An external-cavity diamond Raman laser generating up to 2.0 W at 1240 nm from 3.3 W of 1064 nm pump power is investigated as a function of pump polarization direction. The maximum conversion efficiency was 61%, and the slope efficiency of 84% closely approaches the quantum limit of 85.8%. The lowest threshold for Raman lasing is achieved for pump polarization parallel to the <111> axis, which we show is consistent with theory.

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We report an efficient 532 nm pumped external cavity diamond Raman laser generating output chiefly at the 573 nm first Stokes. At a pulse repetition rate of 5 kHz, the Raman laser generated 1.2 W output with a conversion efficiency of 63.5%, a slope efficiency of 75%, a pulse peak instantaneous conversion efficiency of 85%, and a peak photon conversion efficiency of 91%. The laser generated a maximum output energy of 0.67 mJ by increasing the pump beam size and the pulse energy. The efficiency is commensurate with the highest previously reported for other Raman materials pumped by Q-switched lasers.

We report an efficient 1.485 μm external cavity diamond Raman laser operating on the 2nd Stokes shift of a 1.064 μm Nd:YAG pump laser. 1.63 W pulsed at 5 kHz is produced with a quantum conversion efficiency of 71% and excellent beam quality. Numerical modelling confirms that optimal operation is achieved with low output coupling reflectivity.

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.

We report a pulsed mid-infrared diamond Raman laser with output tuned from 3.38 to 3.80 μm through varying the optical parametric oscillator (OPO) pump wavelength. To our knowledge this is the longest reported wavelength from a solid-state Raman laser. We generated up to 80 μJ with good beam quality and 22% quantum conversion efficiency. Whilst the conversion process itself is efficient, approximately 40% of the generated Stokes light is lost to multiphonon absorption. By introducing a secondary pump beam at the anti-Stokes wavelength to initiate a seed at the Stokes wavelength through Raman resonant four-wave mixing, the laser threshold was reduced by approximately half, and the maximum output increased by 44% to 115 μJ.

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High-power 83 W holmium-doped silica fiber laser operating with high beam quality, Optics Letters, 2007; 32(3):241-243.