Controlling the spontaneous emission rate of single quantum dots in a two-dimensional photonic crystal

We observe large spontaneous emission rate modification of individual InAs quantum dots (QDs) in a 2D photonic crystal with a modified, high-Q single-defect cavity. Compared to QDs in a bulk semiconductor, QDs that are resonant with the cavity show an emission rate increase of up to a factor of 8. In contrast, off-resonant QDs indicate up to fivefold rate quenching as the local density of optical states is diminished in the photonic crystal. In both cases, we demonstrate photon antibunching, showing that the structure represents an on-demand single photon source with a pulse duration from 210 ps to 8 ns. We explain the suppression of QD emission rate using finite difference time domain simulations and find good agreement with experiment.     

Effect of atomic initial phase difference on spontaneous emission of an atom embedded in photonic crystal

<正>We investigate the effect of initial phase difference between the two excited states of a V-type three-level atom on its steady state behaviour of spontaneous emission.A modified density of modes is introduced to calculate the spontaneous emission spectra in photonic crystal.Spectra in free space are also shown to compare with that in photonic crystal with different relative positions of the excited levels from upper band-edge frequency.It is found that the initial phase difference plays an important role in the quantum interference property between the two decay channels.For a zero initial phase,destructive property is presented in the spectra.With the increase of initial phase difference,quantum interference between the two decay channels from upper levels to ground level turns to be constructive.Furthermore, we give an interpretation for the property of these spectra.     

Modification of spontaneous emission rate of micrometer-sized light sources using hollow-core photonic crystal fibers

We investigate numerically and experimentally the modification of the spontaneous emission rate for micrometer-sized light sources embedded in a hollow-core photonic crystal fiber (HCPCF). The diameter of the light source is deliberately chosen such that they could be easily introduced into the central hole of the hollow-core photonic crystal fiber by capillary force. The photoluminescence from the microparticles is measured by using an inverted microscope in combination with a spectrometer. The modification of the spontaneous emission rate is observed in a wavelength region where there is no band gap. The experimental observations are consistent with the simulation results obtained by the plane wave expansion and finite-difference time-domain techniques.     

Spatial and frequency domain effects of defects in 1D photonic crystal

The aim of this paper is to present the analysis of influence of defects in 1D photonic crystal (PC) on the density of states and simultaneously spontaneous emission, in both spatial and frequency domains. In our investigations we use an analytic model of 1D PC with defects. Our analysis reveals how presence of a defect causes a defect mode to appear. We show that a defect in 1D PC has local character, being negligible in regions of PC situated far from the defected elementary cell. We also analyze the effect of multiple defects, which lead to photonic band gap splitting.     

Decay distribution of spontaneous emission from atoms in one-dimensional photonic crystal

Spontaneous emission behavior from atoms (or molecules) in one-dimensional photonic crystal with a defect is investigated. Taken all the TE and TM modes into account, the normalized spontaneous emission rate of the atom is calculated as a function of the position of the atom in the crystal. Results for both nonabsorbing dielectric structure and absorbing dielectric structure are presented. With the increase of the thickness of the defect in which the atoms are embedded, the oscillations of the spontaneous emission rate versus the position of the atom become dense and the lifetime distribution becomes narrow and sharp. The PC effect may lead to the coexistence of both accelerated and inhibited decay processes.     

Modified spontaneous emission of CdTe quantum dots inside a photonic crystal

The angular dependence of the spontaneous emission of CdTe quantum dots (QDs) inside a photonic crystal with a pseudogap is reported. The sensitive dependences of the radiative lifetime and the photoluminescence spectrum of CdTe QDs on the observation angle demonstrate the effect of the photonic bandgap on the spontaneous emission of the QDs.     

