High-harmonic generation in solids using a mid-infrared sub-cycle pulse synthesizer

Abstract

Abstract:We generate high-order harmonics in silicon using a mid-infrared (2.5−9.0 µm) pulse synthesizer. Even and odd harmonics (~19 th order) with few-cycle pulses and near-continuous spectra with sub-cycle pulses, indicating an isolated harmonic emission, are observed.OCIS codes: (320.7110) Ultrafast nonlinear optics; (270.6620) Strong-field processes 1. Introduction High-energy, carrier-envelope phase (CEP)-stable, sub-cycle pulses can provide unique opportunities of exploring isolated phase-sensitive strong-field light-matter interactions in atoms, molecules and solids. At the mid-infrared (mid-IR) wavelength range the Keldysh parameter is much smaller than unity even at relatively modest laser intensities, enabling to study the strong-field sub-cycle electron dynamics in solids via high-harmonic generation (HHG) [1][2][3] without damage as well as the electron tunneling dynamics in nano-devices. These efforts are opening a great opportunity towards petahertz electronics. Regarding the generation of high-energy sub-cycle pulses, pulse synthesis is a very powerful method to overcome the bandwidth limit of conventional laser amplifiers. One can generate and manipulate an optical bandwidth more than one octave by coherently combining ultrashort pulses covering different spectral windows with controlled phase. Single-or sub-cycle pulse synthesizers in the visible-to-near-infrared (IR) spectral region have been demonstrated by coherent multiplexing of pulses from fiber lasers, supercontinuum [4], and optical parametric chirped-pulse amplifiers (OPCPA's) [5]. In this contribution, we present a multi-GW, mid-IR subcycle pulse synthesizer based on an optical parametric amplifier (OPA) and its application to HHG in solids.