Broadband Cherenkov radiation by using group-velocity-matching in index-guiding photonic crystal fiber

Dispersive waves (DW) are radiated when temporal solitons are perturbed by higher-order dispersion (HOD). This is also called optical Cherenkov radiation (OCR). Currently among much efforts of generating optical octave-spanning supercontinuum (SCG), OCR has become an efficient nonlinear frequency conversion in the blue edge of SCG and blue-shifting the edge with the soliton self-frequency shift(SSFS) by the Raman effect. Moreover, a sharp switching of SSFS can occur across a normal group velocity dispersion (GVD) region sandwiched in the anomalous GVD regions, known as soliton spectral tunneling (SST) effect. Its mechanism was attributed to the phase-matching (PM) between the soliton and linear DW in the anomalous GVD. Here we argue first that group-velocity (GV) matching is another necessary condition for such SST effect and present a detailed analysis on the broadband OCR by employing GV-matching in the index-guiding photonic crystal fibers (PCFs). This approach is expected to efficiently generate ultrashort pulses in the near- and mid-IR.