A 3-D bidirectional optical link using a stacked thin-film emitter and detector

The fabrication of a colocated three-dimensional stacked thin-film device, which can be used for single-fiber bidirectional communication, has been demonstrated. A thin-film light-emitting diode (LED) with a diameter of 50 μm has been stacked on top of a thin-film inverted metal-semiconductor-metal (I-MSM) photodetector (PD) with a detecting diameter of 200 μm. Both devices in the stack have been tested, and the I-MSM PD in the PD/LED stack has a responsivity of 0.31 A/W, which is consistent with the theoretical analysis using a uniform illumination approximation.