Observation of discrete supercontinuum spectra from a multi-pulse pumped distributed feedback dye laser

Abstract

A new approach to the generation of uniformly sliced supercontinuum is reported. It is based on a multi-pulse pumped distributed feedback dye laser rather than on the conventional propagation of femtosecond pulses through air or photonic molecules. Recent developments in supercontinuum generation and laser filamentation are critically reviewed to relate our findings to published work. Novelty of the proposed technique, in terms of ease of generation and economy, makes the method an attractive alternative. This work was carried out by pumping dye solution with six beams of a Q. switched and mode-locked Nd:YAG laser. A total energy of 421 μJ was used to generate a 5.5 nm wide discrete supercontinuum consisting of nine distinct coherent lines. The principle of multiple line generation may be extended to any desired spectral range depending upon the available gain medium and number of pumping pulses. Threshold power intensity for sliced supercontinuum generation using a frequency doubled Nd:YAG laser for solution of R6G in ethanol is found to be less than 24×10⁸ W/cm². Successful design and operation of a coherent off-white discrete supercontinuum source is also presented.