Multi-GHz VCSEL electrical packaging analysis

The introduction of the Vertical Cavity Surface Emitting Laser (VCSEL) diode structure has created the need for enhanced performance, low cost, optical packages capable of supporting data rates as high as 4.8 gigabits/second (GBPS). The popular laser packages, such as the TO-46 and the TO-56 "cans", which have traditionally been used for edge emitting diodes at much lower frequencies, cannot support this dramatic increase in data rates. Large package parasitics and severe impedance discontinuities, inherent in the TO-46 and TO-56, impose stringent frequency limitations due to dramatic effects on electrical signal integrity. Because electrical waveform control is essential for proper laser diode operation, these high frequency performance problems must be identified and overcome. This paper will briefly discuss some of the major problems associated with multi-GHz (i.e., >1 GBPS) VCSEL packaging. Spice simulations for the TO-56 laser can are presented and compared to measured laboratory data for model verification. Spice models were used to determine frequency limitations associated with the TO-46 and TO-56 laser cans. The lessons learned from the analysis of the TO-46 and TO-56 cans were used to design and model a conceptual VCSEL package, dubbed OPAL (Optical Package for Advanced Lasers), capable of operation to data rates as high as 4.8 GBPS. The modeling techniques used to match the TO-46 and TO-56 time domain and frequency domain simulations to measurements were extrapolated to create a model of OPAL and evaluate it at high frequencies.