Far Infra-Red Emission and Lasing in Doped Semiconductors

掺杂半导体中的远红外发射和激光

• 批准号: EP/E061265/2
• 负责人: Stephen Lynch
• 金额: $ 20.19万
• 依托单位: CARDIFF UNIVERSITY
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FE061265%2F2
• 关键词: Far; Infra; Red; Emission; Lasing

The terahertz band is located between the visible/near infrared frequencies and millimetre/microwave frequencies. Its physical properties bear some resemblance to light on one side and heat or microwaves on the other. It can be reflected and focused like light using special mirrors and lenses. It transfers energy/heat to materials in a similar way to microwaves, by causing the whole molecular structure to vibrate when radiation of the correct frequency is absorbed. This particular property makes terahertz radiation an ideal tool to study the properties of new materials because each material has a unique absorption signature. Why is this new and exciting? Until very recently there have been no practical sources of terahertz radiation, or indeed ways to detect it. So, in many ways this is uncharted territory. The situation changed radically with the invention (in the UK) of the first terahertz laser along with the development of a number of new techniques for producing powerful terahertz pulses.Current terahertz sources are broadly divided into two classes: broadband and single frequency. Terahertz radiation generated from photoconductive antennae and from surface fields is generally classed as broadband. The main limitation of this type of generation scheme is the low powers achieved. Lasers make up the second class, that is, single frequency terahertz sources. The III-V terahertz quantum cascade laser was first demonstrated in 2002 and considerable progress has been made since then. While the quantum cascade laser is undoubtedly an elegant device, its main disadvantage is that it requires complicated and time consuming epitaxial growth. The quantum cascade active region typically contains many hundreds of epilayers and growth times of 36 hours are not unusual.No practical materials exist with conventional bandgaps at terahertz frequencies and thus some other approach must be adopted. However, there is another fundamental energy gap in certain semiconductor materials where the energy separation lies in the terahertz frequency range. Doped semiconductors contain a series of quantized states either just below the bottom of the conduction band (donor levels) or just above the top of the valence band (acceptor levels). Under the right optical pumping conditions it has recently been shown that a population inversion can be achieved between states and stimulated emission at terahertz frequencies has been observed.The overall aim of this project is to re-visit the subject of shallow level impurities in the broad spectrum of semiconductor materials now available to us, and in doing so, open up a whole new field of terahertz laser research. Since most current commercial off-the-shelf terahertz lasers are cumbersome gas based systems, an optically pumped impurity doped semiconductor system would have an obvious size and weight advantage. Furthermore, an electrically pumped impurity based laser would have an additional advantage in that a CO2 pump laser would no longer be required. The technology, if successfully exploited, has the potential to result in a whole new breed of cheap reliable off-the-shelf sources of FIR radiation.

太赫兹波段位于可见/近红外频率和毫米/微波频率之间。它的物理性质一方面与光相似，另一方面与热或微波相似。它可以像光一样被特殊的镜子和透镜反射和聚焦。它以类似于微波的方式将能量/热量传递给材料，当吸收正确频率的辐射时，使整个分子结构振动。这种特殊的性质使太赫兹辐射成为研究新材料性质的理想工具，因为每种材料都有独特的吸收特征。为什么这是新的和令人兴奋的？直到最近，还没有太赫兹辐射的实际来源，也没有检测它的方法。所以，在许多方面，这是一个未知的领域。随着第一台太赫兹激光器的发明（在英国）沿着许多产生强大太赫兹脉冲的新技术的发展，情况发生了根本性的变化。目前的太赫兹源大致分为两类：宽带和单频。从光电导天线和表面场产生的太赫兹辐射通常被归类为宽带。这种类型的发电方案的主要限制是实现的低功率。激光器构成第二类，即单频太赫兹源。III-V太赫兹量子级联激光器于2002年首次得到演示，此后取得了长足的进展。虽然量子级联激光器无疑是一种优雅的器件，但其主要缺点是它需要复杂且耗时的外延生长。量子级联有源区通常包含数百个外延层，并且36小时的生长时间并不罕见。在太赫兹频率下不存在具有常规带隙的实用材料，因此必须采用一些其他方法。然而，在某些半导体材料中存在另一个基本能隙，其中能量分离位于太赫兹频率范围内。掺杂的半导体包含一系列量子化状态，或者刚好在导带底部（施主能级）之下，或者刚好在价带顶部（受主能级）之上。在适当的光抽运条件下，最近的研究表明，态与态之间可以实现粒子数反转，并观察到太赫兹频率的受激辐射。本项目的总体目标是重新审视我们现在可以获得的宽谱半导体材料中的浅能级杂质的主题，并在此过程中开辟一个全新的太赫兹激光研究领域。由于大多数当前商业现成的太赫兹激光器是笨重的基于气体的系统，因此光学泵浦的掺杂杂质的半导体系统将具有明显的尺寸和重量优势。此外，基于电泵浦杂质的激光器将具有额外的优点，因为将不再需要CO2泵浦激光器。这项技术，如果成功地利用，有可能导致一个全新的品种的廉价可靠的现成的远红外辐射源。

项目成果

Laboratory Scale Water Circuit Including a Photocatalytic Reactor and a Portable In-Stream Sensor To Monitor Pollutant Degradation

实验室规模水回路，包括光催化反应器和便携式流内传感器，用于监测污染物降解

• DOI: 10.1021/ie202366m
• 发表时间: 2012
• 期刊: Industrial & Engineering Chemistry Research
• 影响因子: 4.2
• 作者: Nickels P

Parameters controlling the photocatalytic performance of ZnO/Hombikat TiO2 composites

控制 ZnO/Hombikat TiO2 复合材料光催化性能的参数

• DOI: 10.1016/j.jphotochem.2011.11.001
• 发表时间: 2012
• 期刊: Chemistry
• 作者: Hamdy M

Silicon with an increased content of monoatomic sulfur centers: Sample fabrication and optical spectroscopy

单原子硫中心含量增加的硅：样品制造和光谱

• DOI: 10.1134/s1063782613020048
• 发表时间: 2013
• 期刊: Semiconductors
• 影响因子: 0.7
• 作者: Astrov Y

Time-Resolved Dynamics of Shallow Acceptor Transitions in Silicon

硅中浅受主跃迁的时间分辨动力学

• DOI: 10.1103/physrevx.3.011019
• 发表时间: 2013
• 期刊: Physical Review X
• 影响因子: 12.5
• 作者: Vinh N

Terahertz and Mid Infrared Radiation: Detection of Explosives and CBRN (Using Terahertz)

太赫兹和中红外辐射：爆炸物和 CBRN 的检测（使用太赫兹）

• DOI: 10.1007/978-94-017-8572-3_9
• 发表时间: 2014
• 作者: Lynch S