This PDF file contains the front matter associated with SPIE Proceedings Volume 8727, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

We describe how hyperentanglement may be used to give orders of magnitude throughput improvement over singly entangled photon pairs, for some applications. Next we demonstrate the first measurement of hyperentangled photon pairs, both of which are at telecom wavelengths, via simultaneous polarization tomography and time-bin interference measurements. Without cryogenic cooling of the nonlinear element, we measure polarization entanglement with tangle of 0.4 ± 0.2 and time bin entanglement with visibility of 83% ± 6%, both exceeding classical thresholds by approximately two standard deviations.

We present the development of key technologies for realization of superconducting nanowire single photon detector array system, which enables high counting rates, and allow spatial and pseudo photon number resolution. Toward the realization of practical large-scale SSPD array system, primary issue is how to avoid heat flow into cryocooler system. One of the challenging tasks is the development of their readout electronics. In the conventional readout technique used for single pixel devices, the number of high-frequency coaxial cables increases proportionally with the number of arrays. This causes a significant increase in the heat load from room temperature, which makes the implementation of the SSPD arrays in a compact refrigerator difficult. To overcome this problem, we proposed applying readout electronics with superconducting single-flux-quantum (SFQ) logic circuitsWe show the implementation and successful operation of four pixels SSPD array connected to SFQ readout electronics with parallel bias scheme in a 0.1W GM cryocooler system.

We present our progress in the development of an integrated technology suitable for the photonic quantum information processing, showing the first autocorrelator based on two separated detectors integrated on top of the same ridge waveguide. An efficiency of ~1% at 1300 nm for both detectors and independent of the polarization of the incoming photons, is reported. This ultracompact device enables the on-chip measurement of the second-order correlation function g⁽²⁾(τ) . We will further discuss ongoing work on the integration of detectors with single-photon sources.

A Nth-order (N=1, 2, 3, 4, 5, 6) interferometric autocorrelator based on superconducting nanodetectors is presented. It provides much higher sensitivity as compared to the conventional autocorrelators using all-optical nonlinearities and a temporal resolution of about 20 ps, which is limited by the quasi-particle energy relaxation time in the superconducting films. A semiclassical model is introduced to explain the nonlinear photodetection process. A comparison of sensitivity to conventional autocorrelators is also presented.

We present an InGaAs/InP single-photon detection system operating at 1.25 GHz with detection efficiency above 50 % and per-gate afterpulse probability, measured 24.8 ns after an avalanche, below 0.2 %. The high efficiency and low afterpulse probabilities we observe are achieved with an avalanche discrimination system whose threshold for detection approaches the fundamental limit imposed by Johnson noise on a 50 Ohm load; we measure the threshold to be less than 8 fC. We discuss the design and performance of our approach, and tradeoffs between detection efficiency, afterpulse probability, and maximum count rate.

We present gated silicon single photon detectors based on two commercially available avalanche photodiodes (APDs) and one customised APD from ID Quantique SA. This customised APD is used in a commercially available device called id110. A brief comparison of the two commercial APDs is presented. Then, the charge persistence effect of all of those detectors that occurs just after a strong illumination is shown and discussed.

We demonstrate balanced InGaAs/InP single photon avalanche diodes (SPADs) operated in both pulse-gated mode and sinusoidal gating mode for data transmission rate up to 20 MHz. The photodiode pair is biased in a balanced configuration with only one of the SPADs illuminated. The common-mode signal cancellation realized with the balanced configuration enables detection of small avalanche pulses. Afterpulsing is significantly suppressed due to the capability of detecting small avalanche pulses at high laser repetition rate. For pulse-gated mode operation and laser repletion rate of 20 MHz at 240 K, the dark count probability for photon detection efficiency of 13% is 1.9×10^-5. The afterpulse probability is 0.3% for 2 ns pulse width, hold off time of 20 ns, and 10% PDE, at 240K. For sinusoidal gating a phase shifter has been incorporated to achieve better synchronization between signals. At laser rate of 20 MHz and 240 K, the dark count probability and photon detection efficiency are 2.8×10^-5 and 10.8% respectively.

