Collaborative Proposal: Ultrabroadband Supercontinuum Studies

在过去的两年里，光学领域最令人兴奋的事件可能是微结构光纤的发展。这种光纤的色散特性可以比传统光纤更大程度地定制。因此，它可用于将商业上可用的低能超短脉冲转换为带宽为500 THz的超宽带连续光。这种光在电信、固态光谱学、化学反应的相干控制和超高空间分辨率光学相干断层扫描中有许多深远的应用。它已经彻底改变了光学计量领域，但不幸的是，超宽带光的工作技术仍处于起步阶段。 在这个阶段，除了功率谱之外，不可能测量其属性。 脉冲整形和压缩技术，这是成功的窄带应用，不适用于这种类型的超宽带辐射。 即使是像准直和传播超宽带光这样简单的任务也是不可能的。 例如，超宽带透镜不存在，反射镜也会失效，因为这种光的衍射角超过60 s。 此外，这种光产生的过程最好是知之甚少。因此，我们建议1）进行广泛的建模，以了解连续光的基本机制和性质，2）开发其表征的实验技术，3）设计操纵和压缩这种光的新技术。我们将采取两种不同的方法来产生超宽带光。将利用标准fs Ti：Sapphire激光器和微结构光纤产生光谱从400 nm到1.6 μ m的连续光。第二种方法同样有前途，但尚未开发，将使用IMRA America开发的放大光纤激光器在IR中的传统电信光纤中产生超宽带连续谱：从800 nm到2.5 μ m。这种超宽带光极其复杂，具有超过1000的时间带宽积（TBP），而已经完全表征的最复杂的超短脉冲具有~10的TBP。后一种测量使用频率分辨光学门控（FROG），它将FROG技术推向了极限。因此，我们建议开发一种更宽频带的FROG版本，用于测量具有两个数量级以上额外复杂性的超宽带连续谱。它必然涉及几项创新，包括例如使非线性晶体角度抖动以获得更大的带宽。

Probably the most exciting event in optics in the past two years has been the development of microstructure optical fiber. The dispersion properties of this fiber can be tailored to a far greater extent than conventional optical fibers. As a result, it can be used to transform commercially available, low-energy ultrashort pulses into ultrabroadband continuum light with a bandwidth of 500 THz. This light has numerous far-reaching applications in telecommunications, solid-state spectroscopy, coherent control of chemical reactions, and ultrahigh-spatial-resolution optical coherence tomography. It has already completely revolutionized the field of optical metrology.Unfortunately, techniques for working with ultrabroadband light remain in their infancy. At this stage, it is not possible to measure its properties other than the power spectrum. Pulse shaping and compression techniques, which are successful in narrowband applications, are not applicable to this type of ultrabroadband radiation. Even simple tasks such as collimating and propagating ultrabroadband light are not yet possible. For example, ultrabroadband lenses do not exist, and mirrors also fail because the diffraction angle of this light is over 60s. Furthermore, the process by which this light is created is at best poorly understood.As a result, we propose to 1) perform extensive modeling to understand the underlying mechanisms and the properties of the continuum light, 2) develop experimental techniques for its characterization, and 3) devise new techniques for manipulating and compressing this light. We will take two distinct approaches to ultrabroadband-light generation. One will utilize a standard fs Ti:Sapphire laser and microstructure optical fiber to produce continuum light with spectrum from 400 nm to 1.6 um. The second approach, which is equally promising -but as yet unexplored- will use amplified fiber lasers developed by IMRA America to generate ultra-broadband continuum in conventional telecommunications fiber in the IR: from 800 nm to 2.5 um.This ultrabroadband light is extremely complex, having a time-bandwidth product (TBP) in excess of 1000, whereas the most complex ultrashort pulse that has been completely characterized had a TBP of ~10. This latter measurement used frequency-resolved optical gating (FROG), and it pushed the FROG technique to its limits. As a result, we propose to develop a much broader-band version of FROG for measuring ultrabroadband continuum with more than two orders of magnitude of additional complexity. It will necessarily involve several innovations, including, for example, angle-dithering the nonlinear crystal for much greater bandwidth.