Intermodal Cherenkov Radiation Between Two Transmission Bandgaps in an All-Solid PBG Fiber

We demonstrate nonlinear propagation of femtosecond laser pulses in an all-solid photonic bandgap fiber. A supercontinuum from 560 to 1470 nm is generated from this fiber with an average power of 2 W. Spectral broadening not only occurs within the first bandgap, where the pump laser lies, but it also emits a phase-matched dispersive wave in a different propagation mode within the adjacent bandgap. Energy transfers across the intergap attenuation region with simultaneous mode conversion in the nonlinear process. The intermodal Cherenkov radiation generated across two bandgaps by the perturbed Raman solitons can enrich the nonlinear process in the all-solid photonic bandgap fiber.