Quasi-phase-matching of high-order-harmonic generation using multimode polarization beating

Abstract

The generalization of polarization beating quasi-phase matching (PBQPM) and of multi-mode quasi-phase matching (MMQPM) for the generation of high-order harmonics is explored, and a novel method for achieving polarization beating is proposed. If two (and in principle more) modes of a waveguide are excited, modulation of the intensity, phase, and/or polarization of the guided radiation will be achieved; by appropriately matching the period of this modulation to the coherence length, quasi-phase-matching of high harmonic radiation generated by the guided wave can occur. We show that it is possible to achieve efficiencies with multi-mode quasi-phase matching greater than the ideal square wave modulation. We present a Fourier treatment of QPM and use this to show that phase modulation, rather than amplitude modulation, plays the dominant role in the case of MMQPM. The experimental parameters and optimal conditions for this scheme are explored.Please note that this is an arXiv version of the original APS paper. Please cite original paper L. Z. Liu, K O'Keeffe, and S. M. Hooker, Phys. Rev. A 87, 023810 (2013). APS link here: http://pra.aps.org/abstract/PRA/v87/i2/e023810

Temporal model for quasi-phase matching in high-order harmonic generation

“…As an example, a train of tunable counter-propagating pulses in a hollow-core waveguide has been used to introduce a spatially periodic ionization pattern for the generation of photon energies of several hundred electron volts [5]. Other schemes include waveguides with a spatially periodic diameter [6], multimode beating in a capillary [7] and polarizationbeating in a birefringent waveguide [8,9]. Recently, a small set of periodically spaced dual-gas jets, consisting of the generating gas (argon) and a passive gas (hydrogen), has shown to shift harmonic generation up to the 41 st order (≈19 nm) [10][11][12].…”

Quasi-phase-matched high-harmonic generation in gas-filled hollow-core photonic crystal fiber

“…Here, we report on HHG driven with μJ-level NIR pulses in NC-PCF at photon energies up to 61.6 eV. Further, we demonstrate that multimode quasi-phase-matching (MM-QPM) [18,19] of HHG in a NC-PCF leads to an order of magnitude enhancement of the HHG signal.…”

Harmonic generation from partially ionized plasma [Invited]

“…QPM was studied both theoretically and experimentally by using multiple gas jets whose pressure and separation were properly controlled, as well as by using other methods of gaseous medium modulation [64][65][66][67][68][69][70][71][72][73][74].…”