Soliton Formation through Self-Induced Transparency in Semiconductor Microcavities.

通过半导体微腔中的自感透明形成孤子。

• 批准号: EP/D060958/1
• 负责人: Ortwin Hess
• 金额: $ 55.64万
• 依托单位: University of Surrey
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FD060958%2F1
• 关键词: Soliton; Formation; through; Self; Induced

The passage of light pulses through an optical material shows many interesting and useful effects, especially when the pulse is very bright and very short in duration. Normally, the pulse will spread out in space and time as a result of diffraction and dispersion. However when the pulse is very bright, nonlinear effects can exactly cancel this spreading, and the light pulse propagates without any change in shape: a 'soliton' or 'light bullet'. It is easier to form stable solitons when the light is confined to a small cavity, and 'cavity solitons' are now attracting a lot of interest. They could be useful as a way of storing and manipulating data for optical storage or optical computing.Another type of effect (coherent propagation) is seen when the pulse is very short in duration compared to the material's lifetime (the timescale on which its properties can change). One of the most striking examples is self-induced transparency (SIT), in which a material which normally absorbs light becomes transparent to a bright, short-duration light pulse. This allows another class of light bullet or 'SIT soliton'. During the past few years, interesting properties of cavity-SIT solitons have been predicted using approximate theories, with possible applications in the generation of ultrashort pulse trains (soliton mode-locking). However, their existence has not yet been demonstrated experimentally nor confirmed by a more accurate theory. We have recently developed a new, accurate, theory of nonlinear coherent pulse propagation, based on Richard Feynman's model of atoms in an electromagnetic field. The theory predicts signatures of cavity-SIT solitons which can be detected experimentally. This is the main focus of the grant application. More generally, the new theory will be a useful tool for exploring new physical effects in the extreme nonlinear regime.Semiconductors such as gallium arsenide interact strongly with light, and can form high-quality optical cavities. However the lifetime is very short, and some theorists have stated that coherent propagation effects will be weak. Nevertheless, self-induced transparency effects have been observed experimentally. Our different theoretical method, together with experimental measurements, will be used to understand this discrepancy and to establish the conditions for SIT in semiconductors. The emphasis of the experimental work will be the demonstration of cavity-SIT solitons in semiconductor cavities. Several approaches will be used, including measurements of pulse propagation and light scattering to detect formation of optical gratings. These investigations will exploit the bright, ultrashort light pulses available from the new breed of ultrashort pulse laser amplifiers based on titanium-doped sapphire.If semiconductor crytals are made very small, they form 'quantum dots' (QDs) which have long material lifetimes and are a good starting point for coherent propagation effects. Self-induced transparency in semiconductor QDs was described theoretically in 2002 and demonstrated experimentally in 2003: much work remains to be done to understand this 'hot topic'. We will extend our theory to treat quantum dots, as well as make experimental measurements of coherent propagation.The semiconductor crystals will be grown at the National Centre at Sheffield, and the cavities will be produced by micro-fabrication at both Sheffield and Surrey. Our collaborator in France is an expert in coherent nonlinear experiments, and our US collaborator is the pioneer of exact treatment of atoms in electromagnetic fields. The project makes use of advanced lasers and supercomputers recently installed at the Advanced Technology Institute at Surrey, and is exactly the type of project which the Institute was set up to do: investigating new fundamental phenomena using advanced experimental and theoretical techniques, with applications in information technology and communications.

光脉冲通过光学材料显示出许多有趣和有用的效应，特别是当脉冲非常明亮和持续时间很短的时候。通常情况下，由于衍射和色散，脉冲会在空间和时间上扩散。然而，当脉冲非常亮时，非线性效应可以完全抵消这种传播，并且光脉冲在传播时不会改变形状：一个“孤子”或“光弹”。当光被限制在一个小的腔中时，形成稳定的孤子更容易，而“腔孤子”现在吸引了很多人的兴趣。它们可以作为一种存储和操作光存储或光计算数据的方法。另一种类型的效应（相干传播）是当脉冲的持续时间与材料的寿命（其特性可以改变的时间尺度）相比非常短时看到的。最引人注目的例子之一是自诱导透明（SIT），通常吸收光的材料对明亮的短时间光脉冲变得透明。这就产生了另一种类型的轻子弹或“SIT孤子”。在过去的几年中，利用近似理论预测了腔- sit孤子的有趣性质，并可能应用于产生超短脉冲序列（孤子锁模）。然而，它们的存在还没有被实验证明，也没有被一个更准确的理论证实。我们最近发展了一个新的，精确的，非线性相干脉冲传播理论，基于理查德·费曼的原子在电磁场中的模型。该理论预测了可以通过实验检测到的腔- sit孤子的特征。这是拨款申请的主要焦点。更一般地说，新理论将是探索极端非线性状态下新的物理效应的有用工具。砷化镓等半导体与光发生强烈的相互作用，可以形成高质量的光学腔。然而，它的寿命很短，一些理论家认为相干传播效应很弱。然而，自诱导透明效应已在实验中观察到。我们不同的理论方法，结合实验测量，将用于理解这种差异，并建立半导体中SIT的条件。实验工作的重点将是在半导体腔中展示腔- sit孤子。将使用几种方法，包括测量脉冲传播和光散射来检测光学光栅的形成。这些研究将利用基于掺钛蓝宝石的新型超短脉冲激光放大器提供的明亮、超短光脉冲。如果半导体晶体做得非常小，它们就会形成“量子点”（QDs），这种量子点具有很长的材料寿命，是相干传播效应的良好起点。半导体量子点的自诱导透明在2002年被理论描述，并在2003年被实验证明：要理解这个“热门话题”还有很多工作要做。我们将扩展我们的理论来处理量子点，以及对相干传播进行实验测量。半导体晶体将在谢菲尔德的国家中心生长，空腔将在谢菲尔德和萨里通过微加工生产。我们在法国的合作者是相干非线性实验方面的专家，我们在美国的合作者是在电磁场中精确处理原子的先驱。该项目利用了萨里先进技术研究所最近安装的先进激光和超级计算机，这正是该研究所成立的目的：利用先进的实验和理论技术研究新的基本现象，并将其应用于信息技术和通信。

项目成果

Dynamical model for coherent optical manipulation of a single spin state in a charged quantum dot

带电量子点中单自旋态的相干光学操纵的动力学模型

• DOI: 10.1002/pssc.200880326
• 发表时间: 2009
• 期刊: physica status solidi c
• 作者: Slavcheva G

Model for the coherent optical manipulation of a single spin state in a charged quantum dot

• DOI: 10.1103/physrevb.77.115347
• 发表时间: 2008-03
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: G. Slavcheva