differ from those described below. The claimed inventions are not limitedto apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses or processes described below. It is possible that an apparatus or process described below is not an embodiment of any claimed invention. Any invention disclosed in an apparatus or process described below that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim or dedicate to the public any such invention by its disclosure in this document.

[0040] Furthermore, it will be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. Also, the description is not to be considered as limiting the scope of the embodiments described herein.

[0041] The following detailed description is merely exemplary in nature and is not intended to limit the described embodiments of the application and uses of the described embodiments. As used herein, the word “exemplary” or “illustrative” means “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” or “illustrative” is not necessarily to be construed as preferred or advantageous over other implementations. All of the implementations described below are exemplary implementations provided to enable persons skilled in the art to practice the disclosure and are not intended to limit the scope of the appended claims. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.

[0042] It should also be noted that the terms “coupled” or “coupling” as used herein can have several different meanings depending on the context in which these terms are used. For example, the terms coupled or coupling can have a mechanical, electrical or communicative connotation. For example, as used herein, the terms coupled or couplingcan indicate that two elements or devices can be directly connected to one another or connected to one another through one or more intermediate elements or devices via an electrical element, an electrical signal, a light signal or a mechanical element depending on the particular context.

[0043] It should also be noted that, as used herein, the wording “and / or” is intended to represent an inclusive-or. That is, “X and / or Y” is intended to mean X or Y or both X and Y, for example. As a further example, “X, Y, and / or Z” is intended to mean X or Y or Z or any combination thereof.

[0044] It should be noted that terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree may also be construed as including a deviation of the modified term, such as by 1%, 2%, 5% or 10%, for example, if this deviation does not negate the meaning of the term it modifies.

[0045] Furthermore, the recitation of numerical ranges by endpoints herein includes all numbers and fractions subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.90, 4, and 5). It is also to be understood that all numbers and fractions thereof are presumed to be modified by the term “about” which means a variation of up to a certain amount of the number to which reference is being made if the end result is not significantly changed, such as 1%, 2%, 5%, or 10%, for example.

[0046] Reference throughout this specification to “one embodiment”, “an embodiment”, “at least one embodiment” or “some embodiments” means that one or more particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments, unless otherwise specified to be not combinable or to be alternative options.

[0047] Similarly, throughout this specification and the appended claims the term “communicative” as in “communicative pathway”, “communicative coupling”, and in variants such as “communicatively coupled” is generally used to refer to any engineered arrangement for transferring and / or exchanging information. Examples of communicative pathways include, but are not limited to, electrically conductive pathways (e.g., electrically conductive wires, physiological signal conduction), electromagnetically radiative pathways(e.g., radio waves, optical signals, etc.), or any combination thereof. Examples of communicative couplings include, but are not limited to, electrical couplings, magnetic couplings, radio couplings, optical couplings or any combination thereof.

[0048] A portion of the example embodiments of the systems, devices, or methods described in accordance with the teachings herein may be implemented as a combination of hardware or software. For example, a portion of the embodiments described herein may be implemented, at least in part, by using one or more computer programs, executing on one or more programmable devices comprising at least one processing element, and at least one data storage element (including volatile and / or non-volatile memory). These devices may also have at least one input device (e.g., a keyboard, a mouse, a touchscreen, an input pin, an input port and the like for providing at least one input such as an input signal, for example) and at least one output device (e.g., a display screen, a printer, a wireless radio, an output port, an output pin and the like for providing at least one output such as an output signal, for example) depending on the nature of the device.

[0049] It should also be noted that there may be some elements that are used to implement at least part of the embodiments described herein that may be implemented via software that is written in a high-level procedural language such as object-oriented programming. The program code may be written in C, C++ or any other suitable programming language and may comprise modules or classes, as is known to those skilled in object-oriented programming. Alternatively, or in addition thereto, some of these elements implemented via software may be written in assembly language, machine language, or firmware as needed.

[0050] At least some of the software programs used to implement at least one of the embodiments described herein may be stored on a storage media or a device that is readable by a general or special purpose programmable device. The software program code, when read by the programmable device, which may also be referred to as a computing device, configures the programmable device to operate in a new, specific and predefined manner in order to perform at least one of the methods described herein.

[0051] Furthermore, at least some of the programs associated with the systems and methods of the embodiments described herein may be capable of being distributed in a computer program product comprising a computer readable medium that bearscomputer usable instructions, such as program code, for one or more processors. The program code may be preinstalled and embedded during manufacture and / or may be later installed as an update for an already deployed computing system. The medium may be provided in various forms, including non-transitory forms such as, but not limited to, one or more diskettes, compact disks, tapes, memory chips, and magnetic and electronic storage. In alternative embodiments, the medium may be transitory in nature such as, but not limited to, wire-line transmissions, satellite transmissions, internet transmissions (e.g., downloads), media, digital and analog signals, and the like. The computer useable instructions may also be in various formats, including compiled and non-compiled code.

