Dual-wavelength laser emission from an organic microcavity with terahertz beating

We report on the dynamics of laser emission from an anisotropic organic microcavity filled with the guest-host composite of tris-(8-hydroxy quinoline) aluminium (Alq₃) and 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM). In a single microcavity, a linesplitting of 0.18 THz between two perpendicularly polarized laser modes is observed. We ascribe this effect to an optical anisotropy in the distributed Bragg reflectors surrounding the organic layer. The temporal behavior of the electromagnetic field is studied by an up-conversion technique and shows an optical beating of 0.18 THz. Two modeling approaches are used to gain insight in the temporal evolution and phase behavior of the two modes. Both point towards the presence of a phase-coupling mechanism in this system. PACS 42.55.Sa     

Color-tunable organic microcavity laser array using distributed feedback

Distributed feedback microstructures play a fundamental role in confining and manipulating light to obtain lasing in media with gain. Here, we present an innovative array of organic, color-tunable microlasers which are intrinsically phase locked. Dye-doped helixed liquid crystals were embedded within periodic, polymeric microchannels sculptured by light through a single-step process. The helical superstructure was oriented along the microchannels; the lasing was observed along the same direction at the red edge of the stop band. Several physical and technological advantages arise from this engineered heterostructure: a high quality factor of the cavity, ultralow lasing threshold, and thermal and electric control of the lasing wavelength and emission intensity. This level of integration of guest-host systems, embedded in artificially patterned small sized structures, might lead to new photonic chip architectures.     

Strong exciton-photon coupling in an organic single crystal microcavity

We demonstrate strong exciton-photon coupling of Frenkel excitons at room temperature in a microcavity composed of a melt grown thin film anthracene single crystal and two distributed Bragg reflectors. Angle-resolved reflectivity and normal incidence photoluminescence under weak excitation are observed. The microcavity spectrum is a function of the anisotropy of the crystalline material and the strong exciton-photon coupling of the excitonic resonances to the cavity photon. The photoluminescence spectrum is found to be completely polarized along the crystal axes.     

Simulation of a spectral inhomogeneous broadening

The standard approach that is used to simulate effects of inhomogeneous spectral broadening in a medium consisting of two- or multilevel systems is to calculate the microscopic polarization (the dipole moment of an individual system) as a function of the frequency detuning and further to average this quantity over detunings with corresponding weights. This just leads to the macroscopic polarization that appears in Maxwell’s equations of electrodynamics of continuous media. Here, we study and develop an alternative method that has been recently proposed by N.V. Vysotina, N.N. Rozanov, and V.E. Semenov (Opt. Spectrosc. 106 (5), 713 (2009)) for calculation of the macroscopic polarization and that has been aimed at solving problems of computational quantum optics. In this approach, the frequency detuning is considered as a stochastic function of coordinates; in one-dimensional problems, of longitudinal coordinate z. At each step of evolution, the microscopic polarization is calculated for a randomly chosen fixed value of the detuning. Therefore, calculating the macroscopic polarization does not need an additional averaging over detunings; it is replaced by averaging over spatial coordinates, which is naturally performed when describing the radiation propagation through an ensemble of quantum systems. This radically reduces the amount of computations, especially in the context of the finite-difference time domain (FDTD) method.     

Quasi-linear theory of multimode free-electron lasers with an inhomogeneous frequency broadening

assuming that the number of excited modes is large and their phases are random a quasi-linear theory of interaction of ultrarelativistic electron beam with the field of a high-quality cavity is developed. The saturation effects in FELs with an inhomogeneous frequency broadening are described. It is shown that in the case of very large excesses over threshold the efficiency of FELs tends to 50% but the emitted energy is distributed in a very wide spectral interval.     

Observation of inhomogeneous spectral broadening of stimulated brillouin scattering in an optical fiber

We report experimental results which show that the stimulated Brillouin scattering (SBS) spectrum in an optical fiber is inhomogeneous, exhibiting spectral broadening and hole burning under cw monochromatic laser excitation. This phenomenon arises from the waveguide interaction of the pump and Stokes signals and is a fundamental property of SBS in waveguiding systems due to their ability to confine a fan of radiation wave vector directions.     

The influence of coordinated defects on inhomogeneous broadening in cubic lattices

The joint probability distribution function (JPDF) of electric field gradient (EFG) tensor components in cubic materials is dominated by coordinated pairings of defects in shells near probe nuclei. The contributions from these inner shell combinations and their surrounding structures contain the essential physics that determine the PAC-relevant quantities derived from them. The JPDF can be used to predict the nature of inhomogeneous broadening (IHB) in perturbed angular correlation (PAC) experiments by modeling the G ₂ spectrum and finding expectation values for V _zz and η. The ease with which this can be done depends upon the representation of the JPDF. Expanding on an earlier work by Czjzek et al. (Hyperfine Interact. 14, 189–194, 1983), Evenson et al. (Hyperfine Interact. 237, 119, 2016) provide a set of coordinates constructed from the EFG tensor invariants they named W ₁ and W ₂. Using this parameterization, the JPDF in cubic structures was constructed using a point charge model in which a single trapped defect (TD) is the nearest neighbor to a probe nucleus. Individual defects on nearby lattice sites pair with the TD to provide a locus of points in the W ₁?W ₂ plane around which an amorphous-like distribution of probability density grows. Interestingly, however, marginal, separable PDFs appear adequate to model IHB relevant cases. We present cases from simulations in cubic materials illustrating the importance of these near-shell coordinations.     

