Simultaneous brightness enhancement and wavelength conversion to the eye‐safe region in a high‐power diamond Raman laser

Abstract

Brightness enhancement in an external cavity diamond Raman laser designed for high power conversion of a neodymium (1064 nm) laser to the eye‐safe spectral region is reported. Using a multimode input beam pulsed at 36 kHz pulse repetition frequency, 16.2 W with 40% overall conversion efficiency was obtained at the second Stokes wavelength of 1485 nm. The output beam had a quality factor of M2=1.17±0.08 which is a factor of 2.7 times lower than that of the input beam, resulting in a higher overall brightness. The output power, brightness, and brightness enhancement obtained represent significant advances in performance for Raman lasers as well as other competing kHz‐pulsed eye‐safe technologies.

Diamond Nanophotonics

“…The technology is now looking very promising for compact high power beam converters. It was recently shown that diamond enables brightness conversion of laser beams, in addition to a wavelength shift [147] . The concept underpinning this is well known and established in the 60-70s in gases, however, it is much more challenging for solid-state converters.…”

High-Power, Solid-State, Deep Ultraviolet Laser Generation

“…In detail, the most interesting advantages of diamond includes the high Raman gain (pumping at 1030 nm, gR = 13.5 ± 2.0 cm/GW) and the large frequency shift of the 1st order Raman mode (1332.5 cm −1 ) [22,48], which could achieve a high-power operation and a sufficient frequency shift. Moreover, the high thermal conductivity (2200 W/m • K), which is two to three orders of magnitude higher than conventional Raman materials, and the low thermal expansion coefficient of diamond (1.1 × 10 −6 K −1 ) will be helpful for power scaling to a high level as well as its high damage threshold [45][46][47][48]. Another important advantage of the diamond is the broad transmission band.…”

“…In the past few decades, many Raman materials have been studied [44][45][46], which showed the high conversion efficiency to the first Stokes light from 1 µm. The stimulated Raman scattering (SRS) laser is remarkable for the momentum conservation automatically determined by the scattered phonons, which will induce the Stokes light beam to be a high quality [22,47]. Particularly, by use of the chemical vapor deposition (CVD) diamond, the diamond Raman laser depicted a high power result of 100 W [22] and a high slope efficiency of 84% approaching the quantum limit [23].…”

Diamond — A Laser Engineer's Best Friend

“…This has been seen in a number of materials, but the extreme performance of diamond Raman lasers further enhances this effect. Researchers at Macquarie University have reported improvements in M 2 from pump to Raman beam of a factor of 2.7, whilst converting a pulsed Nd:YAG laser beam from 1064 nm to the eye safe wavelength of 1485 nm [6].…”