A fundamental theoretical investigation of laser ignition is reported. Ignition is happened in an explosion bomb which equipped with visualization windows and all aspects of the phenomenon such as plasmas, shock waves, ignition kernels, and propagating flames are observed by high-speed schlieren photography. The study covers different phases of laser ignition with theoretical interpretations in chronological order, consisting of electrical breakdown and energy transfer from laser to plasma, shock-wave generation and propagation, gasdynamic effects and generation of the third lobe, chemical induction and ignition and turbulent flame initiation.

By using a feedback-stabilized fiber Mach-Zehnder interferometer (MZI) with a PZT-based phase shifter, a novel method for measurement of laser coherence length is demonstrated based on pulses interference. Experimental results show that the coherence length is closed to that measured by the commercial optical spectrometer, and the partial coherence phenomenon is observed. Our scheme can measure not only the high-coherence laser but also low-coherence pulses, which is widely used in coherent laser measurement and application.

We theoretically investigate quantum transport of a two-component quantum gas in a disordered potential and predict a unique disorder-induced splitting of a matter wavepacket. We also demonstrate that the splitting of the mobile component originates from the inter-component interaction and the disordered potential on the localized component.

The angular emission spectra of the distributed feedback (DFB) cavity are investigated theoretically and experimentally. An angular emission model of the relationship between the DFB cavity and its angular emission spectra is proposed. In the model, the DFB cavity can be decomposed into two parts: a grating and an active waveguide layer. So, the angular emission spectra of the DFB cavity are mainly determined by the period of the grating, the thickness of the waveguide and the material absorption during the feedback process. The theoretical model agrees well with the experimental results. It provides a convenient estimate for designing more efficient DFB polymer lasers and highly directional emission devices.

The effect of optical phase modulation instability on the scale factor (SF) in Sagnac interferometer-type optic-fiber current sensor (OCS) is theoretically analyzed in this letter. The inherent temperature dependence of the optical phase modulation and the drive signal noise are the main reasons of increasing SF error. By means of employing calibration process and feedback configuration in modulation depth of the optical phase modulator, the SF error is improved within the range of 1%, verifying the class 0.5 S, which successfully inhibits the effects of those disturbances.

A wavefront reconstruction algorithm based on sub-aperture stitching is proposed to reconstruct a phase from its phase differences to improve calculation efficiency. The proposed algorithm is similar to the sub-aperture stitching interferometry. It divides large phase grids into several small sub-apertures, reconstructs the phase of each sub-aperture from the phase differences through the standard wavefront reconstruction algorithm, and then stitches the results of the sub-apertures together. The proposed algorithm can efficiently reconstruct the phase with much less computer memory and calculation time. Simulations and experiments are conducted to demonstrate the effectiveness of the proposed algorithm.

Carrier-envelope phase effect of the monochromatic high frequency pulse generation from Thomson backscattering is investigated with an analytical model and verified by one dimensional particle in cell simulations. We show that the central frequency of the monochromatic light generated from Thomson backscattering is extremely sensitive to the carrier-envelope phase of the field driving the relativistic electron layers.

Periodic nanostructures spaced by half of the wavelength can be obtained by the technology of laser-focused atomic deposition. Experimental result with single standing wave layer is presented, with a periodicity of 213 ± 0.1 nm, a height of 4 nm, and a feature width of 64 +-6 nm. To further minimize the feature width,focusing and depositing characteristics of double standing wave layers are numerically simulated with optimized particle optics model. It is shown that the spherical aberration is reduced significantly. The predicted feature width is 18.2 nm and the height is approximately 12.6 nm when the powers of the two standing wave layers are 6 and 14 mW, respectively. Well-defined line occurs even when the full-width at half-maximum (FWHM) of transverse angular spread reaches 0.5 mrad.

