Supercritical-Xenon-Filled Hollow-Core Photonic Bandgap Fiber as a   Raman-Free, Dispersion-Controllable Nonlinear Optical Medium
  We propose supercritical xenon in a hollow-core photonic bandgap fiber as a highly nonlinear medium, and demonstrate 200 nm control over the guidance window of the fiber as the xenon goes through its supercritical phase transition. The large optical polarizability and monoatomic nature of xenon are predicted to allow large optical nonlinearity, on the same order as that of fused silica, while maintaining greatly reduced Raman scattering, offering benefits for nonlinear and quantum optics. 
K. E. Lynch-Klarup, E. D. Mondloch, M. G. Raymer, D. Arrestier, F.   Gerome, and F. Benabid
physics.optics