Abstract-On the effect of third-order dispersion on phase-matched terahertz generation via interfering chirped pulses

Spencer W. Jolly, Frederike Ahr, Koustuban Ravi, Nicholas H. Matlis, Franz X. Kärtner, and Andreas R. Maier

Chirp-and-delay experimental setup (a), identical to the previous work in Ahr et al. [18]. This HR-PR combination produces a train of pulses rather than two pulses of equal energy. A waveplate is used to match perfectly the polarization of the IR light to the PPLN crystal axis. The beam is matched to the aperture of the PPLN crystal using a telescope, the parameters of which depend on the PPLN aperture. A Teflon plate separates the drive laser from the generated THz at the output of the crystal, whose energy is detector using a pyroelectric detector (b). The frequency of the generated THz is verified using an interferometer (c).

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-27-24-34769

High-energy narrowband terahertz (THz) pulses, relevant for a plethora of applications, can be created from the interference of two chirped-pulse drive lasers. The presence of third order dispersion, an intrinsic feature of many high-energy drive lasers, however, can significantly reduce the optical-to-THz conversion efficiency and have other undesired effects. Here, we present a detailed description of the effect of third-order dispersion (TOD) in the pump pulse on the generation of THz radiation via phase-matching of broadband highly chirped pulse trains. Although the analysis is general, we focus specifically on parameters typical to a Ti:Sapphire chirped-pulse amplification laser system for quasi-phase-matching in periodically-poled lithium niobate (PPLN) in the range of THz frequencies around 0.5 THz. Our analysis provides the tools to optimize the THz generation process for applications requiring high energy and to control it to produce desired THz waveforms in a variety of scenarios.

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