Resonance fluorescence in an atom + dielectric microsphere system excited by a single photon

The resonance interaction of a two-level atom with a continuum of free-space modes modified by the presence of a dielectric microsphere (modified free-space modes — MFSMs) is studied. In the case that quantized MFSMs are initially excited within the contour of one of the resonance modes of the microsphere, the spectrum of emitted photons depends strongly on the excitation method. Under optimal excitation conditions efficient excitation of the atom accompanied by the formation of a Rabi doublet in the fluorescence spectrum occur. As the excitation conditions depart from optimality, the spectrum becomes a triplet. If the departure from optimality of excitation is large, the atom remains essentially unexcited, and the fluorescence spectrum has a singlet character. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 2, 115–120 (25 July 1998)     

Vacuum splitting of the energy levels of a system consisting of an atom and a dielectric microsphere

Expressions are found for the vacuum splitting of the energy levels of a system consisting of a two-level atom and a dielectric microsphere. These expressions coincide with those obtained from a purely classical approach. Zh. éksp. Teor. Fiz. 111, 44–51 (Janaury 1997)     

Resonance fluorescence spectrum of a three-level atom

We consider the excitation spectrum arising from the interaction between a three-level atom and a strong electromagnetic field in the frequency region where the two atomic transition frequencies are nearly equal to once and twice the frequency of the pump field respectively. Detailed expressions for the spectral functions are derived describing the two-, one- and zero-photon excitations as well as those arising from the coupling between them, in the limit of high photon densities. The zero-photon excitations describe low frequency modes induced by the pump field under resonance conditions.     

Cooperative effects in the two atom resonance fluorescence spectrum

We consider the resonance fluorescence spectrum of two similar interacting atoms in the limit of high photon densities. The excitation spectrum of the symmetric modes contains two sidebands in addition to the usual three peaks which are analogous to those of the isolated atom. These two new sidebands are due entirely to the cooperative behaviour of the two atoms and vanish when the atoms are far apart. The energy shifts and spectral widths for these two sidebands are two and five times larger than those for the isolated atom respectively. The probability of occurrence of these sidebands depends on the parameters V_AB/Ω and γ²₀/Ω², where V_AB is the dipole-dipole interaction energy, γ₀ is the spontaneous emission probability and Ω is the Rabi frequency. The asymmetric broadening of both sidebands depends on the parameter γ₀/Ω. The possibility to measure the dipole-dipole energy through the observation of these sidebands is discussed.     

Two-photon fluorescence bioimaging with an all-semiconductor laser picosecond pulse source

We have demonstrated successful two-photon excitation fluorescence bioimaging using a high-power pulsed all-semiconductor laser. Toward this purpose, we developed a pulsed light source consisting of a mode-locked laser diode and a two-stage diode laser amplifier. This pulsed light source provided optical pulses of 5 ps duration and having a maximum peak power of over 100 W at a wavelength of 800 nm and a repetition frequency of 500 MHz.     

Resonance fluorescence spectrum of a three-level atom. II. Numerical results

Numerical computations are presented for the excitation spectra arising from the interaction between a three-level atom in the cascade configuration and a strong electromagnetic field whose frequency mode is initially populated. The excitation spectra are considered when the laser field is at resonance with the equally spaced levels of the atom as well as a function of the detunings. The physical process of optical amplification occurs without population inversion and it is more pronounced when the laser field is detuned than when it is at resonance. The shapes of the spectral lines for a number of side-bands are of the absorption-amplification type rather than that of the absorption one. In the presence of detunings as well as in the cooperative two-photon cascade process, the resulting spectra are far more complicated than those occuring at resonance. Results of numerical calculations for a wide range of Rabi frequencies and detunings are presented graphically.     

有机染料CSPI的双光子吸收和上转换荧光性质

报道了一种有机染料Trans 4 [p carbazol 9 ylstyryl] ] N methylpyridiniumiodide的线性和非线性光学性质。当用 830nm皮秒激光激发时 ,可以得到强烈的黄绿色上转换荧光 ,中心波长在 538nm附近。该染料的双光子荧光寿命为 95 .6ps。测试了该染料在 72 0～ 1 0 50nm的非线性透过率 ,并求出了该染料在上述波长时的双光子吸收截面。双光子吸收最强在 80 0nm ,吸收截面为 9.2× 1 0 - 48cm4 ·s/ photon。     

The fluorescence spectrum of a three-level atom in two-photon resonance with the laser field

The influence of the two-photon resonant interaction on the fluoresence spectrum of a three-level atom is studied. The levels in questions are the 1S, 2P and 3S states of a two-electron atom. It is shown, that in the case of exact two-photon resonance between the 1S–3S transition and the laser field, and when the 2P state is out of resonance, the fluorescence spectrum contains 4 lines. The properties of these lines are discussed.     

