Development of an Ultrasensitive Ultrafast Phase Spectrometer

佐治亚理工学院的Trebino博士和El-Sayed博士获得了一笔拨款，用于开发一种新型的超灵敏超快强度-相位光谱仪，该光谱仪可以产生与生物学和许多其他领域相关的发光和其他光脉冲的全部强度和相位与时间（或频率）。该光谱仪对于单次测量将具有非常高的灵敏度，对于多次测量将具有每脉冲1光子的灵敏度。这些灵敏度比目前的测量技术大约好6个数量级。所提出的仪器包括将光谱仪与相干参考光脉冲相结合。具体来说，它将使用光谱范围在400纳米到1600纳米之间的超短脉冲，并通过微结构光纤（朗讯技术最近开发的）传播容易获得的低能量100秒脉冲。新仪器的演示将涉及与光生物学相关的简单光化学系统。例子包括7-叠氮素及其类似物中的双质子转移过程（对于理解辐射诱导的DNA突变很重要）和围绕双键的光异构化，例如，在merocyanine染料中（对于理解视觉蛋白质的主要过程很重要，例如视紫红质和细菌视紫红质光合作用）。随后，我们建议使用该装置进一步了解细菌视紫红质复杂的初级动力学，并区分为其初级光动力学提出的不同理论模型。这种仪器的应用也将远远超出生物学。例如，半导体实验经常产生新波长的弱光脉冲，这无法用传统方法测量，但有可能用这种方法测量。此外，天文学家经常测量来自天体物理光源的光的强度与频率（光谱），但他们目前无法测量光谱相位。有了这个仪器，应该可以做到这一点，并获得以前无法获得的关于地外光源的信息。此外，该光谱仪还可以测量宽带光学参数发生器中的信号和空闲光束的相位——这是一个有趣的系统，因为这两束光束的相位在量子力学上纠缠在许多自由度上，因此可以用于量子计算。最后，使用这种高灵敏度仪器，几乎可以研究任何发光介质的超快强度和相位随时间的变化。

A grant has been awarded to Drs Trebino and El-Sayed at the Georgia Institute of Technol-ogy to develop a novel ultrasensitive ultrafast intensity-and-phase spectrometer, which yields the full intensity and phase vs. time (or frequency) of luminescence and other light pulses relevant to biology and many other fields. The spectrometer will have a very high sensitivity for single-shot measurements and a 1-photon-per-pulse sensitivity for multi-shot measurements. These sensitivi-ties are approximately six orders magnitude better than those of current measurement techniques.The proposed instrument involves combining a spectrometer with a coherent reference light pulse. Specifically, it will use an ultra-short pulse with a spectrum ranging from 400 nm to 1600 nm and generated by propagating readily available, low-energy, 100-fs pulses through microstruc-ture optical fiber (recently developed by Lucent Technologies. Demonstrations of the new instru-ment will involve simple photochemical systems relevant to photobiology. Examples include dou-ble proton transfer processes in 7-azaindole and its analogues (important in understanding radiation-induced DNA mutation) and the photo-isomeri-zation around double bonds, e.g., in the merocyanine dyes (important for understanding of the primary processes in proteins of vision, such as rhodopsin and bacteriorhodopsin photosynthesis). Later, we propose to use this device to further understand the complex primary dynamics in bacteriorhodopsin and to distinguish between different theoretical models proposed for its primary photo-dynamics.This instrument will also have applications far beyond biology. For example, semi-conductor experiments often generate weak light pulses of new wavelengths, which cannot be measured with conventional methods, but potentially can with this. Also, astronomers routinely measure the intensity vs. frequency (the spectrum) of light from astrophysical sources, but they cannot currently measure the spectral phase. With this instrument it should be possible to do so and yield information previously unavailable regarding extraterrestrial light sources. In addition, the spectrometer will allow measurements of the phase of signal and idler beams in a broadband optical parametric generators-a system that is interesting because the phase of these two beams is quan-tum-mechanically entangled with many degrees of freedom and so can be used for quantum com-puting. Finally, the ultrafast intensity and phase vs. time of virtually any light-emitting medium could be studied using this highly sensitive instrument.