ACS Photon. 5, 3222–3230 (2018)

By exploiting the capability of direct laser writing on different photopolymerizable materials on the same chip and the versatile properties of different polymers, Sara Nocentini and colleagues from Italy have demonstrated a three-dimensional active and tunable polymeric integrated network for telecommunications at 1,550 nm. They designed, fabricated and characterized straight and bent waveguides, grating couplers, and single and vertically coupled whispering-gallery-mode (WGM) resonators. Passive, rigid photonic components were first fabricated on a low-refractive-index fused silica substrate. To realize tunable photonic resonators, the team integrated liquid-crystalline networks (LCNs) into the photonic circuit. The shape change and the refractive-index variation due to the optically induced rearrangement of LCN polymeric chains were exploited in two different ways to tune the photonic resonators — LCNs were used as an actuator to finely change the shape of the WGM resonators and were also used to make the resonator itself.