Generation of tunable femtosecond pulses in the 1.21-1.27 μm and 605-635 nm wavelength region by using a regeneratively initiated self-mode-locked Cr:forsterite laser

Abstract

A detailed description of the design and operational characteristics of a regeneratively initiated, self-mode-locked Cr:forsterite laser pumped by a continuous-wave Nd:YAG laser is given. Without compensating for the intracavity positive group velocity dispersion, regenerative acoustooptic modulation produced pulses of between 41 and 6.5 ps (FWHM) at 1.23 /spl mu/m with average output powers of between 280 and 380 mW, respectively. Using intracavity negative group-velocity-dispersion compensation, nearly transform-limited femtosecond pulses of 48 fs (FWHM) duration were generated with average TEM/sub 00/ output powers of 380 mW at 1.23 /spl mu/m. By tuning the output of the mode-locked laser from 1.211 to 1.264 /spl mu/m, the dispersion (second and third order) of the Cr:forsterite gain medium has been measured. The operational wavelength range of the laser was extended to the visible region from 605 to 635 nm by external frequency doubling in a LiIO/sub 3/ nonlinear crystal. With approximately 250 mW of fundamental pump power at 1.23 /spl mu/m, red pulses of 116 fs (FWHM) duration at 615 nm were obtained with conversion efficiencies approaching 10 percent. >