Stiffness of optical traps: quantitative agreement between experiment and electromagnetic theory

The first quantitative agreement between measured and calculated stiffnesses of optically trapped particles in the subwavelength regime is presented. It is shown for all three dimensions that the measured extent of harmonic optical trapping potentials for dielectric spheres comes very close to the theoretically predicted extent, provided all known instrumental parameters are considered. The recently predicted strong asymmetry of the trapping potential due to the electric field's linear polarization has been verified in all three directions. This effect vanishes for spheres with diameters d approximately lambda, which exhibit the strongest trap stiffnesses.     

Transient Lamb waves: comparison between theory and experiment

This paper presents an experimental investigation of the generation of transient Lamb waves inside an immersed plate by a time limited signal. The transient Lamb waves are the solutions of the characteristic equation of the plate for complex frequency and real slowness, in contrast to the leaky Lamb waves, for which the slowness is complex and the frequency is real. By using a large transducer in agreement with the real slowness assumption, the excitation of these transient Lamb waves is observed experimentally both in reflection and transmission for a tone burst excitation. Particular attention is paid to the A0 mode for which the amplitude increases exponentially in time. As a result, the total reflected waveform contains in this case a transient contribution, coming from the generation of the A0 mode, that precedes the forced regime. It is shown that there is a very good agreement between the theoretical and the experimental time exponential amplitude variations of the transient Lamb waves. For the A0 mode, the transient signal is qualitatively explained by a group velocity higher than the phase velocity.     

Polariton luminescence and additional boundary conditions: comparison between theory and experiment

Polariton luminescence spectra in semiconductors have been calculated as a function of temperature and impurity trapping rates using a two branch polariton model. Typically, the theoretical spectra show two structures: a peak near the transverse exciton energy and a shoulder near the longitudinal exciton energy. While the lower energy peak is relatively insensitive to the choice of additional boundary conditions (ABC), the higher energy shoulder strongly depends on ABC. The theoretical curves obtained with Pekar's ABC are in quantitative agreement with experimental spectra reported in CdS, CdSe and CuCl. However, significant discrepancies between theory and experiment are found in GaAs and ZnTe.     

Longitudinal parametric oscillation in photorefractive sillenites: comparison between theory and experiment

By using an alternative setup for photorefractive parametric oscillation in which wave mixing between the recording beams is avoided it has become possible to make more detailed comparisons with the space-charge wave theory. In the present paper we compare the experimental features of longitudinal parametric oscillation observed in a crystal of Bi₁₂SiO₂₀ with the theoretical predictions. Received: 24 November 1998 / Revised version: 13 January 1999 / Published online: 7 April 1999     

Spectrum of three-dimensional photonic quantum-ring microdisk cavities: comparison between theory and experiment

The spectrum of a three-dimensional Rayleigh-Fabry-Perot microdisk cavity of a photonic quantum-ring laser is analyzed for angle-dependent emission modes. It is shown that joint consideration of the Fabry-Perot resonance condition and the whispering-gallery mode boundary condition explains the emitting angles and spectral distribution of the cavity modes well.     

Directed motion for delta-kicked atoms with broken symmetries: comparison between theory and experiment

We report an experimental investigation of momentum diffusion in the delta-function kicked rotor where time symmetry is broken by a two-period kicking cycle and spatial symmetry by an alternating linear potential. We exploit this, and a technique involving a moving optical potential, to create an asymmetry in the momentum diffusion that is due to the classical chaotic diffusion. This represents a realization of a type of Hamiltonian quantum ratchet.     

On low frequency sound transmission loss of double sidebranches: a comparison between theory and experiment

The sound power transmission losses of various sidebranches installed along a rectangular duct below the first cut-off frequency of the duct are studied experimentally. Special efforts are made to examine how accurately the plane-wave theory predicts the sound-power transmission loss. Four types of sidebranch impedance are established and their effects to the sound power transmission loss discussed. It is found that under the nonresonant conditions the plane-wave theory can give reasonable prediction when the branch separation is large or the original sound transmission loss of the corresponding single side-branch is weak. The theory always overestimates the sound transmission loss at resonant conditions but gives underestimation if the transmission loss is due to the noise breakout in the sidebranches, especially for short branch separation.     

Nonlinear mixing between the emission of a cw laser and a femtosecond laser

We mix the emission of a femtosecond Ti:sapphire laser with the emission of a continuous wave infrared laser in a beta-barium borate crystal. Green light with a center wavelength of 527 nm and a spectral width of 2.5 nm resulting from sum frequency generation is detected. An intensity study verifies that a nonlinear χ⁽²⁾ process is at the origin of the green light generation. The experimentally obtained conversion efficiency of 7 × 10⁻¹⁰ is in good agreement to simple theoretical considerations.     

Absorption and subsequent emission saturation of two-photon excited materials: theory and experiment

The saturation of two-photon absorption and the subsequent photoluminescence of matter under ultrafast laser pulse excitation are studied. For this purpose the experimental results of using two organic conjugated polymers as model substances are discussed theoretically. One model is based on the commonly used hyperbolic approach, whereas the new theory introduced correctly describes the saturation in two-photon spectroscopy and fits the experiment closely. The new model permits microscopic analysis of the absorption saturation process and makes possible an estimate of the two-photon absorption coefficient from the saturation intensity.     

Leak rate of seals: Effective-medium theory and comparison with experiment

Seals are extremely useful devices to prevent fluid leakage. We present an effective-medium theory of the leak rate of rubber seals, which is based on a recently developed contact mechanics theory. We compare the theory with experimental results for seals consisting of silicon rubber in contact with sandpaper and sand-blasted PMMA surfaces.     

Far-infrared electrodynamics of superconducting Nb: comparison of theory and experiment

Complex conductivity spectra of superconducting Nb are calculated from the first principles in the frequency region around the energy gap and compared with the experimental results. The raw experimental data obtained on thin films can be precisely described by these calculations.     

Bragg-case X-ray thin-crystal rocking curves for Si — A direct comparison between theory and experiment

Symmetrical-Bragg-case X-ray thin-crystal rocking curves for the 422 reflection of Si, measured by Hashizume et al., are shown to agree very well with the predictions of the dynamical theory.     

A new comparison between experiment and theory for the X-ray K absorption edge of nickel

New structure has been resolved in the X-ray K absorption edge of nickel. There is rough qualitative agreement between our spectrum and the calculations of Nagel et al., for which the presence of the core hole is neglected in the computation of the final state wave function. However, the two lowest energy experimental peaks are significantly shifted to lower energies relative to the corresponding theoretical peaks. In addition, the theoretical spectrum is much sharper than the experimental curve even after accounting for instrumental broadening and broadening due to the natural width of the K level, indicating that hot electron broadening effects strongly influence the final ejected electron states.     

Photoelectron angular distributions from O K shell of oriented CO molecules: A critical comparison between theory and experiment

The dynamical information (ten dipole matrix elements and eight phase differences) has been deduced from the measured angular distributions of photoelectrons from O K shell of oriented CO molecules near the ionization threshold in the region of a sigma(*) shape resonance. Light polarization parallel and perpendicular to the molecular axis has been used. An important contribution of six lsigma partial waves with 0相似文献