Efficient generation of Cherenkov-type terahertz radiation from a lithium niobate crystal with a silicon prism output coupler

Abstract

We report on the generation of broadband terahertz (THz) pulses using Cherenkov-type generation in magnesium oxide-doped lithium niobate (MgO:LN). The efficiency of the output coupling process of THz radiation at higher frequencies into free space is considerably increased by the use of a properly cut silicon prism. The achieved spectrum is broader compared to the normal Cherenkov-cut geometry. Due to a considerably reduced propagation length in the absorbing MgO:LN, the effective application of longer crystals is possible. Thus, the measured spectral in tensity is much higher and the spectrum broader

Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers

“…The waveguide lies just below one of the plate surfaces, thus minimizing absorption of the terahertz light within the crystal. We combined, in a non-standard approach, this linear waveguide design with a 45° high resistivity float zone silicon prism, in contact with the upper crystal surface, for efficiently extracting the train of terahertz pulses 26 . Each pulse consists of a single electric field cycle and carries a large spectral content, from 100 GHz up to 6 THz, centred at 1.6 THz (Fig.…”

Terahertz generation by means of optical lasers

“…• ) or a silicon prism [151] were prepared to decrease the losses related to the THz lift-off [152].…”

Recent Advances in Room Temperature, High-Power Terahertz Quantum Cascade Laser Sources Based on Difference-Frequency Generation

“…In a waveguide with a modal phase Photonics 2016, 3, 42 5 of 10 matching scheme, due to a faster frequency-dependent effective index in the THz range with respect to the mid-IR index (n mid-IR ), the modal phase matching is only satisfied within a relatively narrow frequency range for a certain waveguide [25]. In contrast to this narrow-band phase-matching scheme, theČerenkov scheme [26] has been used as an effective broad-band phase matching method for THz generation in the externally-pumped optical rectification or DFG setups [27].Čerenkov nonlinear emission occurs when the nonlinear polarization wave propagates at a higher phase velocity compared to that of the nonlinear radiation, as shown in Figure 4a. For THz DFG in QCLs, the waveguide forČerenkov phase matching scheme can be designed so that the THz refractive index (n THz ) in the QCL substrate is higher than the mid-IR group effective refractive index (n mid-IR ).…”

“…In contrast to this narrow-band phase-matching scheme, the Čerenkov scheme [26] has been used as an effective broad-band phase matching method for THz generation in the externally-pumped optical rectification or DFG setups [27]. Čerenkov nonlinear emission occurs when the nonlinear polarization wave propagates at a higher phase velocity compared to that of the nonlinear radiation, as shown in Figure 4a.…”