Strong enhancement of spontaneous emission in amorphous-silicon-nitride photonic crystal based coupled-microcavity structures

We investigated photoluminescence (PL) from one-dimensional photonic band gap structures. The photonic crystals, a Fabry–Perot (FP) resonator and a coupled-microcavity (CMC) structure, were fabricated by using alternating hydrogenated amorphous-silicon-nitride and hydrogenated amorphous-silicon-oxide layers. It was observed that these structures strongly modify the PL spectra from optically active amorphous-silicon-nitride thin films. Narrow-band and wide-band PL spectra were achieved in the FP microcavity and the CMC structure, respectively. The angle dependence of PL peak of the FP resonator was also investigated. We also observed that the spontaneous emission increased drastically at the coupled-cavity band edge of the CMC structure due to extremely low group velocity and long photon lifetime. The measurements agree well with the transfer-matrix method results and the prediction of the tight-binding approximation. Received: 8 March 2001 / Accepted: 17 March 2001 / Published online: 23 May 2001     

Superprism effect in 1D photonic crystal

It is shown that superprism effect can be observed not only in 2D and 3D photonic crystal but also in 1D photonic crystal. To observe the effect a diffraction grating should be put on the top of the 1D PC. It is shown that the band gap more dramatically appears in 1D PC than in 2D PC. This effect makes all PBG effects including superprism effect more pronounced and also weakens the influence of losses.     

The spontaneous emission of an excited atom embedded in photonic crystals with two atomic position-dependent bands

The spontaneous emission of an excited atom embedded in photonic crystals with two atomic position-dependent bands is investigated.The distribution of the density of states between two bands depends on the atomic position in a unit cell of the photonic crystal and is described with an atomic position-dependent parameter.The result shows that the emitted field and the time evolution of the upper-level population are affected by the atomic position and the gap width.The spontaneous emission spectrum in free space can be shifted and narrowed with the photonic reservoir and the gap width.     

具有态守恒赝隙的光子晶体中两能级原子自发辐射的增强与抑制

论证了在赝带隙光子晶体中存在一个全频率域态总数守恒规则，在完全带隙光子晶体中还存在一个局域态总数守恒规则.态总数守恒规则指出，如果一个光子晶体的态密度在某些频率范围存在相对于等效介质态密度的谷，则一定由其他频率范围内相对于等效介质态密度的峰来补偿.使用符合态总数守恒规则的态密度模型，解释了态密度调制导致的自发辐射谱增强、抑制、变窄、红移、蓝移以及谱分裂等光子晶体中的量子光学现象.该理论比较适合研究在具有赝带隙的光子晶体中大量随机分布的发光原子或分子的自发辐射行为. 关键词： 光子晶体 自发辐射 态密度 光子赝带隙     

各向异性光子晶体中二能级原子和自发辐射场间的纠缠

应用Von Neumann熵和Schmid tnumber K两种纠缠度量讨论了各向异性光子晶体中二能级原子和自发辐射场间纠缠度的演化性质.研究发现,原子-光场纠缠度的演化与原子上能级和光子晶体能带带边的相对位置有关,当原子上能级处于光子晶体禁带内,原子-光场纠缠度将保持稳定,当原子上能级处于光子晶体能带中,原子-光场纠缠度先增大后衰减到零.纠缠度的大小还与原子的初态有关.可以通过控制原子的初态和原子上能级与带边的相对位置来控制原子-光场纠缠度的演化特性.     

Disorder-induced losses in photonic crystal waveguides with line defects

A numerical analysis of extrinsic diffraction losses in two-dimensional photonic crystal slabs with line defects is reported. To model disorder, a Gaussian distribution of hole radii in the triangular lattice of airholes is assumed. The extrinsic losses below the light line increase quadratically with the disorder parameter, decrease slightly with increasing core thickness, and depend weakly on the hole radius. For typical values of the disorder parameter the calculated loss values of guided modes below the light line compare favorably with available experimental results.     

X-ray spontaneous emission control by 1-dimensional photonic bandgap structure

The possibility of controlling the X-ray spontaneous emission of atoms embedded in a 1-dimensional photonic bandgap structure by the so-called Purcell effect, is studied. Calculations of the spontaneously emitted power are presented from Fermi’s golden rule in the framework of the Wigner-time approach extended to absorbing media. Numerical simulations are compared to experimental results for the case of the K emission from silicon atoms excited by electrons within a Mo/Si multilayer Bragg reflector. The inhibition or enhancement of X-ray emission from such structures appear to be feasible.     

