Lasers operate at many wavelengths from the infrared to the ultraviolet, but to completely cover the optical spectrum, nonlinear optics is needed. Nonlinear optics occurs when two or more optical photons interact with an atom or molecule simultaneously. Having two photons in the interaction volume of an atom requires high photon density or laser intensity. In this talk, I will first discuss high intensity lasers and in particular the two-colour lasers developed at Waterloo needed for specific nonlinear interactions. I will then talk about how we use these lasers that operate in the near infrared spectral region to generate other colours. In one set of experiments we are aiming to generate coherent radiation over the "molecular fingerprint" spectral region from 6 to 25µm, where almost every molecule has a distinctive signature in its absorption spectra, but very few coherent sources exist. We generate these long wavelengths with the nonlinear process of difference frequency mixing the two colours. On the high frequency side, we are using the nonlinear technique of multi-frequency Raman generation to produce a rainbow of colours from the infrared to the ultraviolet. The ultimate goal of this research is to generate single-femtosecond, high intensity laser pulses that could be used to watch molecular motion.
