有源纳米等离子体超材料中亮、暗激光态的控制与动态竞争

Coherent amplification and lasing of weak surface-plasmon polaritons in a negative-index metamaterial with a resonant atomic medium

Surface plasmon polaritons (SPPs) lasing requires population inversion, it is inefficient and possesses poor spectral properties. We develop an inversion-less concept for a quantum plasmonic waveguide that exploits unidirectional superradiant SPP emission of radiation to produce intense coherent surface plasmon beams. Our scheme includes a resonantly driven cold atomic medium in a lossless dielectric situated above an ultra-low loss negative index metamaterial~(NIMM) layer. We propose generating unidirectional superradiant radiation of the plasmonic field within an atomic medium and a NIMM lay…

基于光泵石墨烯的损耗补偿和激射太赫兹超材料

Towards loss compensated and lasing terahertz metamaterials based on optically pumped graphene

数值计算表明，光泵石墨烯适合于补偿太赫兹（THz）超材料的固有损耗。第一步，计算了光泵浦下石墨烯的复电导率，确定了单层石墨烯中太赫兹放大的合适条件。它示出，在石墨烯中发生放大的温度高达室温和中等泵浦强度时，在电信波长$λ=1.5~\mathrm{μm}$泵浦。此外，石墨烯的放大性能进行了评估和讨论，在温度低至$T=77~\mathrm{K}$和泵浦强度$I=300~\mathrm{mW/mm^2}$调查石墨烯和等离子体裂环谐振器（SRR）超材料之间的耦合。欧姆和介质损耗机制的贡献进行了研究，通过全波模拟。结果发现，开口环谐振器超材料的损耗可以通过石墨烯中的光受激放大来补偿。此外，它表明，由非对称开口环谐振器和光泵石墨烯组成的混合材料可以超过激光阈值条件，并可以发出相干太赫兹辐射在最小输出功率水平的$6 0~\mathrm{nW/mm^2}$。光泵石墨烯的使用非常适合于太赫兹超材料的损耗补偿，并为新型相干太赫兹源铺平了道路。

Tailoring Nanowire Lasing Modes via Coupling to Metal Gratings

Tailoring the emission of plasmonic nanowire-based lasers represents one of the major challenges in the field of nanoplasmonics, given the envisaged integration of such devices into on-chip all-optical circuits. In this study, we proposed a mode selection scheme based on distributed feedback, achieved via the external coupling of single zinc oxide nanowires to an aluminum grating, which enabled a quasi-single mode lasing action. The nano-manipulation of a single nanowire allowed for a reliable comparison of the lasing emission characteristics in both planar (i.e. nanowire on the metallic subst…

有源超材料中辐射的受激发射对光频左手传输的共振放大

Resonance amplification of left-handed transmission at optical frequencies by stimulated emission of radiation in active metamaterials

我们证明了通过引入有源介质层作为衬底，由周期性排列的双环组成的金属超材料的左手共振传输可以扩展到可见光谱。在这种有源系统中，金属内部在光频处的严重欧姆损耗由辐射的受激发射补偿。由于最近提出的激光spaser的共振放大机制，左手传输带可以恢复到610 nm波长，取决于有源层的增益系数。此外，双环单元的不同缩放级别的阈值增益进行了研究，以评估在不同的频率范围的左手传输恢复的增益要求。

耦合到两级系统增益的等离子体超材料共振的Toy模型

Toy model for plasmonic metamaterial resonances coupled to two-level system gain

我们提出，解决，并讨论了一个简单的模型的超材料纳入光学增益：一个单一的玻色子共振耦合到一个费米子（倒）两级系统共振通过本地场的相互作用。对于给定的稳态反演，该模型可以解析求解，揭示了丰富的各种各样的（法诺）吸收/增益线型。我们还给出了一个解析表达式的固定反转所产生的增益钉扎在稳态条件下。此外，“激光SPASER”的动态响应，即，它的弛豫振荡，可以通过简单的数值计算在同一模型内获得。因此，这个玩具模型可以被看作是通常的激光速率方程的近场光学对应。

Luminescence engineering in plasmonic meta-surfaces

Photoluminescence is a phenomenon of significant interest due to its wide range of technological applications in plasmonics, nanolasers, spasers, lasing spasers, loss compensation and gain in metamaterials, and luminescent media. Nanostructured materials are known to have very different luminescence characteristics to bulk samples or planar films. Here we show that by engineering a nanostructured meta-surface, we can choose the position of photoluminescence absorption and emission lines of thin gold films. The nanostructuring also aids to strong enhancement of the emission from gold, by a fact…

Graphene and active metamaterials: theoretical methods and physical properties

The interaction of light with matter has triggered the interest of scientists for long time. The area of plasmonics emerges in this context through the interaction of light with valence electrons in metals. The random phase approximation in the long wavelength limit is used for analytical investigation of plasmons in three-dimensional metals, in a two-dimensional electron gas and finally in the most famous two-dimensional semi-metal, namely graphene. We show that plasmons in bulk metals as well as in a two-dimensional electron gas originate from classical laws, whereas, quantum effects appear …

Nonlinear, Tunable and Active Optical Metasurface with Liquid Film

Optical metamaterials and metasurfaces which emerged in the course of the last few decades have revolutionized our understanding of light and light-matter interaction. While solid materials are naturally employed as key building elements for construction of optical metamaterials mainly due to their structural stability, practically no attention was given to study of liquid-made optical 2D metasurfaces and the underlying interaction regimes between surface optical modes and liquids. In this work, we theoretically demonstrate that surface plasmon polaritons and slab waveguide modes that propagat…

Tunable Terahertz Amplification Based on Photoexcited Active Graphene Hyperbolic Metamaterials

The efficient amplification and lasing of electromagnetic radiation at terahertz (THz) frequencies is a non-trivial task achieved mainly by quantum cascade laser configurations with limited tunability and narrowband functionality. There is a strong need of compact and efficient THz electromagnetic sources with reconfigurable operation in a broad frequency range. Photoexcited graphene can act as the gain medium to produce coherent radiation at low THz frequencies but its response is very weak due to its ultrathin thickness. In this work, we demonstrate an alternative design to achieve efficient…

Multimode parity-time and loss-compensation symmetries in coupled waveguides with loss and gain

Loss compensation via inserting gain is of fundamental importance in different branches of photonics, nanoplasmonics, and metamaterial science. This effect has found an impressive implementation in the parity-time symmetric (PT-symmetric) structures possessing balanced distribution of loss and gain. In this work, we generalize this phenomenon to the asymmetric systems demonstrating loss compensation in the coupled multi-mode loss-gain dielectric waveguides of different radii. We show that similar to the PT-symmetric coupled single-mode waveguides of identical radii, the asymmetric systems supp…