太赫兹表面极化激元

作为束缚于表面或界面的电磁波与极性元激发的耦合模量子,表面极化激元是克服衍射极限的核心物理.在紫外、可见以及近红外波段,表面等离子极化激元展现出了亚波长特性,具有高分辨成像等应用,并发展成为"表面等离子极化激元亚波长光学"学科;在中红外波段,表面声子极化激元发挥着同样的作用.太赫兹波段曾是人类认识的空白区域,近三十年来得以高速发展,其战略意义重大.具有克服衍射极限能力的太赫兹表面极化激元同样是小型化与集成化太赫兹器件,以及太赫兹超高分辨成像的重要物理基础.近几年来,对以石墨烯为代表的二维材料的研究突飞猛进,诞生了"石墨烯表面等离子极化激元亚波长光学"这门学科,并贡献于太赫兹领域.本文对可在太赫兹波段工作的人工超构材料、掺杂半导体、二维电子气、二维材料、拓扑绝缘体等结构材料的表面极化激元进行了较为全面的总结与介绍,为研制克服衍射极限的太赫兹集成光子学器件提供可资借鉴的物理基础.     

Interaction of valence band excitations and terahertz TE-polarized cavity modes

The strong coupling of THz radiation and material excitations has potential to improve the quantum efficiency of THz devices. In this paper, we investigate a simple structure delivering THz polaritons and antipolaritons based on valence band transitions. The approach can improve the quantum efficiency of THz based devices based on TE mode in the strong coupling regime of THz radiations and intervalence bands transitions in a GaAs/AlGaAs quantum well. A Nonequilibrium Many Body Approach for the optical response beyond the Hartree–Fock approximation is used as input to the effective dielectric function formalism for the polariton/antipolariton problem. The energy dispersions relations in the THz range are obtained based on simplified analytical approximation.     

Phonon-induced polariton superlattices

We show that the coherent interaction between microcavity polaritons and externally stimulated acoustic phonons forms a tunable polariton superlattice with a folded energy dispersion determined by the phonon population and wavelength. Under high phonon concentration, the strong confinement of the optical and excitonic polariton components in the phonon potential creates weakly coupled polariton wires with a virtually flat energy dispersion.     

Quantum optical effects in semiconductor microcavities

Investigations of quantum effects in semiconductor quantum-well microcavities interacting with laser light in the strong-coupling regime are presented. Modifications of quantum fluctuations of the outgoing light are expected due to the non-linearity originating from coherent exciton–exciton scattering. In the strong-coupling regime, this scattering translates into a four-wave mixing interaction between the mixed exciton–photon states, the polaritons. Squeezing and giant amplification of the polariton field and of the outgoing light field fluctuations are predicted. However, polariton–phonon scattering is shown to yield excess noise in the output field, which may destroy the non-classical effects. Experiments demonstrate evidence for giant amplification due to coherent four-wave mixing of polaritons. Noise reduction below the thermal noise level was also observed. To cite this article: E. Giacobino et al., C. R. Physique 3 (2002) 41–52     

Surface phonon–polaritons in rectangular quantum wires of polar ternary mixed crystals

In this paper, the dispersion relations of surface phonon–polaritons in freestanding rectangular quantum wire systems of polar ternary mixed crystals are derived. The numerical calculations for Al_xGa_1−xAs and Zn_xCd_1−xSe quantum wire systems are performed. The results reveal that the frequencies of surface phonon–polariton modes are sensitive to the geometric structures of the quantum wires, the wave-vectors in z-direction, and the compositions of the ternary mixed crystal materials. The effects of the “two-mode” and “one-mode” behaviors of the ternary mixed crystals on the surface phonon–polariton modes are also discussed.     

Terahertz phonon polariton imaging

In this article, we primarily review the time-resolved imaging of THz phonon polariton, which is generated by femtosecond laser in ferroelectric crystal. We pay more attention to the imaging in thin crystal, which can be used as an integration platform for terahertz-optics or terahertz-electrics. The imaging techniques, which can get quantitatively in-focus time-resolved images, are introduced in more detail. They have made enormous progress in recent years, and are powerful tools for the research of phonon polariton, optics, and THz wave. We also briefly introduce the generation principle and general propagation properties of THz phonon polariton.     

Nonclassical Effects in Polariton System

In this paper we study a model polariton system. With the photons and the phonons being initially prepared in coherent state and vacuum state respectively, we show that as time evolves, the distributions of photons, phonons, and polaritons can be sub-Poissonian, and the photon quadrature squeezing, the phonon quadrature squeezing, and the polariton quadrature squeezing can exist in this system.     

