Broadband Blue Lasers Based on Cascaded Quasi-Phase-Matching OPO-SHG Processes Using Fan-out Periodically-Poled Lithium Tantalate

• Main Authors: Han-Tsung Hsu, 許翰棕
• Other Authors: Lung-Han Peng
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/31596930229801533985

碩士 === 國立臺灣大學 === 光電工程學研究所 === 101 === This thesis is composed of three parts：an introduction of the theory of quasi-phase-matching (QPM) and the principle of the optical parametric oscillator (OPO), the fabrication technique of one-dimensional periodically poled congruent grown lithium tantalite (LiTaO3) for cascade OPO-SHG 465nm blue laser and the measurement and analysis of OPO-SHG blue light generators. First of all, the mechanism of nonlinear frequency conversion and QPM theory, and its application to the optical parametric oscillator and second harmonic generation (SHG) are introduced. By using Sellmeier equation, the QPM period of periodically poled LiTaO3 (PPLT) for the above application is designed. By taking advantage of the nickel-diffusion with high-voltage poling process, cascaded OPO-SHG devices on 0.5mm-thick congruent LiTaO3 substrate is fabricated. For cascaded OPO-SHG PPLT device, a multi-period SHG segment composed of single period, three periods , apodized and fan-out structure design for QPM-SHG is proposed. The period for OPO is 7.7576um, and the period for SHG is 4.9865um with single period；4.9514 um, 4.9865 um, and 5.0218 um with three periods；gradually changing from 4.9164um to 5.0749 um with an apodized structure design and gradualy changing from 4.9024 um to 5.0606 um with a parallel fan-out structure design. With this design, a 20mm-long chipwafer for generating OPO-SHG broadband blue light can be achieved. Using a 1064nm infrared laser with 14ns pulse width as the pump source, a cascaded OPO-SHG chip in a concave laser cavity is shown to generate a 465nm broadband blue laser. Discussing the comparison of the optical measurement between single period, three periods, and apodized structure design for SHG, this work also includes the optical measurement of fan-out structure design . An average output power of 26.8 mW blue light laser has been achieved under a 752 mW input green power, which corresponds to a conversion efficiency of 3.56% . The spectrum is shown to have a 1.9 nm bandwidth and 8.3% slope efficiency.