Photon-Number-Resolving-Detection (PNRD) capability is crucial for many Quantum-Information (QI) applications, e.g. for Coherent-State-Quantum-Computing, Linear-Optics-Quantum-Computing. In Quantum-Key-Distribution and Quantum-Secret-Sharing over 1310/1550 nm fiber, two other important, defense and information security related, QI applications, it’s crucial for the information transmission security to guarantee that the information carriers (photons) are single. Thus a PNRD can provide an additional security level against eavesdropping. Currently, there are at least a couple of promising PNRD technologies in the Near-Infrared, but all of them require cryogenic cooling. Thus a compact, portable PNRD, based on commercial Avalanche-Photo-Diodes (APDs), could be a very useful instrument for many QI experiments. For an APD-based PNRD, it is crucial to measure the APD-current in the beginning of the avalanche. Thus an efficient cancellation of the APD capacitive spikes is a necessary condition for the very weak APD current measurement. The detector’s principle is based on two commercial, pair-matched InGaAs/InP APDs, connected in series. It leads to a great cancelation of the capacitive spikes caused by the narrow (300 ps), differential gate-pulses of maximum 4V amplitude assuming that both pulses are perfectly matched in regards to their phases, amplitudes, and shapes. The cancellation scheme could be used for other APD-technologies, e.g. Silicon, extending the detection spectrum from visible to NIR. The design distinguishes itself from other, APD-based, schemes by its scalability feature and its computer controlled cancellation of the capacitive spikes. Furthermore, both APDs could be equally used for the detection purpose, which opens a possibility for the odd-even photon number parity detection.

We demonstrate the importance and utility of Monte Carlo simulation of single-photon detectors. Devising an optimal simulation is strongly influenced by the particular application because of the complexity of modern, avalanche-diode based single-photon detectors. Using a simple yet very demanding example of random number generation via detection of Poissonian photons exiting a beam splitter, we present a Monte Carlo simulation that faithfully reproduces the serial autocorrelation of random bits as a function of detection frequency over four orders of magnitude of the incident photon flux. We conjecture that this simulation approach can be easily modified for use in many other applications.

This paper reports the achievements so far attained in the development of high-performance CMOS SPADs for single photon sensitive 2D imagers, based on photon-counting and 3D ranging cameras. The latters are based on both the direct in-pixel measurement of the Time-of-Flight of each photon bouncing bounce from the scene back to the camera and the “indirect” phase-resolved method to count reflected photons in well-defined time slots, synchronous to the active illumination of the scene. MiSPiA SPADs are the new state-of-the-art among SPADs in CMOS technologies.

In order to fulfill the requirements of many applications, we recently developed a new technology aimed at combining the advantages of traditional thin and thick silicon Single Photon Avalanche Diodes (SPAD). In particular we demonstrated single-pixel detectors with a remarkable improvement in the Photon Detection Efficiency at the longer wavelengths (e.g. 40% at 800nm) while maintaining a timing jitter better than 100ps. In this paper we will analyze the factors the currently prevent the fabrication of arrays of SPADs by adopting such a Red-Enhanced (RE) technology and we will propose further modifications to the device structure that will enable the fabrication of high performance RE-SPAD arrays for photon timing applications.

Single photon avalanche diodes (SPADs) are revolutionizing ultra-sensitive photodetection applications, providing single photon sensitivity, high quantum efficiency and low dark noise at or near room temperature. When aggregated into arrays, these devices have demonstrated the ability to operate as photon number resolving detectors with wide dynamic range, or as single-photon imaging detectors. SPAD array performance has reached a point where replacing vacuum tube based MCP and PMT photodetectors for most applications is inevitable. Compound semiconductor SPAD arrays offer the unique proposition to tailor performance to match application specific wavelength, speed and radiation hardness requirements. We present a theoretical framework describing performance limits to compound semiconductor SPAD arrays and our latest experimental results detailing the performance of GaAs SPAD arrays. These devices achieve nanosecond rise and fall times, excellent photon number resolving capability, and low dark count rates. Single photon number resolving is demonstrated with 4% single photon detection efficiency at room temperature with dark count rates below 7 Mcps/mm². Compound semiconductor SPAD arrays have the opportunity to provide orders of magnitude improvement in dark count rate and radiation hardness over silicon SPAD arrays, as well as the ability to detect wavelengths where silicon is blind.

