Application of Multipass Cell Compression to Achieve High Repetition Rate Lithium Niobate Terahertz Sources With Broadened Bandwidth

Abstract

The performance of high-repetition-rate (e.g., MHz) 1030-nm-pumped lithium niobate (LiNbO₃) terahertz (THz) source is significantly influenced by pulse duration, intensity, and pump wavelength. In this study, we present the application of single-stage multipass cell (MPC) compression technology to compress 1030 nm laser pulses from 200 to 49 fs and investigate its impact on THz emission using the tilted pulse front method. The results show that the compressed 49 fs pulses significantly broaden the THz spectral bandwidth, shifting the center frequency from 0.5 to 0.84 THz and extending the cutoff frequency to 4.1 THz. Although shorter pulses have lower conversion efficiency compared with longer pulses (e.g., 200 fs), they generate a broader THz spectrum. This bandwidth improvement addresses the critical limitations of narrow bandwidth and low temporal resolution in current LiNbO₃-based THz scanning tunneling microscopy (THz-STM) systems. By increasing the THz bandwidth, we provide an efficient approach to achieve better temporal resolution and more affluent spectral information in THz-STM systems. This study demonstrates the potential of MPC compression technology to significantly enhance THz bandwidth in LiNbO₃ crystals, paving the way for more accurate material analysis, imaging, and characterization using THz-STM.