This document provides supplementary information to "Superconducting nanowire single-photon detec... more This document provides supplementary information to "Superconducting nanowire single-photon detectors with 98% system detection efficiency at 1550 nm,"
We report on the integration of superconducting nanowire single photon detectors (SNSPDs) on lith... more We report on the integration of superconducting nanowire single photon detectors (SNSPDs) on lithium niobate waveguides. In particular, we discuss challenges during the fabrication process, characterization methods and efficiency optimization. Lithium niobate is an interesting platform for quantum optics. Waveguide-integrated devices provide a versatile toolbox for complex optical circuits, due to their low-loss waveguiding of TEand TM-polarization modes, electro-optic properties, and high second order susceptibility [1]. Many different tools for quantum optics applications have been realized on this platform including single-photon sources, couplers, switches and modulators. In addition, highly-efficient fiber-coupling can be achieved by direct end-face pigtailing due to an optimized mode overlap with the titanium in-diffused waveguides. However, the integration of single-photon detectors on these waveguides is challenging [2, 3, 4]. State-of-the-art single photon detectors at opti...
Single-quantum emitters are an important resource for photonic quantum technologies, constituting... more Single-quantum emitters are an important resource for photonic quantum technologies, constituting building blocks for single-photon sources, stationary qubits, and deterministic quantum gates. Robust implementation of such functions is achieved through systems that provide both strong light-matter interactions and a low-loss interface between emitters and optical fields. Existing platforms providing such functionality at the single-node level present steep scalability challenges. Here, we develop a heterogeneous photonic integration platform that provides such capabilities in a scalable on-chip implementation, allowing direct integration of GaAs waveguides and cavities containing self-assembled InAs/GaAs quantum dots-a mature class of solid-state quantum emitter-with low-loss Si3N4 waveguides. We demonstrate a highly efficient optical interface between Si3N4 waveguides and single-quantum dots in GaAs geometries, with performance approaching that of devices optimized for each materia...
In contrast to UV photomultiplier tubes that are widely used in physical chemistry, mid-infrared ... more In contrast to UV photomultiplier tubes that are widely used in physical chemistry, mid-infrared detectors are notorious for poor sensitivity and slow time response. This helps explain why, despite the importance of infrared spectroscopy in molecular science, mid-infrared fluorescence is not more widely used. In recent years, several new technologies have been developed that open new experimental possibilities for research in the mid-infrared. In this Account, we present one of the more promising technologies, superconducting nanowire single photon detectors (SNSPDs) by sharing our experience with its use in a typical experiment carried out by physical chemists (laser-induced fluorescence) and comparing the SNSPD to a detector commonly used by physical chemists (InSb at LN Temperature). SNSPDs are fabricated from a thin film of superconducting metal, patterned into a meandering nanowire. The nanowire is cooled below its superconducting temperature, Tc, and held in a constant current...
Quantum Information Science and Technology II, 2016
High-dimensional (dimension d > 2) quantum key distribution (QKD) protocols that encode informati... more High-dimensional (dimension d > 2) quantum key distribution (QKD) protocols that encode information in the temporal degree of freedom promise to overcome some of the challenges of qubit-based (d = 2) QKD systems. In particular, the long recovery time of single-photon detectors and large channel noise at long distance both limit the rate at which a final secure key can be generated in a low-dimension QKD system. We propose and demonstrate a practical discrete-variable time-frequency protocol with d = 4 at a wavelength of 1550 nm, where the temporal states are secured by transmitting and detecting their dual states under Fourier transformation, known as the frequency-basis states, augmented by a decoy-state protocol. We show that the discrete temporal and frequency states can be generated and detected using commercially-available equipment with high timing and spectral efficiency. In our initial experiments, we only have access to detectors that have low efficiency (1%) at 1550 nm. Together with other component losses, our system is equivalent to a QKD system with ideal components and a 50-km-long optical-fiber quantum channel. We find that our system maintains a spectral visibility of over 99.0% with a quantum bit error rate of 2.3%, which is largely due to the finite extinction ratio of the intensity modulators used in the transmitter. The estimated secure key rate of this system is 7.7×10 4 KHz, which should improve drastically when we use detectors optimized for 1550 nm.
