Polariton spin beats in semiconductor quantum well microcavities

Time-resolved Kerr (Faraday) rotation experiments allow for the observation of polariton spin beats in both InGaAs and CdMnTe quantum well (QW) microcavities. The existence of these beats is an unambiguous manifestation of the coherent energy exchange between exciton and photon components of polariton states created by a circularly polarized and spectrally wide femtosecond laser pulse. The polariton states are also shown to be split into a linearly polarized doublet. This splitting is responsible for the polarization transfer between linearly and circularly polarized states. In a highest-quality sample, the resulting spin dynamics could be detected.     

Quantum theory of spin dynamics of exciton-polaritons in microcavities

We present the quantum theory of momentum and spin relaxation of exciton-polaritons in microcavities. We show that giant longitudinal-transverse splitting of the polaritons mixes their spin states, which results in beats between right- and left-circularly polarized photoluminescence of microcavities, as was recently experimentally observed [Phys. Rev. Lett. 89, 077402 (2002)]]. This effect is strongly sensitive to the bosonic stimulation of polariton scattering.     

Resonant modes in monolithic nitride pillar microcavities

GaN-based airpost pillar microcavities are realized by focused-ion beam etching starting from an all-epitaxially grown vertical-cavity surface-emitting laser structure. Pillar diameters below 1 μm are well controllable. The sidewalls are smooth and show a damaged surface layer of a thickness less than 2 nm only. Micro-photoluminescence measurements reveal the longitudinal and transversal mode spectra of the cavities in good agreement with theoretical calculations based on a vectorial transfer-matrix method.     

High-efficiency single-photon sources based on InAs/GaAs quantum dots in pillar microcavities

We have experimentally investigated pillar microcavities containing a low density of InAs/GaAs self-assembled quantum dots. We observe a four-fold reduction in the radiative lifetime of an excitonic state due to the Purcell effect and show that we are able to collect 10% of the photons emitted by this state into a microscope objective. Under quasi-resonant excitation the multi-photon emission probability is more than 50 times lower than a Poissonian source of the same intensity.     

Far-field radiation from quantum boxes located in pillar microcavities

Far-field radiation for quantum boxes located in pillar microcavities was investigated spatially and spectrally at room temperature. We have found that small-diameter pillars show directional emission for the fundamental cavity mode together with a spectral behavior dominated by the pillar's discrete modal structure. These results may be important in the context of single-photon emitters for quantum communications.     

Optical polariton properties in ZnSe-based planar and pillar structured microcavities

Strong coupling is demonstrated in monolithic ZnSe-based microcavities. Under nonresonant excitation the polariton dispersion has been investigated in dependence on the photon-exciton detuning for different excitation densities at low temperatures. For zero detuning indications of a polariton lasing threshold are observed like a k-space and energy dispersion narrowing of the lower polariton branch with increasing excitation density. Furthermore, it is observed that this effect is hampered for measurements at negative detunings as a result of the less effective polariton relaxation to the ground state. Latter results in the formation of a discrete polariton distribution at finite k values as known for the polariton bottleneck. In order to investigate the influence of a three-dimensional optical confinement on the polariton relaxation, pillar structured microcavities were fabricated. The formation of discrete polariton states in the k-space distribution is observed. Furthermore, indications for a softening of the k-conservation arising from the structural confinement are found leading to a more effective polariton relaxation. This process would be beneficial for the realization of efficient polariton lasing processes.     

Far field emission of micropillar and planar microcavities lattice-matched to ZnTe

We investigate light emission from ZnTe-based microcavities containing CdTe quantum dots (QDs), with 2D (planar cavity) and 0D (pillar cavities) photonic confinement. The angular distribution from the planar cavity is presented as well as 2D cross-sections of the far field distribution of radiation from the micropillars. The efficient and desirable modification of the isotropic radiation of the QDs is shown for such structures. The diffraction observed is found to be inherent for such experiments with large numerical aperture of the lens and small diameters of the investigated pillars. This diffraction is successfully modeled.     

Strong coupling of quantum dots in microcavities

We show that strong coupling (SC) of light and matter as it is realized with quantum dots in microcavities differs substantially from the paradigm of atoms in optical cavities. The type of pumping used in semiconductors yields new criteria to achieve SC, with situations where the pump hinders, or on the contrary, favors it. We analyze one of the seminal experimental observation of SC of a quantum dot in a pillar microcavity [Reithmaier, Nature (London) 432, 197 (2004)10.1038/nature02969] as an illustration of our main statements.     

