Optical properties of the direct-coupled Y-branch filters by using photonic crystal slabs

We fabricated a new type of two-dimensional photonic crystal slab filter. The resonant cavities were directly put into the waveguide arms. The optical transmissions of the filters were measured and the results show that the optimized two-channel filters give good intensity distribution at the output ports of the waveguide. A minimum wavelength spacing of 5 nm of the filter outputs is realized by accurately controlling the size of the resonant cavities.

Structural and optical properties of tungsten-doped vanadium dioxide films

Thin films of tungsten （W）-doped thermochromic vanadium dioxide （VO2） were deposited onto soda-lime glass and fused silica by radio frequency magnetron sputtering. The doped VO2 films were characterized by X-ray diffraction, optical transmittance measurement, and near field optical microscopy with Raman spectroscopy. X-ray diffraction patterns show that the （011） peak of W-doped thermochromic VO2 film shifts to a lower diffraction angle with the increase of W concentration. The optical measurements indicated that the transmittance change （AT） at wavelength of 2500 nm drops from 65% （AT at 35 ℃ and 80 ℃ for undoped VO2 film） to 38% （AT at 30 ℃ and 42 ℃ for the doped VO2 film）. At the same time, phase transition temperature drops from 65 ℃ to room temperature or lower with the increase of W concentration. Near field optical microscopy image shows that the surface of W-doped VO2 film is smooth. Raman results show that the main Raman modes of W-doped VO2 are centered at 614 cm 1, the same as that of undoped VO2, suggesting no Raman mode changes for lightly W-doped VO2 at room temperature, due to no phase transition appearing under this condition.

Optical Properties of Co-BaTiO3/Mg（100） Nano-Composite Films Grown by Pulsed Laser Deposition Method

Co nanoparticles embedded in a BaTiO3 matrix, namely Co-BaTiO3 nano-composite films are grown on Mg（100） single crystal substrates by the pulsed laser deposition （PLD） method at 650℃. Optical properties of the CoBaTiO3 nano-composite films are examined by absorption spectra （AS） and photoluminescence （PL） spectra. The results indicate that the concentration of Co nano-particles strongly influences the electron transition of the Co BaTiO3 nano-composite films. The PL emission band ranging from 1.9 to 2.2eV is reported. The AS and PL spectra suggest that the band gap is in the range of 3.28-3.7eV.

Spontaneous emission of “polarized” V-type three-level atoms strongly coupled with an optical cavity

Polarization, an intrinsic ingredient of photon, plays a critical role in its interaction with matter. A general polarization state can be an appropriate superposition of two basic polarization states, say, the vertical and horizontal linear polarized state. Here we study spontaneous emission of a V-type three-level atom（with two upper states close in energy level）strongly coupled with a single-mode damped optical cavity. By defining a general polarization state of atom as a specific superposition of the two upper quantum states, we can prepare atoms with linear polarization at arbitrary direction, left and right circular polarization, and left and right elliptical polarization, similar to photons. We find that the spontaneous emission of light from these ＂polarized＂ three-level atoms shows very different profiles of side and axis spectra. This means that the polarization state of three-level atoms can become an active ingredient to manipulate its interaction with light and control the quantum interference effect. Exploitation of the coherent superposition and interference of quantum states in＂polarized＂ atoms would allow one to deeply explore new frontiers of light–matter interaction.

Third-order optical intensity correlation measurements of pseudo-thermal light

Third-order Hanbrury Brown-Twiss and double-slit interference experiments with a pseudo-thermal light are performed by recording intensities in single, double and triple optical paths, respectively. The experimental results verifies the theoretical prediction that the indispensable condition for achieving a interference pattern or ghost image in Nth-order intensity correlation measurements is the synchronous detection of the same light field by each reference detector, no matter the intensities recorded in one, or two, or N optical paths. It is shown that, when the reference detectors are scanned in the opposite directions, the visibility and resolution of the third-order spatial correlation function of thermal light is much better than that scanned in the same direction, but it is no use for obtaining the Nth-order interference pattern or ghost image in the thermal Nth-order interference or ghost imaging.

Near-field optical observations of surface plasmon wave interference at subwavelength hole arrays perforated in Au film

We image optical near-field patterns at subwavelength circular hole arrays in Au film by using scanning near-field optical microscopy in near-infrared wavelengths. Periodical oscillation features are found in the near-field images at the air/Au interface and exhibit two typical kinds of standing wave oscillation forms at the wavelengths corresponding to the transmission minimum and maximum in the transmission spectrum, and the latter one originates from the excitation and interference of a surface plasmon wave at the metallic hole arrays. Our work indicates that monitoring optical near-field patterns can help to reveal many interesting properties of surface plasmon waves at metallic nanostructures and understand their underlying physical mechanisms.

