Ghost diffraction, lensless system and 2-f system

We investigate two imaging schemes, lensless system and 2-f system which are used to implement ghost diffraction. It is shown that the two schemes have similar intensity fluctuation correlation functions which both realize the function of the Fourier-transform imaging, and the diffraction pattern is in agreement with that in the classical wave optics. The difference of the imaging visibility in the two systems is also discussed.     

Dynamic diffraction behaviors of bacteriorhodopsin film at 532 nm

To show the relations between dynamic diffraction behaviors of two coupled waves and parameters of bacteriorhodopsin (bR) film, we presented a model of numerical simulation, in which the thermal effect is considered. Using wavelength of 532 nm, the relations between dynamic diffraction behaviors and parameters of bR film are revealed and the numerical results are in good agreement with the experimental ones. For different incident intensities, the higher the intensity, the lower the stable normalized diffraction intensity. For different bR molecular concentrations in the M state, the higher the molecular concentration, the higher the stable value of normalized diffraction intensity. For different thickness of bR film, the larger the thickness, the higher the stable value of normalized diffraction intensity. For different lifetime in the M state, the longer the lifetime of the M state, the lower the stable value of normalized diffraction intensity. The normalized diffraction intensity with low stable value corresponds to its fast rising and decaying rate.     

Ghost imaging and ghost interference with pseudo-thermal light: Mode-separation by pure software processing

We report on a new experiment in which ghost imaging and ghost interference with quasi-thermal light are simultaneously obtained from the same set of experimental reference patterns. By sliding the mask along the object arm in a continuous way, one can see imaging and diffraction patterns to come to light and fade out in opposite directions.     

Interference from nonlocal double-slit with pseudo-thermal light

We perform an interference experiment in which a pseudo-thermal light beam illuminates two spatially separated apertures, whose superposition at the same place forms a double-slit. The experimental result exhibits a typical double-slit interference fringe in the intensity correlation measurement, in agreement with the theoretical analysis by means of the property of the second-order spatial correlation of field of the thermal light.     

Enhanced squeezing and entanglement in a non-degenerate three-level cascade laser with injected squeezed light

We consider a non-degenerate three-level cascade laser coupled to a two-mode squeezed vacuum reservoir via the lossy single-port mirror. Applying the pertinent master equation, we analyze the effects of the injected squeezed light on the quadrature squeezing, entanglement and normalized intensity difference fluctuations. We show that the injected squeezed light considerably enhances the degree of squeezing and entanglement in the two-mode light for certain initial conditions. Moreover, the injected squeezed light increases the mean photon number where the squeezing and entanglement is significant. We also show that the presence of the injected squeezed light greatly reduces the noise in the intensity difference.     

Time-resolved detection of atoms diffracted from a standing light wave

We present a time-resolved experimental observation of the diffraction of metastable helium atoms from a nearly resonant standing light wave. The application of a time-resolved detection technique and a pulsed source allows to resolve high diffraction orders, which are populated in the atom-light interaction. Furthermore, the rms momentum transfer from the light field on the atom as a function of the interaction time is investigated. Future applications of this technique may be the detailed investigation of the motion of atoms in standing light waves and the detection of correlations between spontaneously emitted photons and atoms.Dedicated to H. Walter on the occasion of his 60th birthday     

Numerical simulation of atomic diffraction in the Raman-Nath regime

The theory of atomic diffraction from a classical standing wave light field in the presence of spontaneous emission in the Raman-Nath regime was developed by Tanguy et al. [6]. We describe the basis of computationally efficient methods for performing calculations in this regime and show their agreement with recent experimental results of Gould et al. [4].     

Adiabatic following in standing-wave diffraction of atoms

We report experiments on the diffraction of atoms from a standing light wave in the channeling regime, characterized by long interaction time and large potential height. The observed far-field diffraction patterns depend specifically on the way in which the potential is switched on and off. For fast switching, the evolution is non-adiabatic and many diffraction orders are populated. For slow switching, however, the evolution is adiabatic and the number of populated diffraction orders decreases dramatically. The experiments are performed in two different setups employing rubidium and argon atoms, respectively. In one of the setups, we study the dependence of the diffraction pattern on the interaction time, in the other setup that on the incidence angle. Received: 30 November 1998 / Revised version: 5 July 1999 / Published online: 8 September 1999     

Bright entangled light from two-mode cascade laser

We show that a two-mode three-level cascade laser driven by external coherent fields generate intense entangled light. It turns out that external driving fields which are at resonance with the cavity modes substantially improve the intensity of the two-mode light in the cavity in a region where the squeezing and entanglement is significant making the system under consideration a viable source of bright squeezed as well as entangled light.     

Experimental study of light diffraction by standing ultrasonic wave with cylindrical symmetry

We report a new acousto-optic arrangement based on ultrasonic wave with cylindrical symmetry. The theory of light interaction with standing cylindrical ultrasonic wave is experimentally verified in the Fraunhofer region. A very good agreement of experimental results with numerical calculations based on the proposed theory is found. The diffraction pattern consists of ring-shaped diffraction orders which posses a fine structure. The time average light intensity of the whole zeroth diffraction order as a function of the Raman-Nath parameter is investigated. The modulation properties of presented system are examined by means of single photon counting technique. Finally, some potentially useful applications in the laser and fibre technology are suggested.     

Manipulation of Particles with Counter-Propagating Evanescent Waves

Two counter-propagating evanescent beams are used to align and manipulate polystyrene particles on a prism surface. Since the radiation pressure transferred laterally from the evanescent wave is negated on both sides, particles can be stably aligned. By projecting a circular and a linear beam spot onto the interface, both multiple and single arrays of particles are achieved. Arrays of particles trapped on the interface can be easily moved adjusting the intensity of incident beams on either side. We also simulate electromagnetic distribution of scattering light that is converted from the evanescent wave using the FDTD method. The results show that scattering light converts from an evanescent wave propagating through a particle array and has a distance longer than that propagating from a normal evanescent wave.     

