Scalable and modular diode laser architecture for fiber coupling that combines high-power, high-brightness and low weight

The demand for high-power and high-brightness fiber coupled diode laser devices is mainly driven by applications for solid-state laser pumping and materials processing. The ongoing power scaling of fiber lasers requires scalable fibercoupled diode laser devices with increased power and brightness. In particular, applications and technologies that demand a high degree of mobility, such as airborne or field transportable systems, also require a robust and extremely lightweight design. We have developed a scalable and modular diode laser architecture that combines high-power, high-brightness, and low weight that fulfills these requirements for a multitude of applications. At the heart of the concept is a specially tailored diode laser bar with an epitaxial and lateral structure designed such that only standard fast- and slow-axis collimator lenses are required to couple the beam into a 200μm core fiber with a numerical aperture (NA) of 0.22. To fulfill the requirements of scalability and modularity, a reduced size heat sink populated with multiple tailored bars is used. This enables a compact and lightweight design with minimum beam path length. The design concept is capable of providing single wavelength, high-power laser diode modules, with optional volume holographic gratings for wavelength stabilization. Modules with output power levels of more than one kW at a power-to-weight ratio of less than 1 kg/kW are achievable. In this paper, two laser modules based on this concept are presented. The optical output power is above 500W at a module weight less than 500g and 300W at 300g. Both modules are coupled into a 200μm, 0.22NA fiber.