Enhancement of Intracavity-Pumped Terahertz Parametric Oscillator Power by Adopting Diode-Side Pumped Configuration Based on KTiOPO4 Crystal

Zengguang Qin,Na Ming,Feilong Gao,Zhenhua Cong,Xingyu Zhang,Jinjin Xu,Zecheng Wang,Zhaojun Liu,Xiaohan Chen,Peng Wang

doi:10.3390/cryst9120666

Abstract

In this paper, a KTiOPO4 (KTP) crystal is used as the nonlinear medium in an intracavity-pumped terahertz parametric oscillator (TPO) based on stimulated polariton scattering (SPS). Almost all the reported intracavity SPS sources adopt the diode-end pumped configuration, and the THz output power is limited by the serious thermal effect and small fundamental beam size. For improving the THz output power, we propose diode-side pumping for the laser medium to get a higher fundamental power and a larger fundamental beam size. A convex–plane fundamental laser resonator is used to further offset the thermal effect and increase the fundamental beam size. The THz frequency of the intracavity-pumped KTP terahertz parametric oscillator can be discontinuously tuned from 3.19 THz to 5.94 THz with three gaps. The fundamental beam diameter in the KTP crystal is about 1.3 mm. The maximum average THz power is 166 μW at 5.74 THz under a pulse repetition frequency (PRF) of 6 kHz and a diode pump power of 98 W. By means of the diode-side pumped configuration, the maximum THz output power is more than two-fold higher compared to the diode-end pumped configuration reported using the KTP crystal.

Highlights

KiTiOPO4 (KTP) is an outstanding optical nonlinear medium
TPOa with configuration were were The investigated under a diode power of 80 KTP
A KTP crystal was used as the nonlinear medium in an intracavity stimulated polariton scattering (SPS) source

Summary

Introduction

KiTiOPO4 (KTP) is an outstanding optical nonlinear medium. It has many excellent properties such as a large nonlinear coefficient (d33 = 15.4 pm/V) [1], high optical damage threshold The KTP crystal is used as a nonlinear medium to extend the wavelength range of a practical laser source. Spectral range is large, the SPS process must obey the non-collinear phase matching condition This is is the the first time that a nonlinear medium different from the traditional crystal. The crystal is used as the nonlinear medium in intracavity-pumped diode-to-THz conversion efficiencies. In the diode-end pumped configuration, the diode power and the intracavity fundamental are limited by the by thermal fracture of the laser [28]. The fundamental cavity was designed as a laser medium to enhance the THz output power. The maximum THz output than two-fold higher compared to that obtained in the intracavity-pumped SPS laser using a KTP crystal with diode-end pumped configuration

Experimental Set-Up

Results and Discussion

Input–output

Conclusions