Abstract

The development of large area rib waveguide arrays on GaAs, with low crosstalk and low propagation losses, is essential for monolithically integrated advanced optical signal processors.¹ In addition, surface gratings for outcoupling from such arrays are important to access the third dimension of large area integrated optical devices for additional processing capability.^1,2 Here, we report the fabrication of large area rib waveguide arrays with high surface uniformity (660 elements, 8 µm wide, 0.6 µm high, 3 mm long, with 2-µm separations) on GaAs/Al_0.3Ga_0.7As slab waveguides grown by molecular beam epitaxy (MBE), through photolithographic definition and selective argon-ion etching (beam current density ≃0.1 mA/cm² at 300 V). In addition, we have fabricated uniform surface gratings (2- and 4-µm periods, 0.2-µm peak-to-peak, and 1-mm long) on such rib waveguide arrays through a second photolithographic step and ion beam milling process. End-fire coupling of a Nd:YAG laser beam (1.06 µm) into individual waveguides was conducted to excite their guided modes revealing good mode confinement and low cross-talk. In addition, surface gratings were employed to successfully outcouple the guided modes into the third dimension of the rib waveguide arrays.

© 1989 Optical Society of America