The Outlook for Diamond in Raman Laser Applications
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1203-J13-01
The Outlook for Diamond in Raman Laser Applications Richard P. Mildren MQ Photonics Research Centre Department of Physics Macquarie University, New South Wales, 2109, Australia ABSTRACT Efficient and practical Raman lasers based on single crystal diamond are now realizable owing to the availability of optical quality crystals grown by chemical vapour deposition (CVD). In this paper, the performance characteristics of CVD-diamond Raman lasers are summarized and the results compared to those for more established Raman materials. The outlook for diamond Raman lasers is discussed and key challenges for material development highlighted. INTRODUCTION Much like the electronic industry, lasers are being developed with ever increasing power, speed and frequency range. Almost all fields of science and technology now benefit from laser technology in some way and demand a range of specifications that will include output wavelength, beam power, temporal format, coherence and system parameters such as footprint and efficiency. Thus there is an ongoing search for alternatives to the optical gain material that is fundamental to laser performance. Diamond is highly attractive as a laser material as it promises capabilities well beyond that possible from other materials in accordance with its extreme properties. Most diamond laser research to date has concentrated on doped diamond for color center lasers [1], semiconductor diode lasers [2] and rare earth doped lasers [3]. Success has been very limited except from perhaps color center lasers relying on the nitrogen vacancy that have been demonstrated with an optical-to-optical conversion efficiency of 13.5% [1]. The major challenge for diamond as a laser host is the incorporation of suitable concentrations of color centers or active laser ions into the tightly bonded lattice either by substitution or interstitially. On the other hand, Raman lasers rely on stimulated scattering from fundamental lattice vibrations and thus do not require doping [4,5]. Though the principle of optical amplification is distinct from conventional lasers that rely on a population inversion, in many ways Raman lasers have similar basic properties to other laser-pumped lasers. Raman lasers can be thought functionally as laser converters that bring about a frequency downshift and improved beam quality. Their development has been most often driven by the need for laser wavelengths that are not fulfilled by conventional laser media and find use in a diverse range of fields such as in telecommunications, medicine, bio-diagnostics, defence and remote sensing. Synthetic (CVD) single crystal diamond has become available in the last few years with size, optical quality and reproducibility well suited for implementation in Raman lasers. Diamond’s starkly different optical and thermal properties compared to “conventional” materials are of substantial interest for extending Raman laser capabilities. Diamond has the highest Raman gain coefficient of all known materials (approximately 1.5 times higher than bar
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