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Study of non-solitonic blue-green radiation generated in mm-long photonic crystal fibers

We demonstrate highly-efficient generation of green-blue light using 20-fs femtosecond laser pulses propagating in short highly-nonlinear photonic crystal fibres. Three 5-mm-long fibres with different zero dispersion wavelengths were pumped by Ti:Sapphire pulses centred around 800-nm, and the relevant spectral characteristics of the generated radiation were studied as a function of pulse energy and chirp. In addition to the non-solitonic green-blue light, a well-defined infrared peak was simultaneously observed that follows the same power and wavelength dependence found on the green-blue peak. This work shows that short photonic crystal fibres can be used as an efficient source of ultrashort blue-green pulses (and possibly near-IR pulses) since linear dispersion (and consequent temporal broadening) and absorption of fused silica are minimized when using short fibres.