光子晶体二元缺陷微腔的光传输特性

构造和研究了光子晶体插入式二元缺陷和替代式二元缺陷微腔的光学传输特性,结果表明:随着二元缺陷自身周期数增大,微腔透射谱中分立缺陷模的数目增加,且替代式二元缺陷微腔分立缺陷模多于插入式二元缺陷微腔;随着缺陷高折射率介质厚度的增大,二元缺陷微腔的缺陷模向中间靠拢呈现简并趋势,同时禁带两侧出现多组双缺陷模,且高频一侧出现双缺陷模多于低频一侧,但替代式二元缺陷微腔出现的双缺陷模数目多于插入式二元缺陷微腔;随着缺陷低折射率介质厚度增大,插入式二元缺陷微腔的缺陷模向低频方向移动同时呈现耦合分开趋势,且透射率逐渐降低,而替代式二元缺陷微腔的缺陷模则向中间靠拢呈现简并趋势,同时缺陷模整体向高频方向缓慢移动,而透射率保持100%不变。光子晶体二元缺陷微腔的光传输特性为光学滤波器、光学开关和激光器等的设计提供了参考。     

A high quality factor photonic crystal channel-drop filter with a linear gradient microcavity

We design a channel-drop filter (CDF) with a linear gradient microcavity in a two-dimensional (2D) photonic crystal (PC). The model of three-port CDF with reflector is used to achieve high quality factor (Q-factor) and 100% channel-drop efficiency. The research indicates that adjusting the distance between reference plane and reflector can simultaneously influence the Q-factor due to coupling to a bus waveguide and the phase retardation occurring in the round trip between a microcavity and a reflector. The calculation results of 2D finite-difference time-domain (FDTD) method show that the designed filter can achieve the drop efficiency of 96.7% and ultra-high Q-factor with an ultra-small modal volume.     

Very small oxide-confined vertical microcavity lasers withhigh-contrast AlGaAs-AlxOy mirrors

We report the photo-pumped lasing action from a very small oxide-confined 870-nm vertical microcavity lasers with high-contrast AlGaAs-Al_xO_y mirrors. The effective cavity length is as small as 0.37 μm, and the oxide aperture size is 0.73 μm, estimated from the blue-shift of lasing mode due to the lateral confinement. The observed blue-shift of the lasing mode is 13.4 nm, the largest one ever reported for vertical cavity lasers. The optical losses seem to be size-independent for these small microcavity lasers. Our results indicate the possibility of the ultimate microcavity of order of λ³     

Modified suspended membrane photonic crystal D/sub 3/ laser cavity with improved sidemode suppression ratio

We have demonstrated the ability to selectively modify the mode structure of a multimoded photonic crystal laser cavity, based on the detailed knowledge of resonant modes in a suspended membrane D/sub 3/ microcavity. We have designed a microcavity in which the margins between the highest Q mode and the next highest Q modes have been increased. This modified cavity has been shown to have an improved sidemode suppression ratio under high power pumping condition.     

Bloch-wave engineering for high-Q, small-V microcavities

The overall decay rate of the mode in an optical microcavity formed by a defect surrounded by two Bragg mirrors in a monomode waveguide is driven by two mechanisms, the desired coupling to a guided mode and the detrimental coupling to radiation modes. We propose two approaches fully compatible with planar fabrication, which allow to increase the cavity Q's by several orders of magnitude while keeping constant the mode volume V of the cavity. The first approach consists of engineering the mirror to taper the guided mode into the mirror Bloch mode, thus decreasing losses. The second approach is less intuitive and relies on a recycling mechanism of the radiation losses. The study is supported by computational results obtained for two-dimensional silicon-on-insulator geometries, but the results apply as well to other related geometries like three-dimensional photonic-wire cavities.     

Bragg微腔中非线性介质相位共轭波的增强效应

研究了由一维光子晶体构成的Bragg微腔（AB）^N（D）^2（BA）^N中三阶非线性光学介质（NLM）产生的相位共轭波的增强效应。当入射光波与Bragg腔模满足共振条件时,推导了其相位共轭波的增强因子。Bragg微腔中的三阶NLM产生的相位共轭波相对于该介质裸露时产生的相位共轭波具有明显增强,这主要是Bragg微腔对入射泵浦光产生了较大的共轭增强作用。理论分析和数值计算结果还表明,当入射光波与Bragg腔模满足共振条件且周期数N较大时,该结构可等效于由Bragg反射镜组成的Fabry-Perot（F-P）腔。     

Design and Optimization of TE011 Resonant Modes in Metallic-Dielectric Cavities

In this work, we present an innovative approach for designing small-scale microcavity resonators. By introducing a gold cladding around the structure, we may significantly reduce the mode volume and simultaneously increase the cavity's quality Q-factor. By making use of the TE₀₁₁ mode, as opposed to the more traditional HE₁₁₁ mode, we may further reduce the mode volume while taking advantage of decreased loss into the metal layer due to the optimal polarization choice. We demonstrate a means to design and optimize the cavity geometry to obtain desired spectral characteristics through the use of particle swarm optimization, and we present a cavity operating at 1.5 mum with a Q value exceeding 300 000 and a modal volume of less than 0.9(lambda/n)³.     

