Noise will be caused because of the disturbance to the transmission fiber. The Michelson fiber interferometer is used to simulate the optical fiber hydrophone, and a remote optical fiber hydrophone system is built. The reference interferometer demodulation is used to suppress the noise caused by the transmission fiber. The experimental results show that compared with the phase generated carrier (PGC) demodulation, the ability to detect acoustic signal is not reduced by using the reference interferometer demodulation. A broadband noise caused by disturbing the transmission fiber is suppressed by maximal 25 dB at 500 Hz, and the ground noise is suppressed by 17 dB at 100 Hz.

An interferometric distributed fiber optic leakage detection system based on the mixed interferometer principle of Mach-Zehnder (M-Z) and Sagnac is introduced. The working principle of the system and method for locating leaks are described. Experiments are performed in air and underwater environments. Experiments are carried out at 4025 m, 7043 m and 9050 m from the leakage position to the Faraday rotator mirror. The experiments test the impact of different environments and different leakage positions to the detection system. The experiments are carried out at 7043 m from the leakage position to Faraday rotator mirror and repeated 20 times to test the accuracy of detection system. The results show that in the underwater experiment, the interference signal spectrum strength is greater and band is wider. The farther of leakage points from the Faraday rotator mirror, the greater absolute error of the experimental results. The system can detect and locate the slight leakage signal of the gas pressure within the pipeline at 0.5 MPa, with leakage aperture of 2.5 mm, and average relative positioning error is 1.44%.

Fixing the quantity relation between the row′s and column′s size of the reconstructed image matrix is necessary in order to avoid profile distortion in a Fourier telescope; Specializing the row′s and the column′s size is necessary in order to evaluate the reconstructed results of the Fourier telescope. Based on the Fourier analysis, the unconspicuous relation between the transmitter interval and the size of the matrix is explored. Two equations are acquired by rigorously deducing, which are verified by simulation and experiment to keep image profile with no change and make the recostructed target and original matrixs have the same size.

Based on the combination of digital holography and stereo matching technology,a 3D measurement method for 3D shape reconstruction and measurement of digital holography is presented. Firstly, the off-axis Fresnel digital holography system is used, and the single off-axis Fresnel digital hologram of 3D object is obtained. And then,the digital hologram is divided into two parts,two reconstructed images are obtained after the reconsturction,and two reconstructed images exist disparity. At last, the disparity map can be achieved from the matching of two views. Based on geometric relationship, the depth information can be derived from disparity map and used to reconstruct 3D shape of the object. In the experiments,the shape of the scatter and continuous objects are measured by the proposed method, and relative accuracy depth information is derived. The validity of this method is proved by numerical simulation and initial optical experiment.

In order to realize high-precision testing of aspherical surface, the key technology for fabricating computer generated hologram (CGH) by laser-direct writing (DWL) is studied in this paper. To obtain the minimum line-width deviation, the influences of defocus and the wet-etching processes on the line-width are firstly investigated. The position errors under different line-widths are obtained by analyzing the relationship of line-width error and the position error. According to the above-obtained results, a CGH with diameter of 80 mm and the minimum line-width of 1.8 mm is successfully fabricated. Testing results show that the wavefront error is only 0.011l, achieving the l/100 level. The fabricated CGH is expected to be used in the high-precision testing of asphercal surfaces.

In common process of infrared image mosaic, using the traditional random sample consensus (RANSAC) method often takes a long time. In order to shorten the time consuming of image mosaic, a method of infrared image mosaic based on scale- invariant feature transform (SIFT) and improved RANSAC is proposed. Firstly, feature points and descriptors are obtained by SIFT algorithm. Then the wrong corresponding feature points are deleted by improved RANSAC. The image fusion is implemented, using the transformational matrix. In the improved RANSAC, we set thresholds of 0.95 and 0.85. After some iterations, we choose to jump out of the loop, reselect or calculate a new iteration number. The new number must be smaller than the old one, so the time consuming is shortened. Comparing the infrared image mosaic results with those results based on traditional RANSAC, we can find that the time consuming of proposed method is shorter.