We characterize spontaneous parametric downconversion in a domain-engineered, type-II periodicall... more We characterize spontaneous parametric downconversion in a domain-engineered, type-II periodically poled lithium niobate (PPLN) crystal using seeded emission and single-photon techniques. Using continuous-wave (CW) pumping at 775 nm wavelength, the signal and idler are at 1532.5 nm and 1567.5 nm, respectively. The domain-engineered crystal simultaneously phasematches signal and idler pairs: [H(1532.5 nm), V(1567.5 nm)] and [V(1532.5 nm), H(1567.5 nm)]. We observe the tuning curves of these processes through difference-frequency generation and through CW fiberassisted, single-photon spectroscopy. These measurements indicate good matching in amplitude and bandwidth of the two processes and that the crystal can in principle be used effectively to generate polarization-entangled photon pairs.
Conference on Lasers and Electro-Optics 2010, 2010
A semiconductor laser with active layer consisting of a patterned quantum dot lattice demonstrate... more A semiconductor laser with active layer consisting of a patterned quantum dot lattice demonstrates evidence of miniband formation resulting from inter-dot coupling. Excited state lasing is thought to result from a phonon bottleneck-like effect.
ABSTRACTSuperconducting nanowire single-photon detectors (SNSPDs) based on ultra-thin films have ... more ABSTRACTSuperconducting nanowire single-photon detectors (SNSPDs) based on ultra-thin films have become the preferred technology for applications that require high efficiency single-photon detectors with high speed, high timing resolution, and low dark count rates at near-infrared wavelengths. Since demonstration of the first SNSPD using NbN thin films, an increasingly larger number of materials are being explored. We investigate amorphous thin film alloys of MoSi, MoGe, and WRe with the goal of optimizing SNSPDs for higher operating temperature, high efficiency and high speed. To explore material adequacy for SNSPDs, we have measured superconducting transition temperature (Tc) as a function of film thickness and sheet resistance, as well as critical current densities. In this paper we present our results comparing these materials to WSi, another amorphous material widely used for SNSPD devices.
We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon dete... more We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon detectors optimized for high detection efficiency in the near-infrared range. An integrated, readily scalable, multiplexed readout scheme is employed to reduce the number of readout lines to 16. The cryogenic, optical, and electronic packaging to read out the array, as well as characterization measurements are discussed.
ABSTRACT Superconducting devices offer the potential to perform at speeds and detection efficienc... more ABSTRACT Superconducting devices offer the potential to perform at speeds and detection efficiencies higher than what is possible using conventional technologies (such as semiconducting avalanche photodiodes and photomultiplier tubs) for wavelengths from the ultraviolet to the mid-infrared. As a result, there has been increasing interest in using superconducting optical photon detectors in a variety of applications. There has been significant progress in using these types of detectors in areas of basic research such as quantum information science and quantum optics. These applications require detectors that have extremely low dark count rates, high count rates, and high quantum efficiency. I will begin by describing some of our earlier work on superconducting Transition-Edge Sensor (TES). In particular, I will describe some of the engineering involved in the cryogenic, electrical, and optical packaging so that these devices can be easily coupled into fiber-based optics. I will also describe our recent work on developing superconducting nanowire single photon detectors (SNSPD or SSPD). An SNSPD is an ultra-thin, ultra-narrow (nm scale) superconducting meander that is current biased just below its critical current density. When one or more photon is absorbed, a hot spot is formed that causes the superconductor to develop a resistance and consequently a voltage pulse. At NIST and JPL, we have been developing nanowire detectors using an amorphous alloy of tungsten-silicide. We will describe to construct systems using tungsten-silicide nanowires to achieve high detection efficiency (>90% at 1550nm). I will also describe our work to improve the performance of the device by fabricating multiple nanowires in an electrically parallel structure to implement a superconducting nanowire avalanche photodiode (SNAP)[1]. One example of this type of detector is shown in Fig 1. In this case, there are two tungsten silicide layers separated by a dielectric layer to optimize detection of l- ght for any polarization[2]. In addition, progress on other types of SNAP detectors will be described to increase the signal size from a single photon, reduce the recovery time of the device, and to improve the jitter.
