Progress in several fields has enabled the use of LiDAR sensing for a multitude of applications like autonomous driving, pre-crash sensors, gesture recognition, and environmental monitoring. All the applications demand challenging specifications of the sensing system components to achieve the required performance parameters detection range, angular resolution, eye-safety, and several others. In this work, we report on recent advances in our pulsed edge-emitting IR laser diodes, which can be used as laser light sources for scanning-beam and flash-mode time-of-flight LiDAR systems. We developed a technique to reduce the temperature-induced emission wavelength shift in our monolithically stacked epitaxial waveguides from 22nm to only 2.8nm over a heatsink temperature range from 25°C to 120°C, which is the crucial temperature range for many systems. Within this 95K range our Fabry-Perot edge-emitters feature a wavelength shift below the 7nm usually achieved in DFB type edge-emitters and VCSELs. There is no power penalty for the wavelength stabilization. We also demonstrate output power scaling by about 60% by increasing the number of waveguide stages in the stacked epitaxy structure from 3 to 5. This results in a short-pulse peak output power of 260W at 50A from a single device with an emission wavelength of 910nm and a near field width of about 220μm. Finally, we discuss the performance improvements of devices with 900μm and 1200μm long resonators compared to standard 600μm resonators. The demonstrated advances of the pulsed edge-emitting laser light sources enable various system improvements and widespread adoption of LiDAR sensing in many applications.

InGaN lasers in the blue and green wavelength range have opened a wide variety of applications in the past years, which all require unique properties of the employed laser chips. In this paper we will show design and process developments for various InGaN laser designs, each optimized for its specific application. For applications which are very sensitive to energy consumption, like mobile AR/VR devices, we investigated InGaN laser chips with resonator lengths as short as 50 μm. To achieve this, we developed an etched facets technology to overcome the challenges of scribing and breaking for facet generation for such short resonator lengths. The etched facets of these devices are coated on-wafer with a dielectric mirror to achieve the desired reflectivity. Depending on the reflectivity chosen, these devices show ultra-low threshold currents below 3mA and output powers above 50 mW. Combined with a flip-chip design with both contacts on one side, such chips can be integrated into silicon wafer-based beam combiners to generate RBG PIC chips for VR/AR laser projection. For high power applications, we will present data of laser bars. Bars emitting at 430 nm achieved 100 W of continuouswave output power per bar and conversion efficiencies of 50%. Together with bars emitting at 450 nm, that were shown in previous publications, wavelength-multiplexing for materials-processing systems can be realized yielding blue laser light sources with multiple kilowatts of output powers.

Lasers for many applications were established long ago. Recently, LIDAR became more important as very important sensor for autonomous driving. High resolution, high power and efficiency enable real-time environment surveillance. We present status and outlook on EEL and VCSEL for near IR light sources.

High‐power diode lasers are possibly the most efficient way of making electrical energy usable for material processing, like welding, cutting, soldering or other high‐power applications. While IR laser were invented over fifty years ago and have been used in industry for more than two decades, GaN high‐power lasers have only recently been used for material processing, especially for welding and soldering of copper. Although the blue wavelength offers unique and undisputable advantages over IR for the latter application, some difficulties still had to be overcome. Here is an overview of the development steps of GaN lasers from their commercial beginnings as a 1 mW light source in Blue‐ray players to today's 1.5 kW system. Also, important investigations to reach power efficiencies of 40 % will be explained as well as considerations to reach lifetimes of 65 khr and longer. We also venture a prediction of future developments based on a comparison to IR laser diodes.

Blue high-power semiconductor lasers have increased greatly in performance over the recent decade enabling new application fields from high brightness projection up to materials processing beyond 1000W output power systems. Base for best system performance is optimal chip design and reliability of the semiconductor device. In this paper chip design optimization of blue high-power semiconductor laser bars will be shown: In contrast to IR laser bars with high lateral emitter fill factors beyond 50%, optimum design with maximum output power and efficiency for GaN laser bars is currently at very low fill factors in the range of 10%. Laser bar designs ranging from 5% fill factor up to 12.5% fill factor were fabricated and investigated. Additionally, two different emitter pitches with 200μm and 400μm were compared. The design with an emitter width of 30μm and a pitch of 400μm resulted in overall best performance. Additionally, lifetime investigations of single emitters in TO-packages will be discussed. The laser diodes were tested up to 5000h duration at different conditions in operating temperatures ranging from 64°C to 96°C and output power up to 3.5W. Dominating degradation mechanism is wear-out which is accelerated by optical output power and additional thermal activation. Extrapolation of the test results in combination with an acceleration model points towards a median lifetime of up to 65.000h for 25°C operation.

