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The vinyl phytic acid (GPA) was prepared using biophytic acid (PA) and glycidyl methacrylate (GMA), in which double bonds were introduced into the phytic acid molecule to increase the active groups in the phytic acid molecule. Furthermore, itaconic acid (IA) containing two unsaturated double bonds and GPA was polymerized in situ and crosslinked on the surface of cotton fabrics, and flame retardant and crease-proofed fabrics were obtained. The effects of GPA, IA, and the initiator on the flame-retardant and crease-proofing properties of the fabrics were analyzed by a single-factor and double-dip double-nip experiment. A flame-retardant and wrinkle-resistant fabric was obtained when the limiting oxygen index (LOI) and wrinkle recovery angle (WRA) were 28% and 270°, respectively. During combustion, the thermal properties of the fabrics changed; typically, the extrapolated initial temperature (Te) decreased, and moisture release increased. After burning, the fabrics had good shape retention, and the carbon residue content increased to 48%, which effectively inhibited or slowed down the combustion and heat release of the textiles. However, the whiteness, mechanical properties, and washability of the products need to be further improved.

The unbinding force of microtubule-AtMAP65-1 bond is measured with dual-optical tweezers. Force histograms reveal quantized force distributions under physiological condition and with 100 mM NaCl treatment. Based on Bell-Evans-model of multiple bonds, histograms are fitted and kinetic parameters are obtained. Under the force loading rate of 9pN/s, the most probable unbinding forces for the single bond are 16.8 +/- 0.8 and 14.7 +/- 0.8 pN under the physiological and treatment conditions, respectively. Position of transition state of the bond is given to be Delta x = 2.1 +/- 0.1 nm both with and without treatment of NaCl. Intrinsic dissociation rate constants k(0) are 0.0010 +/- 0.0002 and 0.0020 +/- 0.0005 s(-1) corresponding to without and with NaCl treatment, which means that 100 mM NaCl shortens the natural lifetime of the bond by 50%. In addition, the activation barrier also changes by 3.4% after treatment with NaCl, which indicates that NaCl makes the dissociation of the bond easier.

In this paper, we introduced the fabrication of photonic crystals on several kinds of semiconductor materials by using focused-ion beam machine, it shows that the method of focused-ion beam can fabricate two-dimensional photonic crystal and photonic crystal device efficiently, and the quality of the fabricated photonic crystal is high. Using the focused-ion beam method, we fabricate photonic crystal wavelength division multiplexer, and its characteristics are analyzed.

We report experimental observation of enhanced near infrared transmission through periodic H-shaped arrays in metallic thin films. A broad transmission band centered at about 1.6 μm is found and the transmission coefficient can be as high as about 16.3% for an arm width of 120 nm for the H-pattern. The position of the transmission peak shifts to a short wavelength by about 140 nm when the arm width is increased to 200 nm. This variation feature is inverse to that found in periodic hole arrays. It indicates that the localized surface plasmon is an important parameter contributing to the enhanced transmission. The H-shaped arrays exhibit a strong polarization effect consistent with the geometry anisotropy. Numerical simulations by using a transfer matrix method reproduce quite well the obtained transmission spectrum.

Two-dimensional LiNbO 3 nonlinear photonic crystal with octagonal quasilattice was fabricated by applying the external electric field. The higher order collinear quasi-phase matched second harmonics, in the red, orange and blue–green areas, along the midline of the two adjacent basic reciprocal vectors were obtained, in which the efficiency of red harmonics reached 17%. And the higher order non-collinear second-harmonic generations with the input beams parallel to the basic reciprocal vectors were studied systematically, in which the related highest-order reciprocal vector pair was (2 2 1 0) and (−2 0 1 2). All the same results can be obtained when the crystal is rotated by the integral multiples of π/4.

We analyze negative refraction in two-dimensional photonic crystals that are made from electro-optical active materials. Application of an electric field to the photonic crystal changes the dielectric constant of the material and consequently modifies the photonic band and dispersion properties. We have investigated focusing properties of the photonic crystal slab lens at different frequencies within the first two bands and under various magnitudes of electric field. The simulation results reveal that one can dynamically tune negative refraction by means of index-tunable photonic crystals.

