GAAS ALGAAS 1ST-ORDER GRATINGS FABRICATED WITH ELECTRON-BEAM LITHOGRAPHY AND VERY-NARROW-LINEWIDTH LONG-CAVITY DBR LASER-DIODES/

A technique to fabricate GaAs/AlGaAs first-order gratings using electr on beam (EB) lithography and its application to long-cavity distribute d Bragg reflector (DBR) laser diodes is presented. The field stitching error, which limits the application of EB lithography to optical devi ces, was reduced to 5 nm by deflection amplitude calibration using mar ks on the samples. In addition, we have proposed a novel technique to control the coupling coefficient using partially corrugated gratings. These techniques were applied to fabrication of GaAs/AlGaAs first-orde r gratings of GRIN-SCH-SQW DBR laser diodes. The resulting stitching e rror did not influence the single-mode lasing characteristics, and a v ery narrow linewidth of 237 kHz was achieved. The results show that EB lithography with these techniques is useful in the fabrication of var ious optical devices with gratings.