Influence of Dielectric Loss on Quality Factors of Photonic Crystal Microcavity Modes

We numerically investigate the quality factors of two-dimensional （2D） photonic crystal （PC） microcavities using an auxiliary differential equations （ADE） technique in the context of finite-difference time-domain （FDTD） method. The microcavities are formed by point defects in the air hole lattice hexagonally patterned in ZnO （zinc oxide） matrix. The quality factors of these microcavities are limited primarily by the absorption of the background dielectric. We show that the ratio between the quality factors of microcavities in lossy and lossless background dielectric depends on the overlap between the field of cavity modes and the absorbing background dielectric in addition to the magnitude of absorption. These results will be helpful when designing and optimizing photonic crystal microcavities formed in lossy medium.     

Photonic-plasmonic hybrid microcavities: Physics and applications

Photonic-plasmonic hybrid microcavities, which possess a higher figure of merit Q/V (the ratio of quality factor to mode volume) than that of pure photonic microcavities or pure plasmonic nano-antennas, play key roles in enhancing light-matter interaction. In this review, we summarize the typical photonic-plasmonic hybrid microcavities, such as photonic crystal microcavities combined with plasmonic nano-antenna, whispering gallery mode microcavities combined with plasmonic nano-antenna, and Fabry-Perot microcavities with plasmonic nano-antenna. The physics and applications of each hybrid photonic-plasmonic system are illustrated. The recent developments of topological photonic crystal microcavities and topological hybrid nano-cavities are also introduced, which demonstrates that topological microcavities can provide a robust platform for the realization of nanophotonic devices. This review can bring comprehensive physical insights of the hybrid system, and reveal that the hybrid system is a good platform for realizing strong light-matter interaction.     

Optical third-harmonic generation in coupled microcavities based on porous silicon

The resonance features of the third-harmonic generation have been observed in 1D coupled microcavities consisting of three Bragg reflectors and two identical half-wave layers of mesoporous silicon. The third-harmonic intensity increases by a factor of about 10³ in the resonance of fundamental radiation with each of the modes of coupled microcavities. It has been shown that the resonance positions in the angular spectra of the third-harmonic intensity depend on the coupling between microcavities that is determined by the transmission of the intermediate Bragg reflector. In the framework of the transfer-matrix method with nonlinear sources, it has been shown that the basic mechanism of the enhancement of the third-harmonic generation in coupled microcavities based on porous silicon is the constructive interference of the partial third-harmonic waves that are generated by near-surface layers.     

酞菁铜掺杂TiO2微腔的光谱特性和精细结构

化学方法合成了酞菁铜(CuPc)掺杂TiO2微腔,用傅里叶变换红外光谱、拉曼光谱研究了其的光谱特性,用X射线吸收精细结构(XAFS)谱分析了其的精细结构.结果显示,TiO2微腔被CuPc掺杂后,CuPc和TiO2之间发生了相互作用,使红外光谱出现了900.76 cm-1的振动吸收峰;同时,在3 392.75 cm-1的OH振动和2 848.83 cm-1的CH振动发生了"红移";酞菁大环平面的C-C或C-N振动、苯环上C-H面内和C-N面外的弯曲振动也有一定的峰位移动和强度变化.在拉曼光谱图上,CuPc掺杂TiO2微腔中出现的403.4,592.1和679.1 cm-1的TiO2的特征振动峰,但它们发生了波数移动,而在1 586.8和1 525.6cm-1出现的振动峰说明CuPc和TiO2形成了复合体,这些变化与酞菁铜的大环分子结构的平面取向有关.在XAFS上,CuPc掺杂TiO2微腔中的Ti呈现四面体TiO4的结构形式,TiO2的内层的中间距离和表面结构发生了变化.     

Investigation of resonant modes in thin microcavities by using electromagnetic theory

A biharmonic differential equation for 3D thin microcavities with uniform thickness is investigated by use of electromagnetic theory, whose exact solution is determined to govern the electromagnetic field distribution inside the thin microcavities. The resonant field patterns of a thin microdisk and thin rectangular microcavity are obtained accordingly. The governing equation can be verified by comparing the results of the thin microdisk presented with the approximate ones in the literature. The fourth-order partial differential equation and its exact solution should be useful in possible applications of the thin microcavities for optical resonators in laser optics and optical devices.     

