MRI: Development of a single-mode terahertz free electron lasers for research in materials, physics, chemistry and biology

太赫兹频率范围位于电磁频谱的核心，介于电子学和光学领域之间。频率为1太赫兹的电磁波每秒振荡1万亿周--大约比手机使用的电磁波快1000倍，比构成可见光的电磁波慢500倍。到目前为止，社会对太赫兹电磁波的使用相对较少，因为它们很难产生。然而，在光学和电子革命的推动下，这种情况正在迅速改变。加州大学圣巴巴拉分校的自由电子激光器是世界上最明亮的可调谐太赫兹辐射源。该项目将把UCSB自由电子激光设施的用户可用的亮度提高100到1000倍。升级后的设施将使电磁辐射与电子材料、分子和生物物质相互作用的基础研究成为可能。从这项基础性研究中获得的见解将对信息技术、国防和生物技术产生重要影响。太赫兹技术正在迅速发展，现在有桌面源可产生超过1 mV/cm(峰值功率106W)的峰值电场，其脉冲的带宽约为1 THz，而更紧凑的电子源可产生线宽低于khz的兆瓦功率。越来越多的令人着迷的科学问题和重要的技术发展需要获得具有极高光谱亮度的可调谐太赫兹电磁场，它将极高的功率和电场与极窄的线宽结合在一起。将在这里开发的主要研究仪器将极大地提高这一高功率/窄线宽利基领域的技术水平。加州大学圣巴巴拉分校的自由电子激光器可在0.24到4.5太赫兹之间调谐，功率为1千瓦，脉冲功率为几微秒，将通过在整个调谐范围内将发射辐射的线宽减少到1 MHz来增强，同时精确控制和测量发射辐射的频率，并允许切片？将自由电子激光(FEL)输出转换成一系列脉冲，脉冲的持续时间从~1 ns到完整的几微秒脉冲宽度不等。自由电子激光的增强将使凝聚态物理、化学和生物学方面的重要新研究成为可能，方法是：(1)提高加州大学圣巴巴拉自由电子激光设施已经开发的几种实验方法的精确度和控制性，以及(2)实现一些以前无法想象的实验。这一发展在很大程度上利用了加州大学圣巴巴拉分校超过35年的基础设施、投资、机构承诺和专业知识。

The terahertz frequency range lies at the heart of the electromagnetic spectrum, between the domains of electronics and optics. An electromagnetic wave with a frequency of one terahertz oscillates one trillion cycles per second?about 1000 times faster than the electromagnetic waves used by cell phones, and 500 times slower than the electromagnetic waves that constitute visible light. Terahertz electromagnetic waves have been, so far, relatively little used by society because they are hard to generate. However, that is changing rapidly, propelled by revolutions in optics and electronics. The UC Santa Barbara Free-Electron lasers are the brightest sources of tunable terahertz radiation in the world. This project will increase the brightness available to users of the UCSB Free-Electron Laser facility by a factor between 100 and 1000. The upgraded facility will enable fundamental research on the interaction of electromagnetic radiation with electronic materials, molecules, and biological matter. The insights gained from this fundamental research will have important implications for information technology, defense, and biotechnology. Terahertz technology is rapidly advancing, with tabletop sources now available that generate peak electric fields in excess of 1 MV/cm (peak power 106 W) in pulses with bandwidths of ~1 THz, and much more compact electronic sources that generate mW powers with sub-kHz linewidths. An increasing number of fascinating scientific questions and important technological developments require access to tunable terahertz electromagnetic fields with very high spectral brightness, which combine extremely high power and electric field with extremely narrow linewidth. The major research instrumentation to be developed here will greatly enhance the state of the art in this high-power/narrow-linewidth niche. The UC Santa Barbara Free-Electron Lasers, which are tunable from 0.24 to 4.5 THz with 1 kW power in few-microsecond pulses, will be enhanced by reducing the linewidth of the emitted radiation to 1 MHz over their entire tuning range while precisely controlling and measuring the frequency of the emitted radiation and enabling ?slicing? of the Free-Electron Laser (FEL) output into a series of pulses with durations variable from ~1 ns to the full few-microsecond pulse duration. The free-electron laser enhancements will enable important new research in condensed matter physics, chemistry and biology by (1) improving the precision and control of several experimental methodologies that have already been developed at the UC Santa Barbara FEL facility, and (2) enabling some experiments that could not previously be envisioned. This development heavily leverages more than 35 years of infrastructure, investment, institutional commitment, and expertise at UC Santa Barbara.