High-harmonic generation of mid-IR pulses in simple liquids

An investigation of harmonic generation in liquid media with a mid-infrared laser

“…It is well known that the proximity of an electronic resonance [4] can enhance HG in atomic vapors. In addition to this results presented in [3] on a liquid suggest that a vibrational resonance may also offer significant enhancement. Perturbative harmonic generation is described in terms of nonlinear polarization [5].…”

“…While a large fraction of experiments are carried out in noble gas vapors, other media have attracted researchers. For instance, harmonic generation up to the 9th harmonic order (H9) of the fundamental was observed from a 1060 nm laser in sodium [1] vapors and up to H7 of a MIR laser was observed in semiconductor ZnSe [2] as well as liquid chloroform [3]. It is well known that the proximity of an electronic resonance [4] can enhance HG in atomic vapors.…”

“…The purpose of this work is to address these questions in liquids at the longest MIR wavelength available in our laboratory, 3.66 µm. In this paper we discuss liquid H 2 O and D 2 O because they are relatively simple fluids with equivalent electronic, but different nuclear structures, thus allowing an assessment of the role of vibrational resonances [3].…”

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

“…To this end, generation of third, fifth [26][27][28], and seventh [29] harmonics by filamentation of midinfrared laser pulses in air was recently experimentally observed. Generation of low-order odd harmonics was also reported under various experimental settings in semiconductors [30], and in liquid [31,32] and solid-state [15,16,33] dielectric media.…”

Ultrafast and Nonlinear Spectroscopy of Solids with Small Energy Photons

“…Up to the maximum MIR intensity using the picosecond pulses, the second, third, and fourth harmonics are measured to have quadratic, cubic, and quartic dependence with the MIR intensity, respectively. While third and higher harmonics have been observed from solid surfaces, 43,44) and MIR harmonics have been observed in gases 45) and liquids, 46) we observed multiple (up to fifth harmonic) MIR harmonics in bulk semiconductors. With higher MIR intensity (~ 10 11 W/cm 2 ) using shorter (~ 200 fs) pulses at ~ 3.9 µm, we also observed an interesting broadening of the spectrum (in excess of the transform limited bandwidth) of MIR harmonics.…”