Shearing speckle interferometry is a well known optical tool for qualitative as well as quantitative measurements of displacement components′ derivatives of engineering structures subjected either static or dynamic load. Shearing speckle interferometry, based on Mach-Zehnder interferometer, suffers from the disadvantage of low light efficiency due to the structure. A novel digital shearography set-up with two fold which can improve light efficiency for the measurement of first order derivative of out-of-plane displacement (slope) is demonstrated. There is a double aperture mask in front of the imaging lens for spatial phase shifting. Independent control of the shear and the frequency of the spatial carrier can be attained with this set-up. A shear is introduced between the two scattered fields. The double aperture which can introduce spatial carrier fringes within the speckle for spatial phase shifting is employed in this system. Phase extraction is obtained through advanced sinusoidal-fitting method, which is applied to interference patterns with a spatial carrier in the primary fringes. The experimental implementation of the set-up and the results obtained with it are presented and discussed.

Based on the method of monochromator, the spectral response of plane array CCD is tested and the uncertainty of the results is evaluated in all respects. The principle of the test method is introduced, a set of spectral testing device which uses the silicon trap as the standard detector is designed. Within the range of 400~1000 nm, the spectral characteristics of the plane array CCD is obtained, including the peak wavelength of 602 nm, the center wavelength of 580 nm and the spectral band wavelength of 402 nm. According to the spectral response at 632 nm, an uncertainty evaluation model is established to analyze all the factors that have impact on the test results, including the irradiance responsivity non- uniformity of plane array CCD, the stability of bromine tungsten lamp, the repeatability and accuracy of emitting wavelength of monochromator, as well as the stability of the image acquisition and processing system. According to the model, the combined standard uncertainty is 4.3% (k=1), which can meet the requirement of spectral response testing accuracy of plane array CCD.

Morlet wavelet, which has the good localization characteristics both in the spatial and frequency domain, is commonly used to demodulate the phase map of the fringe pattern in wavelet transform profilometry by calculating the similarity between parts of the fringe pattern and the wavelet function. The phase information can be extracted by finding out the“ridge”information of the wavelet transform coefficients. Furthermore, the reconstructed surface of the tested object is obtained by the extracted the phase information and combining the system parameters of the measurement system. However, when the wavelet “ridge” method is used to demodulate the phase map, a first-order Taylor approximation is introduced to deduce the phase analytical description of the deformed fringe from the wavelet coefficients at the“ridge”position, which causes a big phase error in the areas with high height variation rate. Aiming at the shortage of the method, an improved Morlet wavelet transform“ridge”method based on a second-order Taylor expansion is presented. The detailed phase analytical expression from the wavelet transform coefficients at the position of“ridge”is given as well. Compared with the conventional wavelet “ridge” method employing the first Taylor approximation, the improved method has higher accuracy, especially around the zone with higher height variation rate, because a correction related to the second derivative of the tested object is introduced. Computer simulations and experiments verify our analysis.

The characteristics of vertical cavity surface emitting laser (VCSEL) polarization with cholesteric liquid crystal (CLC) overlay is presented. I-P characteristics, output polarization at different pump currents and output power stability are investigated. The experimental results show that threshold current is increased by 0.35 mA comparing with alone VCSEL at the same operating temperature. Polarization state of CLC-VCSEL is greatly sensitive to input current. Stable output power has been obtained at I=1.4 mA, and effective circle polarization at the range of LCLC= 4.62~5.95 mm is also achieved.

Using the birth-and-death elements of ANSYS, the temperature field during laser deposition repair is studied while different preheating temperatures are applied to the substrate forming area and near forming area. The temperature field of TA15 titanium alloy substrate is studied at different heating distances, substrate thicknesses and shapes of the induction heater through adopting induction heating device, and the real-time temperature data of substrate is recorded with the infrared thermal imager during the heating process. The effect of different induction heating parameters on the substrate temperature field is researched. It is beneficial to real-time control of preset temperature field during laser deposition repair process.

Based on the characteristics of laser cladding bio- ceramic coatings, the two- dimensional ribbon heat source is chosen to study and calculate the physical properties of material′s change curves under different temperatures, and the temperature field model is established. The experimental and the simulated results of the prepared coatings are compared in terms of preparation of coatings results in simulative and coating appearance, micro- hardness, bonding strength with substrate and coating phase, which demonstrates the reliability of the model. According to the simulation results, the following conclusion is drawn: both of laser power and scanning speed will affect the depth of molten pool, but the influence of laser power is greater than that of scanning speed. Based on the change trend analysis of simulation, the laser cladding process parameters are P=1700 W, V=165 mm/min. The depth of molten pool under different coating thicknesses and process parameters is simulated and forecasted.

