64 channel flip-chip mounted selectively oxidized GaAsVCSEL array for parallel optical interconnects

We have designed and fabricated a 64 channel optical module using a self-alignment flip-chip packaging technique for two-dimensional (2D) GaAs epitaxial-side emitting vertical-cavity surface-emitting laser (VCSEL) array mounting without substrate removal on Si subcarrier. Light emission is obtained through a wet-chemically etched window in the Si subcarrier. The 2D independently addressable selectively oxidized GaAs laser array is arranged in an 8x8 matrix with a device pitch of 250 mu m and each laser is supplied with two individual top contacts. This metallization scheme allows flip-chip mounting junction-side down on Si subcarrier. The VCSEL array chip is placed above the window in the Si subcarrier and is assembled using a self-aligned bonding technique with PbSn solder bumps. Arrays with 4 mu m active diameter investigated before and after packaging show quite homogeneous optical and electrical continuous wave output characteristics exhibiting threshold currents of less than 1.1 mA and single-mode output powers of 2 mW. Driving characteristics of the lasers in the array are fully compatible to advanced 3.3 V CMOS technology. The modules are used to demonstrate free-space directional transmission applying beam steering.