两种谐振腔长度的微腔有机电致发光器件模拟

微腔的谐振腔长度直接影响微腔有机电致发光器件(MOLED)的发光特性,根据微腔器件的相关计算公式运用传输矩阵法,分别对微腔长度L=λ/2和L=λ(λ:中心波长)时,在微腔内不同位置激子复合发光的电致发光谱(EL)进行模拟计算和比较。发现:微腔长度为L=λ/2时,峰值均为520nm,半峰全宽均为17nm,激子处在微腔的中心位置时,峰值强度和积分强度均为最大。L=λ时,激子在腔内不同位置时,峰值均为520nm,半峰全宽均12nm,在腔的中心区域时,与L=λ/2时正好相反,峰值强度和积分强度最小。分析后判断是因为两种长度的微腔内电场强度分布不同,激子位于腔内电场的最大值处发光性能最好。说明要制作出高效率的MOLED,要区别不同谐振腔长度,并使激子处于腔内电场最大处。     

Multiwavelength ultralow-threshold lasing in quantum dot photonic crystal microcavities

We demonstrate multiwavelength lasing of resonant modes in linear (L3) microcavities in a triangular-lattice 2D photonic crystal (PC) slab. The broad spontaneous emission spectrum from coupled quantum dots, modified by the PC microcavity, is studied as a function of the intensity of incident optical excitation. We observe lasing with an ultralow-threshold power of approximately 600 nW and an output efficiency of approximately 3% at threshold. Two other resonant modes exhibit weaker turnon characteristics and thresholds of approximately 2.5 and 200 microW, respectively.     

Ultracompact biochemical sensor built with two-dimensional photonic crystal microcavity

We report an experimental demonstration of an ultracompact biochemical sensor based on a two-dimensional photonic crystal microcavity. The microcavity, fabricated on a silicon-on-insulator substrate, is designed to have a resonant wavelength (lambda) near 1.5 microm. The transmission spectrum of the sensor is measured with different ambient refractive indices ranging from n = 1.0 to n = 1.5. From observation of the shift in resonant wavelength, a change in ambient refractive index of delta(n) = 0.002 is readily apparent. The correspondence between absolute refractive index and resonant wavelength agrees with numerical calculation to within 4% accuracy. The evaporation of water in a 5% glycerol mixture is also used to demonstrate the capability for in situ time-resolved sensing.     

Phase dependence of the unnormalized second-order photon correlation function

We investigate the resonant quantum dynamics of a multi-qubit ensemble in a microcavity. Both the quantum-dot subsystem and the microcavity mode are pumped coherently. We find that the microcavity photon statistics depends on the phase difference of the driving lasers, which is not the case for the photon intensity at resonant driving. This way, one can manipulate the two-photon correlations. In particular, higher degrees of photon correlations and, eventually, stronger intensities are obtained. Furthermore, the microcavity photon statistics exhibits steady-state oscillatory behaviors as well as asymmetries.     

All-optical tunable photonic bandgap microcavities with a femtosecond time response

An all-optical tunable photonic bandgap microcavity made from a two-dimensional polystyrene photonic crystal is fabricated by focused ion beam etching. The pump and probe scheme is adopted to measure tunability based on the femtosecond optical Kerr effect. An ultrafast response time of less than 120 fs is achieved for the tunable photonic bandgap microcavity. The microcavity resonant wavelength shifts 3.1 nm under excitation of 9.4 GW/cm2 pump intensity, which is in agreement with the theoretical prediction.     

Electro-optical resonant switching in two-dimensional side-coupled waveguide-cavity photonic crystal systems

Photonic crystals have many potential applications because of their ability to control lightwave propagation. We have investigated the electro-optical resonant switching in two-dimensional photonic crystal structures. The optical microcavity side coupled with a waveguide composed of a dielectric cylinder in air is studied by solving Maxwell?s equations using the plane wave expansion method and finite-difference time-domain method. The switching mechanism is a change in the conductance of the microcavity and hence modulating the resonant mode and eventually resonant switching is achieved. Such a mechanism of switching should open up a new application for designing components in photonic integrated circuits.     

