Some possible approaches towards the generation of ultra-fast infra - red CO2 laser pulses are discussed. Of these the technique of injection modelocking in particular, which has been applied to a wide range of CO2 oscillators,appear to be the most suitable for large aperture high power laser systems.This technique, which essentially consists of the injection of a low power shortpulse into the slave laser cavity, to control the temporal behaviour of its emitted radiation, has also permitted the wavelength control of non - dispersiveTEA CO2 laser systems, producing single wavelength ultra - fast CO2 laserpulses in the GW power range. The experimental results obtained are reportedand compared with the predictions of a simple theoretical analysis. Regions of broadening of the injected short pulse have been identified and the pulse compression techniques employed to overcome this intrinsic broadening, along with the simple theoretical models developed to analyse the various pulse shaping effects in the amplifying medium, are also described.