Longitudinal whispering-gallery modes in metal microcavities

Longitudinal waves in microcavities emerging because of spatial dispersion are investigated. It is shown that longitudinal modes similar to whispering-gallery modes exist in microcavities of this kind. These longitudinal modes should exist in metal microcavities in the vicinity of the plasma frequency.     

基于环形微腔的多频段三角晶格光子晶体耦合腔波导光学传输特性

本文理论研究了近红外波段硅基三角晶格光子晶体环形微腔的光场局域特性,通过将微腔在空间周期性排列组成耦合腔光波导,研究了多个导带区域内光束传输时的群速度,最大和最小值分别为0.0028c和0.00028c.将环形微腔在垂直于光传输方向上进行交错排列,通过改变相邻微腔之间的耦合区域,可以大幅降低多频段范围内光束在耦合腔波导中传输时群速度之间的差异,并提高部分频段的透过率数值.在不改变介质柱半径条件下,通过去掉三角晶格光子晶体中距中心介质柱距离分别为2a和√3a的六个介质柱构成了两种微腔,研究了两种微腔所支持的谐振波长之间的差异,在此基础上构造了两种耦合腔波导,进而将这两种耦合腔光波导与W1型输入/输出波导相连,最终实现了在多个不同频率范围内降低群速度的同时实现频段选择和频段分束功能,其导模群速度可降低到0.00047c.     

Fabrication of the Fully Hybrid Microcavities Based on Zn(S)Se Epilayers and Amorphous Dielectrics

A technique of fabrication of fully-hybrid microcavities using II-VI semiconductor compound epilayers and distributed Bragg reflectors based on amorphous dielectric coating is described. The fully hybrid microcavities with Zn(S)Se epilayers are created. High structural and optical quality of the embedded Zn(S)Se thin films was established by atomic-force microscopy and optic studies. The analysis of excitonic spectra for Zn(S)Se epilayers embedded in the fully hybrid microcavities indicates that such structure can be perspective for creation of a new type of light-emitting devices – polariton lasers.     

Optical properties of a system of two coupled vertical microcavities

The interaction of two localized optical states in a structure consisting of a system of two coupled vertical microcavities is studied. It is shown that the interaction of two localized optical modes in coupled microcavities cause the modes to split. The optical properties of a system of coupled microcavities and the dispersion relations for the characteristic optical modes of the system are analyzed. Zh. Tekh. Fiz. 68, 94–97 (May 1998)     

有机吸附物对多孔硅微腔发光的影响

理论上,采用Bruggeman有效介质近似,研究了有机吸附物对多孔硅微腔的折射率及其光致发光谱的影响.实验上,采用计算机控制的电化学腐蚀法制备了多孔硅微腔样品,并利用机械泵油的蒸气分子与该微腔样品进行相互作用.研究发现,多孔硅微腔发射的窄化光致发光谱对泵油蒸气分子的吸附与脱附很敏感,与之伴随的是该窄化光致发光谱发生明显的峰位移动(可达71nm)和强度变化.结合Bruggeman近似和表面态对多孔硅发光的影响,对实验结果进行了定性解释.实验结果与理论模拟结果符合较好. 关键词： Bruggeman近似 吸附物 多孔硅微腔 光致发光谱     

Deformation of a bubble formed by coalescence of cavitation inclusions and shock wave inside it at strong expansion and compression

Dynamics of a cavitation bubble is considered at its strong expansion and subsequent compression. The bubble is formed by merging of two identical spherical cavitation microcavities in the pressure antinode of the intensive ultrasonic standing wave in the half-wave phase with negative pressure. Deformations of bubble and deformations of radially converging shock waves occurring therein at bubble compression are studied depending on the size of microcavities forming the bubble. It is found that compression of the medium in the bubble by the converging shock wave is kept close to the spherical one only in the case, when the radius of merging microcavities is 1800 times smaller than the radius of the bubble formed by merging at the time of its maximal expansion.     

Optimum quantum memory conditions for a spatial frequency resonator grating

The dynamics of the interaction between microcavities connected to a common waveguide in a multiresonator quantum memory circuit is investigated. Optimum conditions are identified for the use of quantum memory and a dynamic picture of the exchange of energy between different microcavities is obtained.