A novel wavelet denoising method is proposed for the pressure surveillance of heavy oil thermal recovery well using white light extrinsic Fabry-Perot interferometric (EFPI) fiber-optic sensor. This method can effectively suppress the non-stationary noises and disturbances in downhole environment. A method for estimating the optimal wavelet decomposition level is proposed based on the analysis of the signal-to-noise ratio (SNR) enhancement varying with decomposition level. No prior knowledge of the real pressure signal spectrum is needed. The optimal wavelet decomposition level is determined by using the downhole pressure data collected in one of the heavy oil thermal recovery wells in Xinjiang, China. Field test results show that the proposed method can increase the SNR of pressure profile by 2.6 dB, and thus further effectively increase the accuracy of the forecasting result of daily oil production.

We design the 2×2 multimode interference (MMI) coupler based on silicon-on-insulator (SOI), which can be used in the array waveguide grating (AWG) demodulation integration microsystem. The coupler is simulated using the beam propagation method (BPM). Taper waveguides are used as input/output waveguides. The footprint of the MMI regions is only 6 μm×57 μm. The excess loss is 0.46 dB and the uniformity is 0.06 dB with TE polarization when the center wavelength is 1.55 μm. The maximum excess loss is 1.55 dB in the range of 1.49~1.59 μm. The simulation results show that the 2×2 MMI coupler with small size exhibits low excess loss, wide bandwidth and good uniformity, which can meet the requirement of system on chip.

The influence which comes from piston error for the Golay6 sparse-aperture optical system is studied by calculating and simulating the pupil function, point spread function and modulation transfer function. According to Strehl requirements, the piston-error tolerance under the different radii and different filling factors is given and imaging simulation is done by the Matlab software. The results show that the affection is not significant within the piston-error tolerance.

A novel algorithm to segment images under the echo broadening effect (EBE) in range-gated laser night vision technology is presented. The proposed algorithm uses average gray value of outline edges information to select the threshold extracting signal areas out. Spatial information of each pixel is applied to detect the noises from the candidate signal areas after the determination of the threshold. This algorithm avoids too much morphological operation and prevents the distortion of the images. The experimental results show that, using this method, it is very effective to segment low quality long distance range-gated images.

A derivation Hilbert backprojection (DHB) reconstruction algorithm based on the filtered backprojection (FBP) algorithm in equispaced fan-beam CT is proposed and realized. Because of the improvement of sharp cut-off characteristic of DHB filtering function in high frequency, the experimental result shows that the reconstructed image using DHB is smoother than that using FBP. Simultaneously, the distance weighting in backprojection operator is got rid of, which leads to the reduction in reconstruction time.

Doppler effect can be used to detect target velocity based on laser radar system. When processing the signal spectrum, error between Doppler frequency and target velocity is caused by picket fence effect. In order to improve the velocity detection accuracy, energy centrobaric correction method is demonstrated to correct discrete spectrum. Experiment data indicate that the velocity accuracy is better than 1 cm/s.

In order to study the third order nonlinear optical property of single-walled carbon nanotube (SWCNT) film, we prepare polymer film of SWCNTs and poly methyl methacrylate (PMMA) on quartz substrate by rotation coating. We obtain linear transmission spectrum and surface morphology of the film. For improving the measurement accuracy of the third order nonlinear coefficient of SWCNT polymer film, we discuss the influence of the changes in related parameters of the Z scanning method upon the measurement accuracy of the material nonlinear coefficient, and build Z scanning system to study the third order nonlinear optical properties of the thin film. Through the simulation and calculation of experimental data, we obtain that the third order nonlinear absorption coefficient (β) and the third order nonlinear refractive coefficient (γ) of this SWCNT film are -7.8×10-7 cm/W and -6.4×10-11 cm2/W, respectively, and the third order nonlinear susceptibility is 2.06×10-9 esu. The results prove that SWCNT/PMMA film owns strong nonlinear optical properties.

A CO2 laser-metal active gas (MAG) hybrid welding is used to weld the high strength steel of 5.0 mm thickness. Droplet transfer is observed with high speed camera and the forces on droplet are investigated in detail. The droplet transfer is strongly affected by laser power, arc power and the distance between laser and arc. The results indicate that laser could make arc plasma more stable and decrease the critical current of spray transfer for its leading and constricting felnctions on the arc by the laser. There are changes in the current distribution within droplet and the magnitude and direction of electromagnetic force. At the same time, a large number of metal gas from the keyhole makes a metal steam reaction, changing the force state of the droplet so that the droplet transfer mode is changed. With the increase of the welding current, the arc becomes more stable and the power of arc is more concentrated, making the plasma drag force decisive. The distance between laser and arc has an effect on the frequency of the droplet transfer. When the distance is 4 mm, the frequency of the droplet transfer is the maximum.

