THz generation using a reflective stair-step echelon

TL;DR

This paper introduces a new reflective stair-step echelon method for efficient THz generation in lithium niobate, achieving high field strengths and conversion efficiency with easier setup compared to traditional gratings.

Contribution

The novel reflective stair-step echelon enables discretely tilted pulse fronts with reduced angular dispersion, improving THz generation efficiency and setup simplicity.

Findings

Achieved THz pulses with up to 500 kV/cm field strength.

Produced THz pulse energies up to 3.1 μJ.

Conversion efficiency reached 0.33%.

Abstract

We present a novel method for THz generation in lithium niobate using a reflective stair-step echelon structure. The echelon produces a discretely tilted pulse front with less angular dispersion compared to a high groove-density grating. The THz output was characterized using both a 1-lens and 3-lens imaging system to set the tilt angle at room and cryogenic temperatures. Using broadband 800 nm pulses with a pulse energy of 0.95 mJ and a pulse duration of 70 fs (24 nm FWHM bandwidth, 39 fs transform limited width), we produced THz pulses with field strengths as high as 500 kV/cm and pulse energies as high as 3.1 $\mu$J. The highest conversion efficiency we obtained was 0.33%. In addition, we find that the echelon is easily implemented into an experimental setup for quick alignment and optimization.