M. Nakao, K. Sakamaki, M. Naganuma
Oct 25, 2004
Journal name not available for this finding
Site dependent nonlinear optical properties are characterized by pumping 140 fs pulses at independently addressable small quasi-cores formed by imperfection in index-guiding photonic crystal fiber (PCF). The positional assignment of pumping site onto the PCF is achieved based on the reflection method to observe in situ the waveguiding structure of PCF input face relative to the fixed focal point of the collimated laser beam. A series of input peak power dependent spectra at several small quasi-cores demonstrate visible light formation down to the violet, which are discussed in comparison with those for the center core leading to supercontinuum generation. Visible light formation at quasi-cores is principally due to an increase of the degree of anomalous dispersion by decreasing the core size. The observations presented in this work classify the nature of nonlinear optical processes through the slightly distorted PCF, leading to nonlinear optical manipulation by individual cores within the single PCF.