Abstract

Besides the gain medium a standard femtosecond KLM laser contains a pair of Brewsterangled prisms providing a negative net group velocity dispersion (GVD) per cavity round trip. The self-phase modulation owing to the Kerr-effect in laser crystal with n₂>0 requires a negative net GVD as a prerequisite for the generation of stable sub-20fs pulses. The necessary intracavity GVD-compensation is a major hindrance for a compact cavity design and higher repetition rates. Moreover the prism pair introduces additional limitations to the system by higher order dispersion and increased sensitivity to cavity and prism alignment. Recently instead of the prism pair carefully designed multilayer dielectric mirrors were successfully used for intra-cavity 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 a negative net nonlinear refractive index per cavity round trip. For the compensation of the positive nonlinear refractive index of the laser crystal we propose to utilise a nonresonant bulk semi-conductor inserted in the tightly focused resonator section. An universal dispersion rule for the electronic Kerr-effect in solids was given in ref.

© 1996 Optical Society of America