Single-crystalline polyhedral $In2O3$ vertical Fabry–Pérot resonators

High-quality $In2O3$ polyhedrons with different morphologies were fabricated and studied as vertical Fabry–Pérot (FP) microcavities. By using the microphotoluminescence technique, we identified a series of FP resonant modes in such systems, whose energies lie in the visible spectral range and are scalable with the cavity size. Experimental results are in good agreement with full-wave numerical simulations and can be well fitted with a plane wave interference model. Compared with the conventional one dimensional nanowire/nanobelt FP cavities, such vertical FP microcavities have much less optical loss and provide efficient optical modulations, which may find many applications in developing optical devices.