Enhancement effect of phase-conjugate waves of third order nonlinear medium in the Bragg microcavity

It is desiredthat the photon mode could be controlledby using photonic crystal ,such as threshold-less laserdevices[1].The key problemin fabricating photonic de-vices is howtointroduce a defect state[2]into a photoniccrystal ,nevertheless it is difficult …     

Self-consistent calculation of lasing modes in a planar microcavity

The self-consistent calculation of lasing modes in a microcavity with infinite plane mirrors is presented. The semiclassical theory is used, with rigorous boundary conditions included for Maxwell's equations to describe both the emitter distribution and the cavity reflectors. The concept of gain-guided versus index-guided modes in such structures can be removed within the semiclassical model, as rigorous boundary conditions for both the radiation source and passive cavity can be handled exactly. We present calculated curves showing the angular dependence of various lasing modes on mirror reflectivity and the threshold gain susceptibility dependence on mirror reflectivity and active diameter. The linewidth dependence on the transverse lasing mode is also considered. Limitations of the semiclassical approach as compared to a fully quantum mechanical approach is emphasized     

Optical Bistable Operations in AlGaAs-Based Photonic Crystal Slab Microcavity at Telecommunication Wavelengths

We report on bistable operations in a microcavity formed on an AlGaAs-based photonic crystal slab at telecommunication wavelengths. We designed the cavity to achieve a high quality ($Q$)-factor, while maintaining a small mode volume; this was accomplished by removal of a single air hole. The fabricated microcavity exhibited a resonant peak with a$Q$-factor of 1900 at 1548 nm. In nonlinear transmission measurement, when the input power was increased, a bistable characteristic which was dependent on the detuned wavelength from the resonance was observed. The bistability was considered to originate from thermal nonlinearity due to two-photon absorption.     

Tapered Photonic Crystal Microcavities Embedded in Photonic Wire Waveguides With Large Resonance Quality-Factor and High Transmission

We present the design, fabrication, and characterization of a microcavity that exhibits simultaneously high transmission and large resonance quality-factor (Q-factor). This microcavity is formed by a single-row photonic crystal (PhC) embedded in a 500-nm-wide photonic wire waveguide - and is based on silicon-on-insulator. A normalized transmission of 85%, together with a Q-factor of 18 500, have been achieved experimentally through the use of carefully designed tapering on both sides of each of the hole-type PhC mirrors that form the microcavity. We have also demonstrated reasonably accurate control of the cavity resonance frequency. Simulation of the device using a three-dimensional finite-difference time-domain approach shows good agreement with the experimental results.     

Spontaneous emission factor of a microcavity DBR surface-emittinglaser

The spontaneous emission factor (SEF) of a microcavity distributed Bragg reflector (DBR) surface-emitting laser has been obtained theoretically to investigate the possibility of the thresholdless lasing operation. Formulas expressing the spontaneous emission in a three-dimensional microcavity were obtained. By introducing the distribution of mode density in wavevector space, it is shown that the radiation pattern of spontaneous emission is deeply modified by the microcavity and is different from that in free space. Based on this result, the SEF and the emission lifetime are calculated as a function of emission spectral width and the size of the active region. It is found that the SEF exceeds 0.1, even though the spectral width is as large as 30 nm when the transverse size is smaller than 0.5 μm and the DBR reflectivity is larger than 90%     

一维光子晶体非线性微腔的缺陷模和双稳态

为了了解一维光子晶体布喇格非线性微腔产生的缺陷模和双稳态特性,采用数值模拟和理论分析相结合的方法,研究了缺陷层厚度变化和布喇格镜准周期性对缺陷模和双稳态的影响。研究结果表明,缺陷层厚度增大和折射率递增时,均可使缺陷模向低频方向移动,即布喇格腔共振模红移,因此,只要较小的入射光强就可使腔共振模红移到入射光模而产生阈值较低的双稳态,数值计算与理论分析是一致的。这对光子晶体微腔的设计有一定的意义。     

Steady-state and transient characteristics of microcavitysurface-emitting lasers with compressively strained quantum-well activeregions

