Almost any application that involves more than one wavelength going through an optical system has same need for color correction. Thus, the common approach is to add more surfaces and balance the optical glass in order to achieve this goal. For some applications, especially when ultrashort laser pulses (pulse durations way below 100fs) are involved, it is quite important to reduce the amount of higher order dispersion in an optical system because it is basically impossible to compensate for them afterwards. Therefore, we pursue a different approach. We present two different specially designed monolithic hybrid optics comprising refraction and diffraction effects for tight spatial and temporal focusing of ultrashort laser pulses. Both aims can be put into practice by having a high numerical aperture (NA=0.5 and 0.7) and low internal dispersion at the same time. The focusing properties of the first example are very promising, due to a design, which provides diffraction limited focusing for 80nm bandwidth at 780nm center wavelength. Thus, pulses with durations as short as 25fs can be focused without pulse front distortion. The outstanding performance of such optics is shown. The approach for the second focusing optics goes even further beyond common designs. It not only combines refraction with diffraction, but also involves total internal reflection for beam shaping and therefore improving focusing quality even further while reducing the spot size. This optics is especially interesting for nonlinear material processing.

Date Published: 16 March 2015
PDF: 7 pages
Proc. SPIE 9353, Laser 3D Manufacturing II, 935307 (16 March 2015); doi: 10.1117/12.2079264

Published in SPIE Proceedings Vol. 9353:
Laser 3D Manufacturing II
Henry Helvajian; Alberto Piqué; Martin Wegener; Bo Gu, Editor(s)