The phase aberrations caused by thermal deformations is one of the main limitations in a beam control system. If left uncorrected, it would significantly reduce the effectiveness of high-power lasers as devices for beaming power over long paths through the atmosphere. For the purpose of overcoming the effects of phase aberrations, the method of conjugation wavefront pre-compensation of incident laser is introduced and theoretically studied. Based on the simulated results of thermal deformations at different irradiations time, choosing the power in the bucket (PIB), Strehl ratio, and the root-mean-square of phase as the characteristic parameters, the beam quality of emitted laser with and without wavefront pre-compensation is calculated respectively and compared. The result shows that under the condition that the conjugation compensation phase is placed on the incident beam, the beam quality of emitted laser is ameliorated prominently especially for a beam control system with serious thermal deformations.

To resolve the variability of the intensity distribution and the divergence of the laser diode (LD) output beam in a beam shaping system, a diffractive optical element (DOE) array is proposed in LD beam shaping. This DOE array can divide the wavefront of input beam. All light diffracted by all DOE array units is super-positioned on the output plane, and the tolerance for the input beam is improved by this means. Using the above DOE array laser shaped method, three rectangles intensity distribution are realized from Gaussian beam with the diffraction efficiency of 90.5% and the uniformity of 96%. When the half divergence angle of the LD varies from 2o to 16o in slow and fast axis directions, respectively, the diffraction efficiency maintains to be approximate 90% and its uniformity is more than 95%. When the defocus of the lens to collimate LD beam varies from -32 to 32 \mu m, numerical experiments indicate that uniformity and the diffraction efficiency of the shaped beam by the DOE array do not vary.

A laser micromachining technique for the fabrication of metallic microstructures is proposed. The fabrication of microstructures is done by laser-induced wet etching that adopts an optical fiber as a machining tool. The laser beam delivered through the multimode fiber directly irradiates on the workpiece while maintaining a proper gap to avoid fiber damage. The manufacture of microstructures with high surface quality and good size uniformity is realized. Microgrooves with aspect ratio over 10 and microholes with a nearly straight cross-section can be produced by the proposed technique. The overall etching results are examined closely with respect to process variables.

Laser shock processing (LSP) is an innovative surface treatment technique with high peak power, short pulse, and cold hardening for strengthening metal materials. This process induces intensive plastic deformation and deeper compressive residual stress and improves the surface performance of materials. The titanium alloy of TC4-DT is the important materials in many industry fields including aviation, which is used widely on hole and welding structure. However, the researches of surface treatment on TC4-DT welding structure using LSP technology are seldom reported by now. The performances of TC4-DT, including mircrohardness and surface profiles, are improved through the technology of LSP.

We present a wave-front sensor-less adaptive optics (AO) system for a Nd:YAG Zigzag slab amplifier. A 39-element rectangular piezoelectric deformable mirror in combination with a stochastic parallel gradient descent (SPGD) algorithm is introduced for both static and thermal aberrations correction. Preliminary experiments demonstrate that the output beam quality can be enhanced greatly at different power levels.

We demonstrate a passively Q-switched Tm-doped fiber laser with carbon nantubes (CNTs), yielding a maximum output average power of around 82 mW and the corresponding pulse energy of 1.2 \mu J. The laser operates at ~1.985 \mu m with repetition rates ranging from 26 to 69 kHz and pulse-duration from 1.5 to 2.6 \mu s. Our proposed laser shows that the CNTs are promising for the potential Q-switched Tm-doped fiber laser with high energy and tunable wavelength operation. To the best of our knowledge, this is the first report of a Q-switched Tm-doped fiber laser with CNTs as saturable absorber.

5 at.-% Yb3+ doped (La0.10Y0.90)2O3 transparent ceramics are fabricated by using commercial nanopowders in H2 atmosphere. Effect of the heat-treatment on the structure, spectral properties of (Yb0.05La0.10Y0.85)2O3 transparent ceramics is investigated. Laser grade ceramic samples are fabricated, and a diode-pumped laser is demonstrated, the maximum output power of 920 mW at 1 075 nm is obtained with a slope efficiency of ~31%, the laser pulse as short as 730 fs is also realized at the central wavelength of 1 033 nm.

