Abstract: In general, in one aspect, the invention features an apparatus that includes a photonic crystal fiber configured to guide a mode of electromagnetic radiation at a wavelength, ?, along a waveguide axis. The fiber includes a core extending along the waveguide axis, and a confinement region extending along the waveguide axis and surrounding the core. The confinement region includes alternating layers of a first and a second dielectric material having thicknesses d1 and d2 and different refractive indices n1 and n2, respectively. The thickness of at least one of the alternating layers of the first material differs from thickness d1QW or at least one of the alternating layers of the second material differs from thickness d2QW, where d1QW and d2QW correspond to a quarter-wave condition for the two dielectric materials given by d1QW=?/(4?{square root over (n12?1)}) and d2QW=?/(4?{square root over (n22?1)}), respectively.

Abstract: In general, in one aspect, the disclosure features a fiber waveguide having a waveguide axis, including a core extending along the waveguide axis and a confinement region extending along the waveguide axis surrounding the core. The confinement region includes a periodic structure along a radial direction extending from the waveguide axis and each period in the periodic structure includes a layer of a chalcogenide glass and a layer of a polymer.

Abstract: In general, in one aspect, the invention features systems, including a photonic crystal fiber including a core extending along a waveguide axis and a dielectric confinement region surrounding the core, the dielectric confinement region being configured to guide radiation along the waveguide axis from an input end to an output end of the photonic crystal fiber. The systems also includes a handpiece attached to the photonic crystal fiber, wherein the handpiece allows an operator to control the orientation of the output end to direct the radiation to a target location of a patient.

Abstract: In one aspect, the invention features a fiber waveguide having a waveguide axis, including a first portion extending along the waveguide axis, and a second portion different from the first portion extending along the waveguide axis surrounding the first portion, wherein at least one of the first and second portions comprises a chalcogenide glass selected from the group consisting of Selenium chalcogenide glasses and Tellurium chalcogenide glasses, both the first and second portions have a viscosity greater than 103 Poise at some temperature, T, and the fiber waveguide is a photonic crystal fiber.