Integrated optical beam splitters formed in glass channel waveguides having variable weighting as determined by mask dimensions

Abstract

Variable-weight beam splitters integrated into glass channel optical waveguides have been fabricated and successfully operated. Variable weighting is achieved by varying mask dimensions. Beam splitting is achieved by introducing notched reflectors of variable size into glass channel waveguides which are formed in shallow grooves having trapezoidal cross sections on silicon substrates. Preferential etching is used to fabricate these grooves and notches. A novel lift-off method incorporating a photoresist, glass, and aluminum sandwich structure is introduced to define glass channel waveguides having smooth edges within the grooves. The extent of the beam splitting notch as determined by scanning electron microscope observation is shown to correspond directly with measured beam splitting ratios for four different ratios. An insertion loss of 0.34 dB is measured for one of the samples.