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Whispering gallery resonator from lithium tetraborate for nonlinear optics

: Fürst, J.U.; Buse, K.; Breunig, I.; Becker, P.; Liebertz, J.; Bohatý, L.


Vodopyanov, K.L. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Nonlinear frequency generation and conversion: materials, devices, and applications XIV : 9 - 12 February 2015, San Francisco, California, United States
Bellingham, WA: SPIE, 2015 (Proceedings of SPIE 9347)
ISBN: 978-1-62841-437-0
Paper 93470A, 6 pp.
Conference "Nonlinear Frequency Generation and Conversion - Materials, Devices, and Applications" <14, 2015, San Francisco/Calif.>
Conference Paper
Fraunhofer IPM ()

For second-order nonlinear-optical processes in the ultraviolet, appropriate materials with a sufficiently large band-gap typically exhibit smaller nonlinear coefficients than materials with comparably smaller band-gap. Whispering gallery resonators, with their outstanding quality factors, provide field enhancement and can compensate for these small coefficients. We report on the successful fabrication of a whispering gallery resonator made of lithium tetraborate, a suitable material for ultraviolet applications with a small nonlinear coefficient of d31 = 0.073 pm/V. Quality factors of the order of 108 are observed from the ultraviolet to the near-infrared spectrum. The inferred absorption coefficients of lithium tetraborate are below 0.2 m-1 in the visible and near-infrared. Continuous-wave second harmonic generation from 490 nm light to 245 nm is observed with conversion efficiencies up to 2.2 %.