A method with a simple configuration is demonstrated to narrow the spectrum line-width of the fiber lasers. The configuration consists of one coupler and four fiber Bragg gratings (FBGs). The number of longitudinal modes is decreased significantly using multi-cavities by comparing multi-cavities configuration with single-cavity configuration. The spectrum line-width is effectively narrowed. The whole system is simple in technology and low in cost.

Nd0.02Y1.78La0.2O3 transparent ceramic is fabricated by conventional ceramic sintering process. The transparent ceramic has excellent spectroscopic properties, with the absorption cross section of 1.53×10-20 cm2 and broad full width at half maximum (FWHM) of about 8 nm at 806 nm, the emission cross section of 3.57×10-20 cm2 at 1 078 nm, and the decay lifetime of 232 \mu s. For Nd0.02Y1.78La0.2O3 ceramic laser, a maximum continuous wave (CW) laser output power of 1.38 W with a slope efficiency of 22.9% is obtained at 1 079 nm under an 808 nm diode pump.

In order to meet high pulse laser output, the laser shock power supply based on insulated gate bipolar transistor (IGBT) inverter technology, constant current-constant voltage charger mode, high voltage pulse spark, and high pulse current discharger technology is designed. The master oscillator stage and two amplifier stages for xenon flash lamp spark and discharge circuits are designed in this power supply. The voltage of energy storage capacitors can be adjusted from 1 000 to 3 000 V. A variety of measures, such as FREE and Q-switch mode, trigger signal delay, water confining layer control, cooling water control are provided for laser shock processing technology optimization.

A comprehensive physical model describing the dependence of the steering performances on the various physical parameters of a liquid crystal optical phased array (LCOPA) is proposed. Then several typical factors affecting the steering performances of the LCOPA are investigated. The quantificational computation and simulation of the influence factors are discussed in details, the relationship between key performances of LCOPA with the influence factors are analyzed numerically, and the optimization methods are conducted based on analysis results. Finally, the experimental results of laser are compared with the simulation results based on the comprehensive model, the simulation far-field diffraction patterns are basically accord with experimental photographs.

Dual beam deflection models based on one dimensional liquid crystal optical phased array (LCOPA) are discussed and compared in this letter. The far-field diffraction performance of the models is influenced by various impact factors, such as fill factor and fringing electric fields. For optimizing far-field diffraction performance, the combined influence of different impact factors is analyzed and a phase iterative algorithm which use the root-mean-square (RMS) phase deviation as a performance index is presented. The proposed algorithm is able to reduce phase deviation and improve the performance of far-field diffraction pattern at the same time. The simulation and experiments used in the letter effectively verify the proposed algorithm.

A subwavelength plasmonic waveguide filter with symmetric grating distribution is proposed by using the metal-insulator-metal (MIM) structure. By cascading two gratings with different widths in a period, we can increase the number of pass bands, as well as the transmittance of each band up to ~70% compared with gratings with the same width. Such a device can find applications in various optical systems as wavelength demultiplexing component.

Polarization-shift keying (PolSK), which is performed based on two orthogonal polarization states, is investigated in detail by experimental and numerical simulation for data rates of 10 and 40 Gb/s. Using a general Mach-Zehnder intensity modulator, a new type of PolSK transmitter is presented and demonstrated by polarization coupling technology. And then the PolSK transmission is experimentally demonstrated in a 50-km single mode fiber system, whose eye diagrams show that the PolSK transmitter works well at 10 Gb/s and the power fluctuation is ~8%. Further simulation reveals that the PolSK has great potential in long distance transmission with data rate of 40 Gb/s, while its error-free distance goes beyond 2 100 km.

The 10-Gb/s non-return-to-zero (NRZ) on-off-keying (OOK) data transmission over a 100-km transmission fiber link employing an all fiber 1.55-\mu m single longitudinal mode (SLM) distributed Bragg reflector (DBR) fiber laser as the signal source is demonstrated. The experimental result is comparable with that of the transmission system by using a commercially semiconductor distributed feedback (DFB) laser.

