Improvement of two-step K+-Na+ and Ag+-Na+ ion-exchanged glass waveguides by surface removal

We introduce a simple approach to improve the properties of waveguides fabricated by two-step K+–Na+ and Ag+–Na+ ion exchange in BK7 glass. By etching a 0.25-μm-thick layer off the waveguide surface, the propagation losses and polarization dependent losses caused by silver colloids formed during the ion exchange process can be significantly reduced. In addition, this method can improve the uniformity of the waveguides with varying waveguide patterns. After 24 h of annealing at 300 °C, the propagation losses of the etched waveguides have a value of 0.25–0.35dB∕cm, which is about 0.1dB∕cm lower than the waveguides without etch. The etch has little impact on the waveguide mode profiles.