Diode laser beam shaping and propagation characteristics

Abstract

Diode lasers are playing an increasingly important role in various applications, including pump sources for solid-state and fiber lasers, optical communications, printing systems, optical data storage, and electro-optical sensors. Compact package size, lower cost, and emission spectra from UV to IR, combined with conversion efficiencies in excess of 50% makes diode lasers a preferred choice over several other laser types. High-power diode laser beams are multimode, and can be described as an incoherent superposition of the limited number of individual lateral modes contained in the beam. The ability to shape and control the output beam characteristics of diode lasers requires establishing an accurate model of the multimode laser beam. We propose a general multimode laser beam model based on incoherent superposition of apodized Hermite-Gaussian modes to describe the spatial intensity distribution and propagation characteristics of the high-power diode laser beams. Free-space propagation characteristics of high power diode laser beams are compared with propagation characteristics of propagation invariant Hermite-Gaussian beams. Diffraction effects caused by micro-optics components will be presented, which show a significant impact on the intensity distributions of the individual lateral modes composing the beam, as well as on the multimode laser beam spatial distribution as a whole.