Visit of Prof. Oliver Wright

这项研究涉及等离子体激元的研究，即被困在金属表面的光量子。它们可以沿着金属表面传播，我们寻求方法来调节它们，使它们相互作用。目前，这些等离子体激元对彼此的存在非常不敏感，但通过适当设计金属三明治，我们可以制造出优化它们相互作用的结构。我们这次短暂的休假是为了尝试一个新的想法，这个想法是我们从另一个领域借来的，在这个领域我们已经成功地展示了有史以来最大的光学非线性，在等离子体激元上尝试这些。今天的商业激光系统提供了可重复的脉冲，短至10 fs，使科学，医学，制造和通信中的无数应用成为可能。这个世界充满了共振，每种物质都有特定的波长，以增强光与物质的相互作用。因此，也许激光器最重要的一个方面是辐射的波长，控制它的方法是最优先考虑的。激光辐射的光波长转换或放大通常通过特定晶体、波导或周期性图案化介质中的非线性光学效应来实现，以通过二阶或三阶光学非线性效应获得谐波产生或光学参量振荡。当使用非线性块状晶体用于这种目的时，必须使用满足光学非线性产生的光学相位匹配条件的材料。入射光的方向和偏振以及晶体的轴必须严格调整，温度也必须严格调整。当在这些应用中使用光波导或周期性图案化介质来提高效率时，输出光的调谐范围受到严格的几何规格要求的限制。基于非线性效应的传统光子器件的尺寸和光功率消耗都可以使用电磁场的强限制来大幅减小。这种限制的一种建议是使用光子晶体结构。然而，这些结构是昂贵的，并受到严格的几何约束，在一个以上的dimensions.We建议，以实现这种限制，利用两个SPP的相互作用，在一个廉价的，紧凑的和简单的结构，有效的光波长转换。这种方法具有在光调制、光放大或光频率转换中广泛应用的潜力。它的多功能性和光学频率可调谐性应使其能够应用于科学，工业和环境应用中的各种情况。该方法应被证明是非常有用的结合脉冲或连续激光器，以扩大可获得的光学频率范围，作为光学参量放大器。这同时提供了一种实现从脉冲激光器产生光学频率的宽带光谱（例如超连续谱）的手段，其在医学和超快光谱学中具有特别重要的应用。此外，本发明提供了一种用于调制从低频到高达太赫兹范围和以上的中频的光辐射的手段。这在未来的电信系统中的超快交换应用中应该是一个布恩。本发明还应该在分析设备中找到应用，例如在激光光谱仪、激光测距系统、遥感系统、成像系统和激光功率传输系统中。

The research concerns the study of plasmons, quanta of light which are trapped at the surface of a metal. These can travel along the metal surface, and we seek ways to modulate and make them interact with each other. Currently, these plasmons are very insensitive to each others presence, but by appropriately designing metal sandwiches, we can make structures that should optimise their interaction. Our aim in this short sabbatical stay is to try out a new idea we have borrowed from another field in which we have successfully shown the largest optical nonlinearities ever produced, to try these out on plasmons.Today's commercial laser systems deliver reproducible pulses as short as 10 fs, making myriad applications possible in science, medicine, fabrication and communication. The world abounds in resonances, each material having specific wavelengths for enhanced light-matter interaction. Perhaps the single most important aspect of a laser is therefore the wavelength of the radiation, and means to control this are a top priority. Optical wavelength conversion or amplification of laser radiation is conventionally achieved by means of nonlinear optical effects in specific crystals, waveguides or periodically patterned media to obtain harmonic generation or optical parametric oscillation through second or third order optical nonlinear effects. When using nonlinear bulk crystals for such purposes it is essential to use a material which meets the optical phase matching conditions for optical nonlinear generation. The direction and polarization of incident light and the axis of the crystal must be strictly adjusted, as must be the temperature. When using optical waveguides or periodically patterned media in such applications to improve efficiency the tuning range for the output light is limited by the tight geometrical specifications required.A drastic reduction of both the size and the optical power consumption of conventional photonic devices based on nonlinear effects may be possible using the strong confinement of the electromagnetic field. One proposal for such confinement is the use of photonic crystal structures. However, these structures are expensive and subject to strict geometrical constraints in more than one dimension.We propose to achieve this confinement by exploiting the interaction of two SPPs for efficient optical wavelength conversion in a cheap, compact and simple structure. This method has the potential to be effective in a wide range of applications in optical modulation, optical amplification or optical frequency conversion. Its versatility and optical frequency-tunability should allow it to be applied to a variety of situations in scientific, industrial, and environmental applications. The method should prove very useful in conjunction with pulsed or continuous lasers to widen the optical frequency range obtainable, as a optical parametric amplifier. This provides at the same time a means to achieve the generation of a broadband spectrum of optical frequencies from a pulsed laser, for example a supercontinuum, with particularly important applications in medicine and ultrafast spectroscopy. Furthermore, the invention provides a means to modulate optical radiation from low frequencies up to ultrahigh frequencies up to and above the terahertz range. This should be a boon in ultrafast switching applications in future telecommunications systems. The invention should also find application inside analytical equipment, such as in laser spectrometers, laser ranging systems, remote sensing systems, imaging systems, and laser power delivery systems.