Continuously tunable coherent vacuum-ultraviolet (VUV) radiation has been generated in the 128.7-135.3-nm region by two-photon resonant four-wave mixing in Cd vapor. The generated VUV has no spectral structure over the tuning range and indicates that Cd vapor is an efficient nonlinear medium for frequency conversion.
Coherent radiation at several wavelengths in the vacuum ultraviolet (VUV) has been generated by four-wave parametric oscillation in mercury vapor. When a powerful ultraviolet pump laser of frequency omega(p) is tuned to a two-photon resonance, VUV signal photons at frequency omega(s), as well as idler photons at frequency omega(i), are generated such that omega(s) + omega(i) = 2omega(p). A frequency-doubled dye laser tuned to two-photon resonance with the 6s6d(1)D(2) level near 280.3 nm produced output at 184.9 and 143.5 nm. A tunable krypton fluoride excimer laser tuned to two-photon resonance with the 6s10s (1)S(0) level near 248.7 nm produced output at 140.1, 130.7, 130.1, 125.9, and 125.0 nm. Approximately 1-microJ, 200-W pulses were observed at 143.5 and 125.9 nm.
Vacuum-ultra violet radiation is generated by 61S0-61D2 or 61S0-63D2 two photon resonant four-wave difference mixing (ω4=2ω1-ω3) in Hg vapor. VUV radiation is tunable when one of the input wave (ω3) is tuned, the tuning range is 184.9-187.5 nm. The mechanism of this frenquency conversion, for example, the two-photon and single-photon resonant enhancement and phase matching have been investigeted. The competing processes and saturation effect on conversion efficiency have been analyzed. Using the generated tunable VUV radiation, we have recorded the absorption spetrum of O2 in air.
Two tunable dye lasers have been used to generate coherent radiation at a tunable sum frequency in the vacuum-ultraviolet spectral region. Spectral ranges of \ensuremath{\sim}3500 ${\mathrm{cm}}^{\ensuremath{-}1}$ around 1895 \AA{} and \ensuremath{\sim}1200 ${\mathrm{cm}}^{\ensuremath{-}1}$ around 1798 \AA{} have been covered. These ranges may easily be extended. Large (\ensuremath{\sim}\ifmmode\times\else\texttimes\fi{}104) enhancements of $2{\ensuremath{\nu}}_{1}+{\ensuremath{\nu}}_{2}$ sum mixing are seen when $2{\ensuremath{\nu}}_{1}$ is tuned to a double-quantum allowed transition from the ground state in Sr vapor.
Summary form only given. The techniques of electromagnetically induced transparency (EIT) may be employed in order to create an effective nonlinear response at a given wavelength which is equal in magnitude to the linear response at that wavelength. Physically, this allows frequency converters wherein 100% photon-to-photon conversion occurs in a single coherence length, i.e., in that distance which causes a /spl pi/ phase slip between the driving polarization and the generated electromagnetic wave. These ideas were first implemented by Jain et al. (1996), to convert 425 nm to 293 nm, in a medium consisting of a single isotope of Pb. This paper reports the demonstration of a vapor-phase VUV frequency converter from 233 nm to 186 nm with an energy conversion efficiency exceeding 35%; the maximum generated signal energy and power were 250 /spl mu/J and 25 kW. The net conversion efficiency to 186 nm, including all beams, is roughly 2%. These wavelengths were chosen to demonstrate the utility of this type of frequency converter to generate wavelengths outside the transparency window of most crystalline media. Our technique involves the application of two strong laser fields which are almost two-photon resonant with a Raman transition of the Pb atoms.