Ultrashort Pulse Generation with a Solid State Cr 4 * : YAG Laser

A prismless ultrafast Cr4*:YAG laser has been designed and constructed. Intracavity dispersion in this laser is compensated through the use of double-chirped mirrors, in contrast to previous work, which used fused silica prisms. The resonator design for Kerr lens modelocking has been optimized through the use of numerical simulation programs, based on the ABCD transfer matrix formalism. Pulses as short as 20 fs were generated directly from the laser. The modelocked spectrum had a FWHM of 190 nm, from 1310 to 1500 nm, with a peak intensity at 1450 nm. Significant spectrum is observable from 1140 nm to >1700 nm. In addition, a novel broadband saturable Bragg reflector was designed and used to self-start modelocking in the Cr 4+:YAG laser. The SBR consists of a 7-pair GaAs/AlxOy quarter-wave mirror and an InGaAs/InP quantum well saturable absorber. The high-index-contrast of the mirror structure allows for broadband reflection, heretofore unattained, and is able to support ultrashort Cr4*:YAG pulses. Modelocked pulses of 35 fs duration were generated directly from the self-starting laser. The spectrum had a maximum at 1490 nm and a FWHM of 68 nm. Two-photon absorption is believed to be the limiting factor in achieving shorter pulse durations in this laser. With the SBR in the resonator, the Cr4 *:YAG laser was also able to generate self-starting picosecond pulses, with center wavelengths tunable from 1400 to 1525 nm. Thesis Supervisor: Erich P. Ippen Title: Elihu Thompson Professor of Electrical Engineering, Professor of Physics