In this work, we report on the use of narrow spectral linewidth DBR lasers at 850-nm with wide tu... more In this work, we report on the use of narrow spectral linewidth DBR lasers at 850-nm with wide tuning ranges as optical heterodyne sources. Using widely tunable laser diodes as sources allows for generation over the entire photodetector range. By utilizing devices that can emit a narrow spectral linewidth without the use of additional feedback systems, the size and complexity
Nanopores are a new class of low dimensional semiconductor nanostructures which have been recentl... more Nanopores are a new class of low dimensional semiconductor nanostructures which have been recently proposed for use in lasers and other photonic applications. This paper provides an overview of patterned nanopore lattices with an emphasis on their electronic and optical properties. The ability to control nanopore properties by geometry and material composition are demonstrated. Two methods for controlled nanopore fabrication
2012 17th Opto-Electronics and Communications Conference, 2012
ABSTRACT The nanopore is a quantum well structure with a periodic array of pores that have been f... more ABSTRACT The nanopore is a quantum well structure with a periodic array of pores that have been filled with wider gap semiconductor material. The fabrication and optical characteristics of smaller, more uniform arrays are presented.
IEEE Transactions on Applied Superconductivity, 2015
Single-pixel fiber-coupled superconducting nanowire single-photon detectors (SNSPDs) operating at... more Single-pixel fiber-coupled superconducting nanowire single-photon detectors (SNSPDs) operating at 1550 nm and utilizing amorphous superconducting tungsten silicide (WSi) films have proven ability to detect photons with: high system-detection efficiency (SDE) of up to 93%, low-jitter on the order of ∼150 ps, dark count rates of ∼1 kcps, and fast reset times on the order of tens of nanoseconds. Additionally, WSi SNSPD devices with 12-pixels have recently demonstrated downlink data rates of 79 Mbps between a terminal in orbit around the moon and a terminal on earth, as part of the Lunar Laser Communication Demonstration (LLCD) at the Lunar Lasercomm OCTL Terminal (LLOT). To further extend the performance of SNSPD devices for optical and quantum communication for terrestrial and space-based applications, the next generation of devices will need to incorporate hundreds to thousands of SNSPD pixels and to be free-space coupled. The wire widths necessary for optimal performance of WSi (∼120-220 nm) devices have to date been achieved using electron-beam lithography (EBL) to pattern photoresists for etch-back fabrication methods. The high cost and time to fabricate kilo-pixel arrays of SNSPDs using EBL will become prohibitive in producing such devices. Here, we report fabrication of a WSi SNSPD test structure with 64 pixels using optical lithography instead of EBL. Specifically, we used Canon EX3 and EX6 deep-UV (DUV) steppers with KrF excimer lasers (λ = 248 nm) in the Micro Devices Laboratory at the Jet Propulsion Laboratory to fabricate the array. Dies with 8 × 8 pixels with 166-nm-wide wires were produced, with pixels having a 100 μm pitch in the vertical and horizontal directions. Two improvements were observed: 1) the time to pattern the 8 × 8 SNSPD pixels on 3.5 mm × 3.5 mm dies filling a 4-in Si wafer required ∼24 hours using EBL while optical lithography wrote the same dies in approximately 15 minutes; and 2) the cost to write one 4-in wafer using EBL was comparable to the cost for one optical mask for use in the stepper to write many 4-in wafers. While fabrication times and costs will vary from facility to facility, the improvements in speed and cost for optical lithography versus EBL are apparent, and
ABSTRACT We discuss the implementation of a receiver for the Lunar Laser Communication Demonstrat... more ABSTRACT We discuss the implementation of a receiver for the Lunar Laser Communication Demonstration based on a 12-pixel array of WSi SNSPDs. The receiver was used to close a communication link from lunar orbit at 39 and 79 Mbps.
ABSTRACT We describe our progress towards building a free-space coupled array of nanowire detecto... more ABSTRACT We describe our progress towards building a free-space coupled array of nanowire detectors with a multiplexed readout. The cryogenic, optical, and electronic packaging to readout the array will be discussed.
Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, 2009
Abstract We demonstrate compact integration of 780 and 850-nm vertical-cavity surface-emitting la... more Abstract We demonstrate compact integration of 780 and 850-nm vertical-cavity surface-emitting lasers into a micro-fluidic microsystem. Absorption at 850 nm and fluorescence pumping at 780 nm of near-infrared fluorescent molecules are presented.
Quantum Dots, Particles, and Nanoclusters VI, 2009
ABSTRACT The conventional approach to fabricate semiconductor based QDs is based on the Stranski-... more ABSTRACT The conventional approach to fabricate semiconductor based QDs is based on the Stranski-Krastnow (SK) growth mode, which has enjoyed considerable success in device applications. However, the SK QD approach is complicated by the randomness of the QD size distribution and inherent presence of the wetting layer. Carrier leakage to the wetting layer has been identified as one of the underlying causes for low optical gain and high temperature sensitivity in diode lasers. To fully exploit the potential advantages of ideal Quantum Dots (i.e. full 3D carrier confinement), elimination of the wetting layer and a uniform mono-modal QD size distribution is needed. Nanopatterning with selective MOCVD QD growth has potential for achieving a higher degree of control over the QD formation, compared with the SK process. Furthermore, the problematic wetting layer states are eliminated and improved optical gain is expected. The QD patterning is prepared by dense nanoscale (20-30 nm diameter) diblock copolymer lithography, which consists of perpendicularly ordered cylindrical domains of polystyrene-block-poly(methylmethacrylate) (PS-b-PMMA) matrix. For selective MOCVD growth, a dielectric template mask was utilized and the polymer patterning is transferred on it. The resulting GaAs QD densities are larger than 5×1010/cm2, comparable to SK growth mode, with a nearly monomodal QD size distribution. Variable temperature PL has been used to characterize the optical properties of capped InGaAs QDs on GaAs (lambda ~ 1.1 mum) and InP (lambda ~ 1.5 mum) substrates.
This document provides supplementary information to "Superconducting nanowire single-photon detec... more This document provides supplementary information to "Superconducting nanowire single-photon detectors with 98% system detection efficiency at 1550 nm,"
We report on the integration of superconducting nanowire single photon detectors (SNSPDs) on lith... more We report on the integration of superconducting nanowire single photon detectors (SNSPDs) on lithium niobate waveguides. In particular, we discuss challenges during the fabrication process, characterization methods and efficiency optimization. Lithium niobate is an interesting platform for quantum optics. Waveguide-integrated devices provide a versatile toolbox for complex optical circuits, due to their low-loss waveguiding of TEand TM-polarization modes, electro-optic properties, and high second order susceptibility [1]. Many different tools for quantum optics applications have been realized on this platform including single-photon sources, couplers, switches and modulators. In addition, highly-efficient fiber-coupling can be achieved by direct end-face pigtailing due to an optimized mode overlap with the titanium in-diffused waveguides. However, the integration of single-photon detectors on these waveguides is challenging [2, 3, 4]. State-of-the-art single photon detectors at opti...
Single-quantum emitters are an important resource for photonic quantum technologies, constituting... more Single-quantum emitters are an important resource for photonic quantum technologies, constituting building blocks for single-photon sources, stationary qubits, and deterministic quantum gates. Robust implementation of such functions is achieved through systems that provide both strong light-matter interactions and a low-loss interface between emitters and optical fields. Existing platforms providing such functionality at the single-node level present steep scalability challenges. Here, we develop a heterogeneous photonic integration platform that provides such capabilities in a scalable on-chip implementation, allowing direct integration of GaAs waveguides and cavities containing self-assembled InAs/GaAs quantum dots-a mature class of solid-state quantum emitter-with low-loss Si3N4 waveguides. We demonstrate a highly efficient optical interface between Si3N4 waveguides and single-quantum dots in GaAs geometries, with performance approaching that of devices optimized for each materia...
