Laser system delivering ultra-short pulses along multiple beam delivery paths

A method of modifying a substrate, the method comprising:

• generating a laser beam comprising ultra-short pulses;
• splitting the laser beam between a first beam delivery path and a second beam delivery path;
• focusing the laser beam from each of the first beam delivery path and the second beam delivery path to a focal point on a predefined plane within the substrate, the first beam delivery path intersecting the predefined plane at a first angle, and the second beam delivery path intersecting the predefined plane at a second angle, wherein a first pulse from the first beam delivery path and a second pulse from the second beam delivery path are coincident at the focal point, the focal point being on a specific layer of the substrate;
• and
• creating a multiphoton non-linear excitation at the focal point.

A laser system comprising:

• a laser source generating a laser beam comprising femtosecond pulses;
• a laser delivery assembly optically coupled to the laser source to receive the laser beam, the laser delivery assembly comprising:
• a beam splitter configured to split the laser beam between a first beam delivery path and a second beam delivery path;
• a first focusing lens optically coupled to the beam splitter and positioned within the first beam delivery path, the first focusing lens configured to focus the laser beam from the first beam delivery path to a focal point on a predefined plane;
• a second focusing lens optically coupled to the beam splitter and positioned within the second beam delivery path, the second focusing lens configured to focus the laser beam from the second beam delivery path to the focal point on the predefined plane;
• wherein the first beam delivery path intersects the predefined plane at a first angle, the second beam delivery path intersects the predefined plane at a second angle, and a first pulse from the first beam delivery path and a second pulse from the second beam delivery path are coincident at the focal point to enable creation of a multiphoton non-linear excitation at the focal point, the focal point being on a specific layer of a target substrate.