Large-area periodically-poled lithium niobate wafer stacks optimized for high-energy narrowband terahertz generation

• Published in: Optics express 2023-01, Vol.31 (3), p.4041-4054
• Main Authors: Mosley, Connor D W, Lake, Daniel S, Graham, Darren M, Jamison, Steven P, Appleby, Robert B, Burt, Graeme, Hibberd, Morgan T
• Format: Article
• Language: English
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.475604

Periodically-poled lithium niobate (PPLN) sources consisting of custom-built stacks of large-area wafers provide a unique opportunity to systematically study the multi-cycle terahertz (THz) generation mechanism as they are assembled layer-by-layer. Here we investigate and optimize the THz emission from PPLN wafer stacks as a function of wafer number, pump fluence, pulse duration and chirp, wafer separation, and pump focusing. Using 135 µm-thick, 2"-diameter wafers we generate high-energy, narrowband THz pulses with central frequencies up to 0.39 THz, directly suitable for THz-driven particle acceleration applications. We explore the multi-cycle pulse build-up with increasing wafer numbers using electro-optic sampling measurements, achieving THz conversion efficiencies up to 0.17%, while demonstrating unique control over the pulse length and bandwidth these sources offer. Guided by simulations, observed frequency-dependence on both stack-mounting and pump focusing conditions have been attributed to inter-wafer etalon and Gouy phase-shifts respectively, revealing subtle features that are critical to the understanding and performance of PPLN wafer-stack sources for optimal narrowband THz generation.