Terahertz Wave Difference Frequency Generation Research Articles

Wavelength Dependence of Output Energy in Terahertz Wave Difference Frequency Generation Pumped by a Tunable Dual-KTiOPO$_{4}$ Optical Parametric Oscillator Source

Wavelength Dependence of Output Energy in Terahertz Wave Difference Frequency Generation Pumped by a Tunable Dual-KTiOPO$_{4}$ Optical Parametric Oscillator Source

Self-Raman Nd-doped vanadate laser: a pump source of organic crystal based difference frequency generation

We analyse a method of high repetition rate, efficient terahertz wave difference frequency generation (DFG) by using a self-Raman Nd-doped vanadate laser to pump 4’-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST). A semi-analytical model is introduced that combines the rate equations (for the self-Raman dual-wavelength laser) and the coupled-wave equations (for the DAST-based DFG). Calculations were performed on a diffusion-bonded Nd:YVO4-YVO4 laser with an acousto-optic Q-switch. Parameters (including transmittances at output mirror and crystal lengths) were optimized to obtain high output. Sub-milliwatt average power is predicted under current pump condition.

Tunable terahertz wave difference frequency generation in a graphene/AlGaAs surface plasmon waveguide

Graphene-based surface plasmon waveguides (SPWs) show high confinement well beyond the diffraction limit at terahertz frequencies. By combining a graphene SPW and nonlinear material, we propose a novel graphene/AlGaAs SPW structure for terahertz wave difference frequency generation (DFG) under near-infrared pumps. The composite waveguide, which supports single-mode operation at terahertz frequencies and guides two pumps by a high-index-contrast AlGaAs/AlOx structure, can confine terahertz waves tightly and realize good mode field overlap of three waves. The phase-matching condition is satisfied via artificial birefringence in an AlGaAs/AlOx waveguide together with the tunability of graphene, and the phase-matching terahertz wave frequency varies from 4 to 7 THz when the Fermi energy level of graphene changes from 0.848 to 2.456 eV. Based on the coupled-mode theory, we investigate the power-normalized conversion efficiency for the tunable terahertz wave DFG process by using the finite difference method under continuous wave pumps, where the tunable bandwidth can reach 2 THz with considerable conversion efficiency. To exploit the high peak powers of pulses, we also discuss optical pulse evolutions for pulse-pumped terahertz wave DFG processes.

Analysis of the effect of phase-mismatch and material absorption on the terahertz-wave generation from GaSe

We analyzed the effect of phase-mismatch and material absorption on the terahertz-wave difference-frequency generation from GaSe theoretically. We calculated the best length of crystal and the corresponding terahertz power under four different conditions and the effect of angle-mismatch on phase-mismatch. The result provided a theoretical basis and reference to nonlinear optical difference-frequency experiments.

Enhancement of terahertz wave difference frequency generation based on a compact walk-off compensated KTP OPO

A compact, walk-off compensated dual-wavelength KTP OPO near the degenerate point of 2.128 μm pumped by a Nd:YAG pulsed laser is employed as the pump for terahertz (THz) source based on difference frequency generation (DFG) in a GaSe crystal. Coherent THz radiation that is continuously tunable in the range of 81–1617 μm (0.186–3.7 THz) is achieved. An enhancement of 76.7% in average for the THz energies at different wavelengths is realized using the walk-off compensated KTP OPO than the common one. Using a 8 mm-long GaSe crystal, the maximum output THz pulse energy is 48.9 nJ with the peak power of 11 W, corresponding to the energy conversion efficiency of 5.4 × 10 − 6 and the photon conversion efficiency of about 0.09%.