Laser-induced, second-order optical susceptibilities of YAB:Cr³⁺ single crystals

Abstract

Complex temperature studies of optically stimulated second harmonic generation (SHG) at 1064 nm for pulsed 10 ns Nd:YAG laser radiation under illumination of two coherent laser beams (at 1064 nm and its 532 nm second harmonic) were carried out by means of the Maker fringe method. The bicolour coherent process allowed detection of some additionally induced non-centrosymmetry. The effect was studied at different temperatures and experimental geometries in YAB:Cr³⁺ single crystals. We found that Cr³⁺ ions play a principal role in the observed effects. The output of optically stimulated SHG was generally non-spherical in the sequence profile, contrary to the traditional non-stimulated SHG. Moreover, we also established that the optimal conditions for obtaining SHG corresponded to the fundamental/writing beam intensities ratio 6:1. A specially performed control of the photo-thermal sample heating showed that the increase of temperature did not exceed 1.2 K, which allowed the influence of photo-thermal heating to be neglected. The optimal input–output laser geometry corresponded to s-p polarisation and to the angle of about 32° between the photo-inducing and fundamental beams. Additionally in the studied temperature range (77–295 K) there was observed an enhancement of the output second-order susceptibilities from 0.72 pm/V up to 1.02 pm/V.

Keywords:

• YAB:Cr³⁺ single crystal
• crystal growth
• nonlinear optics, second-order optical susceptibility
• second harmonic generation

Acknowledgements

This research was supported by Polish Ministry of Sciences and Higher Education, Key Project POIG.01.03.01-14-016/08 “New Photonic Materials and their Advanced Applications.”