With the wide application of aluminum alloy components in various fields, its internal defects will lead to the existence that the product cannot be used properly and even causes great potential safety hazard, and therefore three-dimensional (3D) inversion of the component defects to judge the defect shape has become increasingly important. Using an aluminum alloy cylinder with the internal defect of a center hole as the research object, based on the probe perpendicular incident water immersion ultrasonic testing method, after the obtained time domain signal is transformed into frequency domain signal by Fourier transformation, and according to the signal frequency domain relationship between testing component defect position and the same location of the reference component, the frequency domain and time domain data of the scattering field amplitude by Born approximation method required for defect inversion are obtained, and the 3D inversion of internal defects is performed. The experimental results show that there exists some error between the inversion result and the actual defect, but the internal defects of the aluminum alloy component are still better inversed by the Born approximation method.

The effects of the dispersion mismatch between the reference arm and the sample arm of spectral domain optical coherence tomography (SDOCT) system on the spectral energy distribution in the spectrum of the image obtained with SDOCT are discussed. A method of numerical dispersion compensation in SDOCT is proposed, which is based on the concentration of energy in the image spectrum. It has been shown that when the percentage of energy in the low- frequency area of the spectrum is minimized, the dispersion mismatch is balanced. The plane mirror is taken as the sample in experiment to demonstrate the method, showing that the dispersion mismatch balance achieved with our method is in accordance with that by the full width at half maximum (FWHM) based method. Finally the optical cross- sectional image of a finger is obtained in vivo and the dispersion mismatch is balanced with the method. The results show that the method can effectively compensate the dispersion mismatch and improve the resolution of the images.

In order to obtain high signal-to-noise ratio (SNR) tissue images with deeper imaging depths, the laser scanning confocal technology with the near infrared (NIR) fluorescence imaging is integrated and a laser scanning confocal NIR fluorescence imaging system based on requirements of NIR fluorescence imaging is established. A laboratory mouse injected with NIR fluorescence labeling LDS925 is placed in this system and a non-confocal NIR fluorescence image and a confocal NIR fluorescence images for the tail of laboratory mouse is obtained. The experimental results show that when evaluated by the mean square error and the peak valley (PV) value, the mean square error and the PV value is 864 and 102 respectively for the non-confocal NIR fluorescence image and 1459 and 255 for the confocal NIR fluorescence image, which further shows that the laser scanning confocal technology is applicable to the NIR fluorescence imaging, and the in vivo and high SNR tissue imaging with deeper imaging depths can be achieved.

Considering the properties of its asymmetric large- area illustration, a vector design approaching for LED cyclorama light is proposed to achieve the asymmetric uniform illumination on backdrop. The total distribution light curve is calculated on the basis of the required energy distribution of the target surface and the reflective surface is designed to follow the reflectivity of distribution light curve. Specifically, the coordinates of points on the reflecting surface are calculated by combining photometrics, geometrical optics, the edge- ray principle and the Runge-Kutta method in Matlab. Besides, an illustration simulation is performed in Zemax after modeling the reflective surface in Solidworks. The simulated results indicate that the illumination uniformity meets the design requirements as well as the energy efficiency is able to reach more than 80% , which show that the design is of great relevance to applications.

To overcome the drawbacks of prism and concave gratings commonly used as dispersive devices in the traditional spectrophotometer, including low splitting efficiency, low resolution and little luminous flux, a high performance micro-spectrophotometer for biochemical analyzer (BCA) based on charge coupled devices (CCD) and virtual instrument technique is successfully developed, in which a plane grating is employed as the dispersive device, a linear CCD and a high speed peripheral component interconnect (PCI) bus data acquisition card are combined as the spectral detection system. Meanwhile, a custom-built Czerny-Turner (CT) typed monochrometer with a symmetric crossed structure is designed as the light splitting apparatus in this spectrophotometer. The experimental results demonstrate that this spectrophotometer realizes the capacity of detecting absorption intensity larger than 1000 (a.u.) in the ultra-violet and visible wavebands, the wavelength repeatability is less than 0.5 nm, the stray-light is less than 0.5% at the wavelength of 360 nm, its spectral accuracy is less than ±0.5 nm and its spectral measurement range and resolution reaches 300~800 nm and 1 nm, respectively. In addition, this system has the characteristics of post light-splitting and multi-channel parallel analysis, etc. This spectrophotometer for BCA has the potential value by virtue of optimized imaging system, high accuracy and low cost, etc.

