New strategy for direct laser writing of low loss waveguide

Abstract

Two geometries are usually considered for direct laser writing of waveguide in glass that differ mainly from the way the sample is translated in regard to the laser beam propagation direction, namely transversely or longitudinally. In this contribution we report on waveguide of multi-core type composed of positive refractive index channel aligned on a hexagonal lattice and written using an alternative method. Every channel is obtained by stacking voxels of refractive index variation obtained by femtosecond laser pulse burst in a static position. The dimension of the core is determined by the number of channels and its refractive index contrast with the cladding is controlled by the laser burst duration. Therefore all the characteristics of the waveguide can be fully and independently accessed through simple experimental parameters. We apply this technique to waveguide writing in chalcogenide glass and show that the propagation loss can be reduced down to 0.11 dB/cm. Moreover repeated measurements during 18 month of this loss demonstrate the temporal stability of this value.