A study on free-space optical interconnection module using VCSEL, PIN-PD and CMOS IC

Abstract

This thesis describes the design and fabrication of free-space optical interconnection modules using vertical-cavity surface-emitting laser(VCSEL) arrays, PIN photodetector(PIN-PD) arrays and Tx/Rx Si-CMOS circuits. The modules consist of three major parts - Transmitter module, receiver module and interconnection part. The transmitter module is composed of a VCSEL array and a laser driving IC. The VCSEL array chip has oxide-confined InGaAs/GaAs structure emitting 960nm wavelength, 250$\mum$ pitch, 8$\mum$ aperture diameter and 8-channel produced by CSEM. The laser driving IC was fabricated by MOSIS using 0.35 $\mum$ Si-CMOS process. The VCSEL array chip and the laser driving IC chip were die-bonded on 24-pin IC package using silver epoxy. After the die-bonding, bonding-pads of those chips were connected by 1 mil diameter gold wire. For measurement, the packaged transmitter module was attached on PCB board with SMA connectors. The receiver module consists of a InGaAs/InP PIN-PD array and preamplifier Si-CMOS IC. The PIN-PD has 80$\mum$ active window diameter, 8-channel, and the responsivity of 0.5 at 960nm wavelength. The preamplifier IC fabricated by MOSIS. In addition, both PIN-PD array chip and preamplifier IC chip were die-bonded, wire-bonded and then attached on PCB board for function test. Using the transmitter module and the receiver module, various operational characteristics such as L-I-V curves of VCSEL, dark current of PIN-PD, DC and modulation operation of transmitter/receiver, and interconnection characteristics were measured. As a result, the free-space interconnection module was operated up to 100Mb/s for NRZ signal.