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Degree

Doctor of Philosophy, Ohio State University, Mechanical Engineering, 2006.

Abstract

This thesis has documented the development of a MHz repitition rate pulse burst laser system. Second harmonic and third harmonic efficiencies are improved by adding a Phase Conjugate Mirror to the system. Some high energy fundamental, second harmonic, and third harmonic burst sequences consisting of 1 – 12 pulses separated in time by between 4 and 12 microseconds are now routinely obtained. The reported burst envelopes are quite uniform. We have also demonstrated the ability to generate ultra-high frequency sequences of broadly wavelength tunable, high intensity laser pulses using a home built injection seeded Optical Parametric Oscillator (OPO), pumped by the second and third harmonic output of the pulse burst laser. Typical OPO output burst sequences consist of 6 – 10 pulses, separated in time by between 6 and 10 microseconds. With third harmonic pumping of the OPO system, we studied four conditions, two-crystal Singly Resonant OPO (SRO) cavity, three-crystal OPO cavity, single pass two-crystal Doubly Resonant OPO (DRO) cavity and double pass two-crystal OPO cavity. The double pass two-crystal OPO cavity gives the best operation in burst mode. For single pass OPO, the average total OPO conversion efficiency is approximately 25%. For double pass OPO, the average total OPO conversion efficiency is approximately 35%. We have also demonstrated injection seeding for OPO. The OPO output light linewidth is significantly narrowed. Some preliminary etalon traces are also reported. By mixing the OPO signal output at 622 nm with residual third harmonic at 355 nm, we obtained 226 nm burst sequences with average pulse energy of ~0.2 mJ. Injection seeding of the OPO increases the energy achieved by a factor of ~2. 226 nm burst sequences with reasonably uniform burst envelopes are reported. Using the system we have obtained, for the first time by any known optical method, Planar Laser Induced Fluorescence (PLIF) image sequences at ultrahigh ( 100kHz) frame rates, in particular NO PLIF image sequences, have been obtained in a Mach 2 jet.

Subject Headings

Engineering, Mechanical

Keywords

Flow diagnostics; OPO; Parametric Amplification; High Repetition Rate Laser; Combustion Diagnostics; PLIF

Advisor

Walter R. Lempert

Pages

183p.

Document number: osu1150140816
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=osu1150140816

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