The abstract should summarize the context, content and conclusions of the paper in less than 200 words. We fabricated a two-dimensional Y-branch photonic crystal waveguide in the near infrared region by using focused ion beam etching and depositing system. The light guide characters of the waveguide were measured for three different spaces between branches. Field intensity distributions of TE polarized wave in the branches were simulated by using the transfer matrix method. Both the theoretical and experimental results show that the shortest space between branches of the photonic crystal waveguide is about 1.4 times wavelength of transmitted light. If the space became shorter, the light in the two branches would couple to each other seriously. This result might be helpful for the design of compact wave demultiplexer and all-optical integrated circuits.

We describe a fabrication process of the near-infrared two-dimensional photonic crystal (PC) slab, which is sustained by part of the silica layer underneath the slab and forms a partly air-bridged type. The process involves focused ion beam (FIB) direct write following the selective wet etching of silicon on isolator (SOI) structures. By control the time of dissolving of silica layer in SOI, we successfully fabricated the sample and measured its transmittance spectrum. It is found that the observed spectrum is consistent with the theoretical band structure with FDTD method. For there is partly silica layer remained to support the air-bridge slab, the PC can be fabricated with a large area. If we change the support material under the slab, we might be able to fabricate PC laser with this kind of structure.

Here, we present two newly composite inverse opals: SiO2/TiO2 and SiO2/Al2O3. With their particular properties, they may potentially be applied as carriers of catalyst and photonic band gap crystals. The fabrication processes consist of the vertical co-deposition of colloids and the filling to the templates with TiO2 and Al2O3 precursors.

In an optical tweezers system, the output signal of a photodiode quadrant detector and the temperature in a sample cell are two key factors for the quantitative measurements of mechanical properties of living biological objects such as cells, organelles and macro-molecules. In order to enhance the output of a quadrant detector and effectively control the temperature in a sample cell, the dependence of the temperature in the sample cell and the output of the quadrant detector for different illumination conditions are studied. The results show that appropriate illumination conditions can ensure both nearly constant temperatures in the cell and the desired output signal, which provides for the possibility of high precision and damage-free analysis of living biological objects.

A tunable filter with multichannel is proposed based on a nonlinear ferroelectric photonic crystal made of rhodium doped barium titanate. The filtering properties of the photonic crystal filter, including channel number and frequency, can be tuned by adjusting the thickness of defect layer or by pump light. The dynamical shift of channels with pump intensity is studied in detail. The channel shifts about 90 nm under the excitation of 75 MW/cm 2 pump light. The influences of structural disorders caused by random perturbations in the thickness of dielectric layer or air layer on the photonic crystal filter are analyzed.

We employ an analytical Bloch-mode approach to analyse the dispersion behaviour of localized surface states supported in the surface of a semi-infinite one-dimensional (1D) photonic crystal (PC) that is adjacent to an air background. The crystal can consist of two composite layers or multiple composite layers. We find that the optical properties of the surface modes are quite different between the TM and TE polarizations. The surface state properties are sensitive to the stack sequence of the semi-infinite 1D PC with respect to the air background. In many structures, the dispersion curve of the surface mode for one composite layer at the surface exhibits connectivity with the dispersion curve for the other composite layer at the surface.

In an optical tweezers system, the output signal of a photodiode quadrant detector and the temperature in a sample cell are two key factors for the quantitative measurements of mechanical properties of living biological objects such as cells, organelles and macro-molecules. In order to enhance the output of a quadrant detector and effectively control the temperature in a sample cell, the dependence of the temperature in the sample cell and the output of the quadrant detector for different illumination conditions are studied. The results show that appropriate illumination conditions can ensure both nearly constant temperatures in the cell and the desired output signal, which provides for the possibility of highprecision and damage-free analysis of living biological objects.

Using the response formula of the photonic crystals and the Bloch equations, the lasing threshold in arbitrary 2D photonic crystals was obtained by an investigation of steady-state laser behavior. The lasing threshold is expressed by the population inversion. It shows that the population inversion threshold is proportional to the second order of the group velocity, and to the relaxation coefficient.

