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1.
报道了常压金属有机化学汽相淀积(MOCVD)制备的Zn0.7Cd0.3Se/ZnSe单量子阱的光泵浦受激发射性质。在77K下观测到了n=2的重空穴激子发光峰和n=1的重空穴激子吸收峰。在77K脉冲激光泵浦下受激发射阈值功率密度为116kw/cm2。认为受激发射机理可能是激子局域态的空间填充。 相似文献
2.
Znse—ZnS应变超晶格的吸收光谱及子能带的计算 总被引:2,自引:1,他引:1
我们首次观测到ZnSe—ZnS应变超晶格的n=1,n=2两个子能带的重、轻空穴激子的吸收光谱。根据LCAO理论、应变感应能带结构理论与Kronig-Penney模型,首次计算了ZnSe—ZnS应变超晶格势阱中重、轻空穴子能带。计算结果由实验所测量的吸收光谱所验证。文中指出,这一计算方法同样适用于其它半导体超晶格。 相似文献
3.
纳米结构ZnO晶体薄膜室温紫外激光发射 总被引:4,自引:0,他引:4
文章综述了纳米结构的氧化锌半导体薄膜在室温下自由激子的自发辐射以及由自由激子引起的受激发射的特性,阐述了在不同激发密度下室温紫外受激发射的机理.纳米结构氧化锌半导体薄膜是用激光分子束外延(L-MBE)技术生长在蓝宝石衬底上的.薄膜由密集而规则排列的纳米尺度的六角柱组成.这些纳米六角柱起着限制激子运动的作用,激子的量子尺寸效应,使激子的跃迁振子强度大幅度增强.同时六角柱之间的晶面组成了一个天然的激光谐振腔.室温下用三倍频的YAG脉冲激光激发,可从这些纳米结构的氧化锌薄膜中观测到很强的紫外激光发射.研究发现,在中等激发密度下,紫外受激发射是由于激子与激子间碰撞而引起的辐射复合.在高密度激发条件下,由于激子趋于离化,紫外受激发射主要由电子-空穴等离子体的辐射复合引起.由于纳米结构中激子的跃迁振子增强效应,在室温下测量到的光学增益高达320cm^-1,这比在同样条件下测量到的块状氧化锌晶体的光学增益要高一个量级以上.与传统的电子-空穴等离子体激光辐射相比,激子引起的受激发射可在较低的激发密度条件下实现.这在实际应用上很有价值. 相似文献
4.
采用热极化技术对掺锗玻璃条形光波导进行极化,通过光纤连接 (单模) 的Mach Zehnder Interferometer 系统测量条形波导内诱导出的电光效应,系统地研究了大气环境下极化条件(极化温度、极化时间、极化电压)对电光效应的影响.结果表明:在最佳极化条件下(406℃、-2.4 kV、20 min),波导内的电光系数为rTM=0.059±0.001 pm/V, rTE=0.053±0.001 pm/V,且波导结构中存在一个较低的阈值极化电压(100 V)和阈值极化温度(80℃),此时在波导样品内仍能被激发出可观察的电光效应;实验还发现采用负极化诱导方式产生的电光系数较正极化提高15%左右. 相似文献
5.
本文首次在77K温度的电致发光光谱上,观测到了自由激子和自由激子(Ex-Ex)散射的发射带P。根据半经典理论,得到CdS单晶在高激发密度下的激子有效温度高于晶格温度。并且在77K温度下,通过氮分子激光器3371Å谱线的激发,观察到了Ex-Ex散射的P带的受激发射现象。 相似文献
6.
采用新型有机吡啶盐trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium iodide (ASPI)与有机小分子8-羟基喹啉铝(Alq3)组成能量传递体系,掺杂于惰性聚合物聚甲基丙烯酸脂(PMMA)薄膜中作为增益介质,利用分布布拉格反射镜(DBR)和金属Ag层作为反射镜,制备了垂直微腔结构的有机半导体固体激光器.在纳秒脉冲激光抽运下研究了该有机微腔的受激发射特性,观测到峰值位于600 nm处谱半高全宽为243 nm的单模激光出射;同时观察到明显的激光能量阈值特性,单脉冲的受激发射能量阈值为8?μJ.-----------------2009年《物理学报》第58卷第4期第2781-2784页一文,由于作者的责任,故撤销该文。
关键词:
有机盐
能量转移
微腔
受激发射 相似文献
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9.
