Appl. Phys. Lett. 100, 261107 (2012)

Noud Speijcken and co-workers from The Netherlands and Australia have developed a two-dimensional photonic crystal cavity that has a liquid-induced reversible tuning range. The structure, which is based on hexagonal photonic crystals in 220-nm-thick InGaAsP membranes, has a cavity resonance that can be tuned over 50 nm on a timescale of seconds to minutes by controlling the amount and location of an injected oil. The researchers focused a 660 nm laser to a 2 μm spot on a photonic crystal cavity comprised of six holes arranged in a hexagonal pattern. They investigated the fluid-induced cavity modes by analysing the photoluminescence spectrum around 1,500 nm emitted from InAs quantum dots grown in the membranes. The cavity resonance in the case of complete infiltration was red-shifted by 50 nm with respect to that of the non-infiltrated sample. They successfully reconfigured the position of the oil-infiltrated holes by using the focused laser spot to induce local heating. A laser power of around 0.5 mW was sufficient to evaporate the oil from the membrane. The researchers observed characteristic signs of re-infiltration in the cavity resonance when moving the focal spot slowly from the cavity centre towards the boundary.