We present our latest results on developments of infrared and red light emitting diodes. Both chiptypes are based on the Thinfilm technology. For infrared the brightness has been raised by 25% with respect to former products in a package with standard silicon casting, corresponding to a brightness increase of 33% for the bare chip. In a lab package a wall-plug efficiency of more than 72% at a wavelength of 850nm could be reached. For red InGaAlP LEDs we could demonstrate a light output in excess of 200lm/W and a brightness of 133lm at a typical operating current of 350mA.

High-power near-Infrared LED (IRED) are gaining more and more interest in a large variety of commercial, industrial and military applications. IRED are based on InAlGaAs semiconductor structures which cover a spectral range of 780 nm to 1100 nm. This wavelength range is supposed to be not visible to the human eye. But, depending on the radiant intensity and wavelength, a reddish glow is still evident. Therefore, in covert applications longer wavelength of 940 nm or even higher are preferred due to the much lower sensitivity of the human eye compared to 850 nm. On the other hand at around 850 nm the spectral sensitivity of CMOS or CCD cameras or other silicon based photo detectors is at its maximum. We present the latest developments in high power IRED in the quest for more than 1 W from a single 1mm2 die.

Laser dies in an optical power range of 1-3 Watts are widely assembled in popular TO-packages. TO-packages suffer from high thermal resistance and limited output power. Bad thermal contact between circuit boards and TO-devices can cause overheating of laser chips, significantly reducing the operating life time. We developed a compact high heat-load SMT package for an optical power up to 7 Watts in CW operation with good life time results.The new package for high power laser chips combines highly efficient heat dissipation with Surface-mount technology. A Direct-Bonded-Copper (DBC) substrate acts as a base plate for the laser chip and heat sink. The attached frame is used for electrical contacting and acts as beam reflector where the laser light is reflected at a 45 degrees mirror. In the application the DBC base plate of the SMT-Laser is directly soldered to a Metal-Core-PCB by reflow soldering. The overall thermal resistance from laser chip to the bottom of a MC-PCB was measured as low as 2.5K/ W. The device placement process can be operated by modern high-speed mounting equipment. The direct link between device and MC-PCB allows CW laser operation up to 6-7 watts at wavelengths of 808nm to 940nm without facing any overheating symptom like thermal roll over. The device is suitable for CW and QCW operation. In pulsed operation short rise and fall times of <2ns have been demonstrated.New application fields like infrared illumination for sensing purposes in the automotive industry and 3D imaging systems could be opened by this new technology.

Digital optical data storage has become firmly established through CD, DVD and their derivatives. Future mobile and stationary multimedia applications demand for ever higher storage density, even beyond HD-DVD and Blu-ray Disc with 50 GB maximum storage capacity (dual layer). While holographic recording is in the far future for the consumer domain, the 4th generation of optical storage is being heralded by a leap in technology. Within a European initiative in the scope of the EUREKA project MobileDRIVE and the project 4GOOD (4th-generation omni-purpose optical disc-system), funded by the German Ministry of Economy and Technology, the fundamental technologies are being developed for high-density optical data storage (60...100 Gbit/ inch2) in order to achieve at least 200 GB on a 12 cm disc, or e.g. > 5 GB on a 3 cm miniaturised version (single layer). The contribution describes the technology objectives, challenges, concepts and project status in the key areas of disc development, drive including laser, optics, acceleration sensors for mobile operation, and signal processing.

Laser operation relies on two conditions, stimulated emission of the amplifying medium and feedback by an optical resonator. The threshold of laser operation is obtained if the gain in the resonator compensates for the overall losses, i.e., the propagation losses and the apparent losses due to the extraction of light [2.1]. Both common laser conditions are satisfied in diode lasers in another way than in typical gas or solid-state lasers. The resonator is given by the semiconductor structure itself using the crystal facets as mirrors. The gain in diode lasers involves a whole crystal structure and not only excited single atoms, ions, or molecules. Modern semiconductor lasers restrict the excited volume to reduce the threshold current by applying quantum wells or quantum dots. Technically, this is achieved by growing very thin layers consisting of different crystal compositions for quantum wells or by applying two-dimensional growth for quantum dots. A scheme of a diode laser is shown in Fig. 2.1. The following chapter takes a short tour through the excitation of high-power semiconductor lasers by examining the current injection of carriers, the optical gain, and appropriate resonator structures. More detailed descriptions of several aspects can be found in several textbooks [2.2, 2.3].