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We propose a novel configuration for nonvolatile and reconfigurable tuning of surface lattice resonances (SLRs) based on thin films of phase-change material Ge2Sb2Te5 (GST). The configuration is composed of gold nanorod array embedded in a thin GST film. Results show that, an extremely wide SLR wavelength tuning range reaching 1600 nm, large tuning figure of merit of 21, and high SLR quality factors of 47 and 17 can be achieved in the mid-infrared regime when GST transits from the amorphous state into the crystalline state. The effects of the GST layer thicknesses on the SLR tuning performance are discussed, and the performances of several modified configurations are compared. We expect this work will advance the engineering of SLR tuning based on phase-change materials and promote its applications especially in nanolasing and narrowband filtering.

A novel full-duplex radio-over-fiber system is proposed and demonstrated, in which an external modulator and an optical interleaver are used to generate dual octupling-frequency optical millimeter waves for two base stations and wavelength reuse for uplink connection. This scheme is simplified and low-cost because no additional laser is utilized for uplink connection at two base stations and one laser at central office works for two base stations simultaneously. The frequency of local oscillator signal is reduced largely due to frequency octupling. The theorem about how to generate optical millimeter waves is analyzed. The simulation results show that the bidirectional 5 Gb/s system has a perfect performance because the power penalty for the downlink and uplink signals of two base stations are less than 0.6 dB after successful transmission over 60 km standard single mode fiber.

Mid-Ultraviolet (UVB) has a significant influence on human health. In this study, human erythrocytes were exposed to UVB to investigate the effects of UVB radiation on erythrocytes membrane. And Micro-Raman spectroscopy was employed to detect the damage. Principal component analysis (PCA) was used to classify the control erythrocytes and the irradiated erythrocytes. Results showed that the erythrocytes membrane was damaged by Mid-Ultraviolet (UVB) radiation. The intensity of the Raman peaks at 1126 cm(-1) and 1082 cm(-1) were used to calculate the Longitudinal Order-Parameters in Chains (S(trans)) which can present the liquidity and ionic permeability of erythrocyte membrane. After UVB radiation for 30 min, both the liquidity and ionic permeability decreased. At the same time, the intensity of the peaks at 1302 cm(-1) (α-helix), 1254 cm(-1) (random coil), 1452 cm(-1) and 1430 cm(-1) (CH(2)/CH(3) stretch) have also changed which indicated the membrane protein also been damaged by UVB. In the whole process of radiation, the more UVB radiation dose the more damage on the erythrocyte membrane.

The aim was to test whether the typical NPC cell lines of 5-8F (high tumorigenesis and metastasis) and 6-10B (low tumorigenesis and metastasis) could be differentiated by polarization sensitive optical coherence tomography (PS-OCT). We imaged the two types of low cellular differentiated NPC cell lines 5-8F and 6-10B pellets using PS-OCT; then extracted the optical parameters of attenuate coefficient and anisotropy from the A-scan lines based on the multiple scattering model; and compared their phase retardation. The fitting scattering coefficients were μs=10.91±0.45 and μs=11.33±0.27 cm(-1) for 5-8F and 6-10B pellets (p

Detection efficiency is one of the key parameters that affect the performance of gated-mode avalanche photodiodes in quantum key distribution. In this paper, the impact of the waveform of faint picosecond laser pulses on detection efficiency is investigated both experimentally and analytically. Two kinds of laser pulses are attenuated to the single photon level to measure and plot single photon detection efficiency versus synchronous delay between the detector and the laser source. The results show that the narrower laser pulse with single peak can be detected with about 9% higher detection efficiency and lead to a lower QBER than the pulse with subpeak and a broadened pedestal.

We demonstrate experimentally an intrinsically stable polarization coding and decoding system composed of optical-fiber Sagnac interferometers with integrated phase modulators for quantum key distribution. An interference visibility of 98.35% can be kept longtime during the experiment without any efforts of active compensation for coding all four desired polarization states.

