Terahertz Generation in Lithium Niobate Driven by Ti:Sapphire Laser Pulses and its Limitations

TL;DR

This study explores the efficiency limits of generating terahertz radiation in lithium niobate using Ti:Sapphire laser pulses, identifying key factors that cause saturation and limit scalability.

Contribution

It experimentally investigates the effects of pump wavelength, pulse duration, and fluence on THz generation, revealing fundamental limitations for scaling up the process.

Findings

Achieved 0.12% conversion efficiency with 150 fs pulses.

Observed saturation of efficiency at 15 mJ/cm2 fluence.

Identified spectral broadening and free-carrier absorption as main limitations.

Abstract

We experimentally investigate the limits to 800 nm-to-terahertz (THz) energy conversion in lithium niobate at room temperature driven by amplified Ti:Sapphire laser pulses with tilted-pulse-front. The influence of the pump central wavelength, pulse duration, and fluence on THz generation is studied. We achieved a high peak efficiency of 0.12% using transform limited 150 fs pulses and observed saturation of the optical to THz conversion efficiency at a fluence of 15 mJ/cm2. We experimentally identify two main limitations for the scaling of optical-to-THz conversion efficiencies: (i) the large spectral broadening of the optical pump spectrum in combination with large angular dispersion of the tilted-pulse-front and (ii) free-carrier absorption of THz radiation due to multi-photon absorption of the 800 nm radiation.