Spatial and Temporal Evolution of Ultra-Wide-Band Optical Pulses in Propagation

The propagation of ultrashort coherent electromagnetic pulses with broad spectral bandwidth in free space is studied by using scalar diffraction theory.It is confirmed and experimentally demonstrated that the diffraction not only affects the spatial structure but also changes the temporal waveform of an ultra-wide-band pulse during propagation.The terahertz pulse travelling as basic mode of Gaussian beam is discussed in detail.

The Measurement of Displacement and Optical Force in Multi-Optical Tweezers

We set up a system of multiple optical tweezers based on a spatial light modulator,and measured the displacement and optical force of the trapped particles simultaneously.All of the trapped particles can be clearly imaged in three dimensions by several CCDs.The displacement is obtained by calculating the gray weighted centroid in the trapped particle's image.The stiffness of the trapped particles in the optical traps is measured by oscillating the sample stage in a triangular wave based on Stokes fluid dynamics.The optical force of each trapped particle can be calculated by the measured displacement and stiffness.

Large Third-Order Nonlinear Optical Susceptibility of Rh-Doped BaTiO_(3) Thin Films Prepared by Pulsed Laser Deposition

Rh-doped barium titanate (BaTiO3) epitaxial thin films have been fabricated on SrTiO_(3) (100) substrates by pulsed laser deposition. The nonlinear optical properties of the films were determined using the z-scan method at a wavelength of 532nm with a laser duration of 10hs. The real and imaginary parts of the third-order nonlinear susceptibility χ^((3)) were 5.71 × 10^(-7) esu and 9.59×10^(-8) esu, respectively. The real part value of x(3) of the Rh:BaTiO3 films is about one order larger than that of Ce-doped BaTiO3 thin films. The results show that Rh:BaTiO3 thin films have great potential applications for nonlinear optical devices.

Quantum Fluctuations of a Mesoscopic RLC Circuit in a Displaced Squeezed Fock State

Starting from the equation of motion for a circuit including resistor,inductor and capacitor(RLC),we study the Quantum Huctuations of charge and magnetic Hux of a mesoscopic RLC circuit in a displaced squeezed Fock state.It is found that the Huctuations of charge and.magnetic Hux do not depend on the displacement parameter and there exist squeezing effects between them.We also show how to generate the displaced squeezed Fock state in the RLC circuit.

The characteristics of confined ablation in laser propulsion

Compared with direct ablation, confined ablation provides an effective way to obtain a large target momentum and a high coupling coefficient. By using a transparent glass layer to cover the target surface, the coupling coefficient is enhanced by an order of magnitude. With the increase of the gap width between the target surface and the cover layer, the coupling coefficient exponentially decreases. It is found that the coupling coefficient is also related to the thickness of the cover layer.

The Role of Periodicity in Enhanced Transmission through Subwavelength Hole Arrays

Two kinds of subwavelength hole arrays in metallic films are designed to verify the import, ant role of the periodicity in enhanced transmission of light. The measured optical spectra show that the quasiperiodic hole arrays exhibit an enhanced transmission peak centred at 707nm with a transmission intensity of about 20%, while no plasmon resonance peak is found for the amorphous hole arrays. When the hole diameter decreases in the quasiperiodic structure, the position of the transmission peak shifts slightly, and the transmittance drops, These phenomena indicate the important role of the long-range structural order （particularly the periodicity） in assisting the coupling of incident light wave with the surface plasmon modes of the metallic structures.

Continuous-Wave Output of 5.5 W at 532 nm by Intracavity Frequency Doubling of an Nd:YVO_(4) Laser

A maximum of 5.5 W of cw TEM_(00) mode output at 532nm has been obtained by intracavity frequency doubling with a KTP crystal in an Nd:YVO_(4) laser doubly-pumped with 20 W diode pumping power.The optical-optical conversion efficiency is 27.5%.The influence of thermal lensing at high pumping power in the end-pumped Nd:YVO_(4) laser is discussed.The Nd:YVO_(4) laser has a good power stability of 1.6%.