[0052] Any module, unit, component, server, computer, terminal or computing device described herein that executes software instructions in accordance with the teachings herein may include or otherwise have access to computer readable media such as storage media, computer storage media, or data storage devices (removable and / or non-removable) such as, for example, magnetic disks, optical disks, or tape. Computer storage media may include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. Examples of computer storage media include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information, and which can be accessed by an application, module, or both. Any such computer storage media may be part of the device or accessible or connectable thereto.

[0053] A metamaterial having an array of subwavelength structures is proposed herein. As used herein, the term “metamaterial” refers to an engineered material comprising an arrangement of structures at subwavelength scales that collectively exhibit optical, electrical, or electromagnetic properties. These properties can include enhanced light absorption, tailored refractive indices, and improved photon interaction efficiency.

[0054] In some embodiments, the metamaterial can also be referred to as a “nanowire array” or a “subwavelength structure array,” as these terms describe thephysical configuration of the metamaterial comprising a plurality of nanoscale or subwavelength features arranged in a periodic or non-periodic pattern.

[0055] The metamaterial can be integrated with a sensor device to form a photon detector. The metamaterial-based photon detector can have high efficiency in the SWIR region, wavelength range between 900 nm to 1600 nm, where other semiconductor-based single-photon detectors have limited efficiency. The sensors developed can be portable and have the ability to detect single photons, and can therefore be referred to as quantum sensors.

[0056] Quantum sensors enable light detection at the fundamental limit of nature down to single photons with high sensitivity, speed and precise timing resolution, which can positively impact a variety of applications that is particularly useful in photon-starved scenarios, such as night-time operation, remote sensing of low power signals, and tracking of small moving objects. Single-photon detection also enables light detection and ranging (LiDAR) of targets with longer range and ability to discriminate multiple targets. Moreover, it has applications in dose monitoring for cancer treatment, quantum communication, quantum computing, medical imaging, surveillance systems, and fault tolerant analysis testing of CMOS circuits. There is also a need for high performance single-photon detectors to boost the speed and accuracy of quantum computation. More precise timing resolution allows for finer noise filtering by time-gating and improved depth resolution in quantum sensing, enabling precise measurements crucial for applications such as ranging and 3D imaging with improved signal-to-noise. Enhanced single-photon detection efficiency is essential for quantum communication, as it increases the rate of successfully transmitted photons over long distances, thereby facilitating more robust and reliable quantum state sharing for establishing a secure key for keeping personal data secure. In quantum networks, high timing resolution is needed for enhancing the visibility of two-photon interference, which is needed to perform entanglement swapping for extending the distance of quantum communication. In photonic quantum computing, single-photon detectors require high efficiency, precise timing resolution and low noise for higher readout fidelity and lower error rates.

[0057] Portable single-photon detectors based on semiconductor nanowire arrays for quantum sensing are provided herein. By optimizing the nanowire material layer stackand geometry, the detectors can achieve high efficiencies, for example, exceeding 90% over the wavelength range from 800 nm to 1600 nm.

[0058] FIG. 2A provides a block diagram of the metamaterial. In at least one embodiment, the metamaterial 200 includes a base layer 210. The base layer 210 can also be referred to as a substrate or bulk area 210. A first layer 206 overlays the base layer 210, and can be doped, such as p-type or n-type. The first layer can be made of a semiconductor material. The second layer 202 overlays the first layer 206. In at least one embodiment, the semiconductor layer of the second layer 202 can be doped, such as p-type or n-type. In at least one embodiment and as shown in the subwavelength structure depicted at 208a, the semiconductor layer of the first layer 206 is n-doped, and the second layer 202 is p-doped. In at least one embodiment and as shown in the subwavelength structure depicted at 208b, the semiconductor layer of the first layer 206 is p-doped, and the second layer 202 is n-doped.

[0059] When the first layer 206 and second layer 202 are doped, an active layer or region 204 of semiconductor material between the first layer and the second layer is formed, as shown in the subwavelength structure in 208c. The active region 204 can also be referred to as the intrinsic region (denoted by i) or the depletion region. When acting as a sensor, the active region 204 can be responsible for absorption 212 of the photon, multiplication 216 of electrons (or holes), with the charge layer 214 to maintain the desired electric field profile of the absorption layer 212 and multiplication layer 216.

[0060] In at least one embodiment, the active region 204 and second layer 202 form an array of subwavelength structures 208. In one embodiment, all of the subwavelength structures 208 that form the metamaterial can be formed of the same materials. In another embodiment, the subwavelength structures 208 that form the metamaterial can be formed of varying materials. For example, structures on the top and bottom of the sensor device may be formed of a different material or doping type as compared to structures in the center of the sensor device.

