Treatment of the emission and absorption spectra for a Λ-type three-level atom driven by a single-mode field with nonlinearities

The treatment of a Λ-type three-level atom interacting with a single mode field in a cavity, explicitly taking the existence of forms of nonlinearities of both the field and the intensity-dependent atom-field coupling into account. Analytical expressions of the emission and absorption spectra are presented using the dressed states of the system. The characteristics of the emission and absorption spectra for binomial state and squeezedcoherent state inputs are exhibited. The effects of the mean number of photons, the detuning, and the nonlinearities on the spectra are investigated. It is shown that the features of the fluorescence and absorption spectra are influenced significantly by the kinds of nonlinearities.     

Emission and absorption spectra of a Λ type three-level atom driven by a two-mode cavity field with nonlinearities

An analytical expression of the emission and absorption spectra for a Λ type three-level cavity-bound atom interacting with a two-mode cavity field is given using the dressed states of the system. We take into account explicitly the nonlinearities of both the field and the intensity-dependent atom-field coupling. The characteristics of the emission and absorption spectra when one of the two-mode cavity fields is in a binomial state and the other is in a squeezed coherent state are exhibited. The effects of the mean number of photons, detuning, and the kinds of nonlinearities on the spectra are analyzed.     

Emission and absorption spectra of a general formalism Ξ-type three-level atom driven by a single-mode field with nonlinearities

We study the interaction of a three-level atom with a single-mode field in a cavity. We take explicitly into account the existence of the forms of nonlinearities of both the field and the intensity-dependent atom-field coupling. The wavefunction for the atomic system of the Ξ configuration is obtained when the atom is initially prepared in the excited state. The electromagnetic field may assume a squeezed coherent or binomial state. The analytical forms of the fluorescence and absorption spectra are calculated using the dressed states of the system. We investigate the influences of the mean number of photons, detunings, and the nonlinearities forms on the spectrum of the resulting field states. It is shown that the features of the fluorescence and absorption spectra are influenced significantly by the kinds of nonlinearities.     

光场及原子-光场耦合的非线性对腔内原子辐射谱的影响

研究了包括任意的光场非线性和原子光场非线性依赖强度耦合J-C(Jaynes-Cummings)模型中单原子的辐射谱,分析了上述非线性对辐射谱的影响.结果表明,原子的辐射谱强烈地依赖于光场的非线性项R(a⁺a)及原子光场非线性耦合因子f(a⁺a)的形式,其谱结构与标准J-C模型中原子的辐射谱明显不同.当腔内充满的非线性介质使得f(a⁺a)=1/(a⁺a)^1/2时,对于任意的初始光场态,辐射谱总是显示 关键词： 辐射谱 非线性耦合     

Multi-exciton spectroscopy on a self-assembled InGaAs/GaAs quantum dot

We report about spatially resolved magneto-optical experiments on a self-assembled InGaAs quantum dot. Using electron beam lithograpy for patterning a metal shadow mask we can isolate a single dot. This allows us to study the optical response of a single dot as a function of excitation power and magnetic field. We investigate the influence of many body interaction in the emission spectra for different exciton occupation numbers of the dot. The diamagnetic/orbital shift as well as Zeeman splitting in a magnetic field can be fully resolved and are used to identify the observed emission lines. Further we report on absorption properties of the quantum dot as a function of magnetic field. We analyse in detail the phonon-assisted absorption process connected with the GaAs LO-phonon 36 meV above the single-exciton ground state.     

Spectroscopic study of a representative polar cap of buckminsterfullerene: Cyclopentacorannulene

The spectroscopic properties of corannulene and cyclopentacorannulene are examined by use of absorption and steady-state fluorescence measurements. A red shift in the emission maxima of cyclopentacorannulene is noted with respect to the emission maxima in the corannulene spectrum. Similar differences in the absorption spectra of both molecules are also observed. Reasons for the dissimilarities in the absorption and emission spectra of these molecules are discussed. The fluorescence quantum yields and lifetimes of the molecules measured in organic solvents are reported. The fluorescence quantum yield and lifetime of cyclopentacorannulene are lower than those of corannulene. This difference is attributed to the highly strained and nonplanar structure of cyclopentacorannulene. The effectiveness of nitromethane as a quencher of corannulene and cyclopentacorannulene fluorescence is examined. In contrast to previously reported results, the fluorescence of these molecules is quenched by nitromethane. Fluorescence quenching of the molecules has been attributed to complex formation in the ground state, i.e., static quenching.     