A new approach for an all-fiber coherent beam combining by active phasing a fiber combiner is presented, and effect of fill factor of the fiber combiner on the all-fiber coherent combining is also numerical analyzed. Experimental results show that the power in the bucket (PIB) increases more than a factor of 2.35. The results validate the feasibility of coherent combining using a fiber combiner. The PIBs with different fill factors are calculated and the results show that the coherent combining is reduced with the increasing fill factor.

Harmonic imbalance and phase deviation affect the linearity and sensitivity of fiber-optic current sensor (FOCS). The effects of these two factors are theoretically analyzed. Both the harmonic imbalance and phase deviation must be restricted within a tolerable range of variation. By experimentally optimizing these two factors, the scale factor (SF) error of the current sensor within the range of 0.5% is demonstrated and implemented.

A fiber-based precision synchronization triggering system using fiber pulse stacker combined with high-speed electronics processing technology is presented. The relative timing jitter between two laser pulses achieved with this system is 4.09 ps (rms) in 2 h. The impact of the optical pulse amplitude fluctuation on the timing jitter is effectively reduced by high-speed analog-digital conversion and the reliability of the synchronization measurement system is confirmed.

To solve the problem of calibrating the polarimeter module, we design a vector projection (VP) method which is based on the theorem of vector projection and the principle of calibration. The calibration matrix can be calculated by VP method with the given data. The experimental result shows that, in comparison with the common iterative algorithm, VP method has very high computational efficiency and accuracy. The measured error of the degree of polarization (DOP) is less than 3%.

The practical and effective methods to implement the impairments in optical network are put forward and applied in testing the equipment reliability and transmission quality under the condition of bit errors. The results show that the proposed methods are effective in equipment reliability testing.

Low-density parity-check (LDPC) codes combined with polarization scramblers are used to mitigate polarization mode dispersion (PMD) in 40-Gb/s optical fiber system. The simulations are performed to compare the correction performance of LDPC codes and Reed–Solomon (RS) code used in this PMD mitigation scheme. Results show that LDPC codes can achieve a better performance than the RS code with the same redundancy. The scrambling speed of polarization scramblers for LDPC codes system is also discussed, and the optimal speed of 10 MHz is obtained.

A novel hollow core photonic crystal fiber (HCPCF) temperature sensor that is based on intensity modulation and metal-organic-coordinated Co-cage supramolecular material filled in the air holes of the fiber is introduced. Temperature-dependent character of the structure in the range of 90 to 190 oC has been investigated. The numerical analyses show that the confinement loss is both decreased linearly with temperature at 1 064 and 1 550 nm. For a 6.5-cm long HCPCF, the sensitivity of temperature is experimentally determined to be 9.5 10?2 dB/oC at 1 064 nm, and 7.9 \times 10?2 dB/oC at 1 550 nm, respectively.

Photon scattering from a strongly driven many-particle system is investigated. The second-order correlation function for light emitted from a strongly and near-resonantly driven dilute cloud of atoms is discussed. It is shown that photon scattering from strongly driven multi-atom systems exhibits bunching together with super-Poissonian or sub-Poissonian statistics. Next, squeezing in the resonance fluorescence emitted by a regular structure of atoms is discussed. In a suitable modified environment, squeezing even occurs for a resonant driving field, in contrast to the regular vacuum case.

We propose a novel scheme for trapping ultracold rubidium and ytterbium atoms in a three-dimensional (3D) optical lattice simultaneously, in which the two species of atoms locate on two staggered lattices with the same spatial period and have a spatial separation of 133 nm. Furthermore, we calculate the tunneling and intra- and interspecies interactions of rubidium and ytterbium atoms as a function of light intensity, and find that the mixture of quantum degenerate gases in optical lattices can exhibit more intriguing quantum phases, especially a staggered dual Mott insulator of alkali-metal and alkaline-earth metal atoms.

A combination of transmission electron microscopy (TEM) and laser-assisted three-dimensional atom probe (3DAP) is employed to study the nanostructure of Dy-doped CeO2, which is a promising ionic conductor. Segregation of Dy atoms at grain boundaries is observed by electron energy loss spectroscopy (EELS) elemental maps. The segregation is checked and confirmed by laser-assisted 3DAP. Moreover, the enrichment of Dy and deficiency of Ce at grain boundaries are quantitatively identified by the 3DAP concentration profile. Data such as these are significant to optimize the electrical conductive property in rare-earth doped Ceria.