一种新型光学微腔的理论分析

应用波动光学理论,分析了一种新型锥顶柱状光学微腔的本征模式,得到了谐振腔的谐振波长表达式.在谐振波长1550 nm附近进行了设计与仿真优化,优化结果显示新型谐振腔与传统平行腔相比,在腔长为4512.5 nm,直径为3134.4 nm时,其品质因数可以提高22.4%,达到了49928.5,同时谐振腔的有效模式体积减小了47.8%.     

Enhanced and inhibited spontaneous emission of free excitons in GaAs quantum wells in a microcavity

Spontaneous emission of the free excitons in GaAs quantum wells in a microcavity is enhanced (x 130) or inhibited (x ) by placing excitonic dipoles at either a resonant wavelength and anti-node position or an off-resonant wavelength and node position of the standing-wave vacuum field fluctuations. The resulting spontaneous radiation pattern is highly concentrated into the normal direction for the enhancement case and the spontaneous emission coupling efficiency into a single microcavity resonant mode is estimated to be 0.3. It is expected that semiconductor lasers with substantially reduced threshold currents can be constructed using such a structure.     

Unidirectional high intensity narrow-linewidth lasing from a planar random microcavity laser

Lasing was achieved in a new type of random laser: the planar random microcavity laser. The laser consists of a planar microcavity with a random gain layer. Optical confinement by the two-dimensional random cavity and the one-dimensional planar microcavity drastically reduces the number of resonant modes. As a result, the laser output is highly directional (the divergence angle is 1.68 degrees) with an extremely narrow-linewidth and ultralow threshold. All these phenomena are explained in terms of the coupling of random cavity modes and planar microcavity modes. The results demonstrate an important step towards applications of random lasers.     

Generation of nonclassical light upon resonant excitation of a semiconductor microcavity

Strong correlations in the fluctuations of the intensity of emission from a semiconductor microcavity under resonant laser excitation are observed. The intensity correlation function exhibits an unusual oscillatory behavior with an unexpectedly long oscillation period and decay time. The visibility of the correlation function reaches 0.81. Long oscillation times are attributed to the Rabi frequency characterizing weak coupling between the electromagnetic field of the semiconductor microcavity mode and long-lived exciton states localized by the random potential of the quantum well. For a laser excitation power density of 400 W/cm², the power density of the radiation emitted by the microcavity is 12 W/cm², which corresponds to the total flux of nonclassical light of 1.5 × 10¹⁵ photons/s from an excited spot 50 μm in diameter. Thus, a microcavity can serve as a bright emitter of nonclassical light.     

有机薄膜在平面光学微腔中的光致发光特性

本文研究了有机薄膜在平面光学微腔中的光致发光特性。有机光学微脸以多层介质膜和金属银分别作为反射镜,８－羟基喹啉铝（Ａｌｑ）为发光层。Ａｌｑ薄膜的荧光峰位于５１９ｎｍ,谱线的半高全宽为９０ｎｍ。微腔的荧光峰位于５３０ｎｍ,谱线的半高全宽窄化至１０ｎｍ。谐振波长处的发射强度提高了一个数量级。     

Polymer-based microcavity with photoencoded quadratic nonlinearity

Functional electro-optic polymer thin films embedded in microcavity structures have been poled by an all-optical procedure based on the interference of multiphoton absorption processes. The photoinduced X((2)) tensor was then further addressed at modal resonance for the fundamental wavelength, leading to significant enhancement of the second-harmonic-generation efficiency. An order-of-magnitude enhancement, which is due to electric field resonant conditions inside the microcavity, has been probed by an optical parametric oscillator, in comparison with a single-path thin-film configuration. This configuration opens new perspectives in the realm of nonlinear photonic device processing.     

Cubic self-action effects in photonic-crystal microcavities

Third-order nonlinear-optical self-action effects in photonic-crystal microcavities have been studied. Considerable defocusing has been observed in a nonlinear microcavity layer with a thickness much smaller than the wavelength. The polarization self-action effect that is manifested as the significant rotation of the polarization plane of laser radiation resonant to the microcavity mode has been observed. It has been shown that the polarization rotation angle is a linear function of the radiation power density.     