[0061] FIG. 2B provides another block diagram of the metamaterial, according to another embodiment. In this embodiment, the subwavelength structures 208 are composed of the first layer 206, the active region 204, and the second layer 202. In the embodiment shown in FIG.2B, the first layer 206 is n-doped; and the second layer 202 isp-doped. In an alternative embodiment, the first layer 206 can be p-doped; and the second layer 202 can be n-doped, forming a p-n junction. The active region 204 is formed between the first and second layers.

[0062] In a p-n junction, the formation of an active or depletion region occurs when p-type and n-type semiconductor materials are brought into contact, leading to the diffusion of holes from the p-type region into the n-type region and electrons from the n-type region into the p-type region. This diffusion process results in the formation of a space charge region, where the mobile charge carriers are depleted, leaving behind ionized donor atoms in the n-type region and acceptor atoms in the p-type region. The separation of these charges creates an electric field across the junction, which opposes further diffusion of carriers and establishes equilibrium, thus stabilizing the depletion region. The depletion region is responsible for detecting light, in the form of photons, and converting it into an electrical signal. When a substantially large number of, or higher intensity photons strike the semiconductor material in the depletion region, they generate electron-hole pairs, which are then separated by the built-in electric field. This separation results in the generation of a current that can be measured as a signal corresponding to the intensity of the incident light.

[0063] In the case of very low intensity light or single photon regime, the semiconductor device should operate near or above the avalanche breakdown voltage to detect a single photon. After the single photon is absorbed in the active region of the device, it generates one electron-hole pair. If the electron or hole gains enough energy by the applied reverse bias voltage (electric field), it can create an additional electron-hole pair through the process of impact ionization. When this process of impact ionization continues to occur, more electron-hole pairs are created leading to an avalanche effect such that one absorbed photon leads to a large current pulse as a result.

[0064] FIGs. 3 and 5 provides another block diagram of the metamaterial, according to another embodiments. In the embodiment shown in FIG. 3 and 5, the first layer 306, is deposited on the bulk substrate 310, and is shared amongst a plurality of the subwavelength structures. In FIG. 3, the shown structures have a tapered profile, whereas in FIG. 5, the structures have a vertical profile. The profile of the subwavelength structures can range from entirely vertical (i.e. cylindrical or rectangular prism) to a tapered cone-likestructure. In at least one embodiment, the subwavelength structures are tapered, as shown in FIGs 2A, 2B, and 3. For example, the upper portion of the subwavelength structure (i.e. the second layer) can have a smaller diameter than the lower portion (i.e. the first layer); or vice versa. In at least one embodiment, the subwavelength structures can have varying diameters.

[0065] In the embodiment shown in FIGs. 4A, 4B and 5, the subwavelength structures have vertical side walls, forming cylindrical structures as shown in 408a, rectangular prism structures as shown in 408b, or hexagonal structures as shown in 408c. Any other suitable structure can also be adapted for the subwavelength structures.

[0066] In the embodiment shown in FIG. 6, the active region 604 can be responsible for absorption 612 of the photon. In this embodiment, the metamaterial comprises a base layer 610. A first layer of semiconductor material 609 overlays the base layer 610. A second layer of semiconductor material 602 overlays the first layer 609. An active layer of semiconductor material (made up of sublayers 604, 606, and 607) can be formed between the first layer and the second layer. The active layer (made up of sublayers 604, 606, and 607) and second layer 602 form an array of subwavelength structures or the second layer 602 and 604 form an array of subwavelength structures on the base layer 610.

[0067] In this embodiment, the first sublayer 604 is the intrinsic layer which can be responsible for absorption 612 of the photon. The absorption region is responsible for absorption of the photon as it enters the semiconductor material of the photodetector. The photon is absorbed into the semiconductor layer if its energy exceeds the bandgap energy of the material. This absorption excites an electron from the valence band to the conduction band, creating an electron-hole pair.

[0068] Following the generation of electron-hole pairs from light absorption, a charge separation process occurs due to the built-in or applied electric field to generate a measurable electrical signal. The photodetector includes a depletion region with an internal electric field, which drives the electrons toward the n-type region and the holes toward the p-type region. The charge separation process can be enhanced by increasing the electric field. The charge separation can also minimize carrier recombination, allowing the photogenerated carriers to contribute to the photocurrent. The efficiency of chargeseparation is influenced by the strength of the electric field and the mobility of the carriers within the semiconductor material. The depletion region can be designed to optimize the charge separation.

[0069] In the embodiment shown in FIG. 6, the second sublayer 606 can be a doped layer (such as p or n), or a heavily doped layer (such as p+, p++, n+ or n++). In this embodiment, the second sublayer 606 is the charge layer 614 that is responsible for controlling the electric field profile of the absorption layer 612 and the multiplication layer 616.

