An Organic Electro-Mechanical Cavity Emitting Efficiently Tunable, Continuous-Wave-Pumped Nonlinear-Optical Modes

Organic polar crystals are a promising material platform for achieving unique nonlinear nanophotonic properties. Mainly, tunable second-harmonic generation (SHG) with continuous-wave (CW) pump sources is considered as breakthrough technology for optical switching, actuation, sensing, chip-integrated coherent light sources, and low-threshold tunable microlasers. Here, the discovery of tunable CW SHG in a polar (non-centrosymmetric) electro-mechanical microcrystal cavity of 4-(4-(methylthio)phenyl)-2,6-di(1H-pyrazol-1-yl)pyridine (UOH1) is demonstrated. As a result of total internal reflection in mirror-like light-reflecting facets and its high second-order nonlinear susceptibility, the octahedron-shaped cavities exhibit both bright femtosecond and CW-pumped SHG with coherent whispering gallery mode (WGM) and bow-tie-like (BT) optical modes excited in its spectrum. Moreover, for an external dc electric field of about 23 kV cm(-1) the microcavity displays 0.18 nm resonant wavelength peak shift in the second harmonic signal due to electrostriction (strain effect).