This paper discusses the construction principles and performance of a pulsed time-of-flight (TOF) laser radar based on high-speed (FWHM $100 ps) and high-energy ($1 nJ) optical transmitter pulses produced with a specific laser diode working in an "enhanced gain-switching" regime and based on single-photon detection in the receiver. It is shown by analysis and experiments that single-shot precision at the level of 2W3 cm is achievable. The effective measurement rate can exceed 10 kHz to a noncooperative target (20% reflectivity) at a distance of 9 50 m, with an effective receiver aperture size of 2:5 cm 2 . The effect of background illumination is analyzed. It is shown that the gating of the SPAD detector is an effective means to avoid the blocking of the receiver in a high-level background illumination case. A brief comparison with pulsed TOF laser radars employing linear detection techniques is also made.

No abstract

We report first experimental results on a highpower pulsed semiconductor laser operating in the eye-safe spectral range (wavelength around 1.5 µm) with an asymmetric waveguide structure. The laser has a bulk active layer positioned very close to the p-cladding in order to eliminate current-induced nonuniform carrier accumulation in the p-side of the waveguide and the associated carrier losses. Moderate doping of the n-side of the waveguide is used to strongly suppress nonuniform carrier accumulation within this part of the waveguide. Highly p-doped InP p-cladding facilitates low series resistance. An as-cleaved sample with a stripe width of 90 µm exhibits an output power of about 18 W at a pumping current amplitude of 80 A. Theoretical calculations, validated by comparison to experiment, suggest that the performance of lasers of this type can be improved further by optimization of the waveguide thickness and doping as well as improvement of injection efficiency.

No abstract

A compact laser pulser emitting ~100 ps, ~10 W pulses at >100 kHz is presented. The high pulsing frequency is achieved using a MOSFET-based current driver, whereas the high pulse power is a merit of the used laser diode with an asymmetric waveguide structure leading to enhanced gain switching. The pulsing frequency is higher than with avalanche transistor based current pulsing circuits due to lower heating, and the current pulse width is shown to be even shorter than with avalanche transistor based circuits. The laser diode transmitter was developed especially for the pulsed time-of-flight laser radar application utilizing a single photon avalanche diode (SPAD) matrix as the detector element. A demonstration measurement is done enabling centimeter-precision distance measurement to 50 m in a measurement time of ~5 ms outdoors in sunny weather.