[0070] In a separate embodiment, if holes are being collected, then the p- and n-sides shown in FIG. 6 would be swapped. For example, the p-i nanostructure on top would become n-i. The charge layer would be n-doped and the n-layer above the substrate would be p-doped.

[0071] To enhance the signal generated by absorbed photons, the photodetector may incorporate a multiplication region 616. In devices such as avalanche photodiodes, a high electric field in the multiplication region accelerates charge carriers to sufficient energy levels to initiate impact ionization. This process generates additional electron-hole pairs, amplifying the photocurrent through a chain reaction. The gain achieved through this charge multiplication is carefully controlled to enhance signal strength while avoiding device failure. This amplification mechanism is particularly advantageous in low-light applications, enabling the detection of weak optical signals with high precision and sensitivity. In the embodiment shown in FIG.6, the multiplication region 616 is provided by a third sublayer 607. The third sublayer 607 can be a second active region formed between the heavily-doped second sublayer 606 and the first layer 609.

[0072] Turning now to FIG. 7, which provides an example of the metamaterial shown in FIG. 6, according to at least one embodiment. In this embodiment, the bulk substrate is composed of InP (Indium Phosphide). Other suitable bulk / substrate materials include, but are not limited to: Si (Silicon), Si-Ge (Silicon-Germanium), or any semiconductor that enables the epitaxial growth of top layers, for instance by lattice matching or domain matching.

[0073] In the embodiment shown in FIG. 7, the first layer 709 is n-doped, and the n-doped first layer is composed of InAIAs or InP. Other suitable materials for the first layer include, but are not limited to: other semiconductors that have larger bandgap than the absorption layer including but not limited to Si, InAs, GaAs, AIGaAsSb, etc.

[0074] For example, InGaAs has a bandgap of 0.7eV - 0.8eV. InAIAs has a bandgap ranging from 1.41 eV - 1.51 eV. Therefore, these materials can be used as a material pairing that match for a separate absorption, charge, multiplication layer stack, but the material can change for different wavelength regions of interest. The paired materials are chosen so that the lower bandgap semiconductor acts as the absorption layer for the desired spectral range and the larger bandgap semiconductor constitutes the multiplication layer in which the avalanche process occurs. Aside from epitaxial growth compatibility of the paired semiconductors, the choice of these materials can also depend on the ratio of hole to electron impact ionization coefficients, often referred to as k value. The k value determines the suitability of the semiconductor of the multiplication layer to undergo impact ionization with holes or with electrons.

[0075] An n-type buffer material can be included in some embodiments. The buffer layer helps with the transition between the substrate and the next layer by reducing stain and dislocations between two semiconductors during epitaxial growth of the layers.

[0076] In the embodiment of FIG. 7 shows an example of a separate absorption (layer 704), charge (field control layer 706), multiplication (layer 707) single-photon avalanche diode (SPAD). The second layer 702 is p-doped; and is composed of two separate layers. The InGaAs layer that is indicated as p++, is the contact layer, which entails that it is a highly doped semiconductor that has metal-like characteristics. The n+ layers at the bottom 709 after the substrate is also a contact layer.

[0077] The InAIAs p+ layer is the p-doped layer in the SPAD is also highly doped but will not be in contact with the top metal gate. This layer needs to have a higher bandgap than the absorption region layer 704 to act as the optical window and remain transparent for the target optical range.

[0078] In at least one embodiment, the first layer can alternatively be n-doped. The doping concentration depends on a few factors such as the junction height and thematerials used in the stack. But the main goal is to maintain an internal electric field below the band-to-band tunneling threshold of the small bandgap semiconductor used in the layer stack and to enable impact ionization in the multiplication region. Therefore, the doping concentration can vary by changing some of these parameters. In at least one embodiment, a suitable doping concentration can include a concentration in which the internal electric field is below the band-to-band tunneling threshold of the semiconductors used in the absorption and multiplication layers, while also having sufficient electric field in the multiplication region to initiate impact ionization for the avalanche process.

[0079] An active region (704, 706, 707) is formed between the first layer 709 and the second layer 702. In this case, the active region comprises of the absorption layer 704, field control (charge) layer 706, and multiplication layer 707. In the embodiment shown in FIG. 7, the intrinsic active region is composed of InGaAs (indium gallium arsenide) for the absorption region and InAIAs (indium aluminum arsenide) for the multiplication region. InGaAs nanowire material systems have a lower bandgap than InP, which may be useful to develop a broadband quantum sensor that extends the detection wavelength range from the visible / near-infrared to the SWIR region.

[0080] FIG. 8 is an SEM (scanning electron microscope) image of the metamaterial, according to at least one embodiment. The array of subwavelength structures 800 is provided in the image shown in FIG.8. The term "subwavelength" refers to dimensions or features that are smaller than the wavelength of the light to be detected. The metamaterial having subwavelength structures can be used in optical devices and materials that manipulate light at scales smaller than its wavelength, leading to enhanced optical absorption. For photosensors, the use of subwavelength structures can significantly improve their performance by influencing how light interacts with the sensor material.

