Powerful Broadband Intra-Oscillator THz Generation Inside a Kerr-Lens Mode-Locked Diode-Pumped Laser Cavity

Powerful broadband THz sources have proven to be a promising tool for time-domain spectroscopy and imaging since a decade. Many efforts have been undertaken to push the limit of this technology towards higher THz average powers and broader spectral bandwidths. A popular way for powerful broadband THz generation is optical rectification (OR) of ultrafast near-infrared pulses in nonlinear crystals. However, as OR is a relatively low efficiency process, powerful and complex driving laser systems are typically required. For example, Meyer et al . demonstrated a milliwatt-class broadband THz source using a powerful 112-W sub-100-fs nonlinearly-compressed thin-disk laser oscillator [1] . Although the THz power level of this source is very promising, the complexity and the size of the system might be a limiting factor for many applications. A simpler and more compact alternative is driving OR directly inside the cavity of a standard ultrafast bulk laser oscillator. This way, the THz generation benefits from the high-power levels directly available inside the laser oscillator cavity. While the first intra-oscillator THz generation via OR has already been demonstrated a decade ago [2] , the potential of this technique for high average THz power with a broad spectrum has not yet been exploited.