Synthetic opals with diameters ranging from 700 to 1200 nm monodisperse colloidal SiO2 particles were prepared. We studied the fabrication and the optical characteristics of the synthetic opals, as well as examined the influence of quantitative flux of the colloidal SiO2 particles and the relationship between it and the crystallization rate of the particles within colloidal suspensions on qualities of synthetic opals. (C) 2004 Elsevier B.V. All rights reserved.

The effective high-order quasi–phase-matching second- and third-harmonic generations were realized in a two-dimensional periodically poled LiNbO3 with rectangular lattice. The output spots lay at different symmetric places with respect to the input beam of picosecond pulse and the relative intensities of spots at some certain wavelengths were measured. The experimental and theoretical results are in good agreement. Our studies might be beneficial to the development of optics integration and compact devices.

An optical switching is proposed, which is based on two dimensional nonlinear photonic crystal made of cerium doped barium titanate, and can work in the visible or infrared waveband. The optical nonlinearity originates from the delocalization of the titanium ions in the center of TiO6 octahedrons. The dynamical shift of the photonic bandgap with pump intensity is calculated on the basis of the optical Kerr effect. It is found that the pump light of 6.7 GW/cm(2) can changes the transmittance of the probe light from 0% to 95% for the first sample in the visible waveband and from 0% to 92% for the second sample in the infrared waveband, respectively. The influences of the disorders caused by the random perturbations in the diameter or the position of the air hole on the optical switching are analyzed. (C) 2004 Elsevier B.V. All rights reserved.

A two-dimensional nonlinear photonic crystal of lithium niobate with rectangular lattice was fabricated. In this crystal, the quasiphase-matching conditions can be satisfied in different directions for different wavelengths. As a tunable optical parametric oscillator pumped by an yttritium–aluminum–garnet laser with about 4 ns pulse duration was used, we obtained the second-harmonic output at 676 nm (red) and 571 nm (yellow) by the first-order quasiphase-matching, and at 532 nm (green) and 460 nm (blue) by the second-order quasiphase-matching, respectively. The conversion efficiency of fundamental wavelength 1352 and 1142 nm was 33% and 48.2% when the average input power was 1.47 and 2.8 mW, respectively. Our results imply that by using only one frequency conversion element, coherent beams with various colors may be attained. The application of such a two-dimensional nonlinear photonic crystal in the field of color display is expected.

The distribution of the local density of states (LDOS) in quasiperiodic photonic crystals (QPCs) and the total density of states (DOS) are studied. The distribution of the LDOS shows that it has the same rotational symmetry as the sample. Furthermore, the regions of lowest LDOS and the change of the minimal values of the LDOS with the alteration of the dielectric volume fractions are identified. Meanwhile, the coincidence of gaps displayed in transmission and DOS spectra indicates that QPCs possess absolute gaps for TM polarized modes, the E field is along the axis of the cylinders and the H field is in the 2D plane.

We have derived an analytical expression for light amplification for stimulated emission in arbitrary two-dimensional photonic crystals (PHCs) using the response formula of the PHCs and the Bloch equations. This shows that the gain is proportional to the population inversion, and is inversely proportional to the group velocity and the relaxation coefficient of the phase, which indicates that the gain can be induced by population inversion and enhanced dramatically by small group velocity or anomalous group velocity.

The defect modes of a two-dimensional quasiperiodic photonic crystal (QPC) with defects are studied. It is found that if the defects possess the same rotational symmetry, the resonant frequencies of the defects are identical. On the other hand, uncoupled modes exist when the field symmetry of defect modes is different from that of external exciting waves. A corresponding experiment in the microwave region confirms the phenomenon.

Using the optical response formula for photonic crystals and the Bloch equations, we analyze coherent emission in arbitrary two-dimensional photonic crystals. The transient emission depends not only on the photon density of the states, but also on the intensity and duration of the pump laser pulses. A transient gain exists if the pump pulse area is a certain value and the transition frequency is tuned to the band edge. The sharp structure of the density of states near the band edge leads to a dramatic enhancement of the transient emission intensity and an abrupt change in the oscillation of the emission field.