In contrast to UV photomultiplier tubes that are widely used in physical chemistry, mid-infrared ... more In contrast to UV photomultiplier tubes that are widely used in physical chemistry, mid-infrared detectors are notorious for poor sensitivity and slow time response. This helps explain why, despite the importance of infrared spectroscopy in molecular science, mid-infrared fluorescence is not more widely used. In recent years, several new technologies have been developed that open new experimental possibilities for research in the mid-infrared. In this Account, we present one of the more promising technologies, superconducting nanowire single photon detectors (SNSPDs) by sharing our experience with its use in a typical experiment carried out by physical chemists (laser-induced fluorescence) and comparing the SNSPD to a detector commonly used by physical chemists (InSb at LN Temperature). SNSPDs are fabricated from a thin film of superconducting metal, patterned into a meandering nanowire. The nanowire is cooled below its superconducting temperature, Tc, and held in a constant current...
Quantum Information Science and Technology II, 2016
High-dimensional (dimension d > 2) quantum key distribution (QKD) protocols that encode informati... more High-dimensional (dimension d > 2) quantum key distribution (QKD) protocols that encode information in the temporal degree of freedom promise to overcome some of the challenges of qubit-based (d = 2) QKD systems. In particular, the long recovery time of single-photon detectors and large channel noise at long distance both limit the rate at which a final secure key can be generated in a low-dimension QKD system. We propose and demonstrate a practical discrete-variable time-frequency protocol with d = 4 at a wavelength of 1550 nm, where the temporal states are secured by transmitting and detecting their dual states under Fourier transformation, known as the frequency-basis states, augmented by a decoy-state protocol. We show that the discrete temporal and frequency states can be generated and detected using commercially-available equipment with high timing and spectral efficiency. In our initial experiments, we only have access to detectors that have low efficiency (1%) at 1550 nm. Together with other component losses, our system is equivalent to a QKD system with ideal components and a 50-km-long optical-fiber quantum channel. We find that our system maintains a spectral visibility of over 99.0% with a quantum bit error rate of 2.3%, which is largely due to the finite extinction ratio of the intensity modulators used in the transmitter. The estimated secure key rate of this system is 7.7×10 4 KHz, which should improve drastically when we use detectors optimized for 1550 nm.
We characterize spontaneous parametric downconversion in a domain-engineered, type-II periodicall... more We characterize spontaneous parametric downconversion in a domain-engineered, type-II periodically poled lithium niobate (PPLN) crystal using seeded emission and single-photon techniques. Using continuous-wave (CW) pumping at 775 nm wavelength, the signal and idler are at 1532.5 nm and 1567.5 nm, respectively. The domain-engineered crystal simultaneously phasematches signal and idler pairs: [H(1532.5 nm), V(1567.5 nm)] and [V(1532.5 nm), H(1567.5 nm)]. We observe the tuning curves of these processes through difference-frequency generation and through CW fiberassisted, single-photon spectroscopy. These measurements indicate good matching in amplitude and bandwidth of the two processes and that the crystal can in principle be used effectively to generate polarization-entangled photon pairs.
Conference on Lasers and Electro-Optics 2010, 2010
A semiconductor laser with active layer consisting of a patterned quantum dot lattice demonstrate... more A semiconductor laser with active layer consisting of a patterned quantum dot lattice demonstrates evidence of miniband formation resulting from inter-dot coupling. Excited state lasing is thought to result from a phonon bottleneck-like effect.
ABSTRACTSuperconducting nanowire single-photon detectors (SNSPDs) based on ultra-thin films have ... more ABSTRACTSuperconducting nanowire single-photon detectors (SNSPDs) based on ultra-thin films have become the preferred technology for applications that require high efficiency single-photon detectors with high speed, high timing resolution, and low dark count rates at near-infrared wavelengths. Since demonstration of the first SNSPD using NbN thin films, an increasingly larger number of materials are being explored. We investigate amorphous thin film alloys of MoSi, MoGe, and WRe with the goal of optimizing SNSPDs for higher operating temperature, high efficiency and high speed. To explore material adequacy for SNSPDs, we have measured superconducting transition temperature (Tc) as a function of film thickness and sheet resistance, as well as critical current densities. In this paper we present our results comparing these materials to WSi, another amorphous material widely used for SNSPD devices.