Introducing the finite difference time domain method and perfect match layer absorbing boundary condition, the electro-tunable localized modes in two-dimensional (2D) nematic-liquid-crystal photonic crystal with a point defect (1PD2D-NLCPC) are investigated by numerical simulation. The numerical simulations show that as the direction of the external electrical field varies, the band gap in the 1PD2D-LCPC changes; when the wavelength in the band gap is the wavelength of the sine source wave, the most of optical field energy is localized in the point defect; therefore manipulating the direction of the external electrical field causes the change of the localized mode.

The self-assembled type-II GaSb quantum dots (QDs) are successfully grown on semi-insulting GaAs (100) matrix by liquid phase epitaxy technique. The topography of QDs with high growth temperature is characterized by atomic force microscopy (AFM). The cap layer, which is needed for the device fabrication, is obtained for only some tens of nanometers. The non-resonant Raman spectra are applied to investigate the GaSb-like optical phonons localized in the QDs and to confirm convincingly the existence of GaSb QDs.

The effects of Nd3+ concentration on the visible fluorescence spectroscopic properties of Nd:(Y0.9La0.1)2O3 transparent ceramics are investigated. Under 270 nm excitation, three emission peaks are observed at 396, 426, and 633 nm. When the Nd3+ concentration is increased, intensities of the peaks at 396 and 426 nm increase while the 633 nm peak become weak due to the fluorescence re-absorption effect. Broad luminescence band centered at 426 nm is observed from the fluorescence spectrum stimulated at 358 nm. The emission intensity increases with the increase of Nd3+ ion content firstly, then decreases owing to the concentration quenching of Nd3+ ions.

The influence of technique parameters on the temperature coefficient of resistance (TCR) of reduced graphene oxide (RGO) films is studied. These technique parameters include the ultrasonic time, solution concentration, and heat treatment temperature. Results show that, the best technique parameters are ultrasonic time of 14 h, solution of 0.12 ml, and annealing temperature of 800 oC, and on this point, TCR value of RGO is from -0.67% to -1.36% at the different film thicknesses.

An athermal design for Solc-type filter based on periodically poled KTP (PPKTP) is proposed. The athermal static phase retardation (ASPR) direction in KTP along which the quasi-phase-matched (QPM) condition is insensitive to the temperature is found. The optimal design for Solc-type filter along ASPR direction is obtained. The coupling theory of QPM linear electro-optic effect is employed to study the polarization coupling in PPKTP. The study results demonstrate that the central passing wavelength of Solc-type filter keep unchanged with an almost 100% output when the temperature varies from 268 to 328 K.

The initial carrier-envelope phase dependence of dynamic process for an ultrashort laser pulse propagating non-resonantly in para-nitroaniline (pNA) molecule medium is investigated theoretically, by solving the full Maxwell-Bloch equations. The results show that when the laser pulse propagates with carrier frequency equal to the half of exciting frequency for the molecule’s charge-transfer state, the laser pulse is modulated severely and the population distribution exceeds 1/2 because the two-photon absorption is a resonant process for the interaction of the laser pulse and the dipolar molecule medium. Higher and lower frequencies than carrier frequency occur in the spectrum and even high-order harmonic components approaching to 7th harmonic are produced, forming a continuous spectrum. The sensitivities of the carrier wave reshaping, the high-order harmonic spectrum and the temporal evolution of excited state population to the initial carrier-envelope phase are discussed in detail. It is found that for given pulse width, the phase dependence increases as the laser field grows intense; while for given laser intensity, it decreases when the pulse width becomes narrow. Due to the extra nonlinear effects introduced by the permanent dipole moments of the pNA molecule, the phase sensitivity in this molecule medium is more distinct than in the medium composed of pseudo-molecules without permanent dipole moments.

