Evaluation of polarized terahertz waves generated by Cherenkov phase matching

Abstract

We report terahertz (THz) wave generation by satisfying Cherenkov phase-matching condition in both s and p polarizations. A dual-wavelength optical parametric oscillator is constructed from two potassium titanium oxide phosphate crystals pumped by a frequency-doubled Nd:YAG laser. By rotating the orientation of both a lithium niobate crystal (LiNbO3) and the polarization of the pump waves, the polarization of the THz wave changes. Due to the difference in the refractive index and absorption, the output power for p polarization is one tenth that for s polarization. A tuning range from 0.2 to 6.5 THz is obtained for s polarization, and from 0.2 to 4.2 and 5.4 to 6.9 THz for p polarization. The extraction efficiency is improved by changing the angle of prism for p polarization, and a large phase change occurs at total internal reflection. Consequently, p-polarized THz waves are optimal for spectroscopic applications.

Phase-Matching in Nonlinear Crystal-Based Monochromatic Terahertz-Wave Generation

“…This kind of PM has been demonstrated in ferroelectric LiNbO 3 [13,[110][111][112][113] and in organic DAST [114] crystals. Theoretical models based on the analytical solution via spatial Fourier expansion [18] and coupled wave equations via the split-step method [115] have been reported.…”

Investigation of Terahertz Generation from Bulk and Periodically Poled LiTaO3Crystal with a Cherenkov Phase Matching Scheme

“…Difference frequency generation (DFG) with two closely spaced laser frequencies ω 1 and ω 2 in second-order nonlinear optics crystals is one of the promising processes for efficient monochromatic THz wave output in the wide frequency tuning range and for room temperature operation [5,6]. Recently, high-efficiency THz wave generation based on DFG employing Cherenkov phase matching has been intensively researched [7][8][9]. THz wave generation with Cherenkov phase matching is an attractive scheme because strong THz absorption originated from lattice vibration modes of the nonlinear optical crystal can be overcome.…”

Behavior of three waves in Cherenkov phase matched monochromatic terahertz wave generation investigated by numerical analysis

“…[1][2][3][4][5][6][7][8][9] Cherenkov phase matching is a promising method for efficient THz-wave generation for monochromatic or ultra-short pulse sources. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Cherenkov phase matched THz-wave is generated as surface emission, results in strong absorption of nonlinear crystal for THzwave is minimized and high conversion efficiency is obtained. Previous studies have reported an energy conversion efficiency of 10 ¹5 % under weak pumping using the waveguide structure of a nonlinear crystal.…”