(1) Recent developments in VUV femtosecond pulse generation; (2) proposal for a higher efficiency F₂ (157-nm) laser

The efficiency of the four-wave mixing (2ω1 - ω2), VUV femtosecond source described by us last year (SPIB Vol. 1861) inherently relies upon a two-photon resonance enhancement occurring (in Xe gas) when λ ∼ 248.5 nm. However, it also depends upon the spatial and temporal coherence properties of the input pulses. Development of a new source for producing beams at ω1 with greatly improved coherence properties is here reported. Performance of the four-wave mixing source with these ω1 pulses is described. Femtosecond. VUV pulses with energies as high as ∼60 μ.I are generated. As a separate topic, we propose the use of a pulsed (nanosecond) infrared laser to deplete the terminal state of an F2 (157-nm) laser in order to greatly enhance its performance.