Demonstration of a distributed, directed infrared countermeasure source: The multifunctional laser

In current laser countermeasure technology concepts where frequency conversion is required, each active component has its own laser source. During this paper we show that by using microstructured fibre technology as a delivery system, output in multiple wavebands can be efficiently generated at locations remote from the laser pump source. We demonstrate that laser radiation (with specifications close to those currently on airframes) can be delivered without significant spectral, temporal or modal degradation over lengths representative of that in an airframe. This fibre delivered radiation is used as a pump source for active frequency conversion, generating tuneable laser output in the 2 µm, 3.5 µm and 0.532 µm regions, i.e. in wavebands of interest to countermeasure applications. A Nd:YVO₄ laser (? = 1.064 µm) with 16 W of average power in a train of 15 ns pulses acts as the single pump source for our system. Different types of microstructured fibre are assessed for high power delivery over lengths greater than 6.5 m. Three frequency conversion devices were constructed here to demonstrate the quality of the fibre-delivered radiation - the devices are all based around periodically poled lithium niobate (PPLN) crystals and consist of two optical parametric oscillators converting the pump source to wavelengths of ~2 µm and ~3.5 µm and a second harmonic generator to double the frequency to 0.532 µm. The efficiencies of the frequency conversion sources are comparable whether radiation is delivered through free space or by microstructured fibre. © 2008 SPIE.