Philip A. Hiskett

A photon-counting time-of-flight ranging technique developed for the avoidance of range ambiguity at gigahertz clock rates

This paper describes a rapid data acquisition photon-counting time-of-flight ranging technique that is designed for the avoidance of range ambiguity, an issue commonly found in high repetition frequency time-off-light systems. The technique transmits a non-periodic pulse train based on the random bin filling of a high frequency time clock. A received pattern is formed from the arrival times of the returning single photons and the correlation between the transmitted and received patterns was used to identify the unique target time-of-flight. The paper describes experiments in laboratory and in free space at over several hundred meters range at clock frequencies of 1GHz. Unambiguous photon-counting range-finding is demonstrated with centimeter accuracy.

Multiple wavelength time-of-flight sensor based on time-correlated single-photon counting

This article describes a time-of-flight sensor based on multiple pulsed laser sources which utilizes time-correlated single-photon counting. The sensor has demonstrated good performance at ranges of up to 17 km in daylight conditions. Analysis techniques were developed to examine the returns from targets containing more than one scattering surface.

Enhancement of the infrared detection efficiency of silicon photon-counting avalanche photodiodes by use of silicon germanium absorbing layers

An enhancement of the infrared detection efficiency of Si photon-counting detectors by inclusion of SiGe absorbing layers has been demonstrated for what is believed to be the first time. An improvement of 30 times in detection efficiency at a wavelength of 1210 nm compared with that of an all-Si structure operated under identical conditions has been measured. The Si/Si(0.7)Ge(0.3) device is capable of room-temperature operation and has a response time of less than 300 ps.

Eighty kilometre transmission experiment using an InGaAs/InP SPAD-based quantum cryptography receiver operating at 1.55 μm

A polarization-based receiver for quantum key distribution incorporating an InGaAs/InP single photon avalanche photodiode (SPAD) has been constructed to investigate the potential for increasing the transmission distance in long wavelength quantum key distribution systems beyond the 50 km range.

Analysis of detector performance in a gigahertz clock rate quantum key distribution system

We present a detailed analysis of a gigahertz clock rate environmentally robust phase-encoded quantum key distribution (QKD) system utilizing several different single-photon detectors, including the first implementation of an experimental resonant cavity thin-junction silicon single-photon avalanche diode. The system operates at a wavelength of 850 nm using standard telecommunications optical fibre. A general-purpose theoretical model for the performance of QKD systems is presented with reference to these experimental results before predictions are made about realistic detector developments in this system. We discuss, with reference to the theoretical model, how detector operating parameters can be further optimized to maximize key exchange rates.

Robust gigahertz fiber quantum key distribution

We present recent results on an innovative fiber based short wavelength gigahertz clock rate quantum key distribution system operating over a standard telecommunications optical fiber quantum channel. This system is designed to be robust against environmentally induced changes in the polarization evolution of the photons in the optical fiber quantum channel and against path-length drift in the interferometers which could otherwise compromise system performance. Experimental results are presented for error rate, net bit rate and stability for different silicon single-photon avalanche diode detector types.

Picosecond time-resolved photoluminescence at detection wavelengths greater than 1500 nm.

We report what is to our knowledge the first application of high-efficiency InGaAs/InP photon-counting diode detectors in time-resolved photoluminescence measurements at wavelength greater than 1500 nm. When they were cooled to 77 K and used in conjunction with the time-correlated single-photon counting technique, the detectors were capable of an instrumental response of 230 ps and a noise equivalent power of 2x10(-17)W Hz(-1/2) . Preliminary measurement of a semiconductor heterostructure indicates sensitivity at photogenerated carrier densities as low as 10(14)cm (-3) . This development facilitates the detailed characterization of dominant recombination mechanisms in semiconductor optoelectronic materials and devices designed to operate in the third telecommunications spectral window.

Time-of-flight sensing using time-correlated single-photon counting

Time-correlated single-photon counting techniques using individual optimized detectors have been applied to time-of-flight ranging and depth imaging. This paper describes recent progress in photon-counting systems performing surface mapping of non-cooperative targets. This includes systems designed for short ranges of the order of 1-50 meters, and longer ranges of up to ten kilometers. The technique has also been applied to distributed surfaces. We describe the measurement approach, techniques used for scanning, as well as the signal analysis methodology and algorithm selection. The technique is fundamentally flexible: the trade-off between the integrated number of counts (or acquisition time) against range repeatability or depth resolution allows its application in a number of diverse fields. The inherent time gating of the technique, allied to the spatial filtering provided by small active area single-photon detectors, can lead to operation under high ambient light conditions even with low average optical power pulsed sources. We have demonstrated three-dimensional imaging of meter-dimensioned objects where reverse engineering methods using cooperative targets cannot be routinely employed: e.g. delicate objects, or objects with more than one reflective surface. Using more advanced signal processing algorithms, we have been able to improve the system performance significantly, as measured by the depth resolution at short and long ranges. Furthermore, the application of these methodologies has allowed us to characterize the positions and amplitudes of multiple returns. Hence, the approach can be used for characterization of distributed non-cooperative targets at kilometer ranges, even in environments where low-light level and and/or eye-safe operation is necessary. The technique has also been applied in conjunction with a rapid scanning approach, to acquire three-dimensional information of a target scene with frame times of approximately 1 second.