Phase-matching spectral phase measurement and domain period reconstruction of aperiodic quasi-phase matched gratings by nonlinear spectral interferometry

Chia-Lun Tsai,Shang-Da Yang,Dong-Yi Wu,Ming-Chi Chen,Jui-Yu Lai

doi:10.1364/oe.21.011763

Abstract

We experimentally measured the phase-matching spectral phases of aperiodic quasi-phase matched gratings for the first time (to the best of our knowledge) by nonlinear spectral interferometry. The retrieved information is useful in determining the temporal shape of the nonlinearly converted ultrafast signal and reconstructing the slowly-varying domain period distribution. The method is nondestructive, fast, sensitive, accurate, and applicable to different nonlinear materials. Compared to taking microscopic images of the etched crystal surface, our method can directly measure the domain period distribution in the crystal interior and is free of the artificial random duty period error due to image concatenation.

Highlights

Designs and applications of aperiodic quasi-phase matched (QPM) gratings have been intensively explored during the past two decades [1,2,3,4,5,6,7]
In addition to the enormous time and effort required in sample preparation, image taking, and signal processing, this method suffers from errors due to image concatenation and non-uniformly poled cross-section that could be substantial for short-period or thick QPM gratings (Fig. 1)
We propose a scheme based on nonlinear spectral interferometry (NLSI) to measure the phase of H(Ω) and reconstruct the domain period function Λ(x)

Summary

Introduction

Designs and applications of aperiodic quasi-phase matched (QPM) gratings have been intensively explored during the past two decades [1,2,3,4,5,6,7]. In addition to the enormous time and effort required in sample preparation, image taking, and signal processing, this method suffers from errors due to image concatenation (artificial random duty period error) and non-uniformly poled cross-section that could be substantial for short-period or thick QPM gratings (Fig. 1). The functions of H(Ω) and Λ(x) of aperiodically poled MgO-doped lithium niobate (A-PPMgLN) samples were experimentally measured by NLSI and microscopic images (of the HF-etched surfaces), respectively. They were analyzed and compared with those defined by the lithographic masks. NLSI is nondestructive, fast, sensitive, accurate, and applicable to different nonlinear materials It is free of the artificial random duty period error, and can directly measure the domain period distribution in the crystal interior (where optical beam normally accesses)

Theory

Experimental results

Conclusions