Error reconciliation is a necessary step for quantum key distribution process. In this paper, the correction ability of error reconciliation procedure which is called Winnow protocol is analyzed and estimated, moreover, it gives some expressions about it. The experiment results proved the capability of Winnow protocol are excellent. It is also indicates that the smallest N has the most correction efficiency where from the communication times between the legitimate parties and the data remaining efficiency consideration.

The bandgap properties of 2D 8-fold symmetric photonic quasicrystals (PQCs) composed of a set of rods are numerically investigated for various fill factors, dielectric constants and propagation angles using the finite difference time domain (FDTD) method. Some interesting properties are found besides the known results: (i) the central frequency of the bandgap shifts to low frequency as r/a increases; (ii) an optimum fill factor to obtain the largest gap width exists, which decreases with increasing dielectric constant; (iii) compared with the behavior for a given fill factor, the variation of bandgap width for the optimum fill factor increases much more significantly with the dielectric constant. Selection guidelines for 8-fold symmetric PQC designs are provided for optimum fill factors and variation of the relative bandgap width at different dielectric constants.

We present implementation of quantum cryptography with polarization code by wave-guide type phase modulator. At four different low input voltages of the phase modulator, coder encodes pulses into four different polarization states, 45°, 135° linearly polarized or right, left circle polarized, while the decoder serves as the complementary polarizers.

The surface morphology of GaInP buffer layers mismatched to GaAs substrate is probed to study its impact on the distribution of self-organized InP island. The steps, facet island matrix and mismatch dislocations formed sequentially as Ga content increased in buffer layers. And the lateral distribution of InP island can be controlled efficiently by the steps, island matrix and mismatch dislocation. The island matrix, with about 100nm periodicity, is found to be efficient to obtain InP island lateral distribution with 1μm periodicity on sample 3. The result also shows the dislocation had different functions to control the island distribution along different directions, [110] and [ 1 1 ¯ 0 ] directions.

The effect of frequency chirping on supercontinuum (SC) generation in dispersion flatted and dispersion decreasing fiber has been studied by numerical simulation based on the total field nonlinear Schrodinger equation. Our results show that a positive initial frequency chirp can significantly broaden the supercontinuum spectrum by up to approximate 80 nm, and the SC intensity increase about 5 dB. A range of optimal positive frequency chirps is identified to obtain the maximized supercontinuum bandwidth. The mechanism of this enhancement is also discussed detailedly through the evolutions of temporal and spectral width related to different pre-chirped pulses.

The self-organized InP islands grown on GaInP buffer layers mismatched to GaAs substrate were utilized to find the influence of the stress between the buffer layers and the islands on the shape of the islands and its distribution. The shape of the islands was elongated with the increasing stress. The self-organized islands at the surface of buffer layers were analyzed by scaling theories to show a periodical distribution. Some kinds of buffer layers such as the mismatched GaInP on the GaAs (1 0 0) tilt to (1 1 1) 15° can improve the periodicity of the island separation distribution.

In this paper, a novel configuration of reflection L-band erbium-doped fiber amplifier (L-EDFA) via inserting a 980 nm pump laser diode (LD) in the input part was constructed. By selecting appropriate power ratio of the 980 and 1480 nm pump LD, gain and noise figure (NF) of the L-EDFA are greatly improved in different degree in the wavelength region from 1565 to 1615 nm. Compared to the configuration pumped by only 1480 nm pump LD with given power, the noise figure decreases 1.3–9.4 dB and the gain enhances 1.5–9.9 dB.

Modulation instability (MI) to generate femtosecond pulse in dispersion-decreasing fibers (DDF) is investigated. Higher-order dispersion effect and higher-order nonlinear effects are taken into account when continuous wave or quasi-continuous wave evolves into sub-picosecond or femtosecond pulses by MI in optical fibers. Our research results show that the gain spectrum of the DDF is much wider than that in conventional fibers. The third-order dispersion effect has no contribution to gain spectrum, self-steepening effect reduces the maximum value and gain bandwidth of gain spectrum, and Raman self-scattering effect widens the extent where MI occurs.