Three-dimensionally ordered self-assembly of monodispersed colloidal SiO2 particles involving a structure with periodic alternation of refractive indices represents an advanced field of particuology, colloidal chemistry, materials science, optical physics and information science. Study on such self-assembly not only lays the foundation for the development of advanced functional materials, but also is significant in understanding the principles of nano- and micro-scale processes. Recent progress in three-dimensionally ordered self-assembly of colloidal SiO2 particles is reviewed, inclusive of the authors' investigations.

Monodisperse colloidal SiO2 submicrospheres were prepared by hydrolysis and condensation of tetraethoxysilane. We measured various relative settle velocities of different aggregated submicrospheres and then developed a submicrospheres selection technique separating single spheres from aggregated spheres. Monodispersity Of SiO2 submicrospheres was improved by this submicrospheres selection technique. Higher-quality SiO2 opals were fabricated from selected submicrospheres., (C) 2002 Elsevier Science B.V. All rights reserved.

Through simulations and experiments we found considerable photonic bandgaps (PBGs) in two-dimensional structures with short-range periodicity (SRP) and without any spatial symmetry. A multiple-scattering method is used in our numerical investigations. Our experiments are performed in the microwave region with a microwavevector network analyser. The short-range periodic structures used in the investigations are produced through the arrangement of four certain basic units in a Fibonacci sequence in two dimensions. It is interesting that the PBG positions and widths are invariant for different translational cutouts and for different thickness of these SRP structures, showing that the PBG properties of the structures under consideration are decided by their SRP and not by their patterns. The physics behind the results is explored.

A novel two-dimensional photonic crystal (PC) microcavity composed of a point defect, where a point emitter is placed, and a line defect (waveguide) was proposed and studied numerically. The results show that the light radiated from the point defect can be coupled into the waveguide with a more than 97% coupling efficiency under certain conditions. Because the PC waveguide can guide light around a sharp corner with a high efficiency, the radiation can be directed to any area in a PC by using our design. The microcavity quality factor and coupling efficiency can be adjusted through changing the space and the number of cylinders between the point defect and the waveguide, and the oscillation frequency can be tuned by changing the mode volume of the point defect. This may be valuable for the design of microwave integrated devices and all-optical integrated circuits.

We experimentally and numerically demonstrate dodecagonal and decagonal quasiperiodic photonic crystals in the microwave region. The results show that only a small number of rows are needed to create a frequency gap in the transmission spectrum, and that the gap position is insensitive to the incident angle. In particular, there is no defect state at the first gap of a dodecagonal quasiperiodic photonic crystal when there is a cavity in the center region, even though the cavity volume is much larger than the square of the wavelength. The decagonal quasiperiodic crystal can offer great possibilities for creating defect states. These quasiperiodic photonic crystals may find some important applications in photoelectric devices.

We present a scanning electron microscopy (SEM) investigation of artificial opals prepared by the sedimentation of suspension with sub-micrometer silica spheres. An analysis of the SEM images confirms that the fcc stacking is the most stable phase for the artificial crystals. Optical diffraction and transmission spectrum indicate a good alignment of the top (111) crystal plane. We also show that defects and dislocations of opal crystals are caused mainly by the irregular spheres. Slow sedimentation and uniform size of silica spheres may be the key factors for growing high quality opal crystals.

By means of high resolution electron microscopy (HREM), the orthorhombic (2/1, 1/1) approximant (a = 2.04 nm, b = 1.25 nm and c = 1.48 nm) of the decagonal quasicrystal in Ga-Mn and Ga-Fe-Cu-Si alloys was found to consist of a B-centred rectangular tessellation of the 'crown' or 'concave octagon' subunit, a binary tile composed of one thin and three fat Penrose rhombi with an edge length of 0.66 nm. Based on the atomic decoration of these Penrose rhombi, a structural model of the crown subunit and that of the Ga-Mn (2/1, 1/1) approximant have been put forward. Simulated electron diffraction patterns and HREM images compared favourably with the experimental results. Various periodic tilings of the crown subunit, either alone or intermixed with other binary tiles (hexagon, 72 degrees pentagonal star and/or decagon) were discussed and compared with a number of approximants found experimentally by HREM.

