An 80 x 25 pixel CMOS single-photon sensor with flexible on-chip time gating of 40 subarrays for solid-state 3-D range imaging

Abstract A CMOS solid-state 3-D range imager that uses short (~110 ps) laser pulses and a novel flexible time gating scheme for a single-photon avalanche diode (SPAD) array is presented. The array is divided into 40 subarrays for which a narrow (<0.8 ns) time gating position can be set and scanned independently. The imager can be set to measure multiple regions of interest by means of the flexible time gating of the subarrays. The time gating for each of the subarrays is selected separately with an on-chip delay-locked loop (DLL) block that has 240 outputs and a delay grid of ~ 100 ps. The prototype has 80 x 25 pixels overall with 10 x 5 pixel subarrays. The fill factor of the sensor area is 32%. A 3-D range image is demonstrated at ~ 10 frames/s with centimeter-level precision in the case of passive targets within a range of ~4 m and a field of view of 18° x 28°, requiring an average active illumination power of only 0.1 mW

On two-dimensional rangefinding using a ∼1 nJ/∼100 ps laser diode transmitter and a CMOS SPAD matrix

Abstract A potentially compact 2-D range profiler for noncooperative targets with a distance range of >10 m is demonstrated. A laser diode utilizing enhanced gain switching is used as a transmitter to provide short, high-energy optical pulses (~1 nJ/140 ps). Cylindrical lenses spread the laser beam in one dimension and collimate the beam in the other dimension to illuminate a line shaped field of view of about 45°. A similarly shaped field of view for the detector is realized with a single-photon avalanche diode (SPAD) detector matrix. Compared with a flash 3-D rangefinder, the 2-D rangefinding scheme relaxes the SPAD and time-to-digital converter design requirements, increases the signal irradiance at the detector, can have better tolerance for background illumination, and it can be sufficient or advantageous in some applications. The distance measurement precision to each direction is inherently within a few centimeters (FWHM) since the laser pulse width and SPAD detector jitter both correspond with an optical pulse back-and-forth flight time of about a centimeter. Demonstration measurements show >15 Hz line rate and a lateral resolution of about 5 mrad to noncooperative targets at distances of more than 10 m

High Power 1.5 μm pulsed semiconductor laser design with a bulk active layer and an asymmetric waveguide

Abstract InGaAsP/InP high pulsed power lasers operating in the range of 1.3–1.6 μm have been intensely studied recently, with LIDAR technology being the primary application. We present and analyse a design with a bulk active layer which has a large refractive index step with respect to the optical confinement layer and is located close to the p-cladding. It is shown that such lasers can allow a noticeable performance increase over the state of the art. The dependence of the laser performance on the design parameters including the thicknesses of the active layer and the waveguide, the cavity length, and the waveguide asymmetry, is analysed. It is shown that short cavity lengths (~1 mm or even shorter) can be used in the design considered for achieving high pulsed power. Due to the significant waveguiding properties of the active layer, the use of both symmetric and asymmetric waveguide designs is possible, with only slightly higher output predicted for the asymmetric one. Both designs allow operation with a single, broad transverse mode enabling high brightness

High power 1.5 μm pulsed laser diode with asymmetric waveguide and active layer near p-cladding

Abstract We report first experimental results on a high-power 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