Resonance fluorescence spectrum of a three-level atom driven by coherent and stochastic fields

The dressed-state populations and the resonance fluorescence spectrum of a V-type three-level atom driven by a strong coherent field and a weak stochastic one simultaneously are investigated. There can be significant population inversion due to the effect of the stochastic field. The atomic resonance fluorescence spectrum can be controlled by adjusting the frequency difference between the coherent field and the stochastic one and the coherent Rabi frequency. Peak suppression and line narrowing occur under appropriate conditions. Received 23 June 2000 and Received in final form 18 January 2001     

Two-photon polymerization of an epoxy-acrylate resin material system

Improved material systems are of great interest in the development of two-photon polymerization techniques for the fabrication of three dimensional micro- and nano-structures. The properties of the photosensitive resin are important in the realisation of structures with submicron dimensions. In this study investigation of a custom organic resin, cross-linked by a two-photon induced process, using a femtosecond Ti:sapphire laser, is described. A structural, optical and mechanical analysis of the optimised material is presented. The influence of both material system and laser processing parameters on achievable micro-structure and size is presented as are representative structures. Parameters include: laser power, photo-initiator concentration and material composition.     

电介质或导体表面吸附原子的共振光现象

本文借助于线性响应理论方法求得固体表面附近原子的光学布洛赫(Bloch)方程。借助于光学布洛赫方程和量子回归定理,求得了吸附原子的共振荧光谱。通过对该谱的数值分析可得出下述结论:固体表面的存在将对光谱中峰的高度以及两个边带的位置产生明显的影响。当被吸附的原子非常接近固体表面时,两个边带会向两侧移动,其中一个几乎消失,同时各个峰的高度也会大幅度降低。     

Two-photon fluorescence measurements in a hexagonal CdS crystal

Measurements of two-photon fluorescence (TPF) in a CdS crystal using a dye laser pumped by a Q-switched ruby laser are reported. The TPF is measured as a function of source intensity and wavelength. The total fluorescence shows linear and non-linear dependence on the source intensity; from these measurements the TPF part is determined. The measured transition of the crystal's fundamental gap is 2.5 ± 0.02 eV and another forbidden one-photon but allowed two-photon transition is found at 3.24 ± 0.02 eV.     

Sub-half-wavelength atom localization via probe absorption spectrum in a four-level atomic system

We present a simple scheme of atom localization in a subwavelength domain via manipulation of probe absorption spectrum in a four-level atomic system. By applying two orthogonal standing-wave fields, the localization peak position and number as well as the conditional position probability can be controlled by the intensities and detunings of optical fields, and the sub-half-wavelength atom localization is also observed. More importantly, there is 100% detecting probability of the atom in the subwavelength domain when the corresponding conditions are satisfied.     

Electronic structure and fluorescence spectrum of the HeO+ cation

Quantum-mechanical calculations of the potential curves of the HeO⁺ ion are preformed which correlate with four lower dissociation limits and indicate the excimer type of the ion. The transition dipole moments of the 2²Σ^?→1²Σ^? and 2⁴Σ^?→1⁴Σ ^? transitions are calculated. The energies and radiative lifetimes of vibrational levels are determined and structural and spectroscopic constants of the states 1²Σ^?, 2²Σ^?, 1⁴Σ^?, and 2⁴Σ^? are calculated. The fluorescence spectrum corresponding to the 2²Σ^?→1²Σ^? and 2⁴Σ^?→1⁴Σ ^? transitions is also calculated. The possibility of lasing at these transitions is discussed.     

On the spectrum of the hydrogen atom in an ultrastrong magnetic field

Various approaches to computing the energies of the ground state and excited levels of the hydrogen atom in an ultrastrong magnetic field B that considerably exceeds the field B _a = m _e ² e ³ c/ħ ³ ∼ 10⁹ G are considered. The effects of polarization of vacuum and anomalous magnetic moment of the electron on the position of the atomic levels are discussed. The vacuum polarization effects are negligibly weak for B < 10¹⁵ G but become significant in fields B ≫ 10¹⁶ G, in which these effects qualitatively modify the atomic spectrum in this range. The difference in the behaviors of the even and odd energy levels for B ≫ B _a is analyzed and the formulas for the energies of odd levels as a function of field B are refined.     

农药荧光全光谱检测与分析系统研究

基于有机物农药的荧光机理,利用光纤传感技术、光栅分光技术和多通道图像传感器(Multi-Channel ImageSensor)技术提出了一种用于有机农药的荧光全光谱检测与分析系统。系统以脉冲氙灯为激发光源,采用光纤进行传输和探测荧光,以自制的小型平场光谱仪对荧光进行色散分光,并设计了相应的高速数据采集电路,实验结果由微机进行分析。利用该系统实现了对西维因农药的荧光光谱的检测和荧光强度与农药浓度的分析。结果表明,以319nm波长紫外光为激发光,一次曝光可获得西维因农药的荧光光谱,光谱带宽为160nm;系统的最小检测浓度为4.0×10-3mg/L,农药浓度在4.0×10-3~100.0×10-3mg/L之间时系统具有较好线性关系,线性相关系数r为0.9986。用该仪器对河水和地下水中痕量西维因进行了测量,回收率接近100%。