A 4.25-Gbps Transmitter Optical Sub-Assembly (TOSA) Using an 850-nm Vertical-Cavity Surface-Emitting Laser (VCSEL)

2.1 Structure of the VCSEL In the oxide-confined structure 2) developed in the work described here, the effective confining of current and light by means of an aluminum oxide layer has resulted in the achievement of outstanding characteristics in terms of threshold current, high efficiency 3), 4), etc. What is more, the L/I (optical power/current) and V/I (voltage/current) characteristics are heavily dependent on the diameter of the light-emitting region (oxide aperture size) enclosed by the aluminum oxide layer referred to. This means that it is possible to achieve the desired characteristics by controlling the oxide aperture size.