High-energy sub-nanosecond optical pulse generation with a semiconductor laser diode for pulsed TOF laser ranging utilizing the single photon detection approach

Bulk and quantum well laser diodes with a large equivalent spot size of da/Γa ≈ 3 µm and stripe width/cavity length of 30 µm/3 mm were realized and tested. They achieved a pulse energy and pulse length of the order of ~1 nJ and ~100 ps, respectively, with a peak pulse current of 6–8 A and a current pulse width of 1 ns. The 2D characteristics of the optical output power versus wavelength and time were also analyzed with a monochromator/streak camera set-up. The far-field characteristics were studied with respect to the time-homogeneity and energy distribution. The feasibility of a laser diode with a large equivalent spot size in single photon detection based laser ranging was demonstrated to a non-cooperative target at a distance of a few tens of meters

AlGaAs/GaAs asymmetric-waveguide, short cavity laser diode design with a bulk active layer near the p-cladding for high pulsed power emission

It is shown theoretically that a GaAs/AlGaAs laser diode design using an asymmetric waveguide structure and a bulk active layer, located close to the p-cladding, can provide high output power in a single, broad transverse mode for short-wavelength (< 0.9 m, matching the spectral range of high efficiency of silicon photodetectors) pulsed emission in the nanosecond pulse duration region, typically << 100 ns. The dependences of the laser performance on the thickness of the active layer and the cavity length are analysed. It is shown that the relatively thick bulk active layer allows the of short cavity lengths (<1 mm), for achieving high pulsed power while maintaining a relatively low series resistance and a narrow far field

High Power 1.5um Pulsed Laser Diode with Asymmetric Waveguide and Active Layer Near p-cladding

We report first experimental results on a high-power pulsed semiconductor laser operating in the eye-safe spectral range (wavelength around 1.5 lm) 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 lm 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.publishedVersionPeer reviewe

Strong Doping of the n-Optical Confinement Layer for Increasing Output Power of High- Power Pulsed Laser Diodes in the Eye Safe Wavelength Range

Abstract—An analytical model for internal optical losses at high power in a 1.5 μm laser diode with strong n-doping in the n-side of the optical confinement layer is created. The model includes intervalence band absorption by holes supplied by both current flow and two-photon absorption, as well as the direct two-photon absorption effect. The resulting losses are compared with those in an identical structure with a weakly doped waveguide, and shown to be substantially lower, resulting in a significant improvement in the output power and efficiency in the structure with a strongly doped waveguid

Effect of spatial hole burning on output characteristics of high power edge emitting semiconductor lasers : a universal analytical estimate and numerical analysis

The effect of longitudinal spatial hole burning on the performance of a semiconductor laser with a strongly asymmetric resonator is investigated numerically. The effects of spatial hole burning on, firstly, the non-stimulated recombination in the laser (quantified as an increased effective threshold current) and, secondly, the output efficiency are calculated and compared, and the latter is shown to dominate at high currents. It is shown that the output efficiency at high pumping levels in the presence of the spatial hole burning effect can be estimated using the standard expression as the ratio of output loss to total loss, but with the internal loss enhanced by a factor greater than one and independent on the injection level. A simple universal expression for this factor for a highly asymmetric cavity, as a function of the output mirror reflectance, is obtained and compared to numerical results, with good agreement

Optical loss suppression in long-wavelength semiconductor lasers at elevated temperatures by strong doping of n-waveguides

We show that strong n-doping of the n-waveguide layer substantially decreases the thermal carrier leakage from the active layer and the associated optical losses in III-V semiconductor lasers. The effect is particularly pronounced in devices operating at the wavelength region where the free hole absorption cross-section is much greater than that of free electrons. This is predicted to decrease the threshold current and improve the output efficiency of the lasers. An example of a bulk InGaAsP/InP pulsed lasers is used to demonstrate that lasers with highly doped n-InGaAsP side of the waveguide can retain high output powers at ambient temperatures substantially above room temperature

Effect of spatial hole burning on output characteristics of high power edge emitting semiconductor lasers:a universal analytical estimate and numerical analysis

Abstract The effect of longitudinal spatial hole burning on the performance of a semiconductor laser with a strongly asymmetric resonator is investigated numerically. The effects of spatial hole burning on, firstly, the non-stimulated recombination in the laser (quantified as an increased effective threshold current) and, secondly, the output efficiency are calculated and compared, and the latter is shown to dominate at high currents. It is shown that the output efficiency at high pumping levels in the presence of the spatial hole burning effect can be estimated using the standard expression as the ratio of output loss to total loss, but with the internal loss enhanced by a factor greater than one and independent on the injection level. A simple universal expression for this factor for a highly asymmetric cavity, as a function of the output mirror reflectance, is obtained and compared to numerical results, with good agreement