Coupled THz Waveguide Utilizing Surface Plasmon Polaritons on Thin Dielectric Slab Sandwiched between Two Corrugated Metallic Claddings

We present a comprehensive experimental study of terahertz （THz） wave propagation utilizing surface plasmon polaritons （SPPs） on the interfaces of a thin dielectric core layer sandwiched between two corrugated metallic claddings. THz wave impinges on the structured surfaces at normal incidence. Long-lasting oscillation propagation features are observed in the temporal waveform after traveling through the periodic arrays. The enhanced THz transmission can be achieved due to the coupling between incident waves to SPPs at the bottom and top interfaces. The finite element method is used to simulate the field distribution and the transmission mode in the waveguide. The hybrid waveguide with low absorption has great potential applications in THz integrated devices.     

Cavity plasmon polaritons in monolayer graphene

Plasmon polaritons in a new system, a monolayer doped graphene embedded in optical microcavity, are studied here. The dispersion law for lower and upper cavity plasmon polaritons is obtained. Peculiarities of Rabi splitting for the system are analyzed; particularly, role of Dirac-like spinor (envelope) wave functions in graphene and corresponding angle factors are considered. Typical Rabi frequencies for maximal (acceptable for Dirac-like electron spectra) Fermi energy and frequencies of polaritons near polariton gap are estimated. The plasmon polaritons in considered system can be used for high-speed information transfer in the THz region.     

Dynamics of a parametric exciton-polariton oscillator in a microcavity

We study the dynamics of parametric oscillations of polaritons in a microcavity that consists of a periodic conversion of a pair of pump polaritons into polaritons of signal and idle modes and vice versa. The period and amplitude of oscillations considerably depend on the initial polariton density, the initial phase difference, and the resonance detuning. We show that there is a possibility of phase controlling the polariton dynamics in the microcavity.     

Strong light‐matter coupling between a molecular vibrational mode in a PMMA film and a low‐loss mid‐IR microcavity

Microcavity devices exhibiting strong light‐matter coupling in the mid‐infrared spectral range offer the potential to explore exciting open physical questions pertaining to energy transfer between heat and light and can lead to a new generation of efficient wavelength tunable mid‐infrared sources of coherent light based on polariton Bose‐Einstein Condensation. Vibrational transitions of organic molecules, which often have strong absorption peaks in the infrared and considerably narrower linewidths than organic excitonic resonances, can generate polaritonic states in the mid‐infrared spectral range using microcavity devices. Here, narrow linewidth polaritonic resonances are exhibited in the mid‐infrared by coupling the carbonyl stretch vibrational transition of a polymethyl methacrylate film to the photonic resonance of a low optical‐loss mid‐infrared microcavity, which consisted of two Ge/ZnS dielectric Bragg reflectors. Rabi‐splitting of 14.3 meV is observed, with a 4.4 meV polariton linewidth at anti‐crossing. The large Rabi‐splitting relative to linewidth indicates efficient impedance‐matching between the bare vibrational and photonic states, and suggests molecular‐vibration polaritons incorporated in dielectric microcavities can be an enabling step towards realizing polariton optical switching and polariton condensation in the mid‐infrared spectral range.     

Thermostimulated polariton emission of zinc selenide films on metal substrate

Angular dependences of the spectral radiance for bulk and surface polaritons in ZnSe films on an aluminium mirror have been investigated both experimentally and theoretically. A shift of a surface polariton branch to low frequencies has been observed. The difference between the surface polariton and the transverse optical phonon frequencies turned to be inversely proportional to the metal substrate conductivity. Theoretical results obtained are in good agreement with the experiment.     

基于耦合场量子受激拉曼散射的太赫兹波辐射

使用两块长度各为65 mm的MgO:LiNbO3和无掺杂LiNbO3晶体,以1064nm的Q开关Nd:YAG激光器作为抽运光源,在12 mJ/pulse的抽运光能量下得到频率范围为0.34～2.90 THz的电磁辐射.分析表明,激光入射使LiNbO3晶体中具有电磁特性的横光学声子可以和入射光子形成耦合场量子.作为一种电磁特性的元激发,LINbO3晶体的耦合场量子的辐射场频率覆盖部分太赫兹频段范围,并可通过耦合场量子受激拉曼散射过程辐射THz波.根据耦合场量子辐射理论,通过分析晶体的耦合场量子色散特性曲线,可以确定该晶体能否辐射THz波及其带宽范围.     

Theory of surface polaritons in n-type silicon in the presence of a dc current,including the electron thermal pressure gradient

A theoretical investigation has been made of the effect of a drift current, including the electron thermal pressure gradient, on surface polaritons in n-type Si. The polariton propagation and drift current directions are taken to be either parallel or antiparallel. Retardation is included, but damping is neglected. The specular reflection approach of Kliewer and Fuchs is used to obtain the polariton dispersion relation. The results show that the drift current and surface polaritons interact, leading to evanescent waves for certain frequencies. However, no wave amplification is obtained.     