The origin of the super-resolution via a nonlinear thin film

In laser applications, resolutions beyond the diffraction limit can be obtained with a thin film of strong optical nonlinear effect. The optical index of the silicon thin film is modified with the incident laser beam as a function of the local field intensity n(r)∼E²(r). For ultrathin films of thickness d?λ, the transmitted light through the film forms a profile of annular rings. Therefore, the device can be related to the realization of super-resolution with annular pupils. Theoretical analysis shows that the focused light spot appears significantly reduced in comparison with the diffraction limit that is determined by the laser wavelength and the numerical aperture of the converging lens. Analysis on the additional optical transfer function due to the thin film confirms that the resolving power is improved in the high spatial frequency region.     

Wigner function and tomogram of the excited squeezed vacuum state

The excited squeezed light (ESL) can be the outcome of interaction between squeezed light probe and excited atom, which can explore the status and the structure of the atom. We calculate the Wigner function and tomogram of ESL that may be comparable to the experimental measurement of quadrature-amplitude distribution for the light field obtained using balanced homodyne detection. The method of calculation seems new.     

Quantum nondemolition measurement by optomechanical coupling

 We show that a single-port optical cavity with a movable mirror can provide a quantum non-demolition measurement of the intensity of a light beam. Due to radiation pressure, the cavity length is sensitive to the light intensity and can be measured with a secondary light beam. Signal-meter correlations can be made very large even at non-zero temperature. We study these correlations when the moving mirror is a plane–convex crystal resonator and we show the importance of spatial matching between light and acoustic modes. Received: 12 June 1996/Revised version: 3 September 1996     

The impact of light polarization on imaging visibility of Nth-order intensity correlation with thermal light

The relationship between the imaging visibility of arbitrary Nth-order intensity correlation with thermal light and light’s degree of polarization is investigated. It is shown that for the same order correlation, the value of visibility with partially polarized light is greater than that with natural light but smaller than that with completely polarized light, and the visibility in all three cases is remarkably enhanced as N increases.     

Photofabrication of periodic microstructures in azodye-doped polymers by interference of laser beams

Volume holographic gratings and two-dimensional periodic microstructures in azodye-doped polymethylmethacrylate were fabricated, respectively, by interference of two coherent beams of a femtosecond laser and by interference of three coherent beams of a nanosecond laser. The dependence of the first-order Bragg diffraction efficiency and the photoinduced refractive-index modulation of the gratings on the intensity of the writing light was investigated. The measurements of the absorption spectra before and after irradiation with the writing light suggest that the photoinduced gratings were refractive-index-modulated gratings, which arose from a photoinduced decomposition reaction of the azodye molecules through multiphoton absorption. In the experiments involving the interference of three beams, the period of the two-dimensional periodic microstructures was changed by adjusting the angle between the three writing beams. Received: 10 July 2002 / Revised version: 5 September 2002 / Published online: 20 December 2002 RID="*" ID="*"Corresponding author. Fax: +81-774/955206, E-mail: jhsi@photon.jst.go.jp     

Ultraslow optical solitons in a four-level tripod atomic system

We investigate possible formation and propagation of localized, shape-preserving nonlinear optical pulse in a resonant, lifetime-broadened four-level tripod atomic system via electromagnetically induced transparency (EIT). We prove both analytically and numerically that although in anomalous dispersion regimes near resonance a superluminal optical soliton may appear, such soliton suffers serious absorption. However, by choosing appropriate parameters to make the system work in normal dispersion regimes and within an EIT transparency window, ultraslow optical solitons with very low light intensity can form and propagate stably in the system.     

Experimental Investigation of Quality of Lensless Ghost Imaging with Pseudo-Thermal Light

Factors influencing the quality of lensless ghost imaging are investigated. According to the experimental results, we find that the imaging quality is determined by the number of independent sub light sources on the imaging plane of the reference arm. A qualitative picture based on advanced wave optics is presented to explain the physics behind the experimental phenomena. The present results will be helpful to provide a basis for improving the quality of ghost imaging systems in future works.     

Coherent light transmission by a dew pattern

We study both theoretically and experimentally the transmission of coherent light by a drop pattern (dew). The theory is based on the Kirchhoff scalar approach to diffraction. The polarization of the diffracted wave in the zero diffraction order is analyzed separately. The intensity in the zero diffraction order in the far zone is an oscillatory function of the drop size. These oscillations are observed with a pattern of water drops growing on glass. The model allows for the evolution of the important parameters of the drop pattern (average radius and surface coverage) to be obtained from the light intensity in the zero diffraction order.     

Influence of auxiliary violet light on holographic kinetics at low and high recording intensities in bacteriorhodopsin film

The photochromic bacteriorhodopsin (BR) film can be used as a rewritable holographic recording medium. Due to the saturation absorption and the scattering and reflecting lights from the BR film, the grating contrast-ratio of the hologram is diminished during the hologram recording. When the intensity of the recording light is low, the influence of the saturation absorption and the scatter and reflection of BR film on the grating contrast-ratio is weak. But for the case of intense recording light, this influence is more serious. It is found that the influence of the auxiliary violet light on the holographic kinetics of diffraction efficiency is distinct under different recording intensities. At the low recording light intensity, the steady diffraction efficiency is increased and the peak diffraction efficiency is suppressed by the auxiliary violet light. But for intense recording light, the steady diffraction efficiency and the peak diffraction efficiency are both increased by the auxiliary violet light. Based on the two-state model of BR photochromism, we give a good theoretical explanation to the above phenomena.