High-intensity coherent vacuum ultraviolet source using unfocussed commercial dye lasers

Abstract

Using two or three commercial pulsed nanosecond dye lasers pumped by a single 30 Hz Nd:YAG laser, generation of 0.10 mJ pulses at 125 nm (6 × 10(13) photons∕pulse) has been demonstrated by resonance enhanced four-wave mixing of collimated (unfocussed) laser beams in mercury (Hg) vapor. Phase matching at various vacuum ultraviolet (VUV) wavelengths is achieved by tuning one laser in the vicinity of the 6 (1)S0 → 6 (3)P1 resonance near 253.1 nm. A number of different mixing schemes are characterized. Our observations using broadband lasers (~0.15 cm(-1) bandwidths) are compared to previous calculations pertaining to four-wave mixing of low intensity narrowband laser beams. Prospects for further increases in pulse energies are discussed. We find that VUV tuning curves and intensities are in good agreement with theoretical predictions. The utility of the VUV light source is demonstrated by "soft universal" single-photon VUV ionization in crossed molecular beam studies and for generation of light at 130.2 nm for oxygen atom Rydberg time-of-flight experiments.

High intensity vacuum ultraviolet and extreme ultraviolet production by noncollinear mixing in laser vaporized media

“…Near 11 eV, we measured a factor of two greater usable photon intensity (5 × 10 11 photons/pulse). 9 At 104 nm (12 eV), our usable VUV intensity of 9 × 10 10 photons/pulse, is similar to a previous estimate of ∼10 11 photons/pulse using a much more complex laser system. 24 At 89.6 nm (13.8 eV), we generated an order of magnitude more VUV than previously measured using Hg as a nonlinear mixing medium at that wavelength.…”

“…This is about an order of magnitude smaller than we produce using collimated lasers in a 1 m long Hg cell. 11 Chénais et al reported the dependence of the "enhancement ratio," defined as the ratio of the VUV intensity with the vaporization laser on relative to that with the vaporization laser off, as a function of UV, visible, and ablation laser beam pulse energies. 29 We have carried out similar experiments but instead report the relative intensity of the VUV generated as functions of the three input laser pulse energies, shown in Fig.…”

“…5, the VUV pulse intensities plateau at lower pulse energies than in the standard heat pipe configuration in either a focused or unfocused geometry. 9,11,13 To date we have not studied the effect of using achromatic focusing lenses with different focal lengths. Since VUV conversion efficiencies can be high even using unfocused lasers (2 mm dia.…”

“…9,10 We recently described schemes for mixing of two or three collimated (unfocused) beams from commercial dye lasers in 1 m long Hg heat pipes for production of ∼0.1 mJ pulses (6 × 10 13 photons/pulse) near 125 nm and 130 nm. 11 Because the laser beams are unfocused, by scaling the input laser beams to higher energies, VUV output pulse a) Author to whom correspondence should be addressed. Electronic mail: hfd1@cornell.edu energies in the millijoule range are achievable.…”

“…12,13 In this wavelength range, MgF 2 and LiF optics can be employed for focusing or dispersing the VUV from the much more intense UV and visible beams with modest power losses, e.g., by transmission through a lens held off of the optical axis. 11,13,14 The optical transmission of window materials decreases sharply at shorter wavelengths, falling to zero for LiF at λ < 104 nm. 15 For MgF 2 , the only other material capable of transmitting light at λ < 140 nm, the transmission cutoff occurs at 116 nm.…”