Deposition Forms Buried Grating

Scientists at the University of California at Berkeley have formed a buried oxide grating by growing selectively oxidized AlGaAs on nonplanar GaAs structures. In the experiment, detailed in the Sept. 23 issue of Optics Express, they patterned the substrate with optical lithography and etched trenches 125 to 500 nm deep. After overgrowth of the element in the deposition chamber, they defined a ridge waveguide structure to expose the AlGaAs layer. After oxidation, the result was a sawtooth-pattern oxide front with a period half of the original lithography-defined pitch.

Potential advantages of the structure include high coupling efficiency and a large stop-band. The process may facilitate monolithic integration of devices, and scientists can produce gain- and loss-coupled gratings by electrically pumping through the unoxidized parts of the grating structure.