Fürst, J.U.J.U.FürstBuse, K.K.BuseBreunig, I.I.BreunigBecker, P.P.BeckerLiebertz, J.J.LiebertzBohatý, L.L.Bohatý2022-03-052022-03-052015https://publica.fraunhofer.de/handle/publica/24014210.1364/OL.40.001932A millimeter-sized, monolithic whispering gallery resonator made of a lithium tetraborate, Li2B4O7, crystal was employed for doubly resonant second-harmonic generation with a continuous-wave laser source at 490 nm. An intrinsic quality factor of 2 x 10(8) was observed at the pump wavelength. A conversion efficiency of 2.2% was attained with 5.9 mW of mode-matched pump power. In the lithium tetraborate resonator, it is feasible to achieve phase-matching of second-harmonic generation for pump wavelengths between 486 and 506 nm.en535journal article