Microspectroscopy of ultrafast laser inscribed channel waveguides in Yb:tungstate crystals

Abstract

We report microspectroscopy measurements of crystalline channel waveguides fabricated in Yb:KGd (WO4)2 and Yb:KY (WO 4)2 using the ultrafast laser inscription technique. From these measurements we find that densification of the WO2 W bridge in the double tungstate crystal lattice is responsible for the refractive index increase, which creates the waveguide confinement. We identified that shifts toward lower energies in the ∼760 cm-1 Raman mode indicate regions, which guide light polarized along the crystallographic b axis, while higher energy shifts in the 682 and 898 cm-1 Raman lines correspond to guiding regions for light polarized along the crystallographic a axis. © 2011 American Institute of Physics.