外腔中半导体二极管激光阵列的高阶侧模锁定

 理论分析了外腔较短情况下，宽条半导体二极管激光阵列（LDA）高阶侧模相位锁定的可能性,观察了包含主、旁瓣结构的多侧模远场光强分布。从实验记录结果可以看出，在旁瓣中出现了标志锁相的峰、谷结构，而且该结构的调制度明显高于主瓣中的峰、谷结构的调制度,结果表明：在外腔较短情况下，LDA高阶侧模相位锁定的现象是存在的。     

二维电子气等离激元太赫兹波器件

固态等离激元太赫兹波器件正成为微波毫米波电子器件技术和半导体激光器技术向太赫兹波段发展和融合的重要方向之一。本综述介绍AlGaN/GaN异质结高浓度和高迁移率二维电子气中的等离激元调控、激发及其在太赫兹波探测器、调制器和光源中应用的近期研究进展。通过光栅和太赫兹天线实现自由空间太赫兹波与二维电子气等离激元的耦合,通过太赫兹法布里-珀罗谐振腔进一步调制太赫兹波模式,增强太赫兹波与等离激元的耦合强度。在光栅-谐振腔耦合的二维电子气中验证了场效应栅控的等离激元色散关系,实现了等离激元模式与太赫兹波腔模强耦合产生的等离极化激元模式,演示了太赫兹波的调制和发射。在太赫兹天线耦合二维电子气中实现了等离激元共振与非共振的太赫兹波探测,建立了太赫兹场效应混频探测的物理模型,指导了室温高灵敏度自混频探测器的设计与优化。研究表明,基于非共振等离激元激发可发展形成室温高速高灵敏度的太赫兹探测器及其焦平面阵列技术。然而,固态等离激元的高损耗特性仍是制约基于等离激元共振的高效太赫兹光源和调制器的主要瓶颈。未来的研究重点将围绕高品质因子等离激元谐振腔的构筑,包括固态等离激元物理、等离激元谐振腔边界的调控、新型室温高迁移率二维电子材料的运用和高品质太赫兹谐振腔与等离激元器件的集成等。     

采用多波长光束组合改善二极管激光阵列的光束质量

 基于多波长光束组合技术,利用光栅的衍射和外腔的反馈,将二极管阵列的发光单元锁定在不同的波长上,相邻单元的出射光波长有微小的差异。从外腔耦合镜输出近似平行的光束,其光束质量等同于单个发光单元的光束质量,而组合光束亮度随着组合光束个数定标放大。实验中采用发光单元宽度为100 μm、填充因子为0.5、由49个单元构成的1 cm 阵列获得功率为2.39 W的输出光束,其光谱宽度为27 nm,远场光斑的直径为0.08 mm,对应的远场发散角为1.2 mrad,其光束质量因子约为28,与单个发光单元的光束质量相当。     

Spontaneous emission in micro- and nano-structures

Spontaneous emission of emitters governing the performance of optoelectronic devices is a fundamental phenomenon, and it has strong environment-dependent characteristics. In this article, we mainly review the experimental and theoretical progresses in the control of spontaneous emission by manipulating optical modes with photonic crystals, optical microcavities and metallic nanostructures. The spontaneous emission from emitters in photonic crystals can be modified by the local density of states, and by employing photonic crystals, the devices’ efficiency is enhanced, the angular radiation pattern can be engineered, and highly efficient optoelectronic devices are achieved through decreasing the radiative lifetime. In quantum optical devices, microcavities would alter the lifetime of an excited state through tuning the resonance in the frequency and positioning between the emitters and cavity field, and inducing the emitters to emit spontaneous photons in a desired direction. The emerging enhanced electromagnetic field near metallic nanostructures can help to control and manipulate the spontaneous emission of an emitter. The use of micro- and nano-structures to manipulate spontaneous emission will open unprecedented opportunities for realizing functional photonic devices.     