[0081] To further improve the light-sensing capabilities of the metamaterial, the subwavelength nanostructures can be tapered. For example, the upper portion of the subwavelength structure has a smaller diameter than the lower portion (i.e. the first layer); or vice versa. The tapered shape allows for broadband absorption, enabling the structures to interact with a broad spectral range. In at least one embodiment, the subwavelength structures can have varying diameters.

[0082] The subwavelength structures can also enhance light absorption. By incorporating the subwavelength structures into photo sensors, the photo sensors can more effectively trap and absorb light, increasing their sensitivity and overall efficiency. This increased efficiency is particularly beneficial in applications where detecting low levels of light is essential. The subwavelength structures can be provided in a geometric arrangement such as a pattern or periodically repeating units that resonate with the incident light, confining the local electromagnetic field and thus improving absorption. In one example, the subwavelength structures can be rectangular crosses, or have different shapes.

[0083] Additionally, the subwavelength structures can be used to reduce reflectivity in photosensors. Anti-reflective coatings or surface textures with subwavelength features minimize unwanted reflections, allowing more light to enter the sensor. This not only improves the amount of light captured but also enhances the signal-to-noise ratio, leading to clearer and more accurate detection.

[0084] FIG. 9 provides a side view of the metamaterial having subwavelength structures 900, taken by an SEM. In one embodiment, the subwavelength structures 900 have a diameter ranging between 10 nm to 20000 nm. The pitch 904 of the subwavelength structures refers to the distance between adjacent structures (centre-to-centre). In one embodiment, the pitch of the subwavelength structures can range between 10 nm and 20000 nm. The height of the subwavelength structures can be measured as the distance from the base of the sub-wavelength structures to the top of the subwavelength structures. In one embodiment, the subwavelength structures have a height 902 ranging between 10 nm to 20000 nm. FIG. 10 provides an SEM (scanning electron microscope) image of the single photon sensor 1202, according to at least one embodiment.

[0085] Turning now to FIG. 11, which provides a chart 1100 showing the responsivity of the metamaterial-based photodetector in the valley of death region. The uniform responsivity is obtained over a broad wavelength range from 800 to 1600 nm and increases with higher reverse bias, providing a tunable photodetector.

[0086] FIGs. 12, 13, and 14 are photographs of the sensor 1200, and photodiode 1300 according to various embodiments. The devices shown in these figures feature the metamaterial having subwavelength structures. Specifically, FIG. 12 is a photograph ofnine 3x3 grids of SPADs in an integrated housing fortesting. FIG. 13 is a packaged SPAD with hermetically sealed TO8-header. FIG. 14 is an optical image of one contacted nanowire array for a metamaterial-based SPAD. The device can produce high efficiency in combination with precise timing resolution (below 30 ps), without the need for cryogenic cooling as required by other single-photon detectors such as superconducting systems. To operate the semiconductor subwavelength p-i-n junction array as a single-photon detector, control electronics can be provided for high-speed operation (>10 MHz).

[0087] Using the proposed embodiments of the metamaterial-based photodetector, high efficiency (> 80%) photodetection over a broad operation wavelength range from the visible to near-infrared with precise timing resolution below 20 ps and state-of-the-art gain exceeding 100,000 for single photon sensitivity with thermoelectric cooling operation can be achieved.

[0088] The high photodetection efficiency over a broad bandwidth can be achieved by controlling the subwavelength structures geometry, tapering angle and spacing between the subwavelength structures in an array. The subwavelength structure arrays can then be processed into photodetectors having high optical performance at room temperature with a measured near-unity absorption efficiency from 900 to 1600 nm (93% average).

[0089] FIG. 15 provides a graph 1500 showing the electric field (V / cm) distribution of the metamaterial-based separate absorption, charge, multiplication layer stack for the SPAD. This graph shows how the electric field varies across the different regions 1502, 1504 and 1506 of the device. The electric field is designed to be below the band-to-band tunneling threshold (1508) in the absorption layer 1502 but high enough to transport charges to the multiplication region (layer 1506) where impact ionization occurs for the avalanche process. In this multiplication layer, the electric field is designed to be below the band-to-band tunnelling threshold of the high bandgap material but above the threshold for the impact ionization process to multiply carriers.

[0090] The graph 1500 can help identify the regions optimized for photon absorption and those designed for charge carrier multiplication, based on the bandgap energy and the electric field profile across the device. The doping concentration for the absorption layer should be in the range that maintains an electric field below the tunnellingthreshold of the semiconductor material (see line 1508) and not too low that inhibits efficient carrier transport. The doping concentration for the multiplication region can be selected so that the electric field is above a certain threshold for avalanche but not too high such that band-to-band tunneling occurs making single photon detection impossible. The doping concentration of the field control charge layer 1504 can be critical in controlling the electric field profile of the device ensuring a smooth transition from the absorption region to the multiplication region.

