基于可调谐双Fano共振激发的暗态表面等离激元纳米激光器研究

Recently, spaser (surface plasmon amplification by stimulated emission of radiation)-nanolaser produced coherent nanoscale field is one of the important research field in the world, which is widely applied in physics, chemistry, biology and medicine field. At present, the spaser has been realized by amplifying the surface plasmon of bright mode. And most of the structures only resonate at the wavelength of lasing light. By amplifying the dark mode surface plasmon is another way for realizing spaser. The dark mode surface plasmon has very low radiation loss, and can support very strong localized field. The spaser based on the dark mode can overcome the high radiation loss problem the spaser of the bright mode faces. Fano resonance is one of the means of exciting the dark mode surface plasmon. The project combines double-Fano resonance and amplification of the surface plasmon. Design and fabricate the metal nanostructures which support tunable double-Fano resonance. And then, study the two dark mode surface plasmon amplification by stimulated emission of radiation excited by the double-Fano resonance. This can realize the spaser based on the dark mode surface plasmon, it’s nanostructure also can resonate at the wavelength of pumping and lasing light simultaneously. This project will solve the high radiation loss and the low external energy utilization efficiency the spaser faced.

近年来，表面等离激元纳米激光器是国际上重要的研究热点之一，在物理、化学、生物和医学等领域有重要的应用前景。目前，已实现的该类纳米激光器通常是对亮态表面等离激元的受激辐射放大，其金属纳米结构也只在激射光处共振。而对暗态表面等离激元的受激辐射放大也是实现该类纳米激光器的一种方法。暗态表面等离激元辐射损耗很小，电场局域性更强，基于它的纳米激光器能有效克服亮态表面等离激元纳米激光器所面临的高辐射损耗问题。Fano共振是激发暗态表面等离激元的一种方式。本项目拟将金属纳米结构双Fano共振与表面等离激元受激辐射放大相结合，通过可调谐双Fano共振金属纳米结构的设计及制备，研究其激发的两个暗态表面等离激元的受激辐射放大特性，从而实现泵浦光和激射光处同时共振的暗态表面等离激元纳米激光器。本项目能有效解决表面等离激元纳米激光器所面临的高辐射损耗和对外部能量利用效率低的问题。

表面等离激元纳米激光器能够形成微纳尺度的纳米光源，在物理、化学、生物和医学等领域有重要的应用前景。已实现的该类纳米激光器通常是对亮态表面等离激元的受激辐射放大，其金属纳米结构也只在激射光处共振。利用金属纳米结构双Fano共振与暗态表面等离激元的受激辐射放大，可实现泵浦光与激射光同时共振的暗态表面等离激元纳米激光器。主要利用双环盘金属纳米结构与半导体(如 InGaAsP)或者量子井材料(如，InGaAsN/InP 或者 InGaAsP/InP)相结合，实现室温下对暗态表面等离激元的受激辐射放大的纳米激光，且使得激射光阈值比亮态的纳米激光器要低6倍。且将另一个暗态表面等离激元应用于泵浦光可提高入射光的吸收效率，与亮态的表面等离激元作为泵浦光吸收效率可提高4.2倍。另外，基于双盘环结构的纳米激光，利用环的高调谐性实现调谐范围较大激射光和泵浦光，其调谐范围可达1.49-1.64um和0.88-1.33um。本项目有效解决表面等离激元纳米激光器所面临的高辐射损耗和对外部能量利用效率低的问题，也为实现调谐性能较好的激光提供了一条有效途径。再者，为了实现阈值更低的表面等离激元纳米激光器，还理论研究了二维纳米材料WS2和金银双金属膜结构的金属纳米结构的支持的表面等离激元情况。发现利用二维材料可降低金属结构的共振线宽，提高Q因子，目前只是将此结构应用到SPR传感器方面，发现传感器的灵敏度以及Q值都有一定程度的提高。当将单层Graphene与WS2覆盖在Au-Ag 双金属层上时，灵敏度可提高到 182.5 Deg/RIU，但FWHM 稍微有点增加。当 Graphene 层数为 4，灵敏度可达到最大值（192.5 Deg/RIU），可实现一个更高的灵敏度和分辨率的 SPR 传感器。为降低表面等离激元的半高宽也就是提高Q值提供了一种有效的方法。