GENERATION OF TUNABLE FEMTOSECOND PULSES IN THE 1.21-1.27-MU-M AND 605-635 NM WAVELENGTH REGION BY USING A REGENERATIVELY INITIATED SELF-MODE-LOCKED CRFORSTERITE LASER

A detailed description of the design and operational characteristics o f a regeneratively initiated, self-mode-locked Cr:forsterite laser pum ped by a continuous-wave Nd:YAG laser is given. Without compensating f or the intracavity positive group velocity dispersion, regenerative ac oustooptic modulation produced pulses of between 41 and 6.5 ps (FWHM) at 1.23 mum with average output powers of between 280 and 380 mW, resp ectively. Using intracavity negative group-velocity-dispersion compens ation, nearly transform-limited femtosecond pulses of 48 fs (FWHM) dur ation were generated with average TEM00 output powers of 380 mW at 1.2 3 mum. By tuning the output of the mode-locked laser from 1.211 to 1.2 64 mum, the dispersion (second and third order) of the Cr:forsterite g ain medium has been measured. The operational wavelength range of the laser was extended to the visible region from 605 to 635 nm by externa l frequency doubling in a LiIO3 nonlinear crystal. With approximately 250 mW of fundamental pump power at 1.23 mum, red pulses of 116 fs (FW HM) duration at 615 nm were obtained with conversion efficiencies appr oaching 10 percent.