Fiber-coupled high brightness, high power diode laser for solid-state laser pumping

Bodo Ehlers, Stefan Heinemann

Fraunhofer Center for Laser Technology, 46025 Port Street, Plymouth, Michigan, USA

Abstract:  

The theoretical modeling, design and prototype set-up of a fiber-coupled high brightness, high power diode laser system is presented in this paper. Based on the radiation characteristics from an individual diode laser bar, a system is created to maximize the coupling efficiency of the laser light into a 600 micrometer, NA 0.2 multimode fiber. Two diode laser stacks with six bars each delivering 400 watts of initial laser power are polarization-multiplexed to achieve higher brightness. Each stack incorporates a beam transformation optic that transforms the oblong mode distribution of the diode laser stacks into symmetric beams. The multiplexed beam is passed through a common optical set-up to adapt the square mode distribution to the rotationally symmetric transmitted modes of the fiber. A fiber with a quartz core and a lower index quartz cladding is used to transmit the laser beam. Based on the simulation, an overall transfer efficiency of approximately 60 percent is expected for the first laser system set-up including all optical elements and the fiber transmission.