Third- and fifth-harmonic generation in transparent solids with few-optical-cycle midinfrared pulses

Abstract

We report an experimental and numerical investigation of third-and fifth-harmonic generation in a CaF 2 crystal with 20 fs (three-optical-cycle), 2 μm driving pulses. The double-peaked temporal profile of the third-harmonic pulse and its propagation dynamics was captured by means of the cross-correlation technique, showing that the third-harmonic pulse naturally consists of free and driven components propagating with different group velocities, and which occur without the splitting of the driving pulse at the fundamental frequency. Relevant characteristics of the harmonics generation process, such as the harmonics spectra, energy oscillations, and conversion efficiency, were measured as functions of propagation length and input-pulse energy and intensity. Our results demonstrate that the fifth harmonic is generated solely via cascaded four-wave mixing between the fundamental and third-harmonic frequency pulses due to cubic nonlinearity, without any detectable contribution of six-wave mixing due to quintic nonlinearity in the process.

Ultrafast mid-infrared high harmonic and supercontinuum generation with n2 characterization in zinc selenide

“…4(a). Using a 5 mm thick single crystal ZnSe sample would not necessarily be a fair comparison to a 5 mm thick poly-ZnSe sample, since generated harmonics in a thicker single crystal ZnSe sample would undergo further pulse splitting due to group velocity mismatch [29]. In our case, the choice of 1 mm was based primarily on availability.…”

Non-perturbative generation of DUV/VUV harmonics from crystal surfaces at 108 MHz repetition rate

“…Based on dynamical Bloch oscillations [4,18], non-perturbative generation of HHG in solids is usually explained by interband and intraband transitions of the electrons inside the band-structure of solids as they interact with the incident laser field as bulk processes [10,11,19]. In some cases, the generation of harmonics is also described as perturbative cascaded three-wave [20] or four-wave mixing [21] processes.…”

Filamentation and Pulse Self-compression in the Anomalous Dispersion Region of Glasses

“…As shown in Fig. 4, third harmonic generation is clearly observed before the onset of spectral broadening and supercontinuum generation, in the transient regime of supercontinuum generation [5,13]. Typically, the third harmonic radiation was detected with half the lowest pulse energies indicated in Fig.…”

“…The development of near and mid-infrared laser sources also led to new investigations on the fundamentals of filamentation in transparent solids. Several publications in this area during the last last two years [27,15,5,6,7,13,20,14] uncovered filamentation physics specific to the anomalous dispersion regime and clarified the links between pioneering results [21,18,25].…”