We calculated a theoretical G-factor for the lidar system and compared the calibration effect between this G-factor and a real G-factor in inversion of attenuation coefficient for an appropriately averaged lidar return signal in a homogeneous atmosphere. Examples to consider the effect of misalignment between the transmitter and receiver optical axes in inversion of attenuation coefficient are also presented.

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We generated a white-light continuum array by directing femtosecond laser pulses into a liquid with a microlens array. Experimental evidence demonstrates that the spatial coherence is high within a single light source in the array. We also confirmed that all the light sources in the white-light continuum array are mutually coherent. We found that the simple self-phase modulation model cannot explain this high coherence between the white continuum sources.

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Fused optical fiber grating couplers (FGCs), in which Bragg gratings are written in the coupling regions of fused optical fiber couplers with tapered shapes along them are theoretically and experimentally investigated. By coupled mode analysis considering these tapered shapes, the drop efficiencies of the FGCs, which are inherently zero for the normal fiber couplers without grating, are calculated. The grating offset, which is the difference between the centers of grating and the coupler taper, is found to be effective to increase the drop efficiency of the FGC. It is determined that the tapered shapes influence the wavelength dependence of the drop efficiency and tolerate the grating offset precision. Apodizations for the grating of FGC are found to be effective in suppressing side lobes of the drop efficiency. Measurement of the wavelength characteristics of drop efficiency and the temperature characteristics of drop wavelength of the fabricated fused FGC confirm that the lightwave with specific wavelength can be dropped by the FGC and that the temperature dependence of the drop wavelength is similar to that of Bragg wavelength changes of usual fiber Bragg gratings.

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The multistability of a Fabry-Perot semiconductor diode laser for an injection current is presented when multi-optical inputs detuned from the cavity-resonant wavelength of a semiconductor laser are injected. m+1 Multi-stable states are shown to be produced in the optical output versus injection current characteristics for m detuned optical inputs. It is shown that optical output can be switched in any one of the optical input wavelengths in a relatively fast response time by applying injection current pulses. Analytical expression based on linear stability analysis is presented to predict the switching time to free oscillating mode, and larger optical input power and detuning are effective to shorten the switching time. The results here are believed to be useful to extend wavelength switching to a scope of electronic manipulation without modulation of optical inputs and can be applicable to actual devices.

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We propose a new optical network device photorefractive connection module (PRCM) which operates as optical switch, amplifier and signal distributor controlled by parallel optical signals. Simple optical control bus systems can be realized by cascade connection of PRCMs. PRCM branches off a desired channel from the spatial multiplexed optical bus line by appropriate setting of the control beam pattern. PRCM uses cross polarized four wave mixing (CPFWM) with extraordinary polarized writing beams and an ordinary polarized reading beam to achieve a high connection gain to the next PRCM stage. We analyze the phase matching angle of CPFWM in which the optical paths of two pump beams are slightly different. The phase conjugate reflectivity indicating a branching ratio of optical signal is derived and calculated in consideration of the phase mismatching Δk. The optimum pump ratio and the grating vector orientation for the largest phase conjugate reflectivity and signal amplification factor are discussed for optical design of PRCM. Since the measured signal beam power after passing through the BaTiO₃ crystal is three or four times higher than its incident power, PRCM has a sufficient connection gain for optical bus and interconnection systems.

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We report our experimental results of phase-shifting interferometry with an iterative least-squares fitting technique to estimate both the wave front phases and the phase shifts. The method allows phase retrieval from phase-shifting interferograms even though the calibration data of the phase shifter is unknown. The algorithm is used to analyze two sets of experimental interferograms. One records by moving a piezoelectric transducer shifter randomly and therefore has embedded random phase shifter errors, and the other samples the interference movie recorded by a video recorder while driving a stepping motor and therefore has embedded random intensity noises. The results are comparable with that of the conventional M-frame algorithm. Investigation of the effects of the intensity noises and phase shift errors shows the algorithm to perform well in both. Problems such as convergence, unique solution and reliability are also discussed.

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Reflectance and transmittance of 632.8 nm He-Ne laser light for photonic double barrier structures (consisting of a SF10 prism, SiO₂ layer, Al or Al₂O₃ active layer, SiO₂ layer and SF10 prism) were measured as a function of the angle of incidence for both the p- and s-polarized incidence. Sharp reflection dips and transmission peaks were observed at angles larger than the critical angle of total reflection. The appearance of the transmission peaks can be attributed to resonant photon tunneling through the photonic double barrier structures analogous to resonant electron tunneling through double potential barrier structures. Resonant tunneling is mediated by the long-range surface plasmon polariton in the case of the Al active layer and the electromagnetic guided modes in the case of the Al₂O₃ layer.

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We calculate the scattered local field around a small gold sphere on dielectric substrates which is illuminated by a collimated monochromatic beam. The numerical results show the field between the sphere and the substrate is much enhanced when the sphere is illuminated by a p-polarized beam. The enhanced area is very localized between the sphere and the substrate and the diameter of the enhanced area on the surface of the substrate is one fifth of the sphere diameter. The field increases as the gap distance decreases or as the refractive index of the substrate increases.

