J.S. Massa

Time-of-flight optical ranging system based on time-correlated single-photon counting

The design and implementation of a prototype time-of-flight optical ranging system based on the time-correlated single-photon-counting technique are described. The sensor is characterized in terms of its longitudinal and transverse spatial resolution, single-point measurement time, and long-term stability. The system has been operated at stand-off distances of 0.5-5 m, has a depth repeatability of <30 mum, and has a lateral spatial resolution of <500 mum.

Laser depth measurement based on time-correlated single-photon counting

A method for acquiring range data based on time-correlated single-photon counting is described. This method uses a short-pulse ( approximately 10-ps) laser diode, a detector based on a silicon single-photon avalanche diode, and standard photon-counting timing electronics. The accuracy of the technique has been measured as approximately +/-30 microm in a laboratory experiment and corresponds closely to the results of a theoretical simulation.

Optical design and evaluation of a three-dimensional imaging and ranging system based on time-correlated single-photon counting

The design and operation of a noncontact surface profilometry system based on the time-correlated single-photon-counting technique are described. This system has a robust optomechanical design and uses an eye-safe laser that makes it particularly suitable for operation in an uncontrolled industrial environment. The sensitivity of the photon-counting technique permits its use on a variety of target materials, and its mode of operation does not require the continual presence of an operator. The system described has been optimized for a 1-25-m standoff, has a distance repeatability of <30 microm, and has a transverse spatial resolution of approximately 60 microm at a 2-m standoff and approximately 400 microm at a 13-m standoff.

Time-resolved photoluminescence measurements of InGaAs/InP multiple-quantum-well structures at 1.3-μm wavelengths by use of germanium single-photon avalanche photodiodes

A commercially available germanium avalanche photodiode operating in the single-photon-counting mode has been used to perform time-resolved photoluminescence measurements on InGaAs/lnP multiple-quantum-well structures. Photoluminescence in the spectral region of 1.3-1.48 µm was detected with picosecond timing accuracy by use of the time-correlated single-photon counting technique. The carrier dynamics were monitored for excess photogenerated carrier densities in the range 10(18)-10(15) cm(-3). The recombination time is compared for similar InGaAs-based quantum-well structures grown by use of different epitaxial processes.

Time-resolved photoluminescence microscopy of GaInAs/GaInAsP quantum wells intermixed using a pulsed laser technique

High spatial resolution time‐resolved photoluminescence has been used to study GaInAs/GaInAsP quantum‐well structures selectively intermixed using the pulsed photoabsorption‐induced disordering technique. Photoluminescence decay measurements at wavelengths ≳1.3 μm were obtained using novel high‐efficiency photon‐counting detectors and were found to correlate spatially with the observed luminescence blue shift in these structures. Results indicate a reduction in the nonradiative recombination time of nearly two orders of magnitude as a result of this intermixing technique.

TIME-RESOLVED PHOTOLUMINESCENCE STUDIES OF CROSS-WELL TRANSPORT IN A BIASED GAAS/ALGAAS MULTIPLE QUANTUM WELL P-I-N STRUCTURE

Time-resolved photoluminescence has been used to study the cross-well carrier dynamics in a biased multiple quantum well p-i-n structure at temperatures in the range 5–350 K and for electric fields <200 kV cm−1. The photoluminescence decays have been parameterized using reconvolution analysis with a coupled rate equation model and this has provided strong evidence for the successive recapturing of carriers in adjacent wells. For temperatures <100 K, and for electric fields <60 kV cm−1, the carrier escape appears to be strongly affected by resonant tunneling between hole subbands in adjacent wells. At higher temperatures an increase in the carrier escape rate is observed which corresponds to a field dependent thermal activation energy.

Time resolved photoluminescence study of strained-layer InGaAsP/InP heterostructures

A time-resolved photoluminescence study of strained and unstrained InGaAsP/InP double heterostructures has been performed at low photogenerated carrier densities (i.e. ≤1016 cm−3) using a novel high-efficiency germanium photon-counting detector. The photoluminescenee decay times are observed to decrease with increasing strain. Samples grown on substrates with lattice orientation (3 1 1)B are shown to have shorter excess carrier lifetimes than those grown on lattices orientated (0 0 1) or (3 1 1)A.

Rangefinding using time correlated single photon counting

This paper describes a method for acquiring range data based on time-correlated single photon counting (TCSPC) and details the data analysis techniques used to compute the range measurements. The prototype sensor being built in our laboratory is capable of measuring up to 100 points per second with an accuracy of about 15 /spl mu/m.