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). An organic polar crystal cavity demonstrates continuous‐wave‐laser pumped second‐harmonic optical modes. The organic cavity also displays electrostriction effect thus providing optical mode tunabililty up to Δλ ≈ 0.18 nm for the dc electric field of ≈23 kV cm−1 advantageous for optical switching, microlasing, circuiting, and actuating applications.