In semiconductor micro/nanostructure optical resonators, the transmission of light can be at least restricted and modulated in two dimensions, and the electromagnetic field of light may be precisely controlled.To achieve precise manipulation of the light–matter interaction, the micro/nanostructure usually requires high crystal quality, regular geometrical structure, smooth surfaces and the structure to be approximately the same size as the wavelength.Other kinds of optical cavity are rarely reported due to the difficulty of the sample preparation.Intense efforts have been undertaken over the past decade to attain optical microcavities with different geometrical configurations using ZnO as an optical material.

Researchers at Key Lab Mat High Power Laser——Shanghai Institute of Optics and Fines Mechanics (SIOM/China)have developed a novel but simple approach to obtain single crystalline ZnO microwires with a parallelogram cross-section. They demonstrated for the first time that such parallelogram microwires can be used as wave-guided FP optical resonators. [NANOSCALE,5(10),4123-4128]

They present the synthesis of a novel ZnO microcavity with a parallelogram cross-section, which can effectively control the light field. The optical modulations induced in such ZnO microcavities were directly observed at room temperature using a spatially resolved micro-confocal spectroscopic system. A wave-guided FP mode was identified using calculations based on the plane wave interference model and further confirmed by Finite Element Method (FEM) simulations.

The Sellmeier dispersion function fitted well with the calculated wavelength-dependent refractive indices. Furthermore, the size-dependent cavity modulation behaviours of the optical resonators were also investigated in detail. Such a ZnO optical resonator with a parallelogram cross-section offers another new practical example for investigating cavity physics and developing novel optical devices, such as laser beam shaping devices and filter combined route switchers.

Fig. 1 (a) Typical SEM image of the ZnO microwires. (b) SEM images of a singlemicrowire dispersed on a Si wafer and its cross-section view (inset) from the rectangularregion. (c) XRD pattern and EDS spectrum (inset) of the obtained ZnO microwires. (d) TEM image of a single ZnO nanowire. (e) HRTEM image and the corresponding SAED pattern (inset) from the rectangular region marked in (d).