Frequency doubled diode oscillator and fiber amplifier (DOFA) is frequency-stabilized to a hyperfine line of molecular iodine for calcium spectroscopy. The frequency doubling of DOFA is demonstrated using an Mg-doped periodically poled stoichiometric lithium tantalate crystal for generating a 544-nm beam. Saturated absorption spectroscopy is performed on the molecular iodine at 544 nm to find a hyperfine line for stabilizing the 272-nm beam to the calcium-48 transition. Stabilization of the 272-nm beam using the stabilization of the 544-nm beam to the corresponding 127I2 line is discussed.

High quality z-cut LiNbO3 nonlinear photonic crystals with two-dimensional (2D) dodecagonal and fractal superlattices are successfully fabricated by applying the high voltage pulses. By collinear quasi-phase matching technique, second-harmonics at five wavelengths and ten wavelengths are observed simultaneously in one poled crystal, respectively. The same results can be obtained by rotating around the z axis by integrals of 30o in quasi-periodically poled crystal. In fractal nonlinear photonic crystal, the normalized conversion efficiency can be as high as 0.53%/mW for 499-nm second-harmonic laser spot.

The issue of the letter is focused on the RB-SiC aspherical mirror high frequency surface quality which is fabricated with the different type fixed abrasive pellets. The two-dimensional (2D) surface roughness of the mirror is simulated and experimented. The errors between the simulation and the experiment are 5.97%, 3.19%, 3.59%, 37.37% using W1.5, W3.5, W5, W7 pellets respectively. The error emerging reason is analyzed in detail after the comparison. Also the fractal theory is applied on the analysis of the optical mirror surface fabricated with the fixed abrasive technology. The analysis result shows that the good surface quality of the RB-SiC mirror can be obtained quickly with being polished with the fixed abrasive technology. So the fixed abrasive technology is very suitable for the fast optical surfacing, especially can obtain good surface roughness fast in the stage of grinding mirror which is not suitable for being tested with interferometer.

A new approach is proposed to extract the rectangular building footprints from single high-resolution synthetic aperture radar (SAR) image by combining region-based information with edge-based information. We build multiscale autoregressive (MAR) model and likelihood rate classifier for SAR image to extract region information. Edge information is extracted from SAR image by using constant false alarm rate edge detector. We propose a new optimization criterion which fuses the previous extracted region information and edge information to obtain the final building footprints. The experimental result shows that the proposed method can extract the building footprints effectively.

A modified method of image denoising based on multi-scale mathematical morphology is proposed to be used in the earthquake ruin scene. A new morphological arithmetic operator is desiged according to the basic operations in the mathematical morphology, then the multi-scale operation filter is used based on new operator to realize image denoising. Compared with the other methods, this new method can reduce noise of earthquake ruin scene effectively and has a good practicability.

We establish an accurate and prompt intraoperative sentinel lymph node (SLN) diagnostic system using in laparoscopy for gastric cancer. The system consists of a near infrared (NIR) laser, a near infrared camera, a spectroscope, two optical fibers, a monitor and imaging analyzer. The experiments on animals are performed to assess the availability of this system. It is able to verify fluorescence imaging and spectrum of gastric SLN, after injecting indocyanine green (ICG) (1 ml: 0.5?1 mg/ml) to the subserosa.

The resolution of astronomical imaging from large optical telescopes is usually limited by the blurring effects of refractive index fluctuations in the Earth’s atmosphere. In this letter, we develop a lucky imaging system to restore astronomical images through atmosphere turbulence on large telescope. Our system takes very short exposures, on the order of the atmospheric coherence time. The rapidly changing turbulence leads to a very variable point spread function (PSF), and the variability of the PSF leads to some frames having better quality than the rest. Only the best frames are selected, aligned and co-added to give a final image with much improved angular resolution. Our lucky imaging system is successfully applied to restore the astronomical images taken by a 1.23 m telescope. We get clear images of moon surface, Jupiter, and Saturn, and our system can be demonstrated to greatly improve the imaging resolution through atmospheric turbulence.

