Terahertz Generation from a Spintronic Emitter Pumped by a Two-Optical-Cycle Cr:ZnS Oscillator

Impulsive optical pulses in the terahertz to mid-infrared range are essential for highly sensitive time-domain field resolved molecular spectroscopy, with applications in biomedical sensing [1]. Recently, with nonlinear down-conversion of pulses from Cr:ZnS femtosecond oscillators, the generation of single-cycle pulses spanning between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3-12 ~\mu \mathrm{m}$</tex> was demonstrated [2]. Extending the spectral coverage to longer wavelengths, or even the sub-terahertz regime, would give access to conformational information on large molecules. The common approach of terahertz-pulse generation by optical rectification in nonlinear crystals is limited by phonon absorption in the generation crystal. Recently, spintronic emitters (SE) emerged as promising alternatives to generate clean single-cycle terahertz pulses, free from phonon absorption [3]. In this study, we examined the performance of a SE pumped by few-optical-cycle 2.3-μm pulses from a Cr:ZnS oscillator.