Temperature plays a vital role in the laser cutting glass substrate process. To know the dynamic distribution of temperature and improve the cutting quality, a simulation method for temperature field is proposed. The three-dimensional finite element analytic model of the CO2 laser thermal stress in cutting electronic strengthened glass is put forward and the temperature field is analyzed in finite element analysis software ANSYS. The changes of temperature field with different parameters and the effects on the cutting quality are studied. The relations between distribution of temperature and parameters including laser power, spot size and scanning speed are obtained. Certain guidance in selection of parameters in actual process is manifested.

Metal laminated sheets with fine material and structural performance reveal broad application prospects in ships, automobiles, aircrafts and other equipments. In order to study the influence of process factors on laser bending of metal laminated sheets, a stainless steel-carbon steel laminated sheet is chosen as the object of the research and a systematic experimental study is conducted to investigate the bending angle and transformative law of this metal laminated sheet by laser bending. The results reveal that, there are common features between stainless steel-carbon steel laminated sheet and stainless steel sheet during laser bending. For instance, the bending angle increases with the increase of laser power, scanning times and decreases with the increase of scanning velocity, the sheet thickness. Meanwhile, there are differences between them. With the increase of the sheet width, the bending angle of stainless steel-carbon steel laminated sheet decreases at first, and then increases. The bending angle of stainless steel-carbon steel laminated sheet is bigger than that of the stainless sheet in the same processing condition. And the ultimate bending angle, 85.6°, which approximates right angle, is obtained in one clamping.

To improve the reliability of 980 nm laser diodes, we produce 4 μm ridge waveguide laser diodes with current non-injection regions near both facets by He ion implantation technology, and a conventional device is made from the same wafer for comparison. After long-term aging, all conventional devices are disabled within 1500 h, and all the devices made by He implantation work well after 3000 h. Failure analysis for devices by scanning electron microscopy (SEM), results shows that catastrophic optical damage on the facet, the quality of indium solder bonding and the stain of facets have direct impact on the devices′ reliability.

An all-solid-state blue laser (471 nm) pumped Pr:KYF laser is demonstrated. The incident pump power threshold is 0.4 W. With an incident pump power of 2.5 W, the maximum output power is 212 mW. Moreover, intracavity second-harmonic generation (SHG) is also achieved with a maximum ultraviolet power of 11 mW by using a β-BaB2O4 (BBO) nonlinear crystal. The system emits nearly TEM00 mode with beam quality factor M2=1.25 measured by the knife-edge technique. The optical-to-optical conversion efficiency is 4.4%, and the fluctuation of the output power is about 4.3% in 30 min. The spectra of 305 nm laser are detected using the USB-4000 high resolution spectrometer.

The optical properties of the subwavelength metal structure have become a hotspot of optical research. The influence of metal nano-antenna on optical wave transmission through the subwavelength hole on metal film is investigated by applying the three-dimensional finite-difference time-domain (3D FDTD) method. Nano-antenna is laid in front of and behind a metal film with a hole, respectively. The zeroth-order transmittances are obtained. It is found that the second-order and third-order enhanced transmission is realized under the phase matching condition when the orders of resonances mode of antenna and hole are the same. Energy can be coupled into the hole to enhance the near fields through antenna resonance when the antenna is laid in front of the hole, while coupled out of the hole through antenna resonance when the antenna is laid behind the hole.

The dispersion characteristics of the left-handed material prism and the equal-inclination interference characteristics of parallel plate of the left-handed material are studied. For prism of the left-handed material, the deflecting direction of the exit light deviating from the original propagation direction is contrary to that of prism of the right-handed material. The deviation angle of prism of the left-handed material is larger than that of prism of the right-handed material for the same monochromatic light with equal incident angles. The formulas of intensity distribution of the reflected light and transmitted light at the focal planes are derived for investigating the characteristics of parallel plate the left-handed material. The relation between bright and dark fringes of equal-inclination interference and their orders is analyzed. The formulas of bright rings′ radii and dark rings′ widths in the case of half-wave loss are derived. For the equal-inclination interference characteristics of parallel plate of the left-handed material, the orders of fringes of equal-inclination interference are lower at the center of circular rings, which is different from the case of parallel plate of the right-handed material.