808 nm激光二极管阵列波长光束组合20 W输出

 基于多波长光束组合技术,利用光栅的衍射和外腔的反馈,将激光二极管阵列(LDA)发光单元锁定在不同的波长上,以近似平行光束沿光栅的-1级衍射方向组合输出,改善LDA输出光束质量。实验采用发光单元宽度为100 μm、周期为500 μm,由19个单元构成的1 cm普通商用LDA,在连续运行最大注入电流60.6 A时,自由运转输出功率49.8 W时,获得功率为20.1 W的组合光束稳定输出,其光谱宽度为15 nm,对应的远场发散角由约70 mrad变为1.66 mrad,改善后光束质量因子约为32,其值与单个发光单元的光束质量相当。     

Spontaneous emission in micro- and nano-structures

Spontaneous emission of emitters governing the performance of optoelectronic devices is a fundamental phenomenon, and it has strong environment-dependent characteristics. In this article, we mainly review the experimental and theoretical progresses in the control of spontaneous emission by manipulating optical modes with photonic crystals, optical microcavities and metallic nanostructures. The spontaneous emission from emitters in photonic crystals can be modified by the local density of states, and by employing photonic crystals, the devices’ efficiency is enhanced, the angular radiation pattern can be engineered, and highly efficient optoelectronic devices are achieved through decreasing the radiative lifetime. In quantum optical devices, microcavities would alter the lifetime of an excited state through tuning the resonance in the frequency and positioning between the emitters and cavity field, and inducing the emitters to emit spontaneous photons in a desired direction. The emerging enhanced electromagnetic field near metallic nanostructures can help to control and manipulate the spontaneous emission of an emitter. The use of micro- and nano-structures to manipulate spontaneous emission will open unprecedented opportunities for realizing functional photonic devices.     

Lateral shift dependence of spontaneous emission in a planar cavity with perfect conducting cladding

We consider the effect of lateral shift of the “beams" resulting from the atom emissions on spontaneous decay of an excited atom embedded in a planar cavity with perfect conducting cladding. It is found that the spontaneous decay could be enhanced or suppressed owing to the positive and negative lateral shift at the interfaces of the cavity mirror. Compared with the emission between two perfect conducting plates, the surface guided modes could exist and for very thin planar cavity, the density of surface guided modes may be obviously larger than those of the propagating guided modes.     

Controlled plasmon-enhanced fluorescence by spherical microcavity

A surrounding electromagnetic environment can engineer spontaneous emissions from quantum emitters through the Purcell effect. For instance, a plasmonic antenna can efficiently confine an electromagnetic field and enhance the fluorescent process. In this study, we demonstrate that a photonic microcavity can modulate plasmon-enhanced fluorescence by engineering the local electromagnetic environment. Consequently, we constructed a plasmon-enhanced emitter (PE-emitter), which comprised a nanorod and a nanodiamond, using the nanomanipulation technique. Furthermore, we controlled a polystyrene sphere approaching the PE-emitter and investigated in situ the associated fluorescent spectrum and lifetime. The emission of PE-emitter can be enhanced resonantly at the photonic modes as compared to that within the free spectral range. The spectral shape modulated by photonic modes is independent of the separation between the PS sphere and PE-emitter. The band integral of the fluorescence decay rate can be enhanced or suppressed after the PS sphere couples to the PE-emitters, depending on the coupling strength between the plasmonic antenna and the photonic cavity. These findings can be utilized in sensing and imaging applications.     

Strong Purcell effect for InAs quantum boxes in high-Q wet-etched microdisks

We report on the fabrication of high-quality GaAs microdisks using a new two-step wet-etching fabrication process, and on their optical characterization, using the photoluminescence of InAs Quantum Boxes as an intracavity light source. We measure quality factors as high as 12 000 for the resonant whispering gallery modes, which highlights an excellent smoothness of the cavity sidewalls. Those small-volume/high-Q-confined modes are extremely attractive for performing CQED experiments on solid-state emitters. Using a novel experimental approach, we could in particular observe a record enhancement of the SE rate for emitters on-resonance with such modes (×18), in a cw PL experiment.     