Semiconductor photodetectors at1550nm wavelengths have been widely used in free space optical communications, sensing, infrared imaging, and quantum information processing. These detectors require high sensitivity with high detection efficiency and a large dynamic range. But for fundamental material and device limits, all these performances cannot be achieved in a single device under the same operating conditions. To overcome this bottleneck, we integrate three coupled gain mechanisms in a single element device, operating below breakdown to obtain a high net gain and at the same time utilize the negative feedback mechanism to minimize the gain fluctuation. This results in an improved signal to noise ratio, which is the key to obtaining a superior sensitivity. Integration of gain mechanisms in an InP-InGaAs device was analytically modeled and experimentally demonstrated.

Understanding and controlling the emission efficiency and recombination dynamics of bi-excitonic states (i.e. Q_BX and τ_BX) in semiconductor nanocrystal quantum dots (NQDs) holds the key to many novel technological applications including optical amplification, entangled photon-pair generation and carrier multiplication. Here we present novel single particle spectroscopy approaches capable of measuring these parameter directly. Our approaches are based on second order photon correlation spectroscopy (g⁽²⁾ (τ)) and can also be applied to small clusters of NQDs to determine the number of NQDs in a cluster together with average value of Q_BX and τ_BX. Specifically, first we demonstrate that the ratio of the areas of center and side peaks of the g⁽²⁾ (τ) function of the spectrally integrated PL of a single NQD provide a precise measure of the ratio of the quantum yield of single and bi-exciton states. Next, we present a time gated photon correlation spectroscopy approach that allows separation of the effects of multi-exciton emission and NQD clustering in g(2) measurements. Finally, we present how the emission of bi-excitons can be separated in g⁽²⁾ (τ) measurements and extract decay dynamics of bi-excitons without any ambiguity.

We discuss a novel micro-channel plate (MCP) photomultiplier with resistive screen (RS-PMT) as a detection device for space- and time-correlated single photon counting, illustrated by several applications. The photomultiplier tube resembles a standard image intensifier device. However, the rear phosphor screen is replaced by a ceramic “window” with resistive coating. The MCP output is transferred through the ceramic plate to the read-out electrode (on the air side) via capacity-coupling of the image charge. This design allows for an easy reconfiguration of the read-out electrode (e.g. pixel, charge-sharing, cross-strip, delay-line) without breaking the vacuum for optimizing the detector performance towards a certain task. It also eases the design and manufacturing process of such a multi-purpose photomultiplier tube. Temporal and spatial resolutions well below 100 ps and 100 microns, respectively, have been reported at event rates as high as 1 MHz, for up to 40 mm effective detection diameter. In this paper we will discuss several applications like wide-field fluorescence microscopy and dual γ/fast-neutron radiography for air cargo screening and conclude with an outlook on large-area detectors for thermal neutrons based on MCPs.

Efficient photon detection in gaseous photomultipliers require maximum photoelectron yield from the photocathode surface and also detection of them. In this work we have investigated the parameters that affect the photoelectron yield from the photocathode surface and methods to improve them thus ensuring high detection efficiency of the gaseous photomultiplier. The parameters studied are the electric field at the photocathode surface, surface properties of photocathode and pressure of gas mixture inside the gaseous photomultiplier. It was observed that optimized electric field at the photocathode ensures high detection efficiency. Lower pressure of filled gas increases the photoelectron yield from the photocathode surface but reduces the focusing probability of electrons inside the electron multiplier. Also evacuation for longer duration before gas filling increases the photoelectron yield.

Time Correlated Single Photon counting (TCSPC) with picosecond timing is a key method in many areas of applied physics. One of the most important areas is that of fluorescence lifetime measurement in biophysics and the life sciences. Precisely timed photon counting for the purpose of coincidence correlation is now also emerging as the most common approach to quantum state interpretation in experimental quantum optics. Therefore, time-correlated single photon counting electronics, traditionally mostly used in time-resolved fluorescence research are facing new challenges in different emerging areas. Consequently such instruments are undergoing a fresh cycle of innovation, some of which we try to highlight here. The new picosecond TCSPC system we present provides several interesting new features resulting from a high speed monolithic integration in one of the fastest semiconductor technologies available today. The result is a high timing resolution by direct digital conversion and a very short deadtime. Apart from conventional histogramming over a very long time span, we can implement continouos single photon recording modes hat allow picosecond timing of all photon events with respect both to a sync signal as well as on a virtually infinite time scale. Multiple timing channels can also be operated indpendently and in parallel, e.g. for picosecond correlation analysis between signals from multiple photon detectors.