High-efficiency and stable optical transmitter using VCSEL-direct-bonded connector for optical interconnection

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Abstract
A high-efficiency optical transmitter module for PCB (printed circuit board)-based interconnections was fabricated using a bottom-emitting VCSEL. The bottom-emitting VCSEL was directly bonded by an epoxy on a 90°-bent fiber connector which is inserted into the PCB to couple to the fiber layer embedded in the board. A ray trace simulation indicates that close contact between the VCSEL and the connector removes most of the losses due to Fresnel reflection and beam divergence. This tendency was experimentally identified. Thermal dissipation through the epoxy layer and the connector also improves significantly the power characteristics of the VCSEL. The VCSEL after bonding on the connector shows about 40% higher power compared to that of the bare VCSEL at the current showing a peak power before bonding. The results indicate that direct bonding improves both optical and electrical efficiencies. A successful eye diagram at the speed of 5 Gb/s/ch with 850 nm was accomplished from the VCSEL-direct-bonded transmitter module.