Topic
High harmonic generation
About: High harmonic generation is a research topic. Over the lifetime, 11694 publications have been published within this topic receiving 222650 citations. The topic is also known as: HHG.
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TL;DR: In this article, first-order multiple-scale perturbation theory is used to derive a set of coupledmode equations valid for electromagnetic-wave propagation in a weakly periodic, nonlinear medium with periodicity on the order of a wavelength.
Abstract: First-order multiple-scale perturbation theory is used to derive a set of coupled-mode equations valid for electromagnetic-wave propagation in a weakly periodic, nonlinear medium with periodicity on the order of a wavelength. We apply this to a problem where the medium has a ${\ensuremath{\chi}}^{(2)}$ response and find that the second-harmonic signal generated is enhanced when the fundamental is tuned near the band edge. Results are given for a possible experiment with optical fibers.
68 citations
TL;DR: Investigation of stabilization and harmonic generation in this relativistic regime from a three-dimensional hydrogen atom modeled as a classical system with a distribution of initial conditions derived from a Monte Carlo average finds few harmonics.
Abstract: The magnetic-field component of a very intense laser field interacting with an atom cannot normally be neglected for intensities that lead to relativistic velocities of the electrons. Here we investigate stabilization and harmonic generation in this relativistic regime from a three-dimensional hydrogen atom modeled as a classical system with a distribution of initial conditions derived from a Monte Carlo average. Particular emphasis is placed on the problems of ionization in the direction of propagation of the applied laser field, which will be shown to arise from the inclusion of the magnetic-field component of the laser field. In the harmonic spectra, Doppler shifting occurs for observation directions orthogonal to the direction of laser-field propagation. Retardation effects show up in the harmonic spectra in the forward direction and inhibit the magnetic-field effects of the free-electron contribution of the forward-direction spectrum. In general, few harmonics are observed in our single-atom treatment because of the magnetically induced three-dimensional motion of the electron for intensities approaching the relativistic regime, and because of high ionization probabilities, i.e., also the breakdown of stabilization, for strongly relativistic laser intensities.
68 citations
TL;DR: Relatively weak counterpropagating light is shown to disrupt the emission of laser high-harmonic generation and boosts harmonic production by similar contrast through quasiphase matching where out-of-phase emission is suppressed.
Abstract: Relatively weak counterpropagating light is shown to disrupt the emission of laser high-harmonic generation. Harmonic orders ranging from the teens to the low thirties produced by a 30-femtosecond pulse in a narrow argon jet are ``shut down'' with a contrast as high as 2 orders of magnitude by a chirped 1-picosecond counterpropagating laser pulse (60 times less intense). Alternatively, under poor phase-matching conditions, the counterpropagating light boosts harmonic production by similar contrast through quasiphase matching where out-of-phase emission is suppressed.
68 citations
20 Jan 2015
TL;DR: In this article, the authors demonstrate a continuous-wave low-threshold resonant optical parametric oscillator with optical spectral span ranging from 0.36 to 1.6μm.
Abstract: Optical microresonators are ideal tools for the reduction of the threshold of optical parametric oscillation based on four-wave mixing. Usually, the efficiency and bandwidth of the resonant process are interdependent due to stringent phase matching requirements leading to limitation of the bandwidth of the spectrum generated for a given pump power. We demonstrate a continuous-wave low-threshold resonant optical parametric oscillator with optical spectral span ranging from 0.36 to 1.6 μm. Harmonic generation is observed when a MgF2 microresonator characterized by quality factor approaching 1010 is pumped either at 780 nm, with a standard distributed-feedback semiconductor laser, or at 698 nm, with a reflective amplifier. Pump power does not exceed 25 mW. The nonlinear process is phase matched due to χ(3)-facilitated interaction of different mode families of the resonator. The optical harmonics generated can be used to seed high-power visible lasers, generate correlated photon pairs, and perform spectroscopy measurements.
68 citations
TL;DR: In this paper, it was shown that even for very high fields for which perturbation theory breaks down the even peaks in harmonic generation (HG) spectra are suppressed for a model Hamiltonian which is symmetric with respect to the reflection of coordinate space combined with translation of time by half period of the field.
Abstract: The present work shows that even for very high fields for which perturbation theory breaks down the even peaks in harmonic generation (HG) spectra are suppressed for a model Hamiltonian which is symmetric with respect to the reflection of coordinate space combined with translation of time by half period of the field. The proof presented utilizes the combination of Floquet theory and complex coordinate method. Numerical examples are included, which illustrate that even harmonics appear only when the above mentioned symmetry property of the Hamiltonian is broken.
68 citations