Thermal and spectral effects in intracavity Raman lasers

Stimulated Raman scattering is a convenient way to extend the spectral coverage of well-established solid-state laser sources. In an intracavity Raman laser, a Raman crystal is placed inside the cavity of the fundamental laser, and the output frequency is red-shifted by an amount corresponding to a vibrational energy level of the Raman crystal. Despite the physical simplicity of these lasers, the interactions between the various optical fields are complex, and must be understood in order to realise efficient, high power operation. This thesis presents a detailed investigation of thermal and spectral effects in CW intracavity Raman lasers. A disk geometry was used to reduce the thermal lens in the laser gain crystal, thereby permitting more flexible cavity design. This facilitated experiments to probe and control the thermal and spectral effects. Diamond was assessed as a potential Raman crystal with weak thermal lensing. The optical losses in several crystals were measured and while some low loss material was identified, the supply of such material is not yet reliable. The thermal lens in a common Raman crystal, BaWO₄, was measured and found to be negative and astigmatic. Using a coupled cavity configuration, experiments were performed to disentangle the effects of the thermal lenses in the laser gain and Raman crystals. This information was used to re ne the cavity design and improve the performance of the laser in a more systematic way than would otherwise have been possible. It was shown that Raman lasers using laser gain disks can provide comparable performance to rod-based systems. The first ever detailed investigation into spectral broadening in CW crystalline intracavity Raman lasers was undertaken using a combination of theory and experiment. The use of etalons to limit the broadening was investigated and it was found that these could improve the spectral brightness of the laser.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral-pg

Grantor dc:publisher.institution

University of Strathclyde

Year dc:date.issued

2013

Author dc:creator

• Bonner, Gerald Michael

DOI

10.48730/36vd-mz63

Identifier

T13593

OAI identifier oai:identifier

oai:strathclyde:qz20ss555