Turning Nonlinearity from Limitation to Advantage in Femtosecond Fiber Amplifiers

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Intellectual MeritNonlinear (i.e., intensity-dependent) phase accumulation generally limits the propagation of intense ultrashort pulses of light. Prior work on high-energy pulse generation has focused almost entirely on the harmful effects of nonlinearity. Fiber-based devices offer a unique opportunity to investigate nonlinear effects: because the light is guided, the spatial consequences of nonlinear phase accumulation (which would destroy a beam) are suppressed. A group from Cornell University will perform theoretical and experimental studies of the limits of optical-fiber-based sources of ultrashort pulses of light. Virtually all previous designs of lasers and amplifiers for high-energy pulses are based on avoiding nonlinearity. The Cornell group will pursue new approaches based on harnessing and exploiting nonlinear effects, rather than avoiding them. Initial results of this approach suggest that it should be possible to generate stable pulses with peak powers two orders of magnitude higher than reported previously with fiber devices. This regime of pulse propagation has not been explored previously.Broader ImpactsThe impact of the proposed research will extend beyond nonlinear pulse propagation. The concepts developed in this project range from the fundamental science of nonlinear dynamical systems to practical laser instruments. Fiber lasers have the potential to be extremely compact and robust, and inexpensive compared to other lasers. In addition to facilitating scientific research, fiber-format sources of femtosecond-duration optical pulses have great potential for expanding the range of short-pulse optical techniques into "real-world" applications such as precision machining and diagnosis and treatment of disease. Despite their potential, short-pulse fiber lasers have had limited impact on science and technology, because their performance has lagged behind that of solid-state lasers. The proposed effort provides a route to fiber devices that should combine the performance of solid-state instruments with the practical benefits and reduced cost of fiber. Successes in the proposed research will translate into designs of short-pulse fiber lasers that are likely to be commercially viable, and the commercial development will enable a wide range of applications. Finally, the proposed effort will be coupled to undergraduate and graduate classroom teaching. The instruments proposed for development will be stable and reliable, and thus ideal for part-time use in laboratory demonstrations. The Cornell group has a track record of attracting under-represented minorities, primarily women, to his laboratory. This is expected to continue and expand, through connections to centers at Cornell that have historically attracted substantial numbers of students from under-represented groups.