High harmonic generation in a gas-filled hollow-core photonic crystal fiber

Abstract

High harmonic generation (HHG) of intense infrared laser radiation [1,2] enables coherent vacuum-UV (VUV) to soft-X-ray sources. In the usual setup, energetic femtosecond laser pulses are strongly focused into a gas jet, restricting the interaction length to the Rayleigh range of the focus. The average photon flux is limited by the low conversion efficiency and the low average power of the complex laser amplifier systems [3][4][5][6] which typically operate at kilohertz repetition rates. This represents a severe limitation for many experiments using the harmonic radiation in fields such as metrology or high-resolution imaging. Driving HHG with novel high-power diode-pumped multi-megahertz laser systems has the potential to significantly increase the average photon flux. However, the higher average power comes at the expense of lower pulse energies because the repetition rate is increased by more than a thousand times, and efficient HHG is not possible in the usual geometry. So far, two promising techniques for HHG at lower pulse energies were developed: external build-up cavities [7,8] and

Hollow-core photonic crystal fibre for high power laser beam delivery

“…However, with 74 µJ output pulse energy obtained, no damage to the fibre has been observed. This value is much higher than previously reported ultra-short pulse delivery using HC-PCF which is usually less than 10 µJ [36,37] . Furthermore, the 100 µJ pulse transported by the fibre corresponds to a fluence of 6 J/cm 2 , which is 3 times larger than the fused silica laser damage threshold with subpicosecond pulses.…”

“…As a host for light-matter interactions [16,17] , which is one of the most advanced applications of HC-PCF, bandgap HC-PCF can enhance the interaction intensity by up to a millionfold because of its small core size and low optical attenuation. However, a lot of light-matter interaction phenomena, for example Raman frequency comb generation [26] and high harmonic generation [37] , produce light in a broad frequency range. In such situations, a broadband guiding HC-PCF, like Kagome HC-PCF, is required.…”

Four-wave mixing UV generation in optical microfibers

“…Ultraviolet (UV) generation has traditionally relied on crystals and gases to allow frequency conversion from longer wavelengths [1][2][3][4][5][6][7][8][9][10]. 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].…”

“…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].…”

Low loss hollow optical-waveguide connection from atmospheric pressure to ultra-high vacuum

“…Examples of useful linear and nonlinear processes available in gas-filled PCFs include temporal pulse compression, 14,15 generation of tunable vacuum-UV and deep-UV emission, 5 multi-octave spanning supercontinuum generation, 16 frequency blue-shifting, 17,18 and high harmonic generation of XUV and x-ray radiation. 19 Furthermore, since the transverse profile of the guided mode remains stable even if the fiber is bent or twisted, the transmitted light has excellent spatial coherence and so can be focused to a diffraction-limited spot inside the vacuum chamber.…”