Turning Nonlinearity from Limitation to Advantage in Femtosecond Fiber Amplifiers

非线性（即强度相关）相位积累通常限制了强超短光脉冲的传播。先前关于高能脉冲产生的工作几乎完全集中在非线性的有害影响上。基于光纤的器件为研究非线性效应提供了一个独特的机会：由于光被引导，非线性相位积累的空间后果（这会破坏光束）被抑制。康奈尔大学的一个小组将对基于光纤的超短脉冲光源的极限进行理论和实验研究。实际上，以前所有用于高能脉冲的激光器和放大器的设计都是基于避免非线性。康奈尔大学的研究小组将寻求基于控制和利用非线性效应的新方法，而不是避免它们。这种方法的初步结果表明，应该有可能产生稳定的脉冲，其峰值功率比以前用光纤器件报道的高两个数量级。这种脉冲传播方式以前没有被探索过。更广泛的影响所提出的研究的影响将超出非线性脉冲传播。在这个项目中发展的概念范围从非线性动力系统的基础科学到实用的激光仪器。与其他激光器相比，光纤激光器具有极其紧凑和坚固的潜力，而且价格低廉。除了促进科学研究之外，飞秒持续时间光脉冲的光纤格式源在将短脉冲光学技术的范围扩展到“现实世界”应用（如精密加工和疾病诊断和治疗）方面具有巨大潜力。尽管具有潜力，但短脉冲光纤激光器对科学技术的影响有限，因为它们的性能落后于固态激光器。提出的努力为光纤设备提供了一条途径，它应该结合固态仪器的性能与光纤的实际效益和降低的成本。这项研究的成功将转化为可能具有商业可行性的短脉冲光纤激光器的设计，而商业发展将使广泛的应用成为可能。最后，建议的努力将与本科生和研究生的课堂教学相结合。建议开发的仪器将是稳定可靠的，因此非常适合在实验室示范中兼职使用。康奈尔大学的研究小组一直在吸引代表性不足的少数族裔（主要是女性）到他的实验室工作。通过与康奈尔大学的中心建立联系，这一趋势有望继续并扩大，这些中心历来吸引了大量来自弱势群体的学生。

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.