Date of Award

12-1995

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Engineering Physics

First Advisor

Jeffrey W. Grantham, PhD

Abstract

A dual wavelength Q switched laser cavity has been successfully designed and assembled to evaluate the new neodymium (Nd) based materials. Initial characterization has been achieved for Nd:YAG and Nd:YLF. The results indicate that for a fixed pulse repetition frequency, the delay time can be used to adjust the relative energy between the 1.06 and 1.32 micrometer pulses. Any deficiency in the performance of one transition can be made up by performance in the other simply by changing the relative amount of time the population inversion is allowed to build up for each pulse. The best performance was obtained using a 13cm cavity length, the shortest possible cavity with the available equipment. The gain in the Nd:YLF 1.047 µm cavity was so high, the diffraction efficiency of the acoustooptic Q switch was insufficient to hold off lasing with a 5% output coupler. The transmission of the 1.047 micrometer output coupler used for dual wavelength operation of Nd:YLF was 30% whereas the transmission of the 1.06 micrometer output coupler necessary to achieve dual wavelength operation in Nd:YAG was 5%. At a pulse repetition frequency for each wavelength of 2kHz, and with 820mW of absorbed pump power, Nd:YLF produced pulse energies of 40±2 µJ and 15.3±0.6 µJ, and pulse lengths of 44±1 ns, and 410±10 ns at the wavelengths of 1.047 and 1.32 µm respectively. Nd:YAG produced pulse energies of 33±1 µJ and 27±1 µJ, and pulse widths of 32±0.4 ns and 183±1 ns at the wavelengths of 1.06 and 1.34 µm respectively. A separate set of dual wavelength data is also presented for Nd:YLF at 5.0kHz.

AFIT Designator

AFIT-GEO-ENP-95D-02

DTIC Accession Number

ADA303231

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