Thermophotovoltaic (TPV) cells are fabricated based on lattice-mismatched In0.68Ga0.32As with bandgaps of 0.6 eV grown on InP substrates. The performace of TPV cell is significantly improved for the optimized material quality owing to the strain relaxation of the InAsxP1-x buffer layer, and therefore to suppress the dislocation. Under a standard AM1.5G spectra, the open circuit voltage of TPV cell increases from 0.19 V to 0.21 V, the long wavelength external quantum efficiency reaches 85%, and the conversion efficiency is increased by 30%.

The non-uniform illumination distribution on the solar cell will reduce the solar-to-electric power conversion efficiency and decrease the service life of the cell in concentration photovoltaic system. Moreover, the hot-spots formd on the cell surface will quickly break the cell. Based on multifocal method, we design the ring-shaped-focus Fresnel concentrator, in which each ring of the Fresnel lens has one focus. Taking a Fresnel concentrator whose diameter is 400 mm, ring number is 200 and focused spot radius is 20 mm as an example, under simulated sunlight, using Tracepro software we get an illumination diagram with energy uniform by distributed on the round surface. The optical efficiency is 85.24% and the homogenization is 0.8. The annular focal spot Fresnel concentrator holds higher light utilization and illumination uniformity. Moreover, when the F number is fixed, the focal spot uniformity gradually reduces with the increase of the concentrator diameter.

Remote monitoring for optical fiber grating sensing network making use of existing optical fiber communication network can not only avoid relaying sensing channel, thereby saving the cost, but also increase the sensing network flexibility. A new sensing data digitalization system is proposed based on arrayed waveguide grating (AWG). Quick digitalization of fiber Bragg grating (FBG) reflecting wavelengths which carry sensing information can be achieved. The operating principle and the main error source are analyzed. The sensing data framing module as well as the frame structure is designed. The simulation of a 3×3 fiber grating sensor network is carried out with OptiSystem/Matlab co-simulation approach. The accuracy of 1 ℃ in the range of -50 ℃~100 ℃ is realized, which can satisfy normal temperature monitoring requirement. The simulation results show the feasibility of the scheme.

In order to restore the contrast of celestial simulator-generated starlight with the surrounding dark background, improve the recognition rate of the star map and navigation solution accuracy, a new design of the lens hood for celestial navigation simulation system to decrease environmental stray light is discussed detailedly. Design formula is derived in accordance with its principles, and a new method to calculate the position and size of the vane inside the hood with computer program is proposed. Using the baffle model established in TracePro, 18 different deviation angles between 1°~85° of parallel light source are simulated. The stray light suppression curves for different deviation angles are obtained. Results show that above 25°, suppression ratio of the luminous flux decreases to the order of magnitude of 10-3. A physical test is carried out on semi-physical simulation platform. The actual results show that this design of the lens hood can decrease the environmental stray light and effectively restore the contrast of starlight simulator.

The field emission properties of hydrogen-adsorbed carbon nanotubes (CNTs) are studied using first-principles density functional theory. Open-ended (5,5) single-walled carbon nanotubes models with different numbers of hydrogen molecules adsorbed are built, and the adsorption energy, highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) band gap, the induced dipole moment of the model with and without applied electric field are calculated and analyzed. The calculation results reveal that the structure of carbon nanotubes with hydrogen molecules is stable under field-emission conditions, HOMO-LUMO band gap becomes narrower, the local density of states at the Fermi level increases with the adsorption of hydrogen molecules, and electrons emit more easily.

Terahertz source based on parametric oscillator is an important tunable terahertz device. It has important applications in the security check, biosensors, medical diagnostics, testing and quality control of semiconductor devices. This article summarizes the experimental and theoretical research of domestic and foreign terahertz parametric oscillator in terms of the material properties of the nonlinear crystal, resonator structure, terahertz output coupler, frequency tuning mode and linewidth control. We review the cascaded terahertz parametric process in continuous, pulse, ultrashort pulse operating styles and propose some of its future research directions. With the development of fiber laser technology and periodically poled crystals to further improve the performance, the terahertz parametric oscillator will move to the direction of more efficient, small, practical, portable and easy to operate, and play an increasingly important role in its application fields.

Spatial variations in the refractive index of the biological specimen introduce optical aberrations that degrade image quality. In confocal microscopy this is a serious limitation when imaging penetrates into thick biological specimens, in particular for in vivo tissue imaging. Adaptive optics (AO) enable mirror deformation to compensate the aberration by rapid response deformable mirror. In confocal microscopy, it can correct the aberrations, observe deep tissue activity, perform in vivo tissue imaging, measure and restore the optimum resolution. This review discusses the origins and characteristics of aberrations in confocal microscopy. The correction schemes by using adaptive optics in confocal microscopy and the research progress are discussed. Wavefront sensor, aberration measurement and aberration correction devices of adaptive optics in confocal microscope are discussed. The trends of adaptive optics in confocal microscopy are also reviewed.