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The interaction of gaussian evanescent light with a single dielectric sphere or ordered dielectric spheres in an attenuated total reflection (ATR) geometry was analyzed by the finite-difference time-domain method. Various aspects of this interaction were investigated in terms of spatial visualizations of light intensity, reflectance vs. wavelength characteristics, the transient behavior of reflectances, and so forth. In the case of a single sphere, it was evident that the whispering gallery mode can be excited in ATR geometries, but such excitation cannot be easily confirmed only through the observation of wavelength-scanned ATR spectra. In the case of a closely packed two-dimensional array of dielectric spheres, it was found that an easy axis and also a difficult axis for light propagation exist.

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We describe the operation and performance of an optical fiber trap realized using a tapered hemispherically lensed optical fiber. Axial and transverse trapping forces exerted on a microsphere are experimentally analyzed to corroborate the optical trapping using an optical fiber. Experimental results are as follows. (i) Transverse force F_tr acting on a sphere is a restoring force that acts to pull the microsphere back to the center of trap. (ii) Axial force F_ax always acts to push a sphere in the direction of the beam away from the trapping fiber end. (iii) Vector sum of F_tr and F_ax acting on a sphere gives a restoring force directed back to the stable point. (iv) Transverse force F_tr plays a significant role in trapping a micro-sized object by means of an optical fiber.

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We investigate the dynamics of probability distributions of an initially one-mode coherent field interacting with a four-state molecular system, which is a single magnet with a tunneling across an anisotropic barrier, using a numerically exact approach. The population for each state, the phase properties of <cos²ψ^> and Δ cos² ψ(≡<cos²ψ^>−<cos ψ^>²), and the entropy are calculated for a model system. The model predicts that the molecule and field become asymptotically disentangled at half of the revival time, and that optical Schrödinger-cat and magnetic Schrödinger-cat states are generated.

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We study the third-order optical nonlinearity for some interesting π-conjugated systems involving sulfur (S) atoms. The static second hyperpolarizabilities (γ) for 1,6,6a-trithiapentalene and its donor- and acceptor-disubstituted species are calculated by ab initio molecular orbital and density functional methods. Using the second hyperpolarizability density analysis, these molecules are found to exhibit remarkable differences in spatial π-electron contributions of unusual binding structure, i.e., S-S-S bridged structure, to the longitudinal γ.

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We study the second hyperpolarizabilities (γ) for anion, neutral and cation radicals and find that magnitudes of γ (|γ|) of the radicals are sensitively influenced by features of each charged state. It is also found that electron-correlation dependence of γ could be related to the resonance structure contributing to the ground state of the molecules.

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We use the tapping illumination and synchronous detection in a scanning near-field optical microscopy to obtain a near-field optical signal that is separated from the far-field signal. The illumination light was irradiated from the bent fiber tip vibrating normal to the sample surface. The transmitted light synchronized with the tapping vibration was observed. The obtained image of an organic film shows that this technique is effective for the weak contrast samples.

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We investigate the effectiveness of differential detection, which is a combination of probe-dithering and synchronous detection, in discriminating near-field light interaction from background light interaction in apertureless near-field optical microscopy (NSOM). The lateral differential NSOM with a photocantilever is more effective than the vertical differential detection, which does not always provide sufficient discrimination. The V-dithering-based lateral differential detection provides apertureless NSOM that can image the optical coupling between sample and probe dipoles, which is an interaction through near-field light.

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Accurate simulations of a two-dimensional photon scanning tunneling microscope (2D-PSTM) for incident p-polarized waves (TM-mode) have been performed by the boundary integral equations called guided-mode extracted integral equations. The method used in this paper is a global method and the case of uncoated dielectric probe is treated. Complete and rigorous integral equations for a given configuration of 2D-PSTM have been solved numerically by the conventional boundary-element method with high accuracy. Using three universal laws, i.e., the optical theorem, the energy conservation law and the reciprocity relation for incident p-polarized waves, numerical results have been confirmed. The basic physical characteristics of interaction between probe-tip and near-field for incident p-polarized waves are compared in detail with those of incident s-polarized waves (TE-mode) which are previously reported.

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We have discussed the resolution of submicron photoluminescence (PL) imaging using a solid immersion lens (SIL), which collects an evanescent light field. We apply the SIL microscope to measure PL image of a strip-line-patterned GaAs quantum well structure at low temperature. An improved resolution beyond diffraction limit and high collection efficiency of PL are realized.

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We have experimentally observed the interaction of near-field light excited in a total internal reflection geometry with a periodic two-dimensional array of polystyrene spheres. The angular- and frequency-scanned attenuated-total-reflection (ATR) method was employed to observe the interaction. ATR spectra indicate that there is an easy axis and a difficult axis for the light propagation. When light is incident toward the easy axis, resonant dips appear in the ATR spectra. The experimental results were compared with those obtained by finite-difference time-domain analysis. The numerical results obtained by this method are able to explain a part of the experimental ones. Parts of the dips in the ATR spectra were considered to stem from propagating and whispering-gallery (WG) modes. That is, the propagation of the WG-modes over several spheres may enhance the coupling between the spheres and the incident light, and consequently may induce resonant structures in the ATR spectra.

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We describe an original scanning near field optical microscope setup developed to examine rhythmically beating cardiac myocytes fully immersed in culture media. Scans could be halted at any point to record localized contraction profiles. Contractions could be detected with high sub nanometric vertical sensitivity and changed shape dramatically within adjacent sub micron-sized areas. We believe that the spatial dependency of contractions arises because of system's ability to resolve the dynamic behavior of individual sub membrane actin bundles. Our results, combining imaging and real time recording in localized areas, reveal a new, non-invasive method for studying sub micron morphological activity in live biological samples.

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