The picosecond ultrashort cavity dye laser: Giant pulse analogy and active étalon model

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Abstract
The evolution of a tunable dye laser (TDL) pulse in an ultrashort cavity pumped by a monochromatic picosecond light pulse is described using the appropriate laser rate equations. The ultrashort duration of the excitation pulse typically reduces the treatment into one which is directly analogous to the giant pulse model of Wagner and Lengyel, applied previously to Q-switching dynamics in solid-state lasers. The spectral properties of the TDL pulse are calculated using an active étalon model, in which the bandwidth narrowing of the cavity axial modes is governed by the time-dependent gain derived from the giant pulse model. Theoretical conditions are obtained for achieving operating regimes which correspond to extraction of high pump→TDL conversion efficiencies, to the minimization of TDL pulse durations, or to shot-to-shot stabilization of output properties. The feasibility of extracting ∼45% conversion of 531-nm SHG pulses from the mode-locked Nd3+ : glass oscillator using a 54-nm rhodamine 6G cavity is confirmed experimentally.