Quantum Theory of Surface Polaritons in Semi-Infinite Dielectric Systems

The interaction system of a semi-infinite diatomic dielectric and the electromagnetic field propagating parallelly to the surface is studied. The long-wave optical phonon modes of the semi-infinite dielectric are calculated including the electronic polarizability by a quantum-mechanical theory. Retardation effects are neglected. A quantum field theory method of surface polaritons is developed to calculate the operator describing the interaction between a photon and the phonon polarization fields of the semi-infinite crystal, with explicit inclusion of surface effects. The dispersion relations of the surface phonon-polaritons are derived and discussed. The results are in good agreement with those obtained by the conventional, macroscopic dielectric theory of surface polaritons and experimental ATR (attenuated total reflection) spectra. The dispersion cuwes of polariton leaking modes caused by the interaction between bulk TO mode with surface effect and photons are presented in a graphical form. The k_||-dependence of the electric field strength in each polariton branch is calculated and presented also in a graphical form. We also research the spatial dependence of the field strength in each polariton branch. It is found that these properties are influenced and modulated by the surface phonons because of the interaction between photons and the surface phonon modes of the semi-infinite dielectric system. Hence the divergent nature (diffraction effect) of light propagating along the fib& and waveguides is restrained. We present a method how to use the boundary conditions in the quantum theory, which will be discussed in detail.     

Back-propagating surface polaritons of a one-dimensional photonic crystal containing single negative metamaterials

The existence of the surface polaritons at the interface separating a semi-infinite uniform left-handed metamaterial and a one-dimensional photonic crystal composed of alternating layers of two kinds of single-negative materials is theoretically investigated. The dispersion characteristics of the surface polaritons are analyzed and demonstrated that in the presence of metamaterial, the surface polaritons are sensitive to light polarization, so that there exist only backward TM-polarized (or TE-polarized) kind of the surface polaritons depending on the ratio of the thicknesses of the two periodic stacking layers. The existence regions of the surface polariton modes are determined for both TM-polarized and TE-polarized surface polariton modes.     

含单负材料三明治结构的电磁隧穿特性

在理论分析的基础上,结合实验研究了单负材料/正折射率材料(或单负材料)/单负材料三明治结构的电磁隧穿性质.这种结构的电磁隧穿来源于入射平面波与结构的表面或体极化激元的耦合,从理论上讨论并计算了正入射情况下这种结构中的极化激元的色散关系.发现:由单负材料作为边界而正折射率材料为中间层的三明治结构具有体极化激元,这种极化激元的共振频率随着中间层厚度的增加向低频移动;由不同性质的单负材料构成的三明治结构具有两条色散曲线,这两条色散曲线随着中间层厚度的增加而简并.随后基于L-C传输线技 关键词： 单负材料 极化激元 隧穿 L-C传输线')" href="#">L-C传输线     

Generation of Raman polaritons in three-level atomic media

A theory of formation of Stokes field (Raman) polaritons, which arise due to the coherent stimulated Raman scattering of light in an ensemble of three-level atoms placed in a Fabry-Perot cavity in the case of a strong coupling regime, is developed. The dispersion and absorption properties of Raman polaritons are investigated and the conditions for polariton amplification are found. It is shown that for certain pump power values, nonclassical correlations (entanglement) between light and dark polaritons are observed in the system.     

“Thermal barrier” effect in energy relaxation of polaritons in HgI2

The paper presents the results of measurements of polariton radiation spectra, polariton band excitation spectra and spectra of resonance Raman scattering HgI₂. These are registered at different temperatures and units of energetic derangement between the exciting radiation quantum energy and that of transverse exciton. The threshold value of the temperature (T=12 K) starting from which there is attained the equilibrium between the polariton and phonon subsystems is found. The scattering mechanism that guides the formation of “thermal barrier” favouring the polaritons thermalization, is revealed.     

Dynamic control of the terahertz rainbow trapping effect based on a silicon-filled graded grating

We theoretically propose a scheme to realize the dynamic control of the properties of the terahertz(THz) rainbow trapping effect(RTE) based on a silicon-filled graded grating(SFGG) in a relatively broad band via optical pumping.Through the theoretical analysis and finite-element method simulations, it is conceptually demonstrated that the band of the RTE can be dynamically tuned in a range of ~0.06 THz. Furthermore, the SFGG can also be optically switched between a device for the RTE and a waveguide for releasing the trapped waves. The results obtained here may imply applications for the tunable THz plasmonic devices, such as on-chip optical buffers, broad band slow-light systems, and integrated optical filters.