Use of ZnS as a self-focusing element in a self-starting Kerr lens modelocked Ti:sa

摘要

Abstract: We studied the use of a highly nonlinear self-focusing element made of ZnS in an all solid- state self-starting Kerr lens modelocked Ti:sapphire laser. The results of our calculations show that the relationship between cavity losses and instantaneous intracavity power in such a laser is quite different than previously reported. The use of ZnS eliminates the need for saturable dyes or cavity modulation to initiate self-modelocked operation. We show experimentally that the pump power threshold for self-modelocking of a Ti:sapphire KLM laser can be significantly reduced by the use of a highly nonlinear intracavity element made of ZnS. Modelocking in the laser tested, which produced pulses with duration adjustable from 5 ps to 50 fs, was self-starting by Kerr lens mechanism alone. Because of the broad nonlinear response of ZnS the method is wavelength insensitive unlike quantum well saturable absorber/mirror designs. !26