We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon dete... more We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon detectors optimized for high detection efficiency in the near-infrared range. An integrated, readily scalable, multiplexed readout scheme is employed to reduce the number of readout lines to 16. The cryogenic, optical, and electronic packaging to read out the array, as well as characterization measurements are discussed.
ABSTRACT Superconducting devices offer the potential to perform at speeds and detection efficienc... more ABSTRACT Superconducting devices offer the potential to perform at speeds and detection efficiencies higher than what is possible using conventional technologies (such as semiconducting avalanche photodiodes and photomultiplier tubs) for wavelengths from the ultraviolet to the mid-infrared. As a result, there has been increasing interest in using superconducting optical photon detectors in a variety of applications. There has been significant progress in using these types of detectors in areas of basic research such as quantum information science and quantum optics. These applications require detectors that have extremely low dark count rates, high count rates, and high quantum efficiency. I will begin by describing some of our earlier work on superconducting Transition-Edge Sensor (TES). In particular, I will describe some of the engineering involved in the cryogenic, electrical, and optical packaging so that these devices can be easily coupled into fiber-based optics. I will also describe our recent work on developing superconducting nanowire single photon detectors (SNSPD or SSPD). An SNSPD is an ultra-thin, ultra-narrow (nm scale) superconducting meander that is current biased just below its critical current density. When one or more photon is absorbed, a hot spot is formed that causes the superconductor to develop a resistance and consequently a voltage pulse. At NIST and JPL, we have been developing nanowire detectors using an amorphous alloy of tungsten-silicide. We will describe to construct systems using tungsten-silicide nanowires to achieve high detection efficiency (>90% at 1550nm). I will also describe our work to improve the performance of the device by fabricating multiple nanowires in an electrically parallel structure to implement a superconducting nanowire avalanche photodiode (SNAP)[1]. One example of this type of detector is shown in Fig 1. In this case, there are two tungsten silicide layers separated by a dielectric layer to optimize detection of l- ght for any polarization[2]. In addition, progress on other types of SNAP detectors will be described to increase the signal size from a single photon, reduce the recovery time of the device, and to improve the jitter.
In this work, we report on the use of narrow spectral linewidth DBR lasers at 850-nm with wide tu... more In this work, we report on the use of narrow spectral linewidth DBR lasers at 850-nm with wide tuning ranges as optical heterodyne sources. Using widely tunable laser diodes as sources allows for generation over the entire photodetector range. By utilizing devices that can emit a narrow spectral linewidth without the use of additional feedback systems, the size and complexity
Nanopores are a new class of low dimensional semiconductor nanostructures which have been recentl... more Nanopores are a new class of low dimensional semiconductor nanostructures which have been recently proposed for use in lasers and other photonic applications. This paper provides an overview of patterned nanopore lattices with an emphasis on their electronic and optical properties. The ability to control nanopore properties by geometry and material composition are demonstrated. Two methods for controlled nanopore fabrication
2012 17th Opto-Electronics and Communications Conference, 2012
ABSTRACT The nanopore is a quantum well structure with a periodic array of pores that have been f... more ABSTRACT The nanopore is a quantum well structure with a periodic array of pores that have been filled with wider gap semiconductor material. The fabrication and optical characteristics of smaller, more uniform arrays are presented.
