Subcycle Nonlinear Response of Doped 4H Silicon Carbide Revealed by Two-Dimensional Terahertz Spectroscopy

Abstract

We investigate single-cycle terahertz (THz) field-induced nonlinear absorption in doped silicon carbide. We find that the nonlinear response is ultrafast, and we observe up to 20% reduction of transmission of single THz pulses at peak field strengths of 280 kV/cm. We model the field and temperature dependence of the nonlinear response by finite-difference time-domain simulation that incorporates the temporally nonlocal nonlinear conductivity of the silicon carbide. Nonlinear two-dimensional THz spectroscopy reveals that the nonlinear absorption has an ultrafast sub-picosecond recovery time, with contributions from both sumfrequency generation and four-wave mixing, in the form of a photon-echo signal. The ultrafast nonlinearity with its equally fast recovery time makes silicon carbide an interesting candidate material for extremely fast nonlinear THz modulators.

Terahertz Spectroscopy of Emerging Materials

“…With their impressive bandwidth (∼0.2−10+ THz) and high field strengths, 2,14,15 these organic crystals have enabled a wide variety of new THz measurements, such as 2D THz spectroscopy (i.e., THz-pump THz-probe). 16 In contrast with the aforementioned methods, they often must be pumped in the near-infrared (1200−1700 nm) and have questionable reliability.…”

“…For example, recent work by Tarekegne et al studied THz nonlinearity in 4H-SiC using 2D THz spectroscopy (i.e., THzpump, THz-probe), which is a state-of-the-art technique analogous to 2D-IR spectroscopy that may have applications in studying other emerging materials. 16 The insights provided by THz measurements provide mechanistic information that is unobtainable using other methodologies. In addition, the contact-free nature of the technique and the flexibility in sample geometry make this technique especially useful for emerging materials.…”

“…The current state-of-the-art in OR (and EOS) is the use of organic crystals such as DAST (4- N , N -dimethylamino-4′- N ′-methyl-stilbazolium tosylate) and DSTMS (4- N , N -dimethylamino-4′- N ′-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate). With their impressive bandwidth (∼0.2–10+ THz) and high field strengths, ,, these organic crystals have enabled a wide variety of new THz measurements, such as 2D THz spectroscopy (i.e., THz-pump THz-probe) . In contrast with the aforementioned methods, they often must be pumped in the near-infrared (1200–1700 nm) and have questionable reliability.…”

“…Over the past few decades, THz spectroscopy has matured into a technique that is accessible to new users, yet it is still making improvements at the cutting edge of THz science. For example, recent work by Tarekegne et al studied THz nonlinearity in 4H-SiC using 2D THz spectroscopy (i.e., THz-pump, THz-probe), which is a state-of-the-art technique analogous to 2D-IR spectroscopy that may have applications in studying other emerging materials . The insights provided by THz measurements provide mechanistic information that is unobtainable using other methodologies.…”

2D-Raman-THz spectroscopy with single-shot THz detection

“…9,14-16 2D-THz spectroscopy, with all laser pulse in the THz range, has so far been restricted to solids as well as gases. [17][18][19][20][21][22][23][24][25] In any case, these THz multidimensional methods are time-domain techniques, and their implementation requires multiple mechanical delay stages to time the various laser pulses. Since very many time-points need to be collected to acquire a 2D data set, the total acquisition time can be very long, days up to weeks, 7,[14][15][16]18,26 which severely limits the applicability of the method.…”