The optical pupil filter is regarded as one of the most important devices in the manipulation of intensity distribution in the focal volume. The effect of different incident light distributions on the superresolution performance and the depth of focus (DOF) of superresolsing pupil filters are studied based on the scalar diffraction theory of light. The results indicate that there is little change of superresolution performance and DOF extension when the light with Gauss function distribution incidents compared with uniform light incidence with equal total incident light energy; little change of spot compression ratio is shown, the Strehl ratio is lower and the DOF is extended when the incident light with Gauss function distribution incidents; while for the incident light with the first order Bessel function, the spot compression ratio and the DOF decrease, the Strehl ratio gets large increase. In general, superresolution can be more easily realized with more light intensity distributed along the verge of the pupil, and the increase of either Strehl ratio or DOF is based on sacrifice of the other one.

Large aperture optical element clamping generally use the traditional organic stress- free clamping. In vacuum environment, the clamping will bring about various problems such as the organic pollution. A fixture scheme and the corresponding fixture have been designed for large plane optical element. The scheme uses the metal structure for clamping optical element directly, reduces surface machining accuracy of metal frame, achieves stress- free clamping and avoids organic pollution caused by traditional way with the optical element working at any angles. This scheme can be widely used in the large aperture optical elements clamping in optical engineering and optical experimental device.

Quantum key distribution (QKD) networks are designed to allow multi-users for a dynamically anyto-any security communication. In this paper, three quantum key distribution schemes, compatible with classical optical networks, for future HQC networks are proposed and compared. For small-to-moderate size network, the highest secret key generation rate is supported by the prepare-measure scheme and the longest security distance is offered by entanglement-based scheme. For large networks, measurement-deviceindependent QKD, which is less demanding end-user technology and offers the best key rate, is the most proper solution for a cost-effective and reliable network deployment.

Si-based optical interconnect is an important approach to solve the bottleneck of Si integrated circuits due to its high speed, high bandwidth, low power consumption, and ability to be monolithically integrated on Si. Most of the key devices for Si-based optical interconnect have already been demonstrated, except Si-based light source. In Group IV, Ge has potential application in Si-based light emitting source via proper band engineering and other treatments because of its unique pseudo-direct bandgap structure. During the past years, Si-based emitting materials and light emitters obtained significant developments. We review and summarize the most recent progress in this field, including tensile strain Ge, Ge light emitting diode on Si, Ge laser on Si, and GeSn light emitting diode. Finally, the challenges and opportunities associated with these approaches are discussed.

Group IV material based photodetectors, such as the Si/Ge and Si/GeSn photodetectors, have the advantages of lower cost, high reliability, compatibility with CMOS technology and integration with the waveguide devices. Therefore it can be widely applied in the photo detection systems. Our recent progress on the Group IV material epitaxy and the device application on photodetectors is introduced. The emphasis is on the advance of the normal-incident/waveguide Si/Ge photodetectors, SACM avanlanche photodetectors and GeSn photodetectors.

CMOS technology can be used for the fabrication of passive optical functionality, but efficient light emission and high performance light detection still require Groups III~V semiconductors. Various kinds of bonding techniques for the integration of Groups III~V semiconductors onto SOI waveguide circuits are introduced, and they can be divided into inorganic material and organic material bonding in terms of bonding materials used. Emphatically, the integrated coupling methods of InGaAs/InP photodetector on SOI circuitry and the characteristics of different coupling methods are analyzed and compared. A design of an evanescently coupled InGaAs/InP photodetector on SOI circuitry is proposed and its optical properties are simulated using finite-difference time-domain (FDTD) method and using organic material as bonding agent, the absorption efficiency of 95% is obtained. The simulation results show that the photodetector on SOI circuitry with small size exhibits low excess loss and high responsivity, which can meet the requirement of optical interconnect on chips.

Directed logic circuit is a paradigm which employs the optical switch network to perform the logical operation. The status of each switch in the optical network is determined by an electrical Boolean signal applied to it. The operation of each switch is independent of the operations of other switches in the network and the operation result propagates in the network at the speed of light. Therefore, the directed logic circuit has a very high operation speed and the overall latency of the logic circuit is very small. Silicon microring resonator is an attractive structure to construct optical directed logic owing to its outstanding performances, such as compact size, ultra-low power consumption and CMOS-compatible process. Therefore, the directed logic based on silicon microring resonators is easy to realize large-scale integration and low-cost manufacture in a CMOSphotonics foundry. Directed logic circuits based on silicon microring switches including OR/NOR, AND/NAND, XOR/XNOR, encoder, decoder and half-adder have been proposed and demonstrated by our research group. Our recent research on directed logic circuits based on silicon microring resonators is reviewed and new development in this topic is introduced.

