Sub-300nm optically pumped ultraviolet lasers were realized on low-defect-density (0001) AlN substrates fabricated from single crystalline AlN boules. The AlxGa1xN/AlyGa1yN hetero-structures were grown by metal-organic vapor phase epitaxy near atmospheric pressure. The high structural quality of the pseudomorphically deposited films was confirmed by X-ray reciprocal space mappings and time-resolved photoluminescence (PL) studies of the multiple quantum well emission. The initial PL-decay times for a sample emitting at 267 nm were 0.87 ns and 1.14 ns for T = 295K and T = 14K, respectively. Laser resonators with a length of about 1mm were formed by cleaving the AlN crystal to obtain m-plane mirror facets. Lasing was demonstrated for various wavelengths between 267 and 291nm with the threshold power density as low as 126kW/cm2 for the shortest attempted wavelength. The laser emission was TE polarized for all emission wavelengths.
Wunderer, T.; Chua, C. L.; Northrup, J. E.; Yang, Z.; Johnson, N. M.; Kneissl, M.; Garrett, G. A.; Shen, H.; Wraback, M.; Moody, B.; Craft, H.; Schlesser, R.; Dalmau, R.; Sitar, Z. Optically pumped UV lasers grown on bulk AlN substrates. physica status solidi (c). 2012; 9 (3-4): 822-825.