Tunable three-dimensional diamond photonic crystal made of a liquid medium

A three-dimensional diamond photonic crystal with an ultra-wide tunable bandgap and resonant mode has been proposed based on a liquid medium approach. A bandgap tuning range of up to 12.8 is achieved in the microwave regime. The liquid-infiltrated photonic crystal is realized by using a low-loss liquid medium of which a large refractive index variation from 1.58 to 6.32 is achieved. The weak-dispersion and non-resonant nature of the liquid ensure a broadband and low-loss performance from 12 to 18 GHz. The flexibly tunable bandgap and resonant mode of the proposed photonic crystal were demonstrated by simulation and experimental results.