Silicon photonics based on SOI platform provides a viable solution for photonic network-on-chips (NoCs), since its advantages in large bandwidth, low delay and power-efficient. Optical router which is used to exchange data between the processor cores is a key component for the photonic NoCs. This paper reviews the latest research progress of optical router and introduces the general principle to build N-port non-blocking optical router using microring and Mach-Zehnder switching unit. The simulated results show that the optical router constructed by this method has least number of optical switches, lowest insertion loss, and lowest average power-consumption compared with optical routers of the same size reported before.

Four kinds of wavelength division multiplexer in silicon photonics are introduced, the silicon nanowire arrayed waveguide grating and the etched diffraction grating can increase output channels easily, which fits to high count dense wavelength division multiplexer application; multi-count Mach-Zehnder inteferometer (MZI) and micro-ring wavelength division multiplexer need to be cascaded, but they can not control their wavelength and channel space easily, which fits to low count application. Meanwhile, the silicon nanowire arrayed waveguide grating and the etched diffraction grating are designed and fabricated. The crosstalk of the arrayed waveguide grating by widening the arrayed waveguide width is less than -15 dB, and the insertion loss is reduced by 3 dB using a 2D photonic crystal mirror. Besides, the related monolithic silicon photonic chips are also shown.

Silicon photonic integration has generated an outstanding interest for optical telecommunications, signal processing and for inter and intra-chip interconnects in microelectronic systems. The development of basic building blocks such as waveguides, input/output (I/O) couplers, wave-division multiplexers, modulators and photodetectors has reached such a performance level, the silicon photonics integrated circuit is now considered as an emerging challenge in the research area, because the silicon-based laser is the technical difficulty. The progress of the hybrid integrated III-V/Si lasers in recent years is reviewed, then our recent work on the hybrid integrated III-V/Si lasers is reported. A novel III-V/silicon hybrid single-mode laser is designed and fabricated by adding the micro-structure into the hybrid integrated silicon laser. The laser operates at C band, and the AlGaInAs gain structure is bonded onto a patterned silicon-on insulator wafer (Si/SiO2/Si) directly. The novel mode selection mechanism based on a periodic micro-structured silicon waveguide is applied. At room temperature, 0.85 mW and 3.5 mW output power in continuous-wave and pulse-wave regimes is obtained, respectively. The side-mode suppression ratio of 25 dB is obtained from the experiments.

A new optical frequency comb generation method has emerged using parameter four wave mixing in high quality factor Kerr micro-resonators. Due to the unique characteristics, it has broadened the application fields of the traditional solid state or nonlinear fiber femto-second laser based optical frequency combs, such as precise frequency calibration, precision spectroscopy, astronomy, waveform generation, optical storage and soliton transmission, telecommunication source and so on. In this paper, some principal theoretical modeling methods for Kerr micro-resonators based optical frequency combs are summarized and their inherent relationship is reviewed, then based on the nonlinear Lugiato-Lefever equation (LLE), a new stability analysis method is given to determine the modulation instability areas in both normal and anomalous dispersion resonators and hereby the different combs are classified. Finally the possibility of Kerr resonator with controllable feedback as an integrated multi-wavelength source is discussed and several different probably achieving methods and conditions are demonstrated.

Due to its great achievements over the last few years, silicon photonics is now a focused topic in many conferences and forums. Among the key photonic blocks, an optical modulator based on a silicon substrate is one of the most attractive issues for scientists and engineers. According to the reported state-of-art experimental results, silicon based optical modulators have perfect operation speed (no less than 50 Gbit/s), low power consumption (no more than 40 fJ/bit) and small footprint (no more than 100 mm2). Till now, the most recent tested data rate reaches 60 Gbit/s. More research and development focuse on higher energy efficiency and higher integration density, which are required by optical communication, optical interconnect and optical sensing, to build information infrastructures with ultra-large bandwidth, much high density and very-big data.

Recently, the III- V on silicon bonded lasers, as a fundamental component of complementary metal oxide semiconductor (CMOS) compatible silicon optical interconnects, have attracted great attention and been extensively studied. The metallic structure can enhance the optical confinement inside the laser resonator, increase the reflectivity at the boundary and give a large fabrication tolerance. Thus a small-volume low-powerconsumption laser can be achieved with the metallic confinement structure. The principle and experimental scheme for the III-V on silicon adhesively bonded semiconductor lasers with metal confinement are introduced, and the lasing characteristics are analyzed. Further development of hybrid laser may lay the foundation for the low-power-consumption high-bandwidth optical interconnects.