[0091] FIG. 16 provides a chart 1600 showing the reverse current-voltage (l-V) characteristic curve of the metamaterial-based quantum sensor. This chart illustrates how the current through the device changes as a function of the applied reverse bias voltage. As the reverse bias voltage increases, the chart can show the onset of breakdown voltage, a critical point where the reverse current increases dramatically. This phenomenon is known as avalanche and is dependent on the doping levels and structure of the diode. The breakdown voltage is a fundamental parameter that determines the maximum reverse bias voltage that the device can withstand without sustaining damage.

[0092] Furthermore, in photodiodes, this chart also indicates the photocurrent generated when the device is exposed to light. Under reverse bias, the photocurrent increases with increasing reverse voltage up to a certain point, enhancing the efficiency of charge carrier collection. By analyzing the slope and shape of the l-V curve, one can infer the device's sensitivity, efficiency, and overall performance.

[0093] FIG. 17 provides a chart 1700 showing the absorption efficiency of an InP sensor compared to an InGaAs sensor. The region between 850 nm to 1100 nm is known as the “valley of death” because this is typically where conventional sensors, such as Si or InGaAs are not operable, or have very low detection efficiencies. In contrast, it can be observed that the subwavelength structure-based InGaAs sensors provided herein show high efficiencies in the valley of death region.

[0094] FIG. 18 and 19 provide charts showing the dark count pulses of the metamaterial single-photon detector. FIG. 18 shows many dark count pulses (measured as amplitude in mV) over time (measured in ms). FIG. 19 provides a zoomed-in scale of one of the dark count pulses.Design Considerations

[0095] In a metamaterial single-photon avalanche photodiode (SPAD), the purpose of the metamaterial is to absorb photons with high efficiency at the desired spatial location within the subwavelength structures to increase the probability of an avalanche event, which creates a large enough macroscopic current to be measured. However, to determine subsequent single photon detection events this macroscopic current must be quenched so that the SPAD is ready to absorb and detect another single photon. This quenching mechanism is achieved by integrating a passive or active quenching circuit with the metamaterial SPAD. Note that a SPAD operated below the breakdown voltage without a quenching circuit is an avalanche photodiode (APD) since operating above the breakdown will lead to catastrophic failure in the absence of quenching. An example of a passive quenching circuit is shown in FIG. 20.

[0096] Fabricated subwavelength structures can be surface treated using methods such as annealing and passivation to reduce the dark current. Since semiconductor subwavelength structure arrays have a large surface to volume ratio, the dark current is higher than typical bulk avalanche photodiodes (APDs); and thus, the surface quality of lll-V semiconductor nanowire arrays can be improved, for example by surface treatment.

[0097] In at least one embodiment, the absorption layer can be separated from the multiplication layer. For example, the absorption layer can be composed of InGaAs and the multiplication layer can be composed of InAIAs. This material combination can be preferred for the semiconductor layer stack for an APD in the SWIR region; however, other material combinations can be used when the layer stack comprises of a small bandgap material as an absorber and larger bandgap material as the multiplier. In at least one embodiment, InGaAs can be used for the absorption region and InAIAs can be used for avalanche multiplication.

[0098] In at least one embodiment, the Finite Difference Time-Domain (FDTD) method can be used to design and optimize the subwavelength structure arrays and APD by optimizing the shape for near-unity absorption efficiency from 700 nm to 1600 nm. The height, shape and spacing of the nanowires can be optimized to improve the APD.

[0099] The absorption efficiency of the nanowire APD can be assessed by measuring the transmittance (T) and reflectance (R) and subtracting from unity (1-R-T). The breakdown voltage, external quantum efficiency, responsivity, gain, timing resolution, speed, and dark current can be measured to determine the electronic performance of the APD.

[0100] To realize a single-photon detector, a quenching circuit can be integrated with the APD. For single-photon detection, the APD can be biased above the breakdown voltage (excess bias voltage) of the diode for single-photon counting (i.e. , Geiger mode operation). The purpose of the quenching circuit is to reset the excess bias voltage of the APD to below the breakdown voltage after detecting an avalanche pulse upon absorption of a single photon or dark count event. The active quenching circuit can be integrated with the subwavelength structure APD.

[0101] In one embodiment, a thermoelectric cooler can be integrated with the single-photon detector. One main contributor to the dark count rate is the thermal energy from the environment that can generate electron-hole pairs in the APD active region leading to unwanted avalanche events. A common strategy to decrease the dark count rate is to cool the APDs to temperatures ranging from -70 to -100°C.