This letter presents a correlation tracking algorithm based on edge detection, in allusion to the phenomenon that the target is susceptible to interference in long-wave infrared image. Firstly, the collected imageis processed by median filtering to remove the defects in the detector. Then thegradient information of the background is filtered out by edge detection method. Secondly, to enhance the edge information, the image is dealt with mathematical morphology (MM). And finally, the correlation matching method is done to acquire the miss-distance information of the target in the image. Through theoretical simulation and practical verification, it is proved that the algorithm has a better effect on inhibiting most of the background information, protecting the target's information effectively, enlarging the weight of the target's information in the correlation operation and improving stability of the detector.

The optical characteristics of the magnetic metamaterial (MM) composed of the ferrite rods are theoretically investigated. Firstly, a photonic band-gap (PBG) resulting from the magnetic surface plasmon (MSP) resonance is recognized by observing the photonic band structure. Moreover, the PBG can be manipulated flexibly by using an external magnetic field (EMF). In particular, the effect is very roust against structural perturbations, which can be corroborated by examining the transmittances for a MM slab with different position disorders and size fluctuations. Based on this peculiar property, we design an electromagnetic switch with fast response, which is demonstrated by calculating the electric field patterns of a Gaussian beam incident on a MM slab.

Through finding the derivatives of the group delay and transmittance of the coupled double-ring resonators (CDRRs) with respect to different structure parameters, the dispersion and filtering characteristics of CDRRs varying with different coupling and attenuation/gain coefficients are analyzed systematically. The parameter ranges in that obvious slow and fast light can be achieved are given, and large light delay and advancement without serious attenuation and great distortion are obtained.

Modal filtering in nulling interferometer is based on the capability of single-mode waveguides to transmit only one complex amplitude function to eliminate virtually any perturbation of the interfering wavefronts. In this letter, we focus on realizing single-mode waveguide of chalcogenide glasses in the thermal infrared range 6–20 \mu m by burying a GASIR (Ge-As-Se) fiber core in the substrates of As-Se-S glasses system. To match the single-mode operation, GASIR fiber core of about 15-μm diameter is drawn, the fiber core is buried into As-Se-S substrates by heating two kinds of glasses to a suitable temperature. The propagation mode is tested by guiding a CO2 laser emitting at 9.3 μm into the waveguide. Single-mode out coming signal is obtained by an infrared camera.

A novel inorganic-organic hybrid polymer polysiloxane-liquid (PSQ-L) is introduced for defining waveguides. The PSQ-L polymer film shows good optical properties and high thermal stability. The all polymer microring resonator is fabricated by conventional lithography and ICP etching process. About 3-dB extinction ratio from the through port and 23-dB extinction ratio from the drop port are obtained. A high Q value of 5.7×104 is obtained. The optical loss of the bending waveguides is estimated to be 1.6 dB/cm. The high Q polymer ring resonators show potential in sensing applications.

In order to achieve the goal of the autonomous landing of fixed-wing unmanned aerial vehicles (UAVs), a new method is put forward for using the monocular camera on board to provide the information, which is need for landing. It is not necessary to install additional equipment in the airport. The vision-based method only makes use of the two edge lines on both sides of the main runway and the front edge line of the airport without using the horizon. While the runway width is known, the method can produce the attitude and position parameters of landing. The results of the hardware-in-the-loop simulation show the proposed method has better accuracy and faster computation speed.

Terahertz wave detecting method based on multi-reflection optical lever with nano-scale displacement measuring precision is presented. Multi-reflection optical lever is composed of a pair of plane micro-mirrors, and detecting material is coated on one mirror to absorb terahertz radiation. Affected by radiant thermal effects, tiny mirror deformation is produced while displacement between mirrors is changed. These variations proportional to radiation are amplified and measured by multi-reflection optical lever, and then terahertz wave power can be obtained. Theoretical displacement measuring precision of multi-reflection optical lever method is better than 1 nm. Experimental results show that measuring stability of this method is better than Knife-edge filter method. This method achieves resolution of 4 nm, sensitivity of 5.95 nm/mV, and measurement range of 30 \mu m.

