This PDF file contains the front matter associated with SPIE Proceedings Volume 11984, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

Thermal simulations based on the finite-element method provide an estimation of what the heat management in membrane external-cavity surface-emitting lasers (MECSELs) is capable of: When considering diamond and SiC heat spreaders, double-side cooling (DSC) leads to gain membrane temperatures that are about a factor two lower than with single-side cooling (SSC). For the thermally worse conductive sapphire, the temperature benefit from DSC can be up to four times lower than with SSC. Diamonds as heat spreaders are recommended over SiC if the power for pumping the gain membrane is three times larger, for instance at 30W at a pump beam diameter of 180 μm. Sapphire can be favored over SiC if the pump power is about five times lower, for instance at 2W. Due to the limited lateral heat flow activity of sapphire, a smaller pump beam diameter of 90 μm is suggested. A super-Gaussian pump beam can be used instead of a Gaussian pump beam to lower the gain membrane maximum temperature by a factor of three. Double-side pumping becomes significantly more important as soon as the gain membrane gets thicker than 1 μm.

Sodium laser guide stars (LGS) play an essential role in ground-based telescope adaptive optics. Optically-pumped vertical-external-cavity semiconductor lasers (VECSELs) have long been investigated as possible next-generation LGS sources due to their high optical power, good beam quality, and ability to tune the emission wavelength. Here, we present the design and characterization of an emerging platform that shows potential in a high-power semiconductor laser, specifically in LSG applications. Using membrane external-cavity surface-emitting lasers (MECSELs), we demonstrated a record output power of 28.5 W adopting the in-well pumping technique. This allowed the reduction of the quantum defect, which typically hinders high power operation in standard barrier-pumped semiconductor lasers. Comparing the barrier-pumping and in-well pumping schemes showed slope efficiencies of 21.6% and 39.5%, respectively. A multi-pass scheme was designed for recirculating the in-well pump beam. Moreover, a tuning range of 71 nm from 1124 nm to 1195 nm was achieved with a 2 mm birefringent filter which led to a 1.7 nm linewidth at 1178 nm for future frequency conversion to 589 nm.

Membrane external-cavity surface-emitting lasers (MECSELs) are vertically emitting semiconductor lasers that combine all the benefits of VECSELs (vertical-external-cavity surface-emitting lasers) with the new degree of freedom in creating gain structures without monolithically integrated distributed Bragg reflectors (DBRs). The absence of the DBR and the substrate, and the use of a very thin gain membrane (typically some hundreds of nanometers), which can be sandwiched between two transparent heat spreaders, represents the best solution for heat removal. The membrane configuration also allows the option of double side pumping, which in turn makes it possible to utilize an extensive amount of quantum well (QW) groups as well as multiple kinds of QWs in a periodic laser gain structure. Here we report on design strategy and results of different kinds of approaches on broadband, relatively high power MECSEL gain structures. Especially efficient pump absorption, sufficient gain on several different wavelengths and carrier mobility during laser operation, are discussed. We also present the characteristics of the laser systems created. Results show ∼ 83 nm (∼ 25 THz) tuning range with more than 100 mW of power at all wavelengths at room temperature operation. Strategies for further development are discussed as well.

Potentials for modelocking in membrane external cavity surface emitting lasers (MECSELs) are discussed. The effects of integrated gain in a resonant periodic gain (RPG) in linear and ring cavities are considered, and simple analysis of Kerrlens modelocking of MECSELs in a ring resonator are presented.

A single transverse mode high pulse-energy GaSb VECSEL emitting at 2030 nm was studied. The peak power exceeds 500 W while maintaining good beam quality throughout the operation range. The cavity employs a Pockels cell combined with a low-loss thin film polarizer to selectively dump the intracavity energy in a 10 ns pulse. Thermal mitigation of the gain chip is achieved by both gain-switching and utilizing a long wavelength pump laser at 1470 nm compared to the traditional 980 nm pump for GaSb VECSELs. The laser has promise for incoherent LIDAR, materials processing, gas sensing, and nonlinear optics.

Sodium Guidestar Lasers (SGLs) are an important element of adaptive-optics (AO) image correction techniques for astronomical observatories. In recent years, the astronomy community has employed Raman shifted fiber lasers to meet the need. However, emerging applications would greatly benefit by a reduction in the cost per Watt of on-sky power and the Size Weight and Power (SWAP) required by the laser. Small (meter-class) observatories seek to incorporate AO systems to meet space situational awareness and free space laser communication applications. Simultaneously, large (10 meter class) observatories require larger numbers of lasers on-sky to implement multi-conjugate AO systems. Optically pumped semiconductor lasers (OPSLs), also referred to as Vertical External Cavity Surface Emitting Lasers (VECSELs), represent a technology pathway to realizing Sodium Guidestar Lasers (SGL)s with high performance, compact size, high reliability, and low acquisition and maintenance costs. In pursuit of the next generation of SGL, we demonstrate <15W of single-frequency power at 589 nm based on in intracavity frequency doubling of 1178 nm fundamental wavelength VECSEL. Our work characterizes laser performance with an emphasis on suitability for guidestar laser applications. We examine, wavelength stability, linewidth, tuning and tuning agility and the ability to lock the laser to the sodium transition. In addition, we demonstrate simultaneous generation collinear beams with a frequency spacing of approximately 1.7 GHz.