基于单边傅里叶变换的非马尔科夫自发辐射研究

基于单边傅里叶变换,本文提出一种研究辐射子的自发衰减动力学演化的普适方法.利用该方法研究了辐射子处于均匀介质、理想微腔和泄露微腔中的自发辐射动力学演化问题,最后并把这种方法用于处理光子带隙材料中的辐射动力学演化问题.结果表明:辐射子的自发辐射动力学特性由局域态密度决定,可以通过调控辐射子周围的局域态密度来调控辐射子的自发辐射特性,为实现新型的光电子器件提供了理论基础.该方法不仅适用于马尔科夫热库的情况也适用于非马尔科夫热库的情况.     

Theory and simulation of cavity quantum electro-dynamics in multi-partite quantum complex systems

The cavity quantum electrodynamics of various complex systems is here analyzed using a general versatile code developed in this research. Such quantum multi-partite systems normally consist of an arbitrary number of quantum dots in interaction with an arbitrary number of cavity modes. As an example, a nine-partition system is simulated under different coupling regimes, consisting of eight emitters interacting with one cavity mode. Two-level emitters (e.g. quantum dots) are assumed to have an arrangement in the form of a linear chain, defining the mutual dipole–dipole interactions. It was observed that plotting the system trajectory in the phase space reveals a chaotic behavior in the so-called ultrastrong-coupling regime. This result is mathematically confirmed by detailed calculation of the Kolmogorov entropy, as a measure of chaotic behavior. In order to study the computational complexity of our code, various multi-partite systems consisting of one to eight quantum dots in interaction with one cavity mode were solved individually. Computation run times and the allocated memory for each system were measured.     

二维GaAs 基光子晶体微腔的制作与光谱特性分析

研究了以InAs量子点为有源区的二维GaAs基光子晶体微腔的设计与制作,测试并分析了室温下微腔的光谱特性.观察到了波长约为1137 nm,谱线半高宽度约为1 nm的尖锐低阶谐振模式发光峰.我们比较了不同刻蚀条件下光子晶体微腔的发光谱线,结果表明空气孔洞截面的垂直度是影响光子晶体微腔发光特性的重要因素之一.通过调节干法刻蚀工艺,改变空气孔半径与晶格常数的比率,可以在较大范围内调节谐振模式发光峰位置,达到谐振模式与量子点发光峰调谐的目的.     

一种实现光纤激光器高功率输出的方法

介绍了一种实现光纤激光器高功率输出的新方法——采用螺旋芯光纤，这种光纤是在光纤制作过程中按照一定的弯曲半径使纤芯呈螺旋状排布在光纤包层中。介绍了这种螺旋芯光纤的原理和其提高输出功率的能力，以及目前的理论与实验研究现状。基于该光纤，提出了一种光纤激光器相干合成新思想。     

Cavity-enhanced absorption spectroscopy for shocktubes: Design and optimization

Cavity-enhanced absorption spectroscopy (CEAS) has generated much interest in shocktube kinetics studies because of its recent success in achieving improved sensitivity and high time resolution with robust optical alignment. While recent progress demonstrated experimental schemes including off-axis scanned-wavelength approach and on-axis ps-pulsed laser approach, that both successfully suppressed the laser-cavity coupling noise, this paper develops a theoretical model to predict the CEAS sensor performance that can be used as a design tool applicable to more generalized cases. The method models the optical field in the cavity based on the decentered Gaussian beam model, from which the cavity transmission spectrum and the laser-cavity coupling noise can be numerically calculated. The simulation results predict sensor performance for different cavity configurations and laser characteristics, including various degrees of laser-cavity mode-matching, laser linewidths, scanning rates, and cavity filling conditions. Simulation with example wavelengths in the ultraviolet, near-infrared, and mid-infrared showed increasing mode-matched beam waist size for increasing wavelengths. An off-axis alignment scheme was found to be capable of suppressing the coupling noise by two orders-of-magnitude at a moderate laser linewidth of 1?GHz. Coupling noise level on the order of 1e-5 for scanned-wavelength off-axis alignment case with a narrowband mid-infrared laser was obtained by model calculation and agreed with experimental results within acceptable uncertainty range. The developed method can serve to guide future design and optimization of CEAS system in shocktube studies.     

