Supercritical xenon-filled hollow-core photonic bandgap fiber.

We demonstrate that filling a hollow-core photonic-bandgap fiber with supercritical xenon creates a medium with a controllable density up to several hundred times that at STP, while working at room temperature. The high compressibility of the supercritical fluid allows rapid tuning of the spectral guidance window by making small changes of gas pressure near the critical point. We discuss potential applications of this system in linear and nonlinear optics.