Countermeasures against heat seeking missiles require access to efficient laser sources, which should emit wavelengths at band Ⅰ, Ⅱ and Ⅳ. Efficient diode pumped solid-state lasers, combined with efficient non-linear wavelength shifters, allow the development of practical tuneable mid-IR countermeasure sources. The paper describes the requirements and the development of a tabletop laser source for study of DIRCM techniques. Jamming laser systems must be able of creating pulse sequences in the frequency range between 100 Hz and 10,000 Hz, including the capability to mix and sweep the jam frequency. A Nd: YVO_4 pump laser with maximum pump power of 3 Watt and pulse length of 10 ns, and a maximum modulation frequency of 100 kHz was selected. A linear single resonant OPO cavity with 30 mm long, 1mm thick PPLN crystals was build. With the tabletop laser system we were able to generate wavelengths from 1.5 to 4 micron. In band Ⅰ, at 2 micron we can generate between 400-550 mW, and in band Ⅱ, from 3-4 micron we can generate 130-160 mW laser jam power. The beam quality (M~2) is approximately 2.5. The power efficiency for the idler was 8.8%, while the slope power efficiency was 15%. Jam patterns are generated by use of an acousto-optic modulator.
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