Simultaneous Generation of Two Pairs of Stokes and Terahertz Waves from Coupled Optical Parametric Oscillations with Quasi-Phase-Matching

Zhongyang Li,Yongjun Li,Lian Tan,Sheng Yuan,Pibin Bing,Silei Wang,Bin Yuan,Mengtao Wang

doi:10.3390/cryst8080323

Abstract

We present a theoretical investigation on simultaneous generation of two pairs of Stokes and terahertz (THz) waves from coupled optical parametric oscillations (OPOs) with a quasi-phase-matching (QPM) scheme. The two pairs of Stokes and THz waves are generated by stimulated polariton scattering (SPS) from periodically-inverted GaP. By analyzing the QPM conditions of coupled OPOs we find that the two THz waves with any frequency below the transverse optical (TO) mode frequency of GaP can be simultaneously generated with a suitable pump wavelength. We calculate the photon flux densities of the two THz waves by solving the coupled wave equations. The calculation results indicate that the two THz waves can be efficiently generated with high pump intensities, particularly in lower THz frequency band.

Highlights

In recent years, it has been demonstrated that coupled optical parametric oscillations (OPOs) can simultaneously generate two pairs of signal and idler waves from periodically-inverted KTiOPO4(KTP) plates by a single pump wavelength [1,2]
From the figure we find that two pairs of Stokes and THz waves can be generated by coupled OPOs with a single pump wave
From the figure we find that αT monotonously increases with frequencies, and de f f smoothly decreases first and rapidly increases. de f f is smaller than 70.6 pm/V below the transverse optical (TO) mode frequency of GaP due to the cancellation of ionic and electronic contributions

Summary

Introduction

It has been demonstrated that coupled optical parametric oscillations (OPOs) can simultaneously generate two pairs of signal and idler waves from periodically-inverted KTiOPO4. The wavelengths for each pair of signal and idler waves satisfy quasi-phase-matching (QPM) conditions. Based on the research above, we consider that the frequencies of the two idler waves generated from coupled OPOs with periodically-inverted GaP by stimulated polariton scattering (SPS) can extend to terahertz (THz) frequencies. GaP which has an infrared- and Raman-active transverse optical (TO) mode with frequency of 367 cm−1 is an attractive material for THz wave generation via SPS [15] since GaP has a high second-order nonlinear coefficient (d36 = 70.6 pm/V at 1064 nm) [16] and a low THz wave absorption coefficient below TO mode frequency [15]. We theoretically study simultaneous generation of two pairs of Stokes and THz waves from coupled OPOs with periodically-inverted GaP by SPS. We calculate the photon flux densities of the two THz waves by solving the coupled wave equations

Phase-Matching Characteristics

THz Wave Photon Flux Density

Conclusions