中国物理B ›› 2015, Vol. 24 ›› Issue (2): 24216-024216.doi: 10.1088/1674-1056/24/2/024216
• ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS • 上一篇 下一篇
Masoume Mansouri, Mohsen Askarbioki, Saeed Ghavami Sabouri, Alireza Khorsandi
Masoume Mansouri, Mohsen Askarbioki, Saeed Ghavami Sabouri, Alireza Khorsandi
摘要: To reduce the walk-off angle of the extraordinary third-harmonic ultraviolet wave at 355 nm generated by type Ⅱ KTiOPO4 and type I β-BaB2O4 optical crystals, and the Gaussian output beam of a Q-switched Nd:YAG laser, a simple theoretical model was developed based on a rotatable BK7 plate of variable thickness. By rotating the plate up to 35° along the beam direction, we reduced the walk-off angle up to ~ 13%. The same phenomenon is predicted by the model, confirming the performance of the model. It is found that, due to the walk-off effect, the intensity profile of the third-harmonic generation beam is slightly degraded. To compensate for the observed phenomena and further reduce the walk-off, we used a combination of a convex lens and an axicon to transform the beam profile of the interacting fundamental and second-harmonic generation waves to the zero-order Bessel-Gaussian form. As a result, the walk-off is decreased to ~ 48.81 mrad, providing ~ 30% relative reduction. By using the same BK7 plate rotated up to 35° along the third-harmonic beam direction, the walk-off angle is further reduced to 38.9 mrad. Moreover, it is observed that the beam profile of the emerged Bessel-Gaussian third-harmonic generation beam remains unchanged with no degradation.
中图分类号: (Nonlinear optics)