Monolithic diamond Raman laser

Abstract

A monolithic diamond Raman laser is reported. It utilizes a 13-mm radius of curvature lens etched onto the diamond surface and dielectric mirror coatings to form a stable resonator. The performance is compared to that of a monolithic diamond Raman laser operating in a plane-plane cavity. On pumping with a compact Q-switched laser at 532 nm (16 μJ pulse energy; 1.5 ns pulse duration; 10 kHz repetition-rate; M²<1.5), laser action was observed at the first, second, and third Stokes wavelengths (573 nm, 620 nm and 676 nm, respectively) in both cases. For the microlens cavity, a conversion efficiency of 84% was achieved from the pump to the total Raman output power, with a slope efficiency of 88%. This compares to a conversion efficiency of 59% and a slope efficiency of 74% for the plane-plane case. Total Raman output powers of 134 and 96 mW were achieved for the microlens and plane-plane cavities, respectively.

Sub-100 ps Monolithic Diamond Raman Laser Emitting at 573 nm

“…The highest 1st Stokes output power of 179 mW with conversion efficiency of 47% was achieved with the f=75 mm lens and pump spot diameter of ~47 µm. This conversion efficiency to the 1 st Stokes is higher than that reported for 1.5 ns pump pulses in planeplane configuration (38%) [3]. A slight wedge between the diamond surfaces (which adds losses), differences in coatings and the presence of the 2nd Stokes at high pump powers are the main limiting factors in conversion efficiency.…”

“…5(f) was taken when the diamond was tilted by ~2° with respect to the incoming pump beam to better satisfy the phase-matching conditions required for efficient 2nd anti-Stokes conversion [15]. The 1st Stokes output beam consisted of several concentric rings, similar to results in [3]. For that reason no reliable measurements of the M 2 factor of the beam could be made.…”

“…Analysis [21] shows that conversion efficiency saturates after about 15 round-trips if the output coupler reflectivity is optimised. In [3] the conversion efficiency to the 1st Stokes in the plane-plane cavity configuration was 38% with 1.5 ns pump pulse duration and the diamond (resonator) length of 1.6 mm. The number of round-trips of the Stokes emission in the cavity during the FWHM pump pulse duration in that case was 58.…”

“…While Raman conversion of CW and Q-switched lasers has become routine [3][4][5][6][7], extending the wavelength coverage of ultrafast (pico-and femtosecond) sources is significantly more complex, often requiring synchronous pumping of external cavity Raman lasers to achieve high (>30%) conversion efficiencies [8][9][10][11]. Mode-locked pump sources used in these Raman laser experiments are also rather complex.…”

“…Exploiting the high Raman gain in diamond [12,13], it has been previously demonstrated that near quantum limited conversion efficiencies of 532 nm nanosecond pulses can be achieved in a 2-mm long, monolithic Raman cavity [3]. Such resonators should also be short enough to efficiently convert sub-100 ps pulses by allowing several round trips of the intracavity Raman field per pump pulse.…”