# Simultaneous generation of two THz waves with bulk LiNbO3 and four THz waves with PPLN by coupled optical parametric generation

## TL;DR

This paper theoretically demonstrates the simultaneous generation of multiple THz waves using bulk and periodically poled LiNbO3 through coupled optical parametric generation, highlighting phase matching and efficiency improvements.

## Contribution

It introduces a novel theoretical approach for generating multiple THz waves simultaneously with phase matching in bulk and periodically poled LiNbO3, including efficiency analysis.

## Key findings

- High photon conversion efficiencies for four THz waves.
- Phase mismatch compensation using PPLN grating vectors.
- Effective generation of orthogonally polarized THz waves via stimulated polariton scattering.

## Abstract

We present a theoretical research concerning simultaneous generation of two terahertz (THz) waves with bulk LiNbO3 and four THz waves with periodically poled LiNbO3 (PPLN) by coupled optical parametric generation (COPG). First, we investigate collinear phase matching of COPG generating two orthogonally polarized THz waves with two types of phase matching of o = e + e and o = e + o with bulk LiNbO3. The two orthogonally polarized THz waves are generated from stimulated polariton scattering (SPS) with A1 and E symmetric transverse optical (TO) modes in bulk LiNbO3, respectively. Then, we find that perturbations of phase mismatch for o = e + e and o = e + o can be compensated by a same grating vector of PPLN. As a result, four THz waves are simultaneously generated with a PPLN crystal and a pump laser. We calculate third-order nonlinear optical coefficients of o = e + o generating THz waves from E symmetric TO modes. The intensities of four THz waves are calculated by solving coupled wave equations. The calculation results demonstrate that the COPG generating four THz waves have high photon conversion efficiencies.

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Source: https://tomesphere.com/paper/1904.09701