UC Davis

Ultrafast laser systems based on Cr-doped ZnSe/S gain media can provide powerful, flexible laser light in the mid-infrared. Beyond their mid-infrared output, Cr:ZnSe/S lasers often possess a second-harmonic output. Second harmonic is naturally generated via random quasi-phasematching (RQPM) in polycrystalline ZnSe/S when driven by infrared light. In Cr:ZnSe/S lasers, this second-harmonic generation (SHG) can often reach powers comparable to the output powers of conventional pulsed laser systems, on the order of hundreds of milliwatts. Although interesting, there has been limited experimental investigation into this naturally generated SHG. In this thesis, we tackle the problem of measuring these SHG pulses. The measurement of these ultrafast pulses requires an understanding of nonlinear optical interactions as well as the development of both precision electronics and optics. In this thesis, background is provided on the nonlinear interactions that lead to SHG as well as the techniques and instrumentation necessary to measure ultrafast pulses. Additionally, the development of high-gain, low-noise transimpedance amplifiers for pulse measurement is described. Furthermore, a precision optical system for the measurement of SHG pulses from a Cr:ZnSe/S laser is presented and initial measurement results are discussed.