Closely-spaced VCSEL and photodetector for application requiring their independent operation

A monolithically integrated VCSEL and photodetector, and a method of manufacturing the same, are disclosed for applications where the VCSEL and photodetector require separate operation such as duplex serial data communications applications. A first embodiment integrates a VCSEL with an MSM photodetector on a semi-insulating substrate. A second embodiment builds layers of a p-i-n photodiode on top of layers forming a VCSEL using a standard VCSEL process. The p-i-n layers are etched away in areas where VCSELs are to be formed and left where photodetectors are to be formed. The VCSELs underlying the photodetectors are inoperable, and serve to recirculate photons which are not initially absorbed back into the photodetector. The transmit and receive pairs are packaged into a single package for interface to multifiber ferrules. The distance between the devices is precisely defined photolithographically, thereby making alignment easier. In a further alternate embodiment, a FET is coupled to the p-i-n photodiode to form an integrated detector preamplifier along with the VCSEL transmitter all on the same optical reference plane.