Patent ID: 9488778
Filing Date: 2016-11-08
CPC Classification: B23K,G02B

Claim Text:
1. A method of fabricating a waveguide in a substrate using a femtosecond laser system, such waveguide having a birefringence axis tilted at a fixed angle for at least a segment, comprising: preparing a substrate in which the waveguide is to be fabricated, the substrate having a free surface upon which a femtosecond pulsed laser beam is configured to impinge; positioning an immersion lens apt to focus the laser beam in the substrate; introducing a first optical element; making the laser beam impinge on the first optical element, which directs the laser beam towards the immersion lens; focusing the femtosecond pulsed laser beam at a given depth inside the substrate, in order to induce a refractive index change in a volume of said substrate around the focus, wherein the laser beam propagates in the substrate along a direction, said focusing including making the laser beam impinge on said-immersion lens in a first position; varying the propagation direction of the laser beam in the substrate, maintaining the beam focused, translating or rotating the first optical element, in order to operate a translation of the laser beam, to modify the impinging position of the laser beam on the immersion lens, in order to reach a first propagation direction forming a first non-zero angle with respect to the normal direction to the free surface of the substrate; translating the laser beam focus with respect to the substrate in order to create a first waveguide segment, defined by adjacent volumes in which the refractive index has been modified, wherein the birefringence axis of the formed first waveguide segment is at said fixed angle, which is a function of the first non-zero angle describing the reached first propagation direction of the laser beam in the substrate.