SiN分子外电场情况下的发光特性

为全面分析外电场对分子发光特性的影响, 本文采用密度泛函B3P86方法6-31g(d)基组, 对SiN分子进行了基态结构的优化, 进而使用含时密度泛函方法(time dependent density functional theory, TDDFT), 计算了不同方向及大小的外电场情况下SiN分子的吸收谱、激发能、振子强度、跃迁偶极矩. 通过比较发现外电场对该分子的激发能、吸收谱、跃迁振子强度及跃迁偶极矩影响都比较明显, 说明了电场对SiN分子的激发特性影响比较复杂, 特别是在加场前后分子均有在可见光区波段的吸收谱, 这对研究分子的发光很有意义.同时对该分子所发可见光谱的产生机理进行了分析, 并与已有实验结果进行比较.     

Emission spectra and cross-section spectra of neodymium laser glasses

Amplified spontaneous emission spectra and light amplification spectra of some Nd³⁺:glass rods (silicate glass Schott LG680, phosphate glasses Schott LG760 and Hoya LHG5) are measured by pulsed flashlamp excitation. The spontaneous emission distribution, the stimulated emission cross-section spectra and the excited state absorption cross-section spectra are extracted. Excited state absorption prevents laser action around 1320 nm for the⁴F_3/2-⁴L_13/2 transition of Nd³⁺ in the investigated glasses.     

Double resonance spectra of predissociating states as a probe for continuum structure in a strong electro-magnetic field

The absorption spectrum for a probe field from a bound state to a predissociative resonance is calculated in presence of a second field coupling the same resonance to another bound state. The spectra, which strongly depend on the intensity of the second field, exhibit new features, which are analysed and discussed.     

Absorption and Fluorescence Emission Attributes of a Fluorescent dye: 2,3,5,6-Tetracyano-p-Hydroquinone

Four cyano groups have been substituted on the aromatic ring of p-hydroquinone (2,3,5,6-tetracyanohydroquinone) in order to study the enhanced photoacidity of this molecule. The acid-base equilibria have been studied using absorption (for ground state pK_a) and fluorescence (excited state pK_a) spectra. Three distinct species (neutral, anionic and dianionic forms) were observed in the ground state and only two species (anionic and dianionic forms) were found in the excited state when studied at different pH/H_o in water. Absorption and emission characteristics were studied in various organic solvents, including protic and aprotic solvents. Deprotonation was also investigated using binary mixtures. It has been revealed that absorption and emission spectra are considerably changed with change in media. Proton transfer to the solvent has been observed in various solvents.     

金属钌(Ⅱ)三螯形化合物的吸收光谱和发射光谱

通过对１，１０－菲珞琳及４，７－二苯基－１，１０－菲珞琳与钉三螯形化合物的吸收和发射谱分析，研究了钌离子４ｄ态在Ｄ３场作用下的分裂，发现配体的不同光谱会出现红移及吸光强度的变化，并定性地分析了配体影响光谱的影响。     

Electrically induced Raman emission from planar spin oscillator

We predict that two-dimensional electrons confined by a magnetic field gradient resonantly transfer energy to the electromagnetic field by a process of inverse electron spin resonance that is realized when the frequency of an open orbit equals the Larmor frequency. The calculated emission spectra show multiple peaks modulated by strong optical nonlinearities whose frequencies may be tuned by the magnetic field gradient and the electron concentration.     

Study of Spectroscopic Properties of Yb-doped Calcium Fluorapatite

The spectroscopic performance of Yb-doped calcium fluorapatite (Yb:FAP) was assessed by measuring polarization absorption spectra, polarization emission spectra and fluorescence lifetime. The emission cross section has been evaluated using the absorption cross section and principle of reciprocity. The π polarization absorption and emission cross sections of Yb3+ in FAP are found to be substantially larger than those of other Yb-doped media. Favorable spectroscopic parameters show that Yb:FAP crystal is more desirable for many diode-pumped solid state laser application with low- and medium-power in the near future.     

