Bright Spatially Coherent Wavelength-Tunable Deep-UV Laser Source Using an Ar-Filled Photonic Crystal Fiber

Abstract

We report on the spectral broadening of ~1 μJ 30 fs pulses propagating in an Ar-filled hollow-core photonic crystal fiber. In contrast with supercontinuum generation in a solid-core photonic crystal fiber, the absence of Raman and unique pressure-controlled dispersion results in efficient emission of dispersive waves in the deep-UV region. The UV light emerges in the single-lobed fundamental mode and is tunable from 200 to 320 nm by varying the pulse energy and gas pressure. The setup is extremely simple, involving <1 m of a gas-filled photonic crystal fiber, and the UV signal is stable and bright, with experimental IR to deep-UV conversion efficiencies as high as 8%. The source is of immediate interest in applications demanding high spatial coherence, such as laser lithography or confocal microscopy.

Angle-resolved photoemission spectroscopy with 9-eV photon-energy pulses generated in a gas-filled hollow-core photonic crystal fiber

“…In the deep-UV region (< 300 nm), losses of $1-3 dB/m have previously been measured, 16,17 but they are unknown in the VUV region. Nevertheless, as the VUV emission is generated close to the end of the fiber, the loss is expected to play a minor role.…”

Hollow-core photonic bandgap fibers: technology and applications

“…For example, by appropriate choice of gas it is possible to control the relative strength of the Kerr and Raman nonlinearities (e.g., by selecting mono-atomic gases such as Argon, Raman effects can be effectively eliminated so as to provide a pure Kerr fibre medium, alternatively one can use a mixture of cases of differing Raman responses to generate a tailored Raman gain profile). Using carefully engineered nonlinear/ dispersive gas-filled HC-PBGFs the following exemplar device applications have been demonstrated: pulse compression down to pulses of a few cycles duration [89]; efficient dispersive wave generation at wavelengths in the UV [89] (e.g., allowing conversion efficiencies of ~15% from a pump source operating around 800 nm down to < 200 nm); High Harmonic Generation (HHG) at reduced pulse energies [91] (~100 nJ rather than the ~1 mJ usually required in free space embodiments); and finally access to light-plasma interactions in fibres [92]. For a relatively recent review on ultrafast nonlinear gasfilled fibre optics the interested reader is referred to [93].…”

“…Through appropriate fibre design it is possible to engineer gas-filled HC-PBGFs with well-defined anomalous dispersion and controllable Kerr and Raman nonlinearity such that optical soliton effects previously demonstrated in solid fibres in the near IR can be exploited at wavelengths down into the UV [89] or at far greater than MW peak power levels (around 1000 × higher than in solid fibres) [90]. For example, by appropriate choice of gas it is possible to control the relative strength of the Kerr and Raman nonlinearities (e.g., by selecting mono-atomic gases such as Argon, Raman effects can be effectively eliminated so as to provide a pure Kerr fibre medium, alternatively one can use a mixture of cases of differing Raman responses to generate a tailored Raman gain profile).…”

Four-wave mixing UV generation in optical microfibers

“…These methods involve the use of nonlinear crystals such as KTP, KDP, sapphire, K2Al2B2O7, potassium pentaborate (KB5), the exploitation of nonlinear processes in waveguides such as photonic crystal fibers or the use of hybrid schemes employing both waveguides and nonlinear crystals [1][2][3][4][5][6][7]. Fiberized UV generation in optical fibers typically involve the use of gas-filled hollow core microstructured fibers, or otherwise exploit nonlinear processes such as supercontinuum generation to generate a broad spectrum which extends down to the UV wavelength region [8][9][10][11][12][13][14][15].…”