Nonlinear Optics with Two-Colour Lasers

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Lasers transformed optics research 50 years ago and have now spawned innumerable applications. Lasers operate at many wavelengths from the infrared to the ultraviolet, but to completely cover the optical spectrum, nonlinear optics is needed. Ultrashort pulse lasers can now generate far-infrared radiation through a nonlinear process known as optical rectification and can nonlinearly drive the frequency up to the extreme ultraviolet by high order harmonic generation. However, some spectral gaps still exist and this proposal aims to fill in the "molecular fingerpint" spectral region from 6 to 25µm, where almost every molecule has a distinctive signature in its absorption spectra. Along with applications in environmental monitoring and medical applications, this spectral region is becoming increasingly important for trace gas detection of explosives that have strong absorption lines at these wavelengths. At Waterloo, we are developing a two-colour, short pulse fiber laser system, which will generate mid-infrared wavelengths across the fingerprint region with sufficient power for trace gas detection, by difference frequency mixing the two laser outputs in a nonlinear crystal.