Abstract

Besides I lie gain medium a standard femtosecond KLM laser contains a pair of Brewster-angled prisms providing an overall negative group velocity dispersion (GVD) per cavity round trip. The self-phase modulation owing to the Kerr-effect in the laser crystal with n₂ > 0 requires an effectively negative GVD as a prerequisite for the generation of stable fs-pulses. The necessity of intracavity GVD-compensation is a major hindrance for a compact cavity design and higher repition rates and introduces additional higher order dispersion and increased sensitivity to cavity and prism alignment. Recently instead of the prism pair carefully designed multilayer dielectric mirrors were sucsessfully used for intracavity dispersion compensation allowing for the generation of sub-10fs pulses [1]. In the present talk we propose and theoretically investigate an alternative approach to KLM which avoids the GVD-compensation by use of an overall negative nonlinear refractive index per cavity round trip. For the compensation of the positive nonlinear refractive index of the laser crystal we propose to utilize a nonresonant bulk semiconductor inserted in the lightly focused resonator section.

© 1996 IEEE