The transmission spectra at the high-symmetry points of the first Brillouin zone are measured for three face-centered-cubic colloidal crystals made of silica spheres of different submicrometer sizes. It is found that at the $U$ point the transmission dip exists not only for an $s$ wave, but also for a $p$ wave. Moreover, at the $W$ point the transmission dips of both $s$ and $p$ waves appear at the same wavelength. Our calculations confirm that these dips correspond to the lowest band gaps of the high-symmetry points. The structures and parameters of these crystals are determined by the Kossel-rings analysis as well as by the transmission spectra.

We studied the light emission from a laser pumped suspension of Rh640 dye and micron-size scatterers, TiO2 and SrTiO3. Two different excitation geometries, point area and line area, were tried for examining the relation between the gain length and the properties of the emission. The results show that the spectral width of light emission relates strongly to the concentration of dye and the gain length in the excited suspension. The existence of scatterers is an important factor for enhancing the gain length. The influences of the surface shape and the size of the scatterers seem to be insensitive.

The competition effects between two-photon ionization and XUV photon emission induced by a pulsed laser radiation resonant with the 2 1 S3 1 P and 2 1 S4 1 P transitions in He(2 1 S 0 ) are investigated experimentally. The ion scanning profile around the 2 1 S3 1 P resonance shows a dip very similar to the one reported in a previous experiment, whereas the dip is absent in the case of the 2 1 S4 1 P resonance. A theoretical model for the time evolution of the atomic system and the relative numerical solution allow a quantitative reproduction of the experimental results, demonstrating the influence of the lifetime of the intermediate n P level and of the distribution of the laser power changing in space and time. The difference between the widths of ion and photon scanning profiles is also reproduced with a good agreement by the model.

We demonstrate a continuously tunable photonic crystal with several picoseconds response, which is fabricated through a self-assembly formation method of polystyrene spheres. The large optical nonlinearity originates from the delocalization of the conjugated π-electron along polymer chains. The pump and probe scheme is adopted to measure the transmission changes based on the optical Kerr effect. The dynamic shift of the photonic band gap is studied. It is found that the band gap shifts about 13 nm when the input peak intensity is 40.4 GW/cm2, which is in agreement with the theoretical predictions.

The density of states (DOS) and local density of states (LDOS) for an amorphous photonic material (APM) with a finite size and constructed by hexagonal basic cells are simulated. It is found that there is a frequency interval in which the total DOS is very small, i.e., a photonic gap exists. Near the gap-center frequency, the LDOS drops rapidly from the edge to the center area of the sample. However, at the gap-edge frequency, some discrete spots with high LDOS spread in the sample and corresponding electric field distributions show the occurrence of localized modes. This phenomenon can be attributed to the disordered distribution of the scatterers.

Two-dimensional nonlinear photonic crystals of lithium niobate with square lattices were fabricated. In these crystals, efficient quasiphase-matched second-harmonic generation was demonstrated by using second-order quasiphase matching. As a mode-locked Nd:yttritium–aluminum–garnet laser at 1064 nm with 35 ps pulse was used, we obtained an average power of 0.86 mW at 532 nm with 2.73 mW input, which corresponds to 42% internal conversion efficiency. The variations of second-harmonic output with crystal temperature and incident angle were measured. In addition, the relation between the second-harmonic output and reversed duty cycle was studied. All the experimental results are well consistent with simulations.

The periodic disturbance in transmittance of polystyrene photonic crystal is detected in our experiment. The peak-to-peak intervals of the periodic disturbance vary with the wavelength. It is attributed to the propagation of the whispering gallery mode in polystyrene spheres. The results show that the periodically arrayed particles may affect light transfer outside the gap band, which implies the possibility in applications of photonic crystal films.

Photonic crystals composed of TiO2 and air voids fabricated by the template method exhibit an ultraviolet photonic stop band (∼380 nm) in the Γ–L direction. Scanning electron microscopy images show that the inverse opal possesses face-centered-cubic symmetry with a lattice constant of 240 nm. The transmission spectra show that the change in transmittance is one order of magnitude in the gap, which is in accord with the reflection spectrum.