用射频磁控溅射方法在SiO2衬底上制备ZnO薄膜。在室温下观测到了A、B激子吸收以及在19K下发现的A、B、C激子的反射表明所制备的ZnO薄膜具有很好的纤锌矿结构。我们获得了来自于电子空穴等离子体的受激发射。进一步研究我们发现由大量窄峰所组成的激光发射,窄峰的间距都为0.5nm左右。根据理论计算,产生激光发射的自成腔的长度为31.5 μm。我们认为ZnO薄膜中产生激光发射的自成腔的形成与其六角型结构有重要关系。 相似文献
10.
用LP-MOCVD技术在GaAs衬底上外延生长了ZnCdSe/ZnSe非对称双量子阱(ADQW)结构。通过ps时间分辨光谱、吸收光谱、发射光谱等的研究得到了如下的结果:在弱激发下,观测到ADQW结构中的激子隧穿现象;在强激发下,在ADQW结构中发现了一个内建电场,它将影响激子隧穿;首次观测到由激子隧穿引起的在一定温度范围内宽阱的发光强度随温度上升而增加的现象;首次观测到该ADQW结构中来自宽阱的光泵受激发射。 相似文献
11.
Gersen H Karle TJ Engelen RJ Bogaerts W Korterik JP van Hulst NF Krauss TF Kuipers L 《Physical review letters》2005,94(12):123901
The eigenfield distribution and the band structure of a photonic crystal waveguide have been measured with a phase-sensitive near-field scanning optical microscope. Bloch modes, which consist of more than one spatial frequency, are visualized in the waveguide. In the band structure, multiple Brillouin zones due to zone folding are observed, in which positive and negative dispersion is seen. The negative slopes are shown to correspond to a negative phase velocity but a positive group velocity. The lateral mode profile for modes separated by one reciprocal lattice vector is found to be different. 相似文献
12.
Anju Babu C. Bhagyaraj Jesly Jacob Gishamol Mathew Vincent Mathew 《Optical and Quantum Electronics》2013,45(6):481-490
Surface plasmon propagation in a nano metal strip waveguide with a biaxial substrate material was studied. The dispersion of the four fundamental modes propagating in the strip waveguide structure was analysed using a formalism based on the method of lines. The propagation properties of these modes with respect to the thickness of the metal film was studied, with two different biaxial materials as substrate for the waveguide. The results were then compared with the asymmetric strip waveguide structures with isotropic substrate and a uniaxial anisotropic substrate. Propagation characteristics as a function of longitudinal and transverse anisotropic components of the substrate material were also studied. The characteristics of the fundamental modes are observed to vary depending on the anisotropy of the biaxial material used. 相似文献
13.
I. E. Golentus A. Yu. Gaevskii 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2014,8(3):462-469
The propagation of an X-ray beam through a plane-parallel waveguide is studied with allowance for Bragg grazing diffraction on the crystalline structure of the plates. Expressions for the waveguide modes are obtained and nondecaying waveguide modes are shown to exist at angles that are larger than the critical one (the angle of total external reflection), which permits one to increase the capture angle of radiation incident on the waveguide. The calculated intensity at the waveguide output is compared with the intensity of waveguide modes in the absence of grazing diffraction in the waveguide material. 相似文献
14.
We have analysed the mode structure of a wideband radiofrequency excited waveguide CO2 laser by using different waveguide diameters and optical cavities. In particular we have observed the phase shift of some linear polarized waveguide modes in the transition region between the guided and the free Gaussian propagation. 相似文献
15.
对于晶体光轴平行于波导界面的结构,讨论了光在金属包层对称平面单轴晶体波导(波导层是单轴晶体,两个波导界面均为金属)内的传输特性.解析地得到了这种结构下波导模式场的精确解.模式场的性质因单轴晶体的性质不同而异.对于正单轴晶体,波导的主模是横电波,任何频率的光波均可激励该模式;当频率满足一定条件时,波导内传输单模,否则,将激励起高阶模式.高阶模既非TE波,也非TM波,而是两者耦合而成的混合模.对于负单轴晶体,波导的主模是一种混合模,该模式同样可被任何频率的光波所激励;当频率满足一定条件时,波导内传输单模,否则
关键词:
平面金属波导
单轴晶体
模式场
混合模 相似文献
16.