Single-mode vertical cavity surface emitting laser (VCSEL) has shown great potential ability in optoelectronic applications such as optical interconnection, optical storage, high-speed laser printing and long-wave communication as a result of its advantages in low-power consumption, small divergence angle, high modulation bandwidth and easy two-dimensional (2D) integration. The top and bottom reflective layers can control its vertical mode excellently, but if we want to obtain a single fundamental transverse mode, we must limit the emergent light in the transverse direction. Recently, with the technique of etching 2D photonic crystal holes into the top distributed Bragg reflector, single fundamental mode photonic crystal VCSEL is made successfully. In this review, we focus on the structure, operating principle, researching progress and application fields, and discuss how to improve the output energy, control the polarization and reduce divergence angle. At last, we present the domestic research situation and prospect of future research.

Terahertz pulse shaping has attracted much attention from a variety of applications in fundamental and applied research fields, such as quantum theory, bio-medical imaging, security-checking, sub-milimeter wave communication and so on. A brief review is presented on the latest progress of terahertz pulse shaping based on femtosecond pulse shaping, new terahertz materials and device, and terahertz pulse shaper. The perspective of the terahertz pulse shaping techniques is also presented.

The methods to produce mid-infrared lasers and the features of different mid-infrared lasers are introduced. Combined with the advantages of the second harmonic generation in CO2 laser, the performance of frequency doubling crystals in the CO2 laser are mainly discussed. The performances of the most widely used birefringent phase matching (BPM) and quasi phase matching (QPM) frequency doubling crystals are compared and analyzed. The problems and probable techniques for the development of second harmonic generation in CO2 laser are previewed.

Dark pulses propagate with low noise and low loss in optic waveguides, so dark pulses have an advantage over bright pulses in signal processing. Research progress of dark pulse laser is reviewed. Emphases are placed on dark pulse output schemes based on optical shaping or electrical shaping, and dark pulse output directly from a laser cavity. And the applications and prospect related to dark pulse laser are presented. The remaining problems are pointed out.

Photon sieve is a new nano-imaging device with the advantages of high resolution, light weight, small size and easy to duplicate. It has great significance for the lightweight imaging system and imaging in very short spectral region. The research results of photon sieve are classified based on problems solved. The development status of photon sieve is introduced, including the increase of image contrast, diffraction efficiency, wide spectral imaging, and design of high numerical aperture photon sieve. The technical problems to be solved of these four aspects are analyzed. It is believed that the main directions are also these problems′ resolution. Other problems of photon sieve application are also pointed out. The applying prospects in telescope, microscope, lithography and other areas of photon sieve are addressed.

The acquisition speed and spatial resolution are the key factors in application-oriented terahertz (THz) imaging systems. To solve this problem, the techniques of the THz synthetic aperture radar (SAR) imaging, THz interferometric imaging and THz compress sensing (CS) imaging have been proposed by scholars based on SAR, electromagnetic interference and CS. All of them have a good potential in imaging speed and spatial resolution. We review these techniques and summarize the technical advantages and recent research progress. The prospect of applications of THz imaging techniques in the fields of military, public safety and non-destructive defect identification is given.

Heavy metal element chromium in sewage solution is detected by laser induced breakdown spectroscopy (LIBS). The spectral lines of Cr element are obtained. The calibration curve of the line intensities versus the concentrations of Cr element is acquired by experiment. Atomic lines of CrⅡ(283.43 nm) and CrⅠ(425.45 nm) are analyzed and compared. The experimental results show that the intensity of atomic emission line of CrⅡ(283.43 nm) is three times as large as that of CrⅠ(425.45 nm). The linear correlation coefficient of calibration curve and signal-to-background ratio for CrⅡ(283.43 nm) are better than those of CrⅠ(425.45 nm). The LIBS detection limit of Cr in the solution is 80 μg/mL (283.43 nm) and 170 μg/mL (425.45 nm). The calibration curve for CrⅡ(283.43 nm) has been used for quantification of Cr in sewage solution, and the concentration of Cr is found to be 333 μg/mL. This result is compared with Cr concentration obtained by atomic absorption spectrometry (309 μg/mL), and a close agreement is found. This study indicates that the atomic line of CrⅡ(283.43 nm) is better than CrⅠ(425.45 nm) for LIBS detection. The LIBS technique can be applied in the rapid detection of Cr element in sewage and has good application prospects.