A Versatile Two-Dimensional Terahertz Spectroscopy Platform with Dual Independently Controlled Intense Pulses

We present a two-dimensional terahertz (2D THz) spectroscopy platform employing dual high-intensity THz sources generated in separate LiNbO3 crystals via the tilted-pulse-front technique. An integrated periscope beam combiner enables efficient combination of the two THz beams and precise overlap at both the sample and detection positions. The platform provides independent control over the polarization, spectrum, and intensity of each THz pulse, thereby increasing experimental flexibility. To demonstrate the instrument's performance, we investigate nonlinear wave-mixing in silicon under dual-frequency excitation. Polarization-dependent nonlinear signals up to the eleventh order in a 2D spectrum were resolved at room temperature using this tabletop laser system. These results underscore the capability of the instrument to explore complex material responses at THz frequencies and elucidate underlying nonlinear mechanisms.