Two-Wavelength Neodymium Based Lasers
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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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 NdYAG and NdYLF. 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 NdYLF 1.047 micron 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 NdYLF was 30 whereas the transmission of the 1.06 micrometer output coupler necessary to achieve dual wavelength operation in NdYAG was 5. At a pulse repetition frequency for each wavelength of 2kHz, and with 820mW of absorbed pump power, NdYLF produced pulse energies of 40-2 microJ and 15.3-0.6 microJ, and pulse lengths of 44-1 ns, and 410-10 ns at the wavelengths of 1.047 and 1.32 micrometers respectively. NdYAG produced pulse energies of 33-1micro J and 27-micro J, and pulse widths of 32-0.4 ns and 183-1 ns at the wavelengths of 1.06 and 1.34 micrometers respectively. A separate set of dual wavelength data is also presented for NdYLF at 5.0kHz.
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