Velocity matching by pulse front tilting for large area THz-pulse generation

Abstract

We propose a generally applicable velocity matching method for THz-pulse generation by optical rectification in the range below the phonon frequency of the nonlinear material. Velocity matching is based on pulse front tilting of the ultrashort excitation pulse and is able to produce a large area THz beam. Tuning of the THz radiation by changing the tilt angle is experimentally demonstrated for a narrow line in the range between 0.8- 0.97 times the phonon frequency. According to model calculations broadband THz radiation can be generated at lower frequencies. Advantages of the new velocity matching technique in comparison to the electro-optic Cherenkov effect and non-collinear beam mixing are discussed.

High-precision x-ray FEL pulse arrival time measurements at SACLA by a THz streak camera with Xe clusters

“…The THz radiation was generated in a LiNbO 3 crystal via the tilted pulse-front pumping method [24] optimized for a high-energy pump [25,26] outside of the chamber and then introduced into vacuum through a z-cut quartz window. The laser intensity was monitored on a shot-toshot basis to compensate for the change in the THz field's power in the data analysis.…”

Intense ultrashort terahertz pulses: generation and applications

“…Tilted-pulse-front pumping (TPFP) was proposed and demonstrated by Hebling et al in 2002 for efficient phase-matched THz pulse generation in LN [82]. In this technique, the THz radiation generated by the tilted pulse front of the pump propagates perpendicularly to this front ( Figure 6) with the THz phase…”

FLASH free-electron laser single-shot temporal diagnostic: terahertz-field-driven streaking

“…If the laser pulse has a duration of less than 1 ps, the result will be a single-cycle electromagnetic pulse with frequency contents in the terahertz range. To achieve an efficient THz generation process, the phase matching was optimized by a tilted pulse front of the driving pump-probe laser pulse as described by Hebling et al (2002). We used a setup that consists of a diffractive grating (2000 grooves mm À1 ) and 4f two lenses telescope L 1 ( f = 150 mm) and L 2 (f = 75 mm) to image the laser pulse onto the nonlinear crystal, providing the required pulse front tilt.…”