In conventional semiconductor lasers, the dimensions of the optical cavity greatly exceed the photon wavelength, and the photon density of states forms a continuum since it is essentially that of a bulk system. On the other hand, in an ideal laser, one would like to have a single optical mode coincident with the maximum in the gain spectrum of the active medium. We show that substantial density-of-states quantization and enhancement of the fraction of photons spontaneously emitted into the lasing mode can be obtained by reducing the lateral width of the surface-emitting laser. For emission at λ=0.954 μm, the threshold current density can be drastically reduced by increasing the coupling factor to a few percent. For a cavity structure width of 0.3 μm, the threshold current density is 50 A/cm², compared with 250 A/cm² for the 0.6-μm cavity. At lower still lateral widths, the cavity loses its vertical character, and confinement of the lateral optical mode rapidly deteriorates. The large-signal response of microcavity lasers is slightly improved primarily due to elimination of mode competition in intrinsically single-mode microcavities, with relaxation times close to 1 ns. The enhancement of the spontaneous emission coupling factor results in an increase of the relaxation oscillation frequency and improvement in the standard small-signal response of microcavity lasers. For J=10J_th, the -3 dB modulation frequency exceeds 40 GHz. Since low threshold current densities may be achieved in microcavity lasers, the gains in small-signal performance are primarily extrinsic, i.e., higher modulation bandwidths ace accessible for the same injection     

Characteristics of a photonic bandgap single defect microcavityelectroluminescent device

A microcavity surface-emitting coherent electroluminescent device operating at room temperature under pulsed current injection is described. The microcavity is formed by a single defect in the center of a 2-D photonic crystal consisting of a GaAs-based heterostructure. The gain region consists of two 70-Å compressively strained In_0.15Ga_0.85As quantum wells, which exhibit a spontaneous emission peak at 940 nm. The maximum measured output power from a single device is 14.4 μW. The near-field image of the output resembles the calculated TE mode distribution in a single defect microcavity. The measured far-field pattern indicates the predicted directionality of a microcavity light source. The light-current characteristics of the device exhibit a gradual turn-on, or a soft threshold, typical of single- or few-mode microcavity devices. Analysis of the characteristics with the carrier and photon rate equations yields a spontaneous emission factor β≈0.06     

Fast Calculation of Cavity-Mode Characteristics of Photonic Crystal Cavities

A fast approach based on effective index perturbation method is proposed to evaluate the intrinsic characteristics of photonic-crystal-slab-based microcavity with two-dimensional finite-difference time-domain (2-D FDTD) technique. For two widely used single defect structures, less than 2% computational error was obtained in calculating the defect mode frequencies. Accurate prediction of cavity modal properties and resonant peak frequencies is feasible based on 2-D FDTD simulation by adjusting the effective index to match the dielectric band edge for donor-like defect mode. The correlation between the modified effective index and the cavity (lasing) mode with the highest quality factor$Q$offers an efficient tool in the design of defect mode based photonic crystal microcavities.     

应用于生物传感的光子晶体微腔设计

We have designed an air-bridged PhC microcavity with high sensitivity and a high quality factor.The structure parameters of the microcavity are optimized by three-dimensional finite-difference time-domain method. We compare the performance of a silicon-on-insulator PhC microcavity and an air-bridged PhC microcavity,and analyze the effect of the thickness of the slab and the radius of the defect hole on the performance of the air-bridged PhC microcavity.For a thinner slab and a larger defect hole,the sens...     

Fabrication of Microcavity Light-Emitting Diodes Using Highly Reflective AlN–GaN and Ta2O 5–SiO2 Distributed Bragg Mirrors

We report the fabrication of microcavity light-emitting diodes (MCLEDs) with high reflectivity and crack-free AlN-GaN distributed Bragg reflector (DBR). The 5lambda microcavity structure consists of an n-type GaN, ten pairs InGaN-GaN multiple quantum wells and p-type GaN sandwiched between the hybrid cavity mode of an AlN-GaN and a Ta₂O₅-SiO₂ DBR. The AlN-GaN DBR has 29 periods with insertion of six AlN-GaN superlattice layers showing a crack-free surface morphology and a high peak reflectivity of 99.4% with a stopband of 21 nm. The output power of MCLED is about 11 W at an injection current of 7 mA. The electroluminescence has a polarization property with a degree of polarization of about 51%.     

利用Padé近似理论分析光子晶体微腔结构

利用数学Padé近似理论和时域有限差分(FDTD)方法作为一种谱分析手段,研究了几种具有对称性的光子晶体微腔结构,用较短的时间序列计算得到很高的谱分辨率和精度,通过分析光子晶体微腔的缺陷模式,得到了品质因子高达10~6量级的光子晶体微腔结构,为优选光子晶体材料,提高激光器的功率转换效率提供了一定的理论依据。     

基于微腔和光学Tamm态耦合的全光二极管

为了实现全光二极管的功能设计,采用1维光子晶体非线性微腔,在1维光子晶体两端设置不同厚度的金属薄膜,并运用非线性传输矩阵方法研究了该结构的传输属性。结果表明,两个非对称光学Tamm态和非线性微腔的耦合结构呈现双稳态,且滞回线的位置与入射方向有关,具有全光二极管功能;光二极管的性能依赖于微腔厚度和两个金属薄膜的厚度比。该设计为全光二极管的性能优化提供了参考。