A Doubly Resonant Photonic-Crystal Microcavity for Second-Harmonic Generation

A two-dimensional, photonic-crystal microcavity is proposed in order to achieve efficient second-harmonic generation in the third optical communication window. The simultaneous resonance conditions of the pump beam at the fundamental frequency and second-harmonic field generated inside the structure with a defect provides a considerable enhancement of the conversion efficiency. In the configuration we propose, a transverse-magnetic (TM) polarized beam resonating at the fundamental frequency generates a second-harmonic field corresponding to a transverse-electric (TE) polarized resonant mode. The design of this doubly resonant microcavity is carried out by a linear analysis to search for the resonance frequencies and calculate their field distributions. The nonlinear analysis of the second-harmonic generation is performed using a dispersive finite-difference time-domain code.     

微腔有机电致发光器件的谐振腔反射镜性能

根据微腔原理运用传输矩阵法对构成微腔有机电致发光器件(MOLED)谐振腔的两个反射镜进行模拟计算并比较,可观察到:随金属反射镜的反射率增大,微腔器件的电致发光(PL)谱的半峰全宽(FWHM)逐渐窄化;峰值逐渐蓝移至设计的谐振峰值520nm处;峰值强度和光谱积分强度逐渐增强。结果表明:金属反射镜反射率越大越好。随DBR反射镜的周期数从1增加到9,EL的峰值均为520nm,半峰全宽逐渐窄化,积分强度逐渐减弱;峰值强度由弱增强再减弱,4个周期时峰值强度最大,所以设计微腔器件时,DBR的周期是一项很重要的参数。DBR反射率太大不利于出光,太小微腔效应小。需要根据制作目的和需要进行合理选择。     

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.     

Two‐dimensional microcavity lasers

Advances in processing technology, such as quantum‐well structures and dry‐etching techniques, have made it possible to create new types of two‐dimensional (2D) microcavity lasers which have 2D emission patterns of output laser light although conventional one‐dimensional (1D) edge‐emitting‐type lasers have 1D emission. Two‐dimensional microcavity lasers have given nice experimental stages for fundamental researches on wave chaos closely related to quantum chaos. New types of 2D microcavity lasers also can offer the important lasing characteristics of directionality and high‐power output light, and they may well find applications in optical communications, integrated optical circuits, and optical sensors. Fundamental physics of 2D microcavity lasers has been reviewed from the viewpoint of classical and quantum chaos, and recently developed theoretical approaches have been introduced. In addition, nonlinear dynamics due to the interaction among wave‐chaotic modes through the active lasing medium is explained. Applications of 2D microcavity lasers for directional emission with strong light confinement are introduced, as well as high‐precision rotation sensors designed by using wave‐chaotic properties.     

Multimode lasing from the microcavity of an octagonal quasi-crystal based on holographic polymer-dispersed liquid crystals

An eightfold photonic quasi-crystal (PQC) sample is fabricated holographically using two-beam interference with multi-exposure based on polymer-dispersed liquid crystals. The transmission spectra from the finite-difference time-domain (FDTD) simulation prove the photonic stop band of the rotational symmetry structure of the sample. The resonant mode of the circular microcavity formed in the PQC is calculated. Amplified spontaneous emission and multimode lasing action are demonstrated from the pumped laser-dye-doped PQC microcavity using a Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) pulse laser.     

Circularly polarized fluorescence from light-emitting microcavities with sculptured-thin-film chiral reflectors

A light-emitting microcavity with sculptured-thin-film (STF) chiral reflectors is fabricated to produce narrowband circularly polarized (CP) light. The device is composed of a layer of fluorescent molecules (Alq3) sandwiched between two STF chiral reflectors to form a resonant microcavity with CP-selectivity, which emits narrowband left CP (LCP) and right CP (RCP) light upon photoexcitation. Our results also indicate the possibility of developing STF reflector-based diode laser devices delivering pure and controllable circular polarization.     

太赫兹波段电磁超材料吸波器折射率传感特性

太赫兹超材料吸波器作为一类重要的超材料功能器件,除了可以实现对入射太赫兹波的完美吸收外,还可以作为折射率传感器实现对周围环境信息变化的捕捉与监测.通常从优化表面金属谐振单元结构和改变介质层材料和形态两个方面出发,改善太赫兹超材料吸波器的传感特性.为深入研究中间介质层对太赫兹超材料吸波器传感特性的影响,本文基于金属开口谐...