[0102] To make the single-photon detector compatible with quantum sensing systems, the detector can be tested and characterized. For example, the single-photon detector can be tested at room temperature and the dark count rate, detection efficiency, timing resolution, and speed (maximum count rate possible) of the single-photon detector can be characterized. To test the detector at the single photon level at different wavelengths, a supercontinuum picosecond pulsed laser (400 nm-2000 nm), or a tunable picosecond pulsed laser (Ti:Sapphire: 700 - 1000 nm), and picosecond diode lasers at 1310 nm and 1550 nm can be attenuated down to on average one photon per pulse with neutral density filters. The single-photon detector can be tested at varying temperatures using an optical cryostat to identify the optimum operational temperature. The singlephoton detector performance can be compared at various temperatures within the operating temperature range of the thermoelectric cooler.

[0103] FIG. 21 provides a photograph of the packaged single-photon detector, according to at least one embodiment. The thermoelectric cooler can be integrated,packaged, and tested with the nanowire single-photon detector. The single-photon detector can be hermetically packaged. The single-photon detector can be tested with the attenuated pulsed lasers with on average one photon per pulse at the optimum operating temperature. The dark count rate, detection efficiency, timing resolution, and speed can be characterized with an on-board cooling module in a room temperature environment. The fabricated detector can be a portable, semiconductor nanowire-based single-photon detector operating in room temperature environments.

[0104] Various other applications are also possible with the single-photon detector. In at least one embodiment, the single-photon detector can be integrated with a sensing system; a LiDAR system; and / or a communication system. In at least one embodiment, the single-photon detector can be integrated with an integrated photonic circuit.

[0105] In at least one embodiment, the single-photon detector can be integrated with a quantum computer. In at least one embodiment, the single-photon detector can be integrated with a quantum communication system. In at least one embodiment, the singlephoton detector can be integrated with a quantum repeater node. In at least one embodiment, the single-photon detector can be integrated with a quantum sensing and imaging system. In at least one embodiment, the single-photon detector can be integrated with a quantum LiDAR system.

[0106] In at least one embodiment, the single-photon detector can be integrated with a sensing system used in dose monitoring in cancer treatment. In at least one embodiment, the single-photon detector can be integrated with a Raman spectroscopy system for cancer diagnostics.

[0107] In at least one embodiment, the single-photon detector can be integrated with a sensing and detection system in autonomous vehicles.

[0108] While the applicant's teachings described herein are in conjunction with various embodiments for illustrative purposes, it is not intended that the applicant's teachings be limited to such embodiments. On the contrary, the applicant's teachings described and illustrated herein encompass various alternatives, modifications, andequivalents, without departing from the embodiments, the general scope of which is defined in the appended claims.

Claims

CLAIMS:

1. A metamaterial comprising:a base layer;a first layer of semiconductor material overlaying the base layer; a second layer of semiconductor material overlaying the first layer; and an active layer of semiconductor material between the first layer and the second layer;wherein at least the active layer and second layer form an array of subwavelength structures.

2. The metamaterial of claim 1, wherein the first layer of the semiconductor material is negatively doped; and wherein the second layer of the semiconductor material is positively doped.

3. The metamaterial of claim 1, wherein the first layer of the semiconductor material is positively doped; and wherein the second layer of the semiconductor material is negatively doped.

4. The metamaterial of any one of claims 1 to 3, wherein at least the first, second and active layers form the array of subwavelength structures.

5. The metamaterial of any one of claims 1 to 4, wherein the array of subwavelength structures are pillared structures.

6. The metamaterial of any one of claims 1 to 5, wherein a p-n junction is formed by the first and second layers, and wherein a depletion region is formed at the active layer.

7. The metamaterial of any one of claims 1 to 5, wherein a p-i-n junction is formed by the first, second and active layers.

8. The metamaterial of claim 7, wherein the p-i-n junction is a homojunction.

9. The metamaterial of any one of claims 7 or 8, wherein the p-i-n junction is a heterojunction.

10. The metamaterial of any one of claims 1 to 9, wherein the active layer comprises an absorption region, a charge region, and a multiplication region.

11. The metamaterial of any one of claims 1 to 10, wherein the absorption region, the charge region, and the multiplication region are homojunctions.

12. The metamaterial of any one of claims 1 to 11, wherein the absorption region, the charge region, and the multiplication region are heterojunctions.

13. The metamaterial of any one of claims 10 or 12, wherein at least one of the homojunctions or heterojunctions is in the base layer.

14. The metamaterial of any one of claims 10 to 13, wherein at least one of the homojunctions or heterojunctions is in the subwavelength structures.

15. The metamaterial of any one of claims 1 to 14, wherein the subwavelength structures are tapered.

16. The metamaterial of any one of claims 1 to 15, wherein the subwavelength structures are cylindrical.

17. The metamaterial of any one of claims 1 to 16, wherein the subwavelength structures have varying diameters.

18. The metamaterial of any one of claims 1 to 17, wherein the subwavelength structures are connected to one another through at least one narrow channel.