有机盐掺杂聚合物微腔的受激发射特性研究$lt;font color="#ff0000"$gt;（已撤稿）$lt;/font$gt;

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243 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     

Estimate of inhomogeneous line broadening in steady-state magnetic resonance

We have established relationships between the experimental and theoretical absorption and dispersion line parameters for steady-state magnetic resonance, allowing us to determine both the field characteristics (amplitude of the a.c. magnetic field) and the relaxation characteristics (longitudinal and transverse relaxation times) of the object under study.     

Potential industrial applications of inhomogeneous broadening imaging.

Variations in magnetic susceptibility at air-water interfaces can result in inhomogeneous broadening of the NMR line. By special asymmetrical imaging techniques, originally developed for lung imaging, images can be formed of only those molecules that experience this inhomogeneous broadening. The basic concepts and latest developments in inhomogeneous-broadening-imaging techniques are described. Potential industrial applications are also discussed.     

Optical modes in wavelength-sized organic microcavity structures

We show the impact of lateral structuring on the optical properties of organic thin films in microcavities. The active material tris-(8-hydroxy quinoline) aluminium (Alq₃) was deposited using shadow mask evaporation, resulting in various micron sized shapes. A simplified box model is employed to describe the steady state electric field distribution in these mesa cavities. The complex mode structure measured in transmission and photoluminescence is confirmed by a transfer matrix calculation and a Fourier transform of the internal electric field distribution.     

电致发光色纯性增强的硅基有机微腔

报道了硅基有机微腔的电致发光（EL）.该微腔由上半透明金属膜、中心有源多层膜和多孔硅分布Bragg反射镜（PS DBR）组成.半透明金属膜由Ag（２０nm）构成，充当发光器件的负电极和微腔的上反射镜.有源多层膜由Al (1 nm) / LiF(05 nm) /Alq3/Alq3:DCJTB/NPB/CuPc/ITO/SiO2组成，其中的Al/LiF为电子注入层，ITO为正电极，SiO2为使正、负电极电隔离的介质层.该PS DBR是采用设备简单、成本低廉且非常省时的电化学腐蚀法用单晶Si来制备的；该PS 关键词： 电化学腐蚀 电致发光 窄峰发射 硅基有机微腔     

Effect of inhomogeneous broadening of submonolayer quantum dots on the generation of vertical-cavity laser with saturable absorber

The experimental dependences for a laser based on submonolayer quantum dots (QDs) without an absorber were used to calculate the energy characteristics of a semiconductor laser based on QDs and quantum wells with a saturable absorber under bistable lasing conditions; the data obtained make it possible to implement a monolithic version of this laser. All of the mechanisms of carrier relaxation and QD filling, which are important for experiment, are taken into account. The effect of inhomogeneous QD broadening over resonant frequency is considered. The laser mode shift that is caused by an increase in the pump current is found to limit the lasing power. It is shown that the choice of active and passive layers with inhomogeneously broadened QDs makes it possible to obtain bistable lasing in the entire range of available pump currents.     

Observation of vector vortex lattices in polarization states of an isotropic microcavity laser

We experimentally investigate the formation of a vector polarization pattern from an isotropic microcavity laser. It is found that the orthogonal components of the observed pattern are localized on the geometrical rays. The connection between eigenfunctions and geometrical rays is analytically constructed by using the SU(2) coherent states. With the analytical function form, the observed vector pattern is completely reconstructed and the vector vortex lattice is apparent.     

Combined effects of microcavity and dielectric capping layer on bidirectional organic light-emitting diodes

We report on highly enhanced and controlled light outcoupling of bidirectional organic light-emitting diodes by introduction of an enhanced microcavity structure as well as an organic capping layer (OC). Combining both OC and microcavity, we find that the overall external quantum, as well as current efficiency (CE), can be greatly enhanced. Especially, the CE with an appropriate thickness of OC is almost 1.75 times larger than that of the reference device without OC. Furthermore, we also analyze our devices with a numerical optical model calculating the flux of outcoupled photons, and compare theoretical predictions with our experimental results.     

Revision on the calculation of optically pumped FIR laser spectrum with Doppler broadening and pressure broadening effects

By means of iteration method and also taking into account Doppler broadening and pressure braodening effect of IR pumping laser, the output power density of optically pumped NH₃ molecules FIR laser is calculated by solving density matrix equations of three-level system. The results of theoretical calculation shows that, in comparison with the FIR laser under the assumption of ideal monochromatic IR pumping, the output power density of FIR laser in the case of Doppler broadening and pressure broadening IR pumping decreases much more. Meanwhile, via the revision of Doppler broadening and pressure broadening effect, the theoretical value of optimum operating gas pressure reduces, which is in better agreement with the experimental value. Further study shows that the revision of Doppler broadening effect is more fit for the conventional FIR laser with a 2m sample tuble and the revision of pressure broadening effect is much more suitable for the miniature FIR laser with a short sample tube of 5 to 20cm in length.Supported by the National Natural Sciences Foundation of P.R.China and the NSF of Guangdong Province.     

Effects of inhomogeneous broadening on two-frequency longitudinal wiggler brightness

The two-frequency longitudinal wiggler brightness is further extended to include the effects of betatron oscillations. The analytic expressions and the results with relevant physical consequences are presented for a comparison with the linear two-frequency undulator field, a popular device proposed earlier for side band suppression and quasi-continuous behaviour.     

The eigenmodes of a spatially inhomogeneous laser

The theory of the isothermal Hall-effect in intrinsic material is corrected taking into account arbitrary surface and bulk recombination and the departure from local electrical neutrality. The resulting formulas for the Hall voltage, the Hall field, the charge density, and the electron-hole current are valid for a weak magnetic field.