High-speed red RCLEDs and VCSELs for plastic optical fiber application

Abstract

To investigate the high performance light source for high-speed plastic optical fiber (POF) communication application is important as high-speed short distance communication for the home networks becomes popular. It is straightforward to reduce the size of RCLEDs to increase the small-signal modulation bandwidth (f_-3dB). But reduce the size of RCLEDs not only reduce the output power but also decrease lifetime because higher current density flowed through active region. In this paper, we improve. f_-3dB of RCLEDs with the aperture of 84μm by reducing the number of quantum wells (QWs) in active region. We found the speed of RCLED inverse proportional to the number of QWs. By reducing the number of QWs to one, the device with standard aperture size exhibits high f_-3dB as 235MHz at bias current of 20mA without sacrificing the other performance like maximum output power, high temperature performance, etc. These devices can transmit data rate as high as 500Mb/sec through graded-index POF over 50 meters. Beyond 1Gbits/sec, we have investigated red VCSELs as suitable high-speed light sources. The structure of red VCSELs is similar to RCLEDs except more pairs of DBR yield high reflectivity. Our red VCSEL can have output power as high as 1.5mW at 5mA and transmission data rate up to 2.5Gbits/sec.