Manipulation of terahertz waveforms in nonlinear optical crystals by shaped optical pulses

Generation of arbitrary terahertz wave forms in fanned-out periodically poled lithium niobate

“…A hybrid technique combining the terahertz generation in PPLN with optical pulse shaping is not only adaptive but also has a broad time window. 23 The available bandwidth, however, is less than 0.1 THz.…”

“…We used a 5-mm-long FO-PPLN sample ͑width= 10 mm, height= 0.5 mm͒ continuously tunable from 0.5 to 1.5 THz. 23 A cylindrical lens ͑f =10 cm͒ focused the pump beam ͑0.1 mJ pulse energy͒ into the FO-PPLN crystal with an elliptical beam profile of 3 ϫ 0.3 mm 2 . The optical pump beam generated a spatially dispersed spectrum of terahertz pulses: the bandwidth corresponding to the excited area of the FO-PPLN crystal should be ϳ0.2 THz as the central frequency is 0.67 THz.…”

Generation of Tunable THz Pulses

“…This kind of sequence of ultrashort phase-locked pulses has been used extensively to perform temporal coherent control experiments with optical pulses [3]. It has also been used successfully in the terahertz range to control various processes [15,16,44] (see also section 3.5 for a brief presentation). In these latter experiments, the THz pulse pair was generated from a NIR pulse pair created by a Michelson or a Mach-Zender interferometer.…”

“…On the other hand, interesting examples of tunable narrow-band THz pulses with possibilities of shaping the waveform have also been reported in lithium niobate crystals. For example, Lee et al [16,18,19] employed a single pulse or a pair of temporally separated optical pulses rectified in PPLN crystals with a specially engineered domain structure, generating very narrow THz pulses (bandwidth ∼ 25 GHz) tunable between 0.5 and 2.5 THz. Nevertheless, it requires a new crystal with a specific domain structure for each temporal shape or an adjustment of the crystal position to tune the frequency.…”

Terahertz generation by means of optical lasers

“…(18), engineering of the shapes of THz signals is possible via two different approaches: by spatial or temporal structuring of the pump profile with the necessary C-factor or by engineering of an optimal non-linear grating with the necessary T-function [87]. The first method was realized by arranging spatial masks between the pump beam and a PPLN crystal [176], or using a pair of temporarily separated femtosecond pulses [177]. In these cases the QPM structure was prepared in a fanned-out form available for continuously tunable narrowband THz generation.…”