Abstract
Laser gain materials possessing high thermal conductivity and robust mechanical properties are key prerequisites for high power lasers. We show that diamond, when configured as a Raman laser, enables access to these and other extreme properties, providing an important new route to high power and high brightness beam generation. Recent achievements in pulsed and continuous wave oscillators, beam combining amplifiers, and single longitudinal mode oscillators are summarized, along with wavelength extension of these concepts through adaption to other pumps, use of Raman cascading, and intracavity harmonic generation. To date, diamond laser powers have attained 750 W with efficiency and beam quality so far unperturbed by nonlinear or thermally induced side-effects. Large factor brightness enhancement of low coherence inputs is demonstrated using multiple pump beams (via Raman beam combination) or highly multimode pumps for oscillator and amplifier configurations. Future directions for direct diode pumping, and for realizing extraordinary power and power density through reduced temperature operation and isotopically enriched diamond, are also discussed. Our results indicate that diamond is emerging as a generic high-power laser technology with advantages in terms of brightness (high average power and high beam quality) and wavelength range.
Highlights
D IAMOND has a distinguished position amongst materials as the element of lowest atomic number to form a covalently bonded lattice
We describe our research in the areas of high power oscillators (Section III), brightness enhancement in continuous wave (CW) lasers and pulsed amplifiers and lasers (Section IV), intracavity frequency-doubled lasers (Section V) and single longitudinal mode (SLM) lasers (Section VI)
The only prior report in the literature of a CW, cascaded-Stokes crystal Raman laser operating in an external-cavity geometry was a second-Stokes barium nitrate laser pumped by an argon ion laser operating with a conversion efficiency of less than 1% and an output power of 25 mW [102]
Summary
D IAMOND has a distinguished position amongst materials as the element of lowest atomic number to form a covalently bonded lattice. Just like other precious gemstones such as ruby, garnets and sapphire, its robust mechanical properties, high thermal conductivity and wide transmission range are immediately attractive as a host for fluorescent laser ions [4] These ambitions have gone largely unfulfilled because of the difficulties involved in introducing suitable dopants into the dense lattice structure without compromising its core material advantages [5], [6]. Stimulated Raman scattering (SRS) was observed as early as 1963 by Eckhardt et al using a Q-switched ruby laser pump as part of a study involving a survey of several promising materials [7] Even at this early stage, both diamond and its Group IV sibling silicon were recognized as good candidates for high gain Raman lasers [8]. The article concludes with a discussion of opportunities for future development and applications (Section VII)
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