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Systematic study on visible light collimation by nanostructured slits in the metal surface

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Chinese physics B 2011年第3期20卷 460-465页

作者：傅晋欣华一磊陈宇辉刘荣鹃李家方李志远 laboratory of optical physics Institute of PhysicsChinese Academy of Sciences

We present a systematic experimental investigation on visible light collimation by a nanostructured slit flanked with a pair of periodic array of grooves in gold thin film. A wide variety of aspects are considered, such as the polarization state, the transport path of incident light, the groove-groove spacing, the groove width and depth. Our results clearly show that the relationship between the collimation wavelength and the periodicity of the slit-groove structure accords well with the surface plasmon dispersion model proposed by previous researchers. Furthermore, the surface plasmon wave phase retardation effect induced by the surface structure is also verified via the measurement for samples with different groove widths and depths. These results indicate that the detailed geometry of the groove structure has obvious impacts on the collimation effect and the angular distribution of the diffraction light in the subwavelength plasmonic system.

关键词： surface plasmon collimation

Enhanced light absorption of silicon in the near-infrared band by designed gold nanostructures

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Chinese physics B 2014年第4期23卷 551-556页

作者：刘菊钟晓岚李志远 laboratory of optical physics Institute of Physics Chinese Academy of Sciences

A scheme to enhance near-infrared band absorption of a Si nanoparticle by placing the Si nanoparticle into a designed gold nanostructure is proposed. Three-dimensional （3D） finite-difference time-domain simulations are employed to calcu- late the absorption spectrum of the Si nanostructure and maximize it by generating alternate designs. The results show that in the near-infrared region over 700 nm, the absorption of a pure Si nanoparticle is very low, but when the same nanoparticle is placed within an optimally designed gold nanostructure, its absorption cross section can be enhanced by more than two orders of magnitude in the near-infrared band.

关键词： surface plasmon resonance near-infrared silicon absorption finite-difference time-domain opti-mization

Elementary analysis of interferometers for wave particle duality test and the prospect of going beyond the complementarity principle

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Chinese physics B 2014年第11期23卷 202-214页

作者：李志远 laboratory of optical physics Institute of Physics Chinese Academy of Sciences

A distinct method to show a quantum object behaving both as wave and as particle is proposed and described in some detail. We make a systematic analysis using the elementary methodology of quantum mechanics upon Young＇s two-slit interferometer and the Mach-Zehnder two-arm interferometer with the focus placed on how to measure the interference pattern （wave nature） and the which-way information （particle nature） of quantum objects. We design several schemes to simultaneously acquire the which-way information for an individual quantum object and the high-contrast interference pattern for an ensemble of these quantum objects by placing two sets of measurement instruments that are well separated in space and whose perturbation of each other is negligibly small within the interferometer at the same time. Yet, improper arrangement and cooperation of these two sets of measurement instruments in the interferometer would lead to failure of simultaneous observation of wave and particle behaviors. The internal freedoms of quantum objects could be harnessed to probe both the which-way information and the interference pattern for the center-of-mass motion. That quantum objects can behave beyond the wave-particle duality and the complementarity principle would stimulate new conceptual examination and exploration of quantum theory at a deeper level.

关键词： wave-particle duality complementarity principle atom interferometer

Graphene-like physics in optical lattices

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Chinese physics B 2013年第11期22卷 114-124页

作者：梅锋张丹伟朱诗亮 National laboratory of Solid State Microstructures and School of physics Nanjing University laboratory of Quantum Engineering and Quantum Materials School of Physics and Telecommunication Engineering South China Normal University

Graphene has attracted enormous attention over the past years in condensed matter physics. The most interesting feature of graphene is that its low-energy excitations are relativistic Dirac fermions. Such feature is the origin of many topological properties in graphene-like physics. On the other hand, ultracold quantum gas trapped in an optical lattice has become a unique setting for quantum simulation of condensed matter physics. Here, we mainly review our recent work on quantum simulation of graphene-like physics with ultracold atoms trapped in a honeycomb or square optical lattice, including the simulation of Dirac fermions and quantum Hall effect with and without Landau levels. We also present the related experimental advances.

关键词： graphene Dirac fermions quantum Hall effect optical lattice

Manipulation of plasmonic wavefront and light–matter interaction in metallic nanostructures: A brief review

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Chinese physics B 2014年第4期23卷 25-40页

作者：李家方李志远 laboratory of optical physics Institute of Physics Chinese Academy of Sciences

The control and application of surface plasmons （SPs）, is introduced with particular emphasis on the manipulation of the plasmonic wavefront and light-matter interaction in metallic nanostructures. We introduce a direct design methodology called the surface wave holography method and show that it can be readily employed for wave-front shaping of near-infrared light through a subwavelength hole, it can also be used for designing holographic plasmonic lenses for SPs with complex wavefronts in the visible band. We also discuss several issues of light-matter interaction in plasmonic nanostructures. We show theoretically that amplification of SPs can be achieved in metal nanoparticles incorporated with gain media, leading to a giant reduction of surface plasmon resonance linewidth and enhancement of local electric field intensity. We present an all-analytical semiclassical theory to evaluate spaser performance in a plasmonic nanocavity incorporated with gain media described by the four-level atomic model. We experimentally demonstrate amplified spontaneous emission of SP polaritons and their amplification at the interface between a silver film and a polymer film doped with dye molecules. We discuss various aspects of microscopic and macroscopic manipulation of fluorescent radiation from gold nanorod hybrid structures in a system of either a single nanoparticle or an aligned group of nanoparticles. The findings reported and reviewed here could help others explore various approaches and schemes to manipulate plasmonic wavefront and light-matter interaction in metallic nanostructures for potential applications, such as optical displays, information integration, and energy harvesting technologies.

