Simultaneous production of multiple waveguides for photonic devices by femtosecond laser writing

A novel femtosecond Yb-fiber based amplifier seeded with a cavity-dumped Yb:KYW laser oscillator is employed for the writing of waveguides. The presented results have been achieved with a pulse energy of 1.6 muJ at 420 fs and a repetition rate of 1 MHz. We created simultaneously written waveguide pairs in fused silica with separations varying from 175 mum to 6 mum, using a 20x microscope objective with a numerical aperture of NA = 0.35. When two waveguides are created in close proximity, the guided mode in one of the waveguides couples light through the evanescent field into the other waveguide. By dynamic variation of the phase grating period during the substrate translation, we demonstrated the creation of waveguide coupling devices with single mode guiding for light at 1550 nm.