Dynamic ultrafast laser beam tailoring for multispot photo-inscription of photonic devices in bulk transparent materials

Femtosecond laser processing of bulk transparent materials can generate localized increase of the refractive index. Thus, translation of the laser spot give potential access to three dimensionnal photowriting of waveguiding structures. Increasing the number of machining foci can considerably reduce the processing efforts when complex photonic structures are envisaged such as waveguide arrays. The present report presents a technique of dynamic ultrafast laser beam spatial tailoring for parallel writing of photonic devices. The wavefront of the beam is modulated by a periodical binary (0-pi) phase mask of variable pattern to achieve dynamic multispot operation. The parallel photoinscription of multiple waveguides is demonstrated in fused silica. Using this method, light dividers in three dimensions relying on evanescent coupling are reported and wavelength-division demultiplexing (WDD) devices were achieved in single sample scan.