A novel microring resonator sensor coated with a single negative metamaterial (SNM) layer is proposed. The dispersion relation of hollow cylindrical dielectric waveguide covered with a SNM layer is derived, and resonant frequencies of the corresponding whispering gallery mode are computed. We find that there is a good agreement between the theoretical results and numerical results of resonant frequencies and electric field distributions. Compared with traditional resonator sensor, the sensitivity and resolution are significantly enhanced by SNM, and the Q factor can be tailored by adjusting the distance between the waveguide and the microring.

We present a downhole seismic monitoring system and the field test results using a fiber laser seismometer (FLS). The distributed feedback fiber laser is used as the sensing element of the seismometer. Using the interferometric demodulation system, a minimum detectable acceleration of ~ng is achieved. The FLS is installed in a 400-m-depth well in Puer city, Yunnan Province. A micro-earthquake (M=1.2) in Puer area is detected. Compared with the existing underground electrical seismometer, FLS shows a higher signal-to-noise ratio and good reliability, which indicates that the FLS provides a new approach to deep-well seismic monitoring.

A novel method to measure droplet size and complex refractive index simultaneously by rainbow detecting is presented. A new mathematic model for rainbow pattern of absorbing droplet is built. Based on this model, a series of new formulas to measure droplet imaginary part of refractive index is derived. Then a new inverse algorithm for simultaneously measure droplet size and the complex refractive index is presented, which is verified by simulation experiments under different conditions.

According to the X-ray fluorescence (XRF) spectral characteristics of heavy metals in soil, the application of XRF spectra de-noising using biorthogonal wavelet packet transform technology is analyzed. Wavelet pack decomposition and threshold setting are particularly discussed. Through spectra de-noising, the linear fitting relationship between concentration and intensity of Ni is meliorated. Experimental results demonstrate that this method can effectively overcome the noise interference and preserve characteristic spectra. This method is very useful to increase the accuracy of quantitative analysis, especially for analyzing trace elements in soil.

We present a numerical study on the evolution of the intense femtosecond pulse propagation in argon by solving the extended nonlinear Schr¨odinger equation which includes the beam diffraction, group velocity dispersion, self focusing, absorption and defocusing due to the electron density, and multiphoton ionization processes. The temporal and spatial profiles and the dynamic picture of the ultrashort pulse propagation in argon under different incident conditions such as initial peak intensity, pressure, beam radius, pulse width, and the focal length are discussed. Because the competition between the self focusing and defocusing effects accompanying with other effects as we mentioned above, we can see the splitting into two or even three peaks of the pulse in the time domain.

The optical data which collected in situ in inshore and offshore of Daya Bay in July 26, 2 010 is presented. The data is collected by using the instrument, which synchronously measured the volume scattering function in seven directions from 20o to 160o, the attenuation coefficient, and the depth of water. The analysis of the data indicates that in Daya Bay, in general, the scattering and attenuation increase with depths after 4 m below the surface, while it decreases with depths from near surface layer to 4 m. But not for the area near Daya Bay Nuclear Power Station due to the unique geographical environment of it.

Thermal atomic layer deposited (ALD) Al2O3 films are applied at the front and rear sides of PERC-type c-Si solar cells. At the front side, Al2O3/SiNx as a double-layer antireflection coating reduces the reflection loss, and at the rear side, Al2O3 film as the passivation layer decreases the surface recombination velocity and enhances the internal reflectance at near-infrared (NIR) band together with SiNx layer. Due to the improvement in the reflectance combined with a decrease of the surface recombination velocity, the PERC solar cells show an improved Jsc by 0.2 mA/cm2 compared with the full-area back surface field cell.

Wired local network is used widely in a vehicle. It brings the benefits of sharing information and controlling automatically as well as causes negative reaction and a troublesome problem to vehicle such as weight, cost, electromagnetism and space and so on. Infrared optical wireless communications are an alternative way to break through these limitations for increasing safety, decreasing fuel consumption and high bandwidth. In this letter, we address the issue of design a wireless network in a vehicle with an infrared link and ring topology. We discuss the performance requirement of the network, and analyz its bandwidth, power, link distance choice and message schedule. At last, we simulate the preferred parameters of an optical link system.