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.

From near-UV to long-wave infrared waveguides inscribed in barium fluoride using a femtosecond laser.

Depressed-cladding waveguides (DCWs) of various sizes were inscribed in barium fluoride, allowing single-mode operation in the entirety of its transmission window (=0.2-12µ). Using femtosecond laser pulses at 515 nm, type I laser modified tracks were overlapped to form circular waveguides, whose cross-sectional geometry and numerical aperture were tailored to accommodate 0.