IEEE Transactions on Applied Superconductivity, 2015
Single-pixel fiber-coupled superconducting nanowire single-photon detectors (SNSPDs) operating at... more Single-pixel fiber-coupled superconducting nanowire single-photon detectors (SNSPDs) operating at 1550 nm and utilizing amorphous superconducting tungsten silicide (WSi) films have proven ability to detect photons with: high system-detection efficiency (SDE) of up to 93%, low-jitter on the order of ∼150 ps, dark count rates of ∼1 kcps, and fast reset times on the order of tens of nanoseconds. Additionally, WSi SNSPD devices with 12-pixels have recently demonstrated downlink data rates of 79 Mbps between a terminal in orbit around the moon and a terminal on earth, as part of the Lunar Laser Communication Demonstration (LLCD) at the Lunar Lasercomm OCTL Terminal (LLOT). To further extend the performance of SNSPD devices for optical and quantum communication for terrestrial and space-based applications, the next generation of devices will need to incorporate hundreds to thousands of SNSPD pixels and to be free-space coupled. The wire widths necessary for optimal performance of WSi (∼120-220 nm) devices have to date been achieved using electron-beam lithography (EBL) to pattern photoresists for etch-back fabrication methods. The high cost and time to fabricate kilo-pixel arrays of SNSPDs using EBL will become prohibitive in producing such devices. Here, we report fabrication of a WSi SNSPD test structure with 64 pixels using optical lithography instead of EBL. Specifically, we used Canon EX3 and EX6 deep-UV (DUV) steppers with KrF excimer lasers (λ = 248 nm) in the Micro Devices Laboratory at the Jet Propulsion Laboratory to fabricate the array. Dies with 8 × 8 pixels with 166-nm-wide wires were produced, with pixels having a 100 μm pitch in the vertical and horizontal directions. Two improvements were observed: 1) the time to pattern the 8 × 8 SNSPD pixels on 3.5 mm × 3.5 mm dies filling a 4-in Si wafer required ∼24 hours using EBL while optical lithography wrote the same dies in approximately 15 minutes; and 2) the cost to write one 4-in wafer using EBL was comparable to the cost for one optical mask for use in the stepper to write many 4-in wafers. While fabrication times and costs will vary from facility to facility, the improvements in speed and cost for optical lithography versus EBL are apparent, and
ABSTRACT We discuss the implementation of a receiver for the Lunar Laser Communication Demonstrat... more ABSTRACT We discuss the implementation of a receiver for the Lunar Laser Communication Demonstration based on a 12-pixel array of WSi SNSPDs. The receiver was used to close a communication link from lunar orbit at 39 and 79 Mbps.
ABSTRACT We describe our progress towards building a free-space coupled array of nanowire detecto... more ABSTRACT We describe our progress towards building a free-space coupled array of nanowire detectors with a multiplexed readout. The cryogenic, optical, and electronic packaging to readout the array will be discussed.
Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, 2009
Abstract We demonstrate compact integration of 780 and 850-nm vertical-cavity surface-emitting la... more Abstract We demonstrate compact integration of 780 and 850-nm vertical-cavity surface-emitting lasers into a micro-fluidic microsystem. Absorption at 850 nm and fluorescence pumping at 780 nm of near-infrared fluorescent molecules are presented.
Quantum Dots, Particles, and Nanoclusters VI, 2009
ABSTRACT The conventional approach to fabricate semiconductor based QDs is based on the Stranski-... more ABSTRACT The conventional approach to fabricate semiconductor based QDs is based on the Stranski-Krastnow (SK) growth mode, which has enjoyed considerable success in device applications. However, the SK QD approach is complicated by the randomness of the QD size distribution and inherent presence of the wetting layer. Carrier leakage to the wetting layer has been identified as one of the underlying causes for low optical gain and high temperature sensitivity in diode lasers. To fully exploit the potential advantages of ideal Quantum Dots (i.e. full 3D carrier confinement), elimination of the wetting layer and a uniform mono-modal QD size distribution is needed. Nanopatterning with selective MOCVD QD growth has potential for achieving a higher degree of control over the QD formation, compared with the SK process. Furthermore, the problematic wetting layer states are eliminated and improved optical gain is expected. The QD patterning is prepared by dense nanoscale (20-30 nm diameter) diblock copolymer lithography, which consists of perpendicularly ordered cylindrical domains of polystyrene-block-poly(methylmethacrylate) (PS-b-PMMA) matrix. For selective MOCVD growth, a dielectric template mask was utilized and the polymer patterning is transferred on it. The resulting GaAs QD densities are larger than 5×1010/cm2, comparable to SK growth mode, with a nearly monomodal QD size distribution. Variable temperature PL has been used to characterize the optical properties of capped InGaAs QDs on GaAs (lambda ~ 1.1 mum) and InP (lambda ~ 1.5 mum) substrates.
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Papers by Varun Verma