Tunable photonic crystal with 50 nanometer tuning range and 100 millisecond response time

Tunable photonic crystals (PhCs) with wide tuning range mostly have long response time. Oppositely, PhCs with short response time mostly has narrow tuning range. In this work, we demonstrated a capillary-driven tunable PhC with 50 nanometer tuning range and 100 millisecond response time. A 1-D photonic crystal composed of porous silicon with periodic porosity was hydrophobically modified to allow liquid infiltration and exfiltration. The PhC was tuned by alternately washing the PhC surface with ethanol and water. Capillary attraction induced by the low surface tension of ethanol contributed the liquid infiltration of the PhC. Capillary repulsion induced by the high surface tension of water contributed the liquid exfiltration of the PhC.