关键词： surface plasmons surface wave holography surface plasmon amplification fluorescence enhance-ment gold nanorods

Unidirectional emissions from dielectric photonic circuits decorated with plasmonic phased antenna arrays

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Chinese physics B 2014年第3期23卷 482-488页

作者：丁伟陈宇辉李志远 laboratory of optical physics Institute of Physics Chinese Academy of Sciences

Thanks to resonant characteristics of metallic nanoparticles, optical waves scattered from plasmonic nanoantennae can be well tailored in both amplitude and phase. We numerically demonstrate that, by varying the lengths and the lateral positions of gold nanorods in vicinity of a silicon waveguide, unidirectional emissions with typical forward-backward contrast ratio of 15 dB and directivity of 12 dB can be acquired in a plasmonic phased antenna array with sub-wavelength device length. The properties, i.e., the emission directionality and the size compactness, can be employed to control the far-field radiation pattern from a dielectric photonic circuit. Moreover, by altering the orientations of the dielectric waveguides decorated with plasmonic phased antenna arrays, we propose wireless light transportations in a layered photonic infrastructure, which may have applications in high-density photonic integrations.

关键词： surface plasmons optical properties of nanoparticles optical structures light scattering

Spontaneous emission of two quantum dots in a single-mode cavity

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Chinese physics B 2013年第9期22卷 431-438页

作者：邱柳张珂李志远 laboratory of optical physics Institute of PhysicsChinese Academy of Sciences

The spontaneous emission spectrum from two quantum dots （QDs） that are strongly coupled with a single-mode nanocavity is investigated using rigorous numerical calculations and simple analytical solutions of quantum dynamics. The emission spectra both from the side and along the axis of the cavity are considered. Modification of two parameters, the coupling strength and the detuning between the transition frequencies of the two quantum dots, allows us to efficiently control the shape of the spontaneous emission spectrum. Different profiles and their physical origins can be well understood in the dressed-state picture for the light-QD interaction in the on-resonance and off-resonance situations. In the on-resonance situation, the emission spectra exhibit symmetric features, and they are not altered by the asymmetry in the coupling pa- rameters. The axis spectra show two emission peaks while the side spectra have three emission peaks. In the off-resonance situation, the emission spectra always show an asymmetrical three-peak feature. When the two QDs have different decay parameters, singular features （a peak or a dip） can take place at the frequency of the cavity mode, and this is attributed to the unbalanced process of the emission and absorption of a single photon.

关键词： spontaneous emission quantum dot single-mode cavity

Spontaneous emission of “polarized” V-type three-level atoms strongly coupled with an optical cavity

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Chinese physics B 2015年第3期24卷 169-175页

作者：薛艳丽朱诗灯李家方丁伟冯宝华李志远 laboratory of optical physics Institute of PhysicsChinese Academy of Sciences

Polarization, an intrinsic ingredient of photon, plays a critical role in its interaction with matter. A general polarization state can be an appropriate superposition of two basic polarization states, say, the vertical and horizontal linear polarized state. Here we study spontaneous emission of a V-type three-level atom（with two upper states close in energy level）strongly coupled with a single-mode damped optical cavity. By defining a general polarization state of atom as a specific superposition of the two upper quantum states, we can prepare atoms with linear polarization at arbitrary direction, left and right circular polarization, and left and right elliptical polarization, similar to photons. We find that the spontaneous emission of light from these ＂polarized＂ three-level atoms shows very different profiles of side and axis spectra. This means that the polarization state of three-level atoms can become an active ingredient to manipulate its interaction with light and control the quantum interference effect. Exploitation of the coherent superposition and interference of quantum states in＂polarized＂ atoms would allow one to deeply explore new frontiers of light–matter interaction.

关键词： spontaneous emission polarization state three-level atoms

Photonic crystal cavities and integrated optical devices

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Science China(physics,Mechanics & Astronomy) 2015年第11期58卷 11-22页

作者： GAN Lin LI ZhiYuan laboratory of optical physics Institute of Physics Chinese Academy of Sciences

This paper gives a brief introduction to our recent works on photonic crystal(Ph C) cavities and related integrated optical structures and devices. Theoretical background and numerical methods for simulation of Ph C cavities are first presented. Based on the theoretical basis, two relevant quantities, the cavity mode volume and the quality factor are discussed. Then the methods of fabrication and characterization of silicon Ph C slab cavities are introduced. Several types of Ph C cavities are presented, such as the usual L3 missing-hole cavity, the new concept waveguide-like parallel-hetero cavity, and the low-index nanobeam cavity. The advantages and disadvantages of each type of cavity are discussed. This will help the readers to decide which type of Ph C cavities to use in particular applications. Furthermore, several integrated optical devices based on Ph C cavities, such as optical filters, channel-drop filters, optical switches, and optical logic gates are described in both the working principle and operation characteristics. These devices designed and realized in our group demonstrate the wide range of applications of Ph C cavities and offer possible solutions to some integrated optical problems.

关键词： photonic crystal cavities optical filter optical switch optical logic gates