High Average Power Mid Infra Red Generation

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In the mid infra-red region, from about 3 to 10 microns, with the exception of some notable cases, such as the carbon dioxide laser, high average power continuous wave, wavelength flexible laser based sources with average powers in the range of 10W and above are uncommon and technically challenging . In the atmospheric transmission windows, application of such potential sources includes machining of polymers, remote sensing and military countermeasures. The objective of this research programme is the application of difference frequency mixing techniques deploying high average power fibre lasers to enable power scaling in this important spectral region, with emphasis initially placed on the atmospheric transmission window in the region of 3-4 microns. In the first instance, use will be made of industrial scale Yb and Er based fibre lasers, with average powers in the region of 300 W and 100 W , respectively, the difference frequency of which will allow relatively broad tunable operation around the 3.5 micron region. Difference frequency mixing will be undertaken in periodically poled lithium niobate. To extend the tunability, highly efficient spectral shifting using stimulated Raman will be used, however for operation beyond the 3-4 micron atmospheric transmission window the use of alternative non linear crystal will be investigated.