半导体激光器列阵在外腔下的光谱特性

使用普通高反镜作为19个单元的半导体激光器列阵(LDA)的外腔,通过调节高反镜的位置和角度,使LDA发出的光反馈回有源层,从而压窄了输出光谱并降低了LDA的阈值电流.实验中,运行于外腔下的LDA在不同的驱动电流下的输出光谱均被压窄到了原来的1/10左右,阈值电流从7 A降到了5.5 A,并且在9 A的偏置电流下输出功率提高了2倍.     

利用场耦合理论研究微波谐振腔

 根据Maxwell方程，微波腔中的实际微波场可以按微波腔的模式展开，从而确定微波腔的工作特性（如：工作频率、场分布等），但是实际微波腔的模式很难求解。从Maxwell方程出发，根据微波腔的具体边界，将微波腔分成：规则形状微波腔和非规则部分，建立实际微波腔模式同规则形状微波腔模式之间的场耦合方程，从而确定微波腔模式的频率和场分布。     

Optimum small-scale management of random beam perturbations in a femtosecond laser pulse

The geometric phase of a three-level atom interacting with single-mode in the presence of the one-dimensional photonic band gap material is studied. We consider dipole emitters situated in the thin slab region between two semi-infinite one-dimensionally periodic photonic crystals, a situation reminiscent of planar cavity laser structures. It shows that the Pancharatnam phase depends crucially on the presence of the photonic band gap. This feature is attributed to the fact that in the photonic band gap region electromagnetic modes are not allowed to propagate into the dielectric slab and hence no interaction can take place in this region. The outcomes are illustrated with numerical simulations applied to GaAs. PACS 03.67.-a; 32.80.Pj; 42.50.Ct; 42.65.Yj; 03.75.-b     

耦合孔对微波腔的影响研究

从Maxwell方程出发,将微波腔中的实际微波场按其本征模式展开,进行微波腔的工作特性(如工作频率、场分布等)的研究.在具体处理过程中,根据复杂结构微波腔的具体边界,将微波腔分成规则形状微波腔和非规则(含耦合孔)部分,建立实际微波腔模式同规则形状微波腔模式之间的场耦合方程,从而确定耦合孔对微波腔模式的影响,并对开耦合孔的圆柱腔进行了相应的理论和模拟研究. 关键词： 微波腔 模式 场耦合 圆柱微波腔     

缓变回旋管谐振腔研究

在高次模回旋管中, 模式竞争是亟待解决的问题. 本文基于广义传输线理论, 得到能准确描述缓变结构谐振腔模式耦合的一阶传输线方程组; 通过分析耦合系数, 优化得到了一种新型光滑渐变(缓变)谐振腔. 与直线连接的(折变)谐振腔相比, 该腔体有更强的模式抑制能力, 腔中非工作模式归一化幅值可达-100 dB, 输出行波段非工作模式归一化幅值可达-88.6 dB.     

Quantum correlations between two cavity QED systems coupled by a mechanical resonator

Achieving quantum correlations between two distant systems is a desirable feature for quantum networking. In this work, we study a system composed of two quantum emitter-cavity subsystems spatially separated. A mechanical resonator couples to either both quantum emitters or both cavities leading to quantum correlations between both subsystems such as non-local light-matter dressed states and cavity–cavity normal mode splitting. These indirect couplings can be explained by an effective Hamiltonian for large energy detuning between the mechanical resonator and the atoms/cavities. Moreover, it is found that the optimal conditions of the physical parameters maximize the entanglement of phonon-mediated couplings.