Ray L. Frost Jií ejka Matt L. Weier Wayde N. Martens Godwin A. Ayoko 《Journal of Raman spectroscopy : JRS》2007,38(4):398-409
Uranopilite, [(UO2)6(SO4)O2(OH)6(H2O)6](H2O)8, the composition of which may vary, can be understood as a complex hydrated uranyl oxyhydroxy sulfate. The structure of uranopilite from different locations has been studied by Raman spectroscopy at 298 and 77 K. A single intense band at 1009 cm−1 assigned to the ν1 (SO4)2− symmetric stretching mode shifts to higher wavenumbers at 77 K. Three low‐intensity bands are observed at 1143, 1117 and 1097 cm−1. These bands are attributed to the (SO4)2− ν3 anti‐symmetric stretching modes. Multiple bands provide evidence that the symmetry of the sulfate anion in the uranopilite structure is lowered. Three bands are observed in the region 843 to 816 cm−1 in both the 298 and 77 K spectra and are attributed to the ν1 symmetric stretching modes of the (UO2)2+ units. Multiple bands prove the symmetry reduction of the UO2 ion. Multiple OH stretching modes prove a complex arrangement of OH groupings and hydrogen bonding in the crystal structure. A series of infrared bands not observed in the Raman spectra are found at 1559, 1540, 1526 and 1511 cm−1 attributed to δ UOH bending modes. U‐O bond lengths in uranyl and O H/dotbondO bond lengths are calculated and compared with those from X‐ray single crystal structure analysis. The Raman spectra of uranopilites of different origins show subtle differences, proving that the spectra are origin‐ and sample‐dependent. Hydrogen‐bonding network and its arrangement in the crystal structure play an important role in the origin and stability of uranopilite. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
17.
Photoluminescence spectra of oxygen-doped chloro- and bromosodalites and sulfur-doped chloro-, bromo- and iodosodalites were measured at temperatures between 4.2 and 300 °K. At 4.2 and 77 °K, the emission spectra of oxygen-doped sodalites consisted of a series of peaks in the wavelength range 400–700 nm, with an average energy separation of ∼ 1000 cm-1. In addition, fine structure, attributed to lattice modes, was observed in each vibrational band. At 4.2 and 77 °K, the sulfur-doped samples showed a multiband spectrum in the 500–750 nm range, with an average separation of ∼ 570 cm-1 between bands. The spectrum at 4.2 °K exhibited some asymmetry not observed at 77 °K, but no fine structure was resolved. At 300 °K weak, broad-band luminescence was observed from both oxygen- and sulfur-doped samples, with no vibrational structure evident. The results compared very favorably with those reported for oxygen- and sulfur-doped alkali halides, and by analogy the spectra were attributed to luminescence from O-2 and S-2 molecular ions. 相似文献
18.
We propose nondegenerate four-wave mixing mirrorless oscillation in a multimode silicon nonlinear waveguide. Thanks to the large modal dispersion between two spatial modes caused by the high-index-contrast waveguide structure, two counterpropagating pumps of one spatial mode can generate two new optical waves of the other spatial mode at different frequencies. The phase-matching condition can be satisfied with the higher-order modes involved; therefore, frequencies of the newly generated light can be tuned by simply changing the pump frequency. The threshold power and conversion efficiency of the proposed mirrorless oscillation are investigated under different waveguide parameters. 相似文献
19.
We propose and numerically analyze a novel mode converter based on two-dimensional photonic crystal waveguides with square arrays of cylindrical dielectric rods in air. The mode converter uses small perturbation defects to decouple various modes in the multimode waveguide, thereby permitting propagation of only one mode at any given frequency, which permits one-to-one mode conversion without exciting unwanted modes. The mode converter can efficiently convert a TM0 mode supported in a single-mode photonic crystal waveguide into a TM2 mode supported in the multimode waveguide that is laterally coupled to the single-mode waveguide section for a wide wavelength range. Influences of different sizes and positions of perturbation rods on the band structure of the multimode waveguide are studied. 相似文献