X-ray lasers pumped by ultra-short light pulses

Short pulsed lasers have become a popular means to drive X-ray lasers. A nu mber of different schemes have been demonstrated by which population invers ion, and hence gain, may be achieved. The compactness and relatively high r epetition rate of such pump lasers may make them a potential source for 'ta ble-top' operation. This paper will survey a number of approaches, using op tical field ionisation (OFI) to pump both collisional and recombination sof t X-ray lasers, We examine some of the underlying features of OFI lasers an d assess their potential as future small-scale laboratory systems.