Elementary analysis of interferometers for wave particle duality test and the prospect of going beyond the complementarity principle

A distinct method to show a quantum object behaving both as wave and as particle is proposed and described in some detail. We make a systematic analysis using the elementary methodology of quantum mechanics upon Young＇s two-slit interferometer and the Mach-Zehnder two-arm interferometer with the focus placed on how to measure the interference pattern （wave nature） and the which-way information （particle nature） of quantum objects. We design several schemes to simultaneously acquire the which-way information for an individual quantum object and the high-contrast interference pattern for an ensemble of these quantum objects by placing two sets of measurement instruments that are well separated in space and whose perturbation of each other is negligibly small within the interferometer at the same time. Yet, improper arrangement and cooperation of these two sets of measurement instruments in the interferometer would lead to failure of simultaneous observation of wave and particle behaviors. The internal freedoms of quantum objects could be harnessed to probe both the which-way information and the interference pattern for the center-of-mass motion. That quantum objects can behave beyond the wave-particle duality and the complementarity principle would stimulate new conceptual examination and exploration of quantum theory at a deeper level.

Nonlocal Imaging by Conditional Averaging of Random Reference Measurements

We report the nonlocal imaging of an object by conditional averaging of the random exposure frames of a reference detector,which only sees the freely propagating field from a thermal light source.A bucket detector,synchronized with the reference detector,records the intensity fluctuations of an identical beam passing through the object mask.These fluctuations are sorted according to their values relative to the mean,then the reference data in the corresponding time-bins for a given fluctuation range are averaged,to produce either positive or negative images.Since no correlation calculations are involved,this correspondence imaging technique challenges our former interpretations of “ghost” imaging.Compared with conventional correlation imaging or compressed sensing schemes,both the number of exposures and computation time are greatly reduced,while the visibility is much improved.A simple statistical model is presented to explain the phenomenon.

Sixth Harmonic of A Nd：YVO4 Laser Generation In KBBF for ARPES

We report that a deep ultraviolet （DUV） laser from the sixth harmonic of a 1064nm laser has been firstly used as light source in an ultrahigh energy-resolution angle-resolved photoemission spectroscopy （ARPES）. The wavelength is 177.3nm obtained by using the second harmonic KBe2BO3F2 crystal with a frequency tripled 1064nm Nd：YVO4 laser. The large flux （10^14 - 10^15 photons/s） and narrow line width （0.26 meV） are suitable for the ultrahigh-energy resolution ARPES. The laser-ARPES can be a powerful tool to study the electronic structure at and near the Fermi level of the superconductor and correlated materials. The laser-ARPES has worked more than 500 h already.

Spectral and laser properties of Yb and Ho co-doped(YLa)_2O_3 transparent ceramic

Highly transparent Yb,Ho doped（YLa）2O3 ceramic was fabricated by conventional ceramic processing with nanopowders.The absorption and emission spectra of the ceramic was investigated.The energy transfer mechanism between Yb3＋ and Ho3＋ was also discussed.The strong emission band around 2 μm indicated that the Yb-Ho：（Y 0.90 La 0.10）2O3 transparent ceramic is a promising gain medium for the generation of 2 μm laser emissions.The laser operation of Yb-Ho co-doped（YLa）2O3 ceramic at 2.1 μm is first reported.

Comparison of Nd：YAG Ceramic Laser Pumped at 885 nm and 808 nm

Laser performance of 1064 nm domestic Nd：YAG ceramic lasers for 885 nm direct pumping and 808 nm traditional pumping are compared. Higher slope efficiency of 34% and maximum output power of 16.5 W are obtained for the 885nm pump with a 6ram length 1 at.% Nd：YAG ceramic. The advantages for 885nm direct pumping are discussed in detail. This pumping scheme for highly doping a Nd：YAG ceramic laser is considered as an available way to generate high power and good beam quality simultaneously.

Surface oxidation of vanadium dioxide films prepared by radio frequency magnetron sputtering

This paper reports that the thermochromic vanadium dioxide films were deposited on various transparent substrates by radio frequency magnetron sputtering, and then aged under circumstance for years. Samples were characterized with several different techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, and Raman, when they were fresh from sputter chamber and aged after years, respectively, in order to determine their structure and composition. It finds that a small amount of sodium occurred on the surface of vanadium dioxide films, which was probably due to sodium ion diffusion from soda-lime glass when sputtering was performed at high substrate temperature. It also finds that aging for years significantly affected the nonstoichiometry of vanadium dioxide films, thus inducing much change in Raman modes.

Efficient Pumping Scheme by Direct Excitation of Upper Laser Level in Nd：CNGG

We report an efficient pumping scheme which involves a direct excitation of the upper lasing level of a four-level laser in a Nd-doped Caa （NbGa）2-x Ga3O12 （Nd：CNGG） by using a tunable Ti：sapphire, 700-920nm, cw pump source. The slope efficiency is improved from 10.5% of the traditional band pumping at 808nm to 21.8% of the direct pumping at 882nm. The influence of pumping wavelength on lasing is discussed. We present a scheme of double pumping for lasing.