Richard P. Mildren

Efficient, all-solid-state, Raman laser in the yellow, orange and red

We report efficient operation of a KGd(WO(4))(2) Raman laser pumped by a small, 1 W, 532 nm laser module. By changing the output coupler and Raman crystal orientation, more than 8 wavelengths in the yellow-to-red spectral region were generated including 555 nm, 559 nm, 579 nm, 589 nm, 606 nm, 622 nm, 636 nm and 658 nm, ie., the first 4 Stokes orders on the two orthogonal high-gain Raman shifts of KGd(WO(4))(2). We have also demonstrated spectrally pure output (typically >90% pure) for selected Stokes order with output power up to 400 mW. High slope efficiency (up to 68%) and high beam quality (M(2)~1.5) of Stokes output are obtained even at the highest pump power.

1240 nm diamond Raman laser operating near the quantum limit

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.

CVD-diamond external cavity Raman laser at 573 nm

Recent progress in diamond growth via chemical vapor deposition (CVD) has enabled the manufacture of single crystal samples of sufficient size and quality for realizing Raman laser devices. Here we report an external cavity CVD-diamond Raman laser pumped by a Q-switched 532 nm laser. In the investigated configuration, the dominant output coupling was by reflection loss at the diamonds uncoated Brewster angle facets caused by the crystals inherent birefringence. Output pulses of wavelength 573 nm with a combined energy of 0.3 mJ were obtained with a slope efficiency of conversion of up to 22%.

Highly efficient diamond Raman laser

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.

Optical Engineering of Diamond

1. Intrinsic Optical Properties of Diamond 2. Optical Quality Diamond Grown by Chemical Vapour Deposition 3. Polishing and Shaping of Mono-Crystalline Diamond 4. Refractive and Diffractive Diamond Optics 5. Nitrogen-Vacancy Colour Centres in Diamond: Properties, Synthesis and Applications 6. n-Type Diamond Growth and Homoepitaxial Diamond Junction Devices 7. Surface Doping of Diamond and Induced Optical Effects 8. Diamond Raman Laser Design and Performance 9. Quantum Optical Diamond Technologies 10.Diamond-based Optical Waveguides, Cavities and Other Microstructures 11.Thermal Management of Lasers and LEDs using Diamond 12.Laser in Synthesis, Micro and Nanoprocessing of Diamond Materials 13. Fluorescent Nanodiamonds and their Prospects in Bioimaging

Discretely tunable, all-solid-state laser in the green, yellow, and red

We report an all-solid-state intracavity Raman laser with intracavity nonlinear sum-frequency generation providing visible output wavelengths selected from second harmonics and sum frequencies of the fundamental and Stokes fields. The laser comprises a diode end-pumped Nd:YAG laser, an acousto-optic Q switch, a KGd(WO4)2 Raman crystal, and a lithium borate nonlinear converter in a resonator designed to accommodate dynamic thermal lensing. For 20 W of pump power, output powers up to 1.8 W are demonstrated at wavelengths of 532, 555, 579, and 606 nm, selectable by angle and temperature tuning of the nonlinear medium.

Deep ultraviolet diamond Raman laser.

We present a synchronously pumped diamond Raman laser operating at 275.7 nm pumped by the 4th harmonic of a mode locked Nd:YVO4 laser. The laser had a threshold pump pulse energy of 5.8 nJ and generated up to 0.96 nJ pulses at 10.3% conversion efficiency. The results agree well with a numerical model that includes two-photon absorption of the pump and Stokes beams and uses a Raman gain coefficient of diamond of 100 cm/GW. We also report on the observation of nanometer scale two-photon assisted etching of the diamond crystal surfaces.

Continuous-wave wavelength conversion for high-power applications using an external cavity diamond Raman laser

We demonstrate continuous-wave (cw) operation of a diamond Raman laser at 1240 nm in an external cavity configuration. The output power increased linearly with pump power with a 49.7% slope efficiency and reached 10.1 W at the maximum available pump power of 31 W. The combination of resonator design with diamond provides a novel approach to power-scalable cw wavelength and beam conversion.

Mode-locked picosecond diamond Raman laser

We present a mode-locked diamond Raman laser synchronously pumped by a mode-locked laser running at 532 nm and pulse duration 26 ps. The diamond laser generated up to 2.2 W of average power with output pulses of duration 21 ps at a yellow wavelength of 573 nm. The output pulse duration varied notably with small changes in cavity length and decreased to a minimum of 9 ps. The power and pulse duration behavior as a function of cavity length is explained well by a model that includes phonon dephasing and group velocity dispersion of the pump and Stokes fields.

High-pressure (>1 bar) dielectric barrier discharge lamps generating short pulses of high-peak power vacuum ultraviolet radiation

We have investigated the scaling of peak vacuum ultraviolet output power from homogeneous Xe dielectric barrier discharges excited by short voltage pulses. Increasing the Xe fill pressure above 1 bar provides an increased output pulse energy, a shortened pulse duration and increases in the peak output power of two to three orders of magnitude. High peak power pulses of up to 6 W cm−2 are generated with a high efficiency for pulse rates up to 50 kHz. We show that the temporal pulse characteristics are in good agreement with results from detailed computer modelling of the discharge kinetics.