19. The metamaterial of any one of claims 1 to 18, wherein the subwavelength structures are rectangular crosses.

20. The metamaterial of any one of claims 1 to 19, wherein the subwavelength structures are different shapes.

21. The metamaterial of any one of claims 1 to 20, wherein the subwavelength structures have a height ranging between 10 nm to 20000 nm.

22. The metamaterial of any one of claims 1 to 21, wherein the base layer comprises the multiplication region.

23. The metamaterial of any one of claims 1 to 22, wherein the subwavelength structures comprise the absorption region.

24. The metamaterial of any one of claims 1 to 23, wherein the base layer is chosen from the list consisting of: InP, Si or any other substrate that is lattice matched to the first layer.

25. The metamaterial of any one of claims 1 to 24, wherein the first layer is chosen from the list consisting of: type IV semiconductors including but not limited to Si, Ge and type lll-V semiconductors including but not limited to InAIAs, InP, InGaAs, AllnAsSb, InGaAs, InGaAIAs, AIGaAsSb, GaAs, InAs, and InGaAsP.

26. The metamaterial of any one of claims 1 to 25, wherein the active layer is chosen from the list consisting of: type IV semiconductors including but not limited to Si, Ge and type lll-V semiconductors including but not limited to InAIAs, InP, InGaAs, AllnAsSb, InGaAs, InGaAIAs, AIGaAsSb, GaAs, InAs, and InGaAsP.

27. The metamaterial of any one of claims 1 to 26, wherein the second material layer is chosen from the list consisting of: type IV semiconductors including but not limited to Si, Ge and type lll-V semiconductors including but not limited to InAIAs, InP, InGaAs, AllnAsSb, InGaAs, InGaAIAs, AIGaAsSb, GaAs, InAs, and InGaAsP.

28. The metamaterial of any one of claims 1 to 27, wherein the subwavelength structures that individually constitute a diode are forward biased to act as a light emitting diode (LED).

29. The metamaterial of any one of claims 1 to 28, wherein the subwavelength structures are reverse biased to act as a photodetector.

30. The metamaterial of any one of claims 1 to 29, wherein a combination of LED regions and SPAD (single-photon avalanche diode) regions can be created on the metamaterial array;wherein each of the LED regions and SPAD regions are addressed electrically separately, to make a compact light source-photodetector, which emits light through the LED regions and detects the scattered light, from the surrounding environment, by the photodetector regions; andwherein the subwavelength structures are light sources and / or detectors depending on how they are electrically biased.

31. The metamaterial of any one of claims 1 to 30, wherein the metamaterial is adapted for any one or more of: LiDAR, sensing, and imaging.

32. The metamaterial of any one of claims 1 to 31, wherein optical interconnects are used to connect a high bandwidth memory (HBM) to the CPU and GPU to reduce the thermal budget imposed by the system.

33. A single-photon detector, the detector comprising:the metamaterial as claimed in any one of claims 1 to 32; and a readout electronic circuit coupled to the metamaterial for receiving electronic signals generated from the metamaterial.

34. The single-photon detector of claim 33, further comprising a thermoelectric cooler integrated with the single-photon detector.

35. The single-photon detector of claim 34, wherein the detector is hermetically packaged.

36. A single-photon detector of any one of claims 33 to 35, wherein the singlephoton detector is integrated with a sensing system; a LiDAR system; and / or a communication system.

37. A single-photon detector of any one of claims 33 to 36, wherein the singlephoton detector is integrated with random number generation utilizing noise, signal detection, detection timing, detection location, wavelength, polarization, and phase.

38. A single-photon detector of any one of claims 33 to 37, wherein the singlephoton detector is integrated with an integrated photonic circuit.

39. A single-photon detector of any one of claims 33 to 38, wherein the singlephoton detector is integrated with a quantum computer.

40. A single-photon detector of any one of claims 33 to 39, wherein the singlephoton detector is integrated with a quantum communication system.

41. A single-photon detector of any one of claims 33 to 40, wherein the singlephoton detector is integrated with quantum repeater nodes.

42. A single-photon detector of any one of claims 33 to 41 , wherein the singlephoton detector is integrated with a quantum sensing and imaging system.

43. A single-photon detector of any one of claims 33 to 42, wherein the singlephoton detector is integrated with a quantum LiDAR system.

44. A single-photon detector of any one of claims 33 to 43, wherein the singlephoton detector is integrated with a sensing system used in dose monitoring in cancer treatment.

45. A single-photon detector of any one of claims 33 to 44, wherein the singlephoton detector is integrated with a Raman spectroscopy system for cancer diagnostics.

46. A single-photon detector of any one of claims 33 to 45, wherein the singlephoton detector is integrated with a sensing and detection system in autonomous vehicles.

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