Active Fiber Tips With Optoelectronic Integration: State-of-the-Art, Future Trends, and Challenges

The integration of conventional silica optical fibers with optoelectronic materials and electrical structures opens the door to miniaturized and multifunctional all-fiber optoelectronic systems with actively controllable capabilities. The flat endface of an optical fiber tip offers a naturally light-coupling microscopic platform for optoelectronic integration using optimized micro- and nano-fabrication techniques. In recent decades, the increasing demand for active fiber devices has created opportunities to develop various optoelectronic structures on fiber tips, from integrating high-performance single modules for specific applications to integrating multi-function multiple modules for more complex applications. In this paper, we review the rapid development of fiber-compatible fabrication technologies for building optoelectrical circuits on fiber endfaces. Then, we discuss the fast-progressing field of active fiber tips along with its wide applications, including photodetection, modulation, lasing, sensing, and light-emitting. Finally, we discuss challenges and opportunities for future development in this field. We believe that this scheme of active fiber tips will pave the way for next-generation ultracompact optical fiber systems with diverse optical and optoelectronic applications.