Intense narrow band terahertz generation via type-II difference-frequency generation in ZnTe using chirped optical pulses

Abstract

We developed a tabletop source of intense, narrow band terahertz pulses via type-II difference-frequency generation in ZnTe crystal using two linearly chirped and orthogonally polarized optical pulses. The pulse energy is in the range of 1-3 nJ depending on the variable pulse duration from 1 to 5 ps. The amplitude of electric field reaches ϳ10 kV/ cm. The central frequency of the spectrum is continuously tunable from 0.3 to 2.5 THz with the bandwidth at 0.2-0.5 THz.

Generation of Tunable THz Pulses

“…To this end, we assume that the NIR pulse is a plane wave in the crystal, so that k ⊥ = 0andG(k ⊥ )=1 in Eq. (8). With these assumptions, it is clear that, apart from the sinc term, this is the power spectrum, i.e.…”

The chirp-control of frequency-tunable narrowband terahertz pulses by nonlinearly chirped laser pulse beating

“…Although this paper only presents the generation of the negatively chirped THz pulses, it is also possible to generate positively chirped THz pulses by using a grating pair with internal lenses. 24 This method is applicable, not only to photomixing in the photoconductive antenna but also to various other THz pulse generation mechanisms, such as the difference-frequency generation in nonlinear crystals, 25 accelerated electrons interacting with laser pulses, 26,27 THz radiation sources with magnetic structures, 28,29 and plasma sources. 30 The generation of narrow-band chirped THz pulses with desirable frequencies, pulse widths, and frequency sweep rates will help to open the way for the realization of the coherent-control of quantum systems in the THz regime, such as the ARP.…”

Analysis and design of efficient passive components for the millimeter-wave and THz bands

“…Furthermore, the laser beams interact along the crystal, this interaction usually required to be of the order several hundred of µm or even mm [257], [309]. Therefore, CW operation is hardly achievable, noting that to ensure phase-matching over this extremely long interaction length, and an acceptable average power results rather challenging [302].…”

“…Although, photomixing scheme usually provides higher average power levels, in [257] and [311] is pointed out that photoconductive antennas are incapable of sustaining the high peak power of strong ps pulses. Furthermore, saturation appears due to their finite capacitance and it is a fact that photoconductive switching drops rapidly beyond 1 THz due to finite carrier relaxation times of the substrate materials (≈ 0.5 ps).…”

“…Other classifications are possible, however, here, sources are spitted in two big groups attending to the origins of the technology used: electronics and optics/photonics. Also, it should be keep in mind that important features that characterize a sources include if it is CW [255] or pulsed [256], narrowband [257] or wide-band [258], coherent [259] or non-coherent [260], tunable [261] or rather fixed [262]. Each kind of application will demand from a specific choice between these features, [110], [166], [172], [247].…”