The effects of intensity in resonance fluorescence

The probability of resonance fluorescence with account of intensity influence is calculated on the basis of the semiclassical radiation theory. In the case of a monochromatic external field the results confirm those of Mollow. Scattering probabilities in the case of a bichromatic external field are also obtained.     

Two-time photon correlations in resonance fluorescence

The factorization formula for the two-time intensity correlation of the fluorescence produced by a two-level atom in a coherent field is generalized for an arbitrary quantum state of the field. The formula is then applied to a Fock state.     

Intensity correlations in resonance fluorescence from two atoms

The intensity correlation function of resonance fluorescence radiation from a two atom system is calculated in the weak-field limit.     

Nonclassicality of resonance fluorescence via amplitude-intensity correlations

Conditional homodyne detection (CHD) allows a fresh view of the nonclassicality of optical fields. A balanced homodyne detector replaces a photodetector in the Hanbury-Brown-Twiss setup of photon correlations, thus measuring a quadrature (amplitude) of the field on the cue of a photon detection. In CHD, both quadratures of a quantum field violate classical inequalities even if photon correlations look classical. We calculate the amplitude-intensity correlations for the resonance fluorescence of a two-level atom and a three-level atom in the V configuration, notable producers of quantum effects (antibunching, squeezing, and sub-Poissonian statistics). In the V atom, where we consider that the ground state is coupled strongly (weakly) to a short (long) lived state, the strong transition resembles the two-level atom features, albeit with larger oscillations and a slower decay. However, the autocorrelation of the fluorescence of the weak transition is clearly asymmetric around a zero delay, indicating the breakdown of detailed balance, and violating the inequalities by orders of magnitude due to the low photon flux. Cross correlations of strong and weak channels also display antibunching and the loss of bounds.     

Relationship between linewidth and electric field intensity of guide-mode resonance filter

In this paper, relationship between linewidth and maximum electric field intensity (MEFI) at resonance of guided-mode resonance filter (GMRF) is investigated. It is demonstrated that the linewidth will vary inversely with the MEFI as one of some of the parameters of the GMRF increasing (e.g. period, thickness, and filling factor of the grating in the GMRF and cover refractive index) and with others maintained. Also it is demonstrated that resonant wavelength will shift to longer wavelength as any one of the parameters of the GMRF increasing. Moreover, the changes of period and thickness of grating have good linear relation with wavelength shifting. This will be of interest for optical sensor systems.     

Finite-size effects on intensity correlations in random media

The correlations between waves transmitted through random media are analyzed by use of a random-matrix approach and numerical simulations of rough waveguides. Although the intensity and conductance fluctuations are practically independent of the sample length, the correlations present a strong dependence on the length of the disordered region. In waveguide geometries the long-range correlations C((2)) and C((3)), usually associated to intensity and conductance fluctuations, respectively, become negative as the length of the system decreases. Our results provide a new interpretation of recent optical experiments on disordered slab geometries.     

Time development of the light intensity in resonance fluorescence

The time evolution of the fluorescent light emitted by a two-level atom that is driven by an external quantum field close to resonance, has been calculated. Although the treatment lies within the framework of QED, it is found that the answer in no way depends on any quantum properties of the field.     

Intensity correlations in resonance fluorescence excited by intense incoherent fields

A general rigorous theory of the intensity correlations in resonance fluorescence excited by markovian incoherent fields of arbitrary bandwidth and average intensity is presented. Both single and many independent two-level atom fluorescence are considered.     

Frequency effects on the conduction electron spin resonance linewidth in aluminium

The CESR linewidth of pure aluminium is shown to have a temperature dependent phonon contribution which is largely frequency independent. A second term in the linewidth is found to be temperature independent but linearly dependent upon frequency giving 0.11 mT per GHz. Finally it is shown that if partial breakdown of motional narrowing occurs it contributes a term proportional to the frequency and not, as expected, to the frequency squared.     

Observation of phase-sensitive temporal correlations in the resonance fluorescence from two-level atoms

We have made what we believe is the first observation of phase-dependent temporal correlations in the fluorescent field emitted by coherently driven two-level atoms in free space. We measured the temporal fluctuations of the fluorescent field when the resonant driving field was in phase and out of phase with the local-oscillator field.     

