Extended phase matching of high harmonic generation by plasma-induced defocusing

Extended phase matching of second-harmonic generation in periodically-poled KTiOPO4 with zero group-velocity mismatch

Under extended phase-matching conditions, the first frequency-derivative of the phase-matching function is zero and the phase-matching bandwidth is greatly increased. We made extensive three-wave mixing measurements to identify the operating point for extended phase matching, thus permitting us to observe a type-II phase-matching bandwidth of 100 nm centered at the fundamental wavelength of 158...

High-Efficiency Broadband High-Harmonic Generation from a Single Quasi-Phase-Matching Nonlinear Crystal.

Nonlinear frequency conversion offers an effective way to expand the laser wavelength range based on birefringence phase matching (BPM) or quasi-phase-matching (QPM) techniques in nonlinear crystals. So far, efficient high-harmonic generation is enabled only via multiple cascaded crystals because of the extreme difficulty to simultaneously satisfy BPM or QPM for multiple nonlinear up-conversion...

Voltage-controlled phase matching in quadrupole second-harmonic generation.

We have observed strong phase-matched (PM) quadrupole optical second-harmonic generation (SHG) from nematic liquid crystals that possess inversion symmetry. PM conditions were achieved for two configurations by voltage control of the molecular orientation and thus of the refractive indices. Quadrupole SHG was separated from electric-field-induced dipole-type SHG with the help of time-gated meas...

Collinear phase matching for second harmonic generation using conoscopic interferometry

Intensity-dependent phase-matching effects in harmonic generation

In high-order harmonic generation by an intense laser, intrinsic phases can develop at the atomic level between the laser field and the individual emitted harmonics. Because intrinsic phases can vary rapidly with the laser intensity, they can strongly influence phase matching to the extent that the laser intensity varies within the generating medium. Previously reported measurements of broad fa...