Modified spontaneous emission and qubit entanglement from dipole-coupled quantum dots in a photonic crystal nanocavity

The modified spontaneous emission dynamics of two photon-coupled quantum dots in a planar-photonic crystal are theoretically investigated. Based on a photon Green function technique for quantizing the electromagnetic fields in arbitrary surroundings, pronounced vacuum Rabi oscillations and dipole-dipole interactions are self-consistently incorporated and are shown to result in a high degree of quantum-bit entanglement. Quantum dots with different optical dipole moments are also found to yield a very rich display of quantum dynamics and offer several advantages over coupling identical atoms.     

一维多缺陷光子晶体的缺陷模

设计了一个多缺陷的一维光子晶体,并利用传输理论研究其透射谱.利用泰勒展式的一级近似,得到了缺陷模频率的解析表达式,进而得到紧束缚理论中的耦合因子.这些结论与实验结果或数值模拟相符合,可以很好地描述缺陷模的有关规律,对多通道滤波器的设计具有指导意义. 关键词： 光子晶体 缺陷模 紧束缚方法 耦合因子     

Inhibited spontaneous emission of quantum dots observed in a 3D photonic band gap

We present time-resolved emission experiments of semiconductor quantum dots in silicon 3D inverse-woodpile photonic band gap crystals. A systematic study is made of crystals with a range of pore radii to tune the band gap relative to the emission frequency. The decay rates averaged over all dipole orientations are inhibited by a factor of 10 in the photonic band gap and enhanced up to 2× outside the gap, in agreement with theory. We discuss the effects of spatial inhomogeneity, nonradiative decay, and transition dipole orientations on the observed inhibition in the band gap.     

Enhancement of spontaneous emission from the resonant modes of a photonic crystal slab single-defect cavity

Modification of the spontaneous-emission lifetime in photonic crystal single-defect resonant modes is studied with the finite-difference time domain method. We investigate spontaneous-emission enhancement from the monopole and the dipole modes of a hexagonal lattice cavity, considering the effects of the finite emitter linewidth and spectral detuning. Large spontaneous-emission enhancement of > 50 is achieved numerically from the high-quality-factor monopole mode when the emitter linewidth is comparable with the resonant-mode linewidth. However, if broad-linewidth material is used and a detuning effect is included, the dipole mode with a low quality factor and a smaller mode volume could be more advantageous for spontaneous-emission enhancement.     

Dynamics of spontaneous emission from SiN with two-dimensional photonic crystals

We investigated the dynamics of spontaneous emission from a photonic crystal etched into a SiN slab. After fitting the decay curves of the emission to double exponential functions, we divided the dynamic process of the spontaneous emission into a fast process and a slow process. It was observed that the presence of the photonic crystal increased the proportion of the fast decay component, and consequently, the emission rate and time-integrated emission intensity were also enhanced. These enhancements were a result of the coupling of the guide modes to the leaky modes of the photonic crystal slab waveguide.     

向列相液晶缺陷光子晶体透射光谱偏振敏感特性研究

研究了向列相液晶缺陷TiO2和SiO2交替的光学多层膜一维光子晶体透射谱偏振敏感特性。外电压下透射光谱测试和模拟结果显示,对于平行取向的向列相液晶,当自然光垂直入射时,禁带中两处出现e(TE模式)光和o光(TM模式)透射峰,具有偏振敏感性。随着电压增大,e光透射峰蓝移与o光透射峰合二为一,光谱可调谐范围分别为31和34nm;而对于取向混乱的向列相液晶,禁带中两处出现独立的透射峰,无偏振敏感性。随着电压增大峰位也蓝移,光谱可调谐范围分别为64和15nm。通过混乱取向液晶分子,可以使o光和e光有效折射率值相等,获得偏振不敏感特性。     

Modulation bandwidth of planar waveguide laser with 1D photonic crystal mirrors

An analysis of the 3-dB modulation bandwidth in planar waveguide laser based on 1D photonic crystal structures is presented. The theoretical model takes into account the gain saturation effect, transverse and longitudinal field distribution. A small-signal perturbation solution of the coupled laser rate equation is used to obtain relations describing the dynamic operation. In paper, the distributed Bragg resonator DBR created as 1D photonic crystal is considered. The active waveguide is surrounded by 1D photonic crystal mirrors consisting of alternately placed stripes with different refractive indices. In particular, the influence of the photonic crystal parameters on the 3-dB modulation bandwidth is investigated.