Abstract

High-power, phase-stable, single-cycle THz pulsed sources driven by near-infrared (NIR) ultrafast lasers are ubiquitous tools in scientific research and industrial applications fields. One of the most common methods to generate few-cycle, phase-stable THz light is by optical rectification (OR) in χ⁽²⁾ crystals. To scale OR to high average driving power, usually several compromises need to be met between conversion efficiency, bandwidth, velocity matching, nonlinear absorption, thermal damage and finally cost and complexity. THz generation inside a high-power modelocked laser can provide an elegant alternative to these problems combining high-efficiency and high-power, by making use of intracavity enhancement. Several attempts have been made in the past to enhance the driving power by passive enhancement [1] or intracavity of low-power lasers [2,3]. However, so far, this method remained only demonstrated at power levels where the use of intracavity enhancement was questionable in terms of advantage compared with extracavity performance. Here, we demonstrate for the first time OR inside a high-power thin-disk laser (TDL), generating record high THz average power for an intracavity scheme of 1.2 mW (driven intracavity at 183 W 218 fs pulses). This is achieved using cost-efficient thin LN (~50 µm) which enabled us to do intracavity pumping with minimized nonlinear losses, thermal effects, and no need for intracavity velocity matching schemes.

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