Novel photonic devices based on the concept of space-time duality

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Nontechnical Description This project explores the interaction of light pulses inside optical fibers. Specifically, intense light pulses can change the optical properties, like the index of refraction, of a glass fiber. Just as the change in the index of refraction between air and a piece of window glass causes some of the incident light to be reflected, the index of refraction change caused by an intense optical pulse can also alter the propagation of light. This change is transient and propagates at the speed of light in the fiber. If two light pulses of different frequencies propagate in an optical fiber, they will travel at different velocities. If one of those pulses is intense enough to change the material properties of the fiber, the second pulse will split into two pulses at two new frequencies. A temporal version of total internal reflection can also occur such that the entire pulse energy never crosses the temporal boundary across which the index of refraction changes its numerical value. These phenomena have been predicted but have not yet been observed. Observing these interactions will enable a new class of photonic devices where light is controlled by light. The proposed research will further advance our understanding in the field of ultrafast optics and provide us new tools for pulse manipulation and shaping. Such devices are likely to find applications in a variety of technical areas ranging from telecommunications to biomedical engineering.Technical Description The concept of space-time duality will allow us to apply the techniques known from spatial diffraction of optical beams to control short pulses in the time domain. The proposed research will develop novel photonic devices through well-thought experiments that will be guided by the theoretical and numerical expertise the PIs have developed in recent years. The initial experiments will realize a temporal waveguide using the nonlinear phenomena of cross-phase modulation inside an optical fiber. The resulting waveguide will be used to control timing jitter between two pulse trains emitted by independently running mode-locked lasers. Another objective is to synthesize pulses of arbitrary shapes using an electro-optic phase modulator. Since our approach is based mostly on phase changes, it is expected to have lower insertion losses compared to alternatives and would be suitable for applications where energy efficiency is a top requirement. We shall also employ the temporal version of the Talbot effect to convert a continuous-wave signal into a source of optical pulses whose repetition rate is tunable. In this project, we will work with graduate and undergraduate students to explore fully the implications of space-time duality and develop novel photonic devices with functionalities and applications in the areas of ultrafast science and technology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.