Intracavity THz Generation Using a Thin Lithium Niobate Plate in a Compact Kerr-Lens Mode-Locked Yb:CALGO Bulk Oscillator

Abstract We demonstrate intracavity terahertz (THz) generation via optical rectification in a 50-µm-thick lithium niobate crystal placed inside a compact diode-pumped Kerr-lens mode-locked (KLM) Yb:CALGO bulk oscillator. The oscillator operates at a repetition rate of 85 MHz and delivers 83-fs pulses with up to 71 W of average intracavity power, obtained with only 21.4 W of low-cost multimode diode pump power. We generate single-cycle THz pulses with a spectrum extending up to 3 THz, detected by electro-optic sampling with 60-dB dynamic range within 156 s of measurement time (313 averaged traces) and up to 120 µW of THz average power. This work combines the high damage threshold, power-handling capability, and cost-effectiveness of thin-LN plates with simplicity, compactness, and low-cost multimode diode-pumped solid-state bulk lasers, offering an attractive alternative for high-repetition-rate THz time-domain spectroscopy systems.