Single wall carbon nanotubes of tubule diameter 1.0–1.7 nm were synthesized by the irradiation of continuous CO 2 laser (500–900 W) onto a graphite–Co/Ni composite target at room temperature. We suggest that the high temperature plays a unique key role in the growth of single-wall carbon nanotubes in the laser ablation method, while laser wavelength is less important. The transmission electron microscope observations show that the average diameter of single wall carbon nanotubes produced by the CO 2 laser is larger than one produced by YAG laser vaporization, and the tube diameter increases with increasing laser power. We present the Raman spectrum of single-wall carbon nanotubes produced by using CO 2 continuous laser vaporization with laser excitation wavelengths 632.8 and 514.5 nm, and these Raman scattering are compared with those of nanotubes produced by other laser ablation of previous reports.

The nonlinear Schroedinger equation (NLSE) in erbium-doped fiber (EDF) is obtained. Based on this NLSE, a more generalized form of the propagation equation in the erbium-doped fiber amplifiers (EDFA) is given which has included the phase shift that the erbium ions induce. The cross-phase modulation (XPM) in the EDFA is studied according to that erbium ions induced phase shift. An analytical expression is given to the frequency chirp that the doped-erbium ions induce. It was found that the frequency chirp dose not change much with the wavelength except at the neighbouring wavelengths (around 1.531 μm) where absorption and the emission cross-sections of the erbium ions reach their maximum, and the frequency chirp has opposite sign on the two sides around 1.531 μm. Furthermore, it was found that the frequency chirp will increase with increasing length of the EDF.

The effect of preparation parameters on the particle size of silicon nanocrystallite produced by laser-induced chemical vapour deposition (LICVD) was studied. It is found that the particle size of nano-Si prepared by LICVD is related to preparation parameters. We obtained the optimum synthesis parameters for preparation of the right sized nano-Si powder produced by LICVD. The effect of different annealing treatments on the infrared (IR) absorption bands of the nanosized silicon was also investigated.

Differential phase shift quantum key distribution scheme has been improved by introducing a passive path selection structure at the transmitter including two polarization controllers used to mark the photon pulses and a polarizing beam splitter to distinguish these pulses so that can make different time delay at the receiver. Theoretical analysis indicates that a free-space-based differential phase shift quantum key distribution system with this proposed improvement will have high efficiency with the utilization ratio of photons reaching 100% under ideal condition.

Nonlinear chirped gratings are numerically demonstrated to have a direction-dependent switching behavior. For the two incident directions, bistability exists with different switching-on powers, and the instable high transmissivity states have different critical powers. The direction-dependent bistability is due to the difference of the energy contained in the gratings for the two incident directions; the direction-dependent critical powers for instability origin from the different modulation instability threshold. Furthermore, it is first reported that for instable output there are spectral side lobes whose frequency shifts relative to carrier frequency have jumps at some input powers.

Cyanine (Cy) dye was embedded in (or absorbed by) an arachidic acid monolayer on an air-water interface and multilayer samples deposited on glass slides were obtained. The studies of their absorption spectra showed that Cy in Langmuir-Blodgett (LB) films formed H aggregates. The enhanced large third-order susceptibility has been measured to be 5 × 10 -8 e.s.u. for the LB films, which is three orders of magnitude larger than that deduced from the measured second-order hyperpolarizability of Cy monomers in bulk solution. The origin of this large third-order susceptibility for the LB films, due to the near-reaonant effect and indirect transformation between H aggregate and monomers and delocalized exciton enhancement in the aggregates, has been discussed as well.

The nanotubes were prepared by the dc arc-discharge method in helium and argon gas ambient under controlled pressure, and subsequently purified by oxidation in air. The room temperature electron spin resonance (ESR) spectra of purified carbon nanotubes prepared under different inert gases and their pressure were measured. The dependence of the ESR line shape, linewidth, g-value of the nanotubes on the inert gases and their pressures is found and discussed.

Multiple diffraction rings are observed after a pulsed laser beam passes through an absorbing dye LB film. The theoretical analysis, based on the model of transverse self-phase modulation, is also given. The saturated nonlinear refractive index n2 is estimated to be 2.0×10−6 cm2W from the number of rings induced in the LB films. The main contribution to this larger nonlinearity is believed to be from laser-induced transformation between H-aggregates and monomers of molecules in the LB films.