Cascaded third-harmonic-generation converter based on a single ADP crystal**Project supported by the National Natural Science Foundation of China (Grant Nos. 61178060, 51202129, and 91022034), the Independent Innovation Foundation of Shandong University, China (Grant No. 2011GN056), and the Natural Science Foundation for Distinguished Young Scholar of Shandong Province, China (Grant No. 2012JQ18).

Abstract

Based on a specially designed optical structure, an efficient cascaded third-harmonic-generation (THG) output of a 1064-nm, pico-seconds pulse laser is successively realized by using an NH4H2PO4 (ADP) crystal that acts as the second-harmonic-generation component and sum-frequency-generation component. The maximum THG output is 1.61 mJ, and the highest conversion efficiency from 1064 nm to 355 nm reaches 35%, which are obviously superior to the results obtained using a KDP crystal under the same circumstance. The further phase-matching analysis indicates that this THG configuration of ADP crystal can be applied to various fundamental wavelengths in a range of 1 μm–1.1 μm. Compared with the previously reported KDP THG converter, which is based on a similar principle, the present ADP THG converter is favorable for large-energy, high-efficiency operation because of the larger effective nonlinear optical coefficient deff and higher laser damage threshold.