Fabrication of ultra-low bend loss optical waveguides

We present a novel way to fabricate low bend loss femtosecond-laser written optical waveguides [1] via a two-step process: We first fabricate large-diameter waveguides which are multimode at 1550 nm and exhibit a relatively complex refractive index distribution. In a second step, thermal post-processing [2] results in the selective removal of part of the previously induced refractive index change, leaving behind a very high index contrast waveguide that enables single mode operation in the C-band. We demonstrate that this procedure enables the fabrication of waveguides with unprecedented small bends (down to 16.6 mm radius) [3] with high (80%) normalized throughputs.1 page(s