Technology of high power lasers

Peter Unger 

University of Ulm, Department of Optoelectronics, Ulm 89069, Germany

Abstract

Semiconductor lasers are gaining increasing interest because of their small size, a high electrical-to-optical power conversion efficiency, the excellent reliability of the devices, and the electronic modulation properties up to frequencies of several GHz. When properly designed, laser diodes exhibit single-mode beam properties at low output powers. At high output powers however, the beam properties are degraded due to filamentation effects. Additionally, the power is limited by device heating and Catastrophic Optical Mirror Damage (COMD). In this presentation, two approaches are discussed to achieve high optical output powers in semiconductor lasers while maintaining an excellent beam quality. The first approach uses dry-etched curved mirror facets to realize a lateral unstable resonator design. A process technology based on Chemically Assisted Ion-Beam Etching (CAIBE) is presented, which allows the etching of smooth mirror facet. The devices show good beam quality in continuous-wave operation at high output power. A scanning electron micrograph of the curved mirror of an instable resonator laser is depicted in the figure on the left-hand side. The second approach is an optically pumped semiconductor disk laser as sketched on the right-hand side. This novel laser unifies the benefits of solid-state thin disk lasers and Vertical-Cavity Surface-Emitting Lasers (VCSELs). The undoped epitaxial structure consists of a Bragg mirror and a resonant gain region which is optically pumped by a broad-area laser diode. The second mirror is an external concave dielectric mirror resulting in a stable concentric resonator configuration enforcing single-mode operation. The whole concept is scalable allowing high optical output powers. Due to the external mirror, additional elements can be positioned inside the laser cavity like nonlinear crystals to achieve frequency doubling. Devices are presented
which emit in the blue and the orange-yellow wavelength range.

 

Presentation: invited oral at E-MRS Fall Meeting 2003, Symposium C, by Peter Unger
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-05-13 10:21
Revised:   2009-06-08 12:55