Applications

Highly focused ultrashort pulses enable volume modification of transparent materials, such as glass, sapphire, and other crystals. The robust control of laser parameters and precise intra-volume positioning of laser focal spot allows inscription of complex structures like Bragg gratings and waveguides.

The process is typically driven by multiphoton absorption, which requires high intensities so that the material is modified only at the focal spot. The laser-induced material volume modification impacts the density of the material and, subsequently, the refractive index. This is a key principle utilized in the creation of fiber Bragg gratings (FBGs) as alternating structures are written into the transparent material by inducing refractive index change rather than optically damaging the fiber. FBGs have been demonstrated in both single-mode and dual-cladding fibers.

Furthermore, the modified material can be chemically etched away. This two-step process is called selective laser etching. After volume modification, the glass or sapphire gains different etching properties. Thus, using material-dependent etching solutions, various mechanically stable and durable structures, like curved waveguides or even 3D forms, are obtained.

PHAROS and CARBIDE femtosecond lasers are widely used for all of the aforementioned volume modification applications, making a strong impact in the development of future technologies.