Effectively this is a way of producing optical waveguides by using lasers to adjust optical properties of glass blocks. It uses less energy than previous methods to achieve similar or better results (speed, focus).

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Such a method could be used to write continuous light-guiding waveguide patterns connecting any two points within a continuous block of a suitable material, or make other optical devices, such as Bragg gratings

https://en.m.wikipedia.org/wiki/Fiber_Bragg_grating

While the mechanism of the interaction of the glass with the fs-laser is not clear, it is believed that because of the shortness of the pulse duration, the excited photo-electrons cannot thermally relax since the pulse duration is shorter than the lattice thermalization time. With high enough intensities and the inability for the electrons to relax, one can build up a relatively high electron density. It is sufficiently high to be considered a plasma. (A plasma is a collection of electrons essentially acting as a free electron gas). How the structure is permanently changed as a result of this is not known.

The invention can also be used to make interferometers or phased arrays. Also, integrated optical waveguide devices in a single glass body which utilizes multiple optical waveguide structures and paths integrated and combined together to manipulate and operate on light transmitted through the glass, such as performing a function of an inputted optical waveguide channel and an integrated optical waveguide devices which separates/combines optical waveguide channels based on wavelengths, can be made.