Self-assembled PN semiconductor detectors on optical fibers

Recent work in the fabrication of self assembled quantum dot (QD) detectors on active structural fibers and for the implementation of optical fiber sensors is reported in this paper. The ability to develop the QD based devices and materials via the electrostatic self-assembly (ESA) process has been demonstrated by Hand and Kang in prior work. The QD precursor nanocluster materials involved in ESA have been designed and synthesized to proper size, stabilized in an aqueous-based solution, and functionalized to allow self-assembly. Optical fiber sensor instrumentation has been developed to monitor the reflected optical power with the buildup of the QD layers on the fiber endface during the ESA process. The results are confirmed by observing the effects of low-finesse QD Fabry-Perot interferometric cavities formed via such processes on the ends of optical fibers. The photocurrent-voltage characteristics show a diode-like behavior with linear photocurrent in the reverse bias and non-linearity in the forward bias. It is suggested that fast response times can be achieved due to the high carrier mobilities that arise in part due to structure of the materials formed via the solution-based ESA process. This paper reviews this prior work and shows examples of deposition of devices on both fiber endfaces and cladding surfaces.