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

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 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.     

Compact and efficient kinetically enhanced copper-vapor lasers of high (100-W) average power

We report on severalfold increases in the output power of kinetically enhanced copper-vapor lasers operating in a regime of high specific input power and reduced tube insulation. Three laser tubes, of length 1 m and bore diameters 17.5, 25, and 32 mm, were investigated at constant input power. Output power of 104 W at 1.4% wall-plug efficiency was obtained for the largest tube. When the bore diameter was decreased to 17.5 mm, the output power and efficiency remained high (90 W at 1.0% efficiency), whereas the specific output power increased threefold. The output powers were as much as fivefold higher than those of previous small-scale (i.e., <25-mm-diameter) copper lasers of any type.     

Investigation of the pump wavelength influence on pulsed laser pumped Alexandrite lasers

Recent theoretical modelling and experimental results have shown that excess lattice phonon energy created dur ing the non-radiative energy transfer from the ⁴T₂ pump manifold to the ²E storage level in Alexandrite when pumped with wavelengths shorter than ∼645 nm causes chaotic lasing output. Shorter pump wavelengths have also been associated with increased non-radiative energy decay and reduced laser efficiency. We report studies of fluorescence emission spectra of Alexandrite illuminated at a range of wavelengths from green to red, which demonstrate reduced fluorescence yield for shorter pump wavelengths at elevated crystal temperatures. Investigations of pulsed laser pumping of Alexandrite over the same spectral range demonstrated reduced pump threshold energy for longer pump wavelengths. High repetition rate pulsed pumping of Alexandrite at 532, 578 and 671 nm showed stable and efficient laser performance was only achieved for red pumping at 671 nm. These results support the theoretical model and demonstrate the potential for scalable, red laser pumped, all-solid-state Alexandrite lasers.PACS 42.60.Lh; 42.60.Mi