Design and Performance of Optically Pumped Semiconductor Disk Lasers with Wide Tuning Ranges

Licentiatavhandling, 2010

In this work I present a strategy for providing the possibility to select the wavelength, or color, of a semiconductor laser over a very large range, by cleverly designing the vital part of the laser: the gain element of a so called optically pumped semiconductor disk laser. Optically pumped semiconductor disk lasers (OP-SDLs) are a relatively new class of lasers showing great promise for future applications. The advantages include the wavelength versatility that is common for all semiconductor lasers, but also adds the ability to deliver multi-Watt output powers into a nearly diffraction-limited beam, and a free-space cavity for the easy insertion of various optical elements. These properties have generated great interest in the OP-SDL for use in life science, metrology, entertainment applications, forensics, and many other fields. Recently, efforts have also been made to extend the tuning range for use in spectroscopic applications such as intra-cavity laser absorption spectroscopy. The work underlying this thesis has focused on the design of the gain element of an OP-SDL and how to obtain a wide tuning range while keeping the output power at a high level. The strategy has been to balance the effects of the spectral dependencies of material gain, subcavity resonance, and spatial overlap of quantum wells and optical field. Experimental evaluations show that the strategy has been successful and a relative tuning range of 4.3% with a maximum output power of 2.6 W was obtained. Furthermore, a new measurement technique for the full characterization of a laser beam has been developed. This technique is well suited for the high-intensity beam from an OP-SDL.