Liquid-Crystal Alignment by a Nanoimprinted Grating for Wafer-Scale Fabrication of Tunable Devices

A simple technology is demonstrated for the wafer-scale fabrication of liquid-crystal (LC) microcellsthat can be integrated in active optoelectronic devices. Fabrication of 1.55- $\mu \text{m}$ tunable Fabry–Perot optical micro-filter arrays is achieved owing to the insertion of a single nanoimprinted polymer grating dedicated to LC alignment and to the soft thermal transferof a dry thick resist film between two highly reflective mirrors. The filter exhibits a spectral tuning range of 102 nm with only 18 V applied, as well as negligible internal loss, which makes it suitable for being inserted in a laser cavity. This constitutes a key step toward the large-scale integration of widely tunable photonic devices such as vertical-cavity surface-emitting lasersusing LC technology.