We have prepared a silica colloidal crystal with ethanol, which has a face-centered cubic structure and a corresponding photonic band gap located in the visible region, determined by Kossel ring analysis and the transmission spectra. A special feature is an apparent variation of its lattice constant, as well as the gap frequency, with sample height. The Raman scattering induced by a picosecond laser at different heights of the colloidal crystal has been measured. It is found that the intensity of the Raman scattering is not related sensitively to the photonic gap, even though the Raman-Stokes wavelength is inside the gap.

Based on numerical simulation it is found that three-dimensional periodic patterns with micrometer or submicrometer lattice constants, such as those with simple cubic, face-centered cubic, body-centered cubic, or body-centered tetragonal symmetry, can be formed by use of multiple laser beam interference. Changes in the number and angle of the incident beams result in different spatial patterns, whereas variation of the incident wavelength affects only the lattice constant of the patterns. Face-centered cubic and body-centered tetragonal patterns have been observed experimentally. Our results, combined with the optical trapping of dielectric particles, might provide a promising approach to the realization of a new kind of material-a photonic crystal.

As the metastable state 4p 3P of Zn atoms is excited by a laser, a series of sensitive fluorescence from higher levels appears. Because of its longer lifetime the collisional effect can be identified. The results show that the pressure of filled argon gas affects the peak intensities and pulse duration of these fluorescences. A rate equation model is proposed and the agreement between theory and experiment is qualitatively established. The pooling process is found to be spin related.

A two-dimensional octagonal quasiperiodic photonic crystal composed of alumina cylinders is prepared. The transmission spectra of the quasicrystal are measured in the microwave region for the TM wave. We find that the position and width of the band gap do not depend on the incident direction, while the band structure can appear for quite a small piece of the quasicrystal. Two types of waveguide, a straight guide and a bending guide with two sharp 90° corners, are fabricated by removing three rows of cylinders. The measured transmittances show that the guiding efficiency for both waveguides is high.

Three kinds of square metallodielectric photonic crystals have been fabricated. In these crystals, a very small metal cylinder is inserted into the center of each unit cell, while the dielectric cylinders are located at the corners of each unit cell. The transmissions of these photonic crystals have been measured in the microwave region. Compared with dielectric photonic crystals, the first photonic band gap is enlarged by a factor of 2. The experimental results agree well with the simulation obtained by the multiscattering approach. This method may be valuable for the design of photonic crystals with a large band gap.

A novel two-dimensional photonic crystal that possesses absolute photonic band gaps for both transverse-magnetic and transverse-electric polarized waves is proposed. Plane wave method is used for calculating their photonic band structures. Results show that, for this structure, two absolute photonic band gaps appear in dielectric cylinders periodically imbedded in an air background.

We present a novel design of enhanced second-harmonic generation in a periodically poled ferroelectric crystal. It profits from enhanced light intensity and slowed group velocity, which occur near photonic band edges through electro-optic modulation. The designed structure, with 108 periods and a length of 322 microm, can generate a second-harmonic beam whose conversion efficiency is 2 orders of magnitude larger than the one produced by an equivalent length of quasi-phase-matching bulk medium. This result might be beneficial to the development of optics integration and compact devices.

In this paper, we study negative refraction of electromagnetic waves in three-dimensional (3D) inverse opal photonic crystals (PCs). We employ the plane-wave expansion method to calculate the equifrequency surface of the PC structure, from which the frequency window where negative refraction might occur can be determined. We then investigate the propagation of electromagnetic waves radiating from a point source through a flat PC slab by means of a finite-difference time-domain method. We find that wave focusing can be achieved in such a 3D inverse opal PC structure at the negative-refraction frequency window. Because the inverse opal photonic crystal can be routinely synthesized in the optical regime by means of the self-assembly approach, our study opens a way for realization and application of 3D negative-refraction superlenses in the visible and infrared regimes.

The influence of the irregular shape of atom on the optical characteristics of photonic crystal devices was demonstrated. A multi-channel filter based on this theory was designed to demonstrate the shape tuning capability.