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Highly efficient DUV generation at 100 kHz via Yb pumped four-wave mixing in stretched hollow-core fibers

Ruaridh Forbes, Paul Hockett, Rune Lausten

Abstract

We report the generation of the fifth harmonic of Yb at 206 nm with pulse energies exceeding 16 $μ$J and durations of approximately 100 fs at a repetition rate of 100 kHz. The deep ultraviolet pulses are produced using four-wave difference frequency mixing in a He-filled stretched hollow-core fiber, driven by a pump at 343 nm and seeded at 1030 nm. Guided by simulations, we carefully optimize the process, resulting in a conversion efficiency of $\sim$30% from the 343 nm pump beam.

Highly efficient DUV generation at 100 kHz via Yb pumped four-wave mixing in stretched hollow-core fibers

Abstract

We report the generation of the fifth harmonic of Yb at 206 nm with pulse energies exceeding 16 J and durations of approximately 100 fs at a repetition rate of 100 kHz. The deep ultraviolet pulses are produced using four-wave difference frequency mixing in a He-filled stretched hollow-core fiber, driven by a pump at 343 nm and seeded at 1030 nm. Guided by simulations, we carefully optimize the process, resulting in a conversion efficiency of 30% from the 343 nm pump beam.

Paper Structure

This paper contains 1 equation, 4 figures.

Figures (4)

  • Figure 1: (a) Wave vector diagram for the phase matching between the $\omega$ and 3$\omega$ beams in the FWDFM process. (b) Experimental setup of the HCF used to generate the fifth harmonic. The fundamental, and third harmonic beams are recombined on a dichroic mirror (DM), mode-matched to the fiber EH$_{11}$ mode. L1 is a thin fused silica lens with f=250 mm, and L2 is a thin CaF$_{2}$ lens with f=450 mm. The fiber chamber is filled with He to the phase matching pressure of 3.08 bar. The fifth harmonic is separated from the driving beams with dielectric mirrors, and either sent to a spectrometer (MayaPro, Ocean-Optics), or to a powerhead (3A-FS, Ophir Optics). (c) The setup for measuring the pulse length of the DUV pulse, though two-photon absorption autocorrelation in CaF$_{2}$. Details are in the main text.
  • Figure 2: Experimental phase-matching curve (circles with dashed line), with the simulation results from Eq. \ref{['eq:simple-PM']} overlay (solid line). Both the calculated curve and the experimental data are normalized.
  • Figure 3: Conversion efficiency, $\eta$, of the 343 nm pump into DUV as a function of the pump/seed power for the fixed HCF geometry used. Circles are the experimental points, recorded with an He filled HCF. Pump and seed energies were varied together.
  • Figure 4: (a) Measured spectrum (Ocean Optics MayaPro) of the generated DUV pulses at 206 nm, with an full width at half maximum (FWHM) of 0.73 nm, corresponding to a transform-limited pulse length of 85 fs. (b) Two-photon absorption autocorrelation trace of the DUV pulse, measured in CaF$_{2}$. The FWHM of 136 fs corresponds to a deconvolved pulse duration of 96 fs.