Abstract

We report continuous pulse width tunability in a femtosecond linear hybridly mode-locked cw dye laser by means of variable intracavity spectral windowing. Controlled limitation of the oscillation bandwidth is achieved by adjustable aperturing of the transversely dispersed spectrum present in an intracavity Brewster prism sequence. The Brewster prism arrangement was previously introduced for controlling group velocity dispersion in femtosecond dye laser cavities.¹ The aperture provides tunability of the pulse duration in the range <100 up to 500 fs. It is also found that translating the aperture transversely results in wavelength tunability of the laser output. The cavity used in this work has generated pulses as short as 69 fs without spectral windowing. The gain medium was rhodamine 6G (2 × 10^–3 M) in ethylene glycol and a mixture of DODCI (1.2 × 10^–5 M) and DQOCI (1.8 × 10^–5 M) in ethylene glycol was used as the saturable absorber. We note that this technique is the intracavity analogy of pulse shaping by spectral filtering within a fiber-and-grating pulse compressor.²

© 1986 Optical Society of America