Optimization of fs-laser-induced voxels in nonlinear materials via over-correction of spherical aberration.

In this Letter, over-correction of spherical aberration is used to counteract nonlinear effects such as Kerr self-focusing and plasma effects, resulting in more spherical and small-sized femtosecond laser-inscribed voxels within nonlinear materials. By strategically redirecting marginal focusing rays toward the beginning of the laser modification zone, the induced plasma prevents any rays from causing a structural modification beyond this zone, irrespective of any focus elongation caused by nonlinear effects. The method has been effectively validated across a range of materials, including ZnS, ZnSe, BIG, GeS, and SiO.

Compact 3-8 μm supercontinuum generation in a low-loss AsSe step-index fiber.

A mid-infrared supercontinuum source spanning from 3 to 8 μm is demonstrated using a low-loss AsSe commercial step-index fiber. A maximum average output power of 1.5 mW is obtained at a low repetition rate of 2 kHz.