An international science team from Penn State and the University of Southampton, United Kingdom, has developed a process for growing a single-crystal semiconductor inside the tunnel of a hollow optical fiber. The device adds new electronic capabilities to optical fibers, whose performance in electronic devices such as computers typically is degraded by the interface between the fiber and the device. The research is important because optical fibers -- which are used in a wide range of technologies that employ light, including telecommunications, medicine, computing and remote-sensing devices -- are ideal media for transmitting many types of signals.