Comparative study of the frequency-doubling performance on ring and linear cavity at short wavelength region

Wenhai Yang,Yaohui Zheng,Yajun Wang,Huadong Lu

doi:10.1364/oe.23.019624

Abstract

We theoretically and experimentally perform a comparative study on performance of the linear standing-wave cavity and ring cavity for external cavity frequency doubling at the wavelength from 795 nm to 397.5 nm. The two cavities show obvious differences of the thermal effect of nonlinear crystal, cavity sensitivity, and maximum output power. The results show that ring cavity as the external enhancement cavity is a better choice than standing-wave cavity at short wavelength region. At last, a 397.5 nm violet laser with 408 mW corresponding to an input power of 992 mW is obtained by using the ring cavity, considering the original mode-matching efficiency of 98% between the 795 nm laser and frequency doubling cavity, the conversion efficiency is 41.9%.

Highlights

Generating the squeezed state resonant on the atomic transition line is a critical task for quantum information and for ultraprecise measurement of atomic spins [1, 2]
By comparing the thermal effect of the nonlinear crystal, resonant cavity sensitivity, and maximum output power of the two cavities, we find that ring cavity (RC) is a better choice than standing-wave cavity (SWC) to obtain a high power and good beam quality second-harmonic generator (SHG) beam at the short wavelength region
We have theoretically and experimentally compared performance of linear standing-wave cavity and ring cavity for external cavity frequency doubling at the wavelength from 795 nm to 397.5 nm

Summary

Introduction

Generating the squeezed state resonant on the atomic transition line is a critical task for quantum information and for ultraprecise measurement of atomic spins [1, 2]. The wavelength of 397.5 nm is at the cut-off wavelength of many non-linear optical crystals (i.e the most popular crystal, periodically poled potassium titanyle phosphate PPKTP) along with high absorption coefficient, which induces severe thermal effect and grey tracking, when it is used for second-harmonic generator (SHG) at higher power density level [9, 13]. It faces the challenge of obtaining enough output power. A 397.5 nm violet laser of 408 mW with an input power of 992 mW is obtained by using the RC, considering the mode-matching efficiency of 98% between the 795 nm laser and frequency doubling cavity, the conversion efficiency is 41.9%

Experimental setup

Comparison of thermal effect

Comparison of resonator sensitivity

Comparison of maximum output power

Findings

Conclusion