Red VCSELs for POF Data Transmission and Optical Sensing Applications

We have fabricated VCSELs in the visible red spectrum. The emission wavelength ranges from approximately 650nm to 690nm depending on application. The devices are grown on GaAs substrates by MOVPE and processed using standard VCSEL processing technology. The active layer consists of three InGaP quantum wells. The Bragg mirrors are AlGaAs/AlAs multilayer structures. The bottom mirror is n-doped, the top mirror is p-type doped. The threshold current of the devices is less than 2mA. The maximum operating temperature is beyond 60°C. The optical output power is limited by eye-safety conditions to a maximum of 390μW. The modulation bandwidth of the devices is in excess of 3GHz even for low operating currents below 5mA. This enables IEEE1394b S800 and Gigabit Ethernet transmission speed over POF as well as higher speed applications such as optical links for high definition TV. Any real application requires highly reliable devices and hence intensive life time testing of these red VCSELs has been undertaken. From aging test results applying various operating temperatures and currents we have inferred a conservative estimate for the activation energy of 0.6eV. The 1%-time-to-failure (1%TTF) of the devices is over 100,000 hrs at use conditions. Continuous testing of more devices over thousands of operating hours is poised to improve reliability data further.