Ti:Sapphire Regenerative Amplified Laser System for ultrafast, high-field terahertz photonics

太赫兹（THz）区域的电磁波谱跨越微波和中红外之间的频率范围。在过去的十年中，太赫兹频率辐射已经引起了人们对新成像和光谱技术发展的极大兴趣，因为它能够在化学上区分样品，识别晶体结构的变化，并穿透干燥材料，从而实现地下或隐藏样品的调查。特别是，像太赫兹时域光谱（TDS）这样的技术可以实现许多低能激发，包括分子旋转、晶格振动、自旋进动和电子-空穴对的激发。然而，当强烈的太赫兹瞬变被用于共振控制和操纵物质的电子、自旋和离子特性时，而不仅仅是监测它时，人们对丰富的物理学可以进行研究的兴趣越来越大。这些新兴的非线性技术远远超出了吸收和发射的弱光-物质相互作用，如线性太赫兹光谱所体现的，并且正在成为研究广泛的非平衡系统，非线性现象和量子系统的强大工具。然而，这些途径直到最近才开始在太赫兹频谱范围内进行探索，尽管在这些频率上具有基本跃迁的丰富材料及其在量子技术，光子学和信号处理中的应用潜力。为了释放这些机会，需要为窄带和宽带激发产生高场（~kV/cm- mv /cm）的超快太赫兹脉冲，这些脉冲必须以飞秒精度进行控制、操纵和检测。超快再生放大激光（URAL）系统代表了唯一可行的台式技术，能够在<100 fs的时间尺度上提供超稳定的光学激光脉冲，脉冲能量为>mJ，这是产生这些超快、强太赫兹脉冲所必需的。通过这笔资金，我们将建立一个专门的以乌拉尔为基础的太赫兹设施，该设施将为非线性太赫兹科学和物质相干控制这些新兴领域开辟大规模和持久的途径。量子态的相干操纵将在一系列范例系统中进行探索，包括有源太兹量子级联激光器件、半导体中的浅杂质、固体材料中的稀土离子和自组装InGaAs量子棒。尽管这些测量本身具有根本的意义，但对这些系统的研究有望支撑许多应用，从量子信息系统中基于自旋的量子比特的固态实现，到单光子源、光纤放大器、室温垂直腔表面发射太赫兹激光器的开发，以及长期寻求的利用自诱导透明现象的锁模激光器。但这还不是全部。我们还将利用这项技术来探索化学反应途径的控制，包括与爆炸反应引发有关的化学反应途径。这种产生超快、强太赫兹脉冲的基础技术不仅将支持利兹大学未来的一系列研究方向，而且将使我们能够为英国建立一个非线性太赫兹科学和物质相干控制的国际设施，这将影响物理、化学和生物科学的许多研究领域。

The terahertz (THz) region of the electromagnetic spectrum spans the frequency range between microwaves and the mid-infrared. Over the past decade, THz frequency radiation has attracted much interest for the development of new imaging and spectroscopy technologies, owing to its ability to discriminate samples chemically, to identify changes in crystalline structure, and to penetrate dry materials enabling sub-surface or concealed sample investigation. In particular, techniques such as THz time-domain spectroscopy (TDS) have enabling access to numerous low-energy excitations including molecular rotations, vibrations of crystal lattices, precession of spins and excitations of electron-hole pairs.Nevertheless, there is growing interest in the rich physics that can be investigated when intense THz transients are used to resonantly control and manipulate the electronic, spin, and ionic properties of matter, rather than to merely monitor it. These emerging non-linear techniques go far beyond the weak light-matter interactions of absorption and emission, as embodied by linear THz spectroscopy, and are becoming powerful tools enabling the study of a wide range of non-equilibrium systems, nonlinear phenomena and quantum systems. Yet, these avenues have only recently begun to be explored within the THz spectral range, despite the wealth of materials that possess fundamental transitions at these frequencies and their potential for applications in quantum technology, photonics and signal processing.To unlock these opportunities requires the generation of high-field (~kV/cm-MV/cm), ultrafast THz pulses for both narrowband and broadband excitation, which must be controlled, manipulated and detected with femtosecond precision. Ultrafast regenerative amplified laser (URAL) systems represent the only viable bench-top technology capable of delivering ultra-stable optical laser pulses on timescales <100 fs and with pulse energies >mJ, which are required for the generation of these ultrafast, intense THz pulses.Through this funding we will establish a dedicated URAL-based THz facility that will open-up wide-scale and lasting access to these emerging fields of non-linear THz science and coherent control of matter. The coherent manipulation of quantum states will be explored in a range of exemplar systems including active THz quantum cascade laser devices, shallow-impurity-in-semiconductors, rare earth ion-in-solid materials, and self-assembled InGaAs quantum rods. Although these measurements are of fundamental interest in their own right, the investigation of such systems promises to underpin a number of applications ranging from solid-state implementations of spin-based qubits for quantum information systems to the development of single photon sources, optical fibre amplifiers, room-temperature vertical-cavity surface-emitting THz lasers, and long-sought mode-locked lasers exploiting the phenomenon of self-induced transparency. But this is not all. We will also exploit this technology to explore the control of chemical reaction pathways, including those associated with the initiation of explosive reactions.This underpinning technology for the generation of ultrafast, intense THz pulses will not only support a range future research directions within the University of Leeds, but will enable us to establish for the UK an international facility for non-linear THz science and coherent control of matter that will impact over many research fields across the physical, chemical and biological sciences.