Study of Spectroscopic Properties of Yb-doped Calcium Fluorapatite

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Vertex correction effects on nonlinear optical response

The effects of vertex corrections due to frequency modulation are exactly evaluated on the emission spectra from the two-level electronic system pumped by the laser of arbitrary intensity and the absorption spectra of the weak probe field of this system. Here the frequency modulation is assumed to obey the Gaussian-Markoffian process. The two-time correlation function of the polarizations which describe the emission and absorption spectra is represented as the product of two propagators and a vertex correction. This correction is described in the form of the summation of the products of the matrix continued fractions. This correction is numerically demonstrated to be quite large for the emission spectrum in the case of the slow or strong frequency modulation and weak laser field, and for the absorption spectrum in the case of intermediate modulation and laser intensity.     

Enission spectra Of aΞ-type three-1evel atom in a Kerr medium

We investigate the emission spectra of a Ξ-type three-level atom interacting with a single-mode optical field in an ideal cavity filled with a Kerr medium and discuss the structure of emission spectrum when the optical field is initially in a pure number state and a coherent state, respectively. It is shown that the structure of emission spectrum depends not only on the photon number distribution, but also on the strength of incident field and the coupling of Kerr medium to the field.     

Excited state properties of 5H-dibenzo(a,d) cycloheptene

A number of photophysical properties of 5H-dibenzo(a,d) cycloheptene have been measured including the emission and triplet-triplet absorption spectra. The quantum yields and decay parameters for the triplet state of this molecule as a function of temperature have also been measured. The results are discussed and compared to those of molecules.     

Photophysical properties of novel organic europium (III) complexes

Based on fluorescence and absorbance spectroscopy, the photophysical properties and mechanisms of novel organic europium (III) complexes in the case of different concentration in ethanol solution and solid flour were studied at room temperature. It was found that the complex absorption spectra are mainly due to the Phenanthroline ligand, gradually exhibit saturated absorption from shortwave to long wave with the concentration increased, and stretch and broaden to long wave. And four characteristic peaks of the fluorescence spectra are all emission spectra of Eu3+ in the complex, and the strongest emission wavelength was 617 nm corresponding to the (5)D0-->(7)F2 transition of Eu2+. And then, it is presented that the perturbation of acetanil ligand changes the parity state of Eu3+ energy field, resulting in the increase of (5)D0-->(7)F2 transition probability, making phenanthroline transfer its energy absorbed to Eu3+, and inducing 617nm strong emission of fluorescence peak.     

The Role of Intermolecular Interactions in Solid State Fluorescent Conjugated Polymer Chemosensors

A functionalized fluorescent conjugated polymer, tolylterpyridine poly(p-phenyleneethynylene-thienyleneethynylene (ttp-PPETE), was designed and synthesized to detect trace amounts of toxic transition metal pollutants in ground water. Photophysical studies in tetrahydrofuran (THF) successfully demonstrated this polymer as a selective and sensitive chemosensor for Ni²⁺ and Co²⁺ in aqueous solution. Solid state composites of these chemosensors have now been prepared which can be modified to provide for inexpensive and portable field based chemical detection. A solid composite of ttp-PPETE, blended with poly (methyl methacrylate) shows UV–vis absorption and fluorescence emission spectra which are red- shifted when compared to solution phase spectra, suggesting an increase in conjugation in the solid state. An additional absorption peak, not present in solution, is also observed in the solid state. The presence of this new peak provides evidence of interacting FCP chains in the solid state. Concentration dependent experiments were done on the solid composite showing red-shifted emission peaks accompanied by a significant reduction in the fluorescent quantum yield. These observations are consistent with the formation of aggregated polymer species in the solid state. Intermolecular interactions of this type can be manipulated in the design of sensitive and selective solid state fluorescent conjugated polymer sensors.     

Electromagnetically Induced Transparency and Absorption of A Monochromatic Light Controlled by a Radio Frequency Field

Electromagnetically induced transparency and absorption of a monochromatic light controlled by a radio frequency field in the cold multi-Zeeman-sublevel atoms are theoretically investigated. These Zeeman sublevels are coupled by a radio frequency(RF) field. Both electromagnetically induced transparency and electromagnetically induced absorption can be obtained by tuning the frequency of RF field for both the linear polarization and elliptical polarization monochromatic lights. When the transfer of coherence via spontaneous emission from the excited state to the ground state is considered, electromagnetically induced absorption can be changed into electromagnetically induced transparency with the change of intensity of radio field. The transparency windows controlled by the RF field can have potential applications in the magnetic-field measurement and quantum information processing.