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.     

Ferromagnetic resonance linewidth in CoNi/FeMn bilayers

Out-of-plane ferromagnetic resonance (FMR) spectra of sputtered Co₄₀Ni₆₀/FeMn bilayers with various CoNi layer thicknesses were measured and analyzed by the Landau–Lifshitz–Gilbert equation. With increasing CoNi layer thickness, the effective demagnetizing field increases and the Landé g factor decreases. At the same time, the peak-to-peak linewidth H_pp in the parallel and perpendicular configurations decreases. The angular dependence of the FMR linewidth can be described very well by the intrinsic Gilbert damping effect and the magnetic inhomogeneity. The Gilbert damping G factor is inversely proportional to the CoNi layer thickness and proportional to (g-2)² with the variation of the CoNi layer thickness. PACS 75.70.-i; 76.50.+g; 75.30.Gw     

Combined effect of light intensity and temperature on the magnetic resonance linewidth in alkali vapor cell with buffer gas

One of the peculiar phenomenons in non-zero magnetic resonance magnetometer is that, with the increase of the temperature, the magnetic resonance linewidth is narrowed at first instead of broadened due to the increasing collision rate. The magnetometer usually operates at the narrowest linewidth temperature to obtain the best sensitivity. Here, we explain this phenomenon quantitatively considering the nonlinear of the optical pumping in the cell and did experiments to verify this explanation. The magnetic resonance linewidth is measured using one amplitude-modulated pump laser and one continuous probe laser. The field is along the direction orthogonal to the plane of pump and probe beams. We change the temperature from 53℃ to 93℃ and the pumping light from 0.1 mW to 2 mW. The experimental results agree well with the theoretical calculations.     

Quantum theory of resonance fluorescence with recoil effects

A quantum statistical theory of resonance fluorescence, which is valid to all orders in the interaction with the laser field and which takes the recoil into account by explicit quantization of the center of mass motion, is presented. The recoil shifts are calculated both in the limit of weak and strong fields. In the limit of strong fields and when the laser field is at resonance with the atomic frequency, the theory predicts essentially a symmetric spectrum, centered at the recoil shifted frequency.     

On the theory of cyclotron resonance linewidth

Using self-consistent perturbation theory a formula for the a.c. magneto-conductivity is derived. This formula takes account of both self-energy and vertex correction effects and can be used to calculate the cyclotron resonance linewidth. For realistic values of the strength and the range of the impurity potential good agreement with results of experiments on InSb is obtained.     

Nonpolarizing guide-mode resonance filter with ultra-narrow linewidth

Ultra-narrow linewidth,nonpolarizing guide-mode resonance (GMR) filters with single and double common resonance wavelengths are designed.The guide-mode resonance filters consist of a single grating layer with asymmetric profiles.By choosing appropriate parameters,same resonance wavelengths for both transverse electric (TE) and transverse magnetic (TM) polarizations can be achieved.Results show that high reflection (more than 99.9%) is obtained at every resonance wavelength,and the full-width at halfmaximums (FWHMs) of TEand TM-polarized light are only 0.008 and 0.215 nm,respectively.     

Kondo anomaly of impurity spin resonance linewidth

Using the method of Baym and Kadanoff a kinetic equation is derived for the impurity susceptibility in thes-d model. Summing up the most important diagrams the impurity self-energy can be expressed in terms of Suhl'sT-matricest andτ. The contribution of the spin non flip amplitudet to the spin relaxation time is cancelled by a corresponding vertex correction. Thus the final result can be expressed in terms of the spin flip amplitudeτ alone which causes an anomalous temperature dependence of the relaxation time.     

About the linewidth of cyclotron resonance in band-gap graphene

The critical amplitude of circularly polarized electromagnetic wave when the hysteresis of cyclotron absorption takes place, was found for band-gap graphene. The dependence of critical amplitude on the gap value and on the relaxation time was investigated. The conditions of applicability of linear theory describing the electromagnetic response of band-gap graphene in a non-zero magnetic field were found. The power of the circularly polarized electromagnetic radiation absorbed by band-gap graphene in the presence of a magnetic field was calculated. The linewidth of cyclotron absorption was shown to be not zero even for pure band-gap graphene.