Diode lasers providing nanosecond optical pulses with high peak optical powers are key components in systems for freespace communication, metrology, material processing, spectroscopy, and light detection and ranging (LIDAR) as employed for, e.g., autonomous driving. Here, we report on laser sources for line-scanning automotive LIDAR systems. The laser sources are implemented as distributed Bragg reflector diode lasers bars featuring 48 broad area emitters each with a 50 μm wide mesa structure. The epitaxial layer structure comprising an AlGaAs-based waveguide and InGaAs single quantum well is optimized for pulsed operation at a wavelength of around 905 nm. For a temperature-dependent wavelength shift as low as approx. 60 pm/K, each emitter features a surface-DBR grating. The DBR laser bars are mounted p-side down on CuW submounts and sandwiched between a thin electronic driver board and a mount to minimize inductances. The in-house developed electronic driver generates 2 ns to 10 ns long current pulses with peak current up to 1000 A. With 8 ns long optical pulses and a peak current of about 900 A, a peak optical power of about 640 W is achieved at 25°C. Integration of the diode laser with micro-lenses and a beam twister provides a homogeneous line by individual projection of each of the 48 emitters with divergence angles of 24 deg x 0.1 deg (full width at 1/e2 intensity) in the vertical and horizontal direction, respectively.
We present a detailed experimental investigation of 48 emitter distributed Bragg reflector laser bars, developed for LIDAR applications, that emit nanosecond pulses under pulsed high current excitation round 905 nm. The in-house developed electrical interface provides nanosecond pulses with peak currents up to 900 A. The influence of chip length, active region design, and operation parameters are investigated. Experimental results including the optical pulse power, the spectral emission characteristics, and temporal characteristics will be presented. Peak optical pulse powers exceeding 440 W at >600 A and 650 W at >900 A for 2 ns and 10 ns long pulses, respectively, at 10 kHz and 25 °C can be achieved.
Nowadays cold atom-based quantum sensors such as atom interferometers start leaving optical labs to put e.g. fundamental physics under test in space. One of such intriguing applications is the test of the Weak Equivalence Principle, the Universality of Free Fall (UFF), using different quantum objects such as rubidium (Rb) and potassium (K) ultra-cold quantum gases. The corresponding atom interferometers are implemented with light pulses from narrow linewidth lasers emitting near 767 nm (K) and 780 nm (Rb). To determine any relative acceleration of the K and Rb quantum ensembles during free fall, the frequency difference between the K and Rb lasers has to be measured very accurately by means of an optical frequency comb. Micro-gravity applications not only require good electro-optical characteristics but are also stringent in their demand for compactness, robustness and efficiency. For frequency comparison experiments the rather complex fiber laser-based frequency comb system may be replaced by one semiconductor laser chip and some passive components. Here we present an important step towards this direction, i.e. we report on the development of a compact mode-locked diode laser system designed to generate a highly stable frequency comb in the wavelength range of 780 nm.