A technique for demodulating the fiber Fabry-Pérot (F-P) cavity sensor is presented based on the dual-path and dual-wavelength demodulation principle. The dual-path sensor system is constructed. Theoretical analysis, simulation calculations and experimental result of the dual-path and dual-wavelength demodulation F-P cavity sensor are presented. It is proved that the method can eliminate errors resulting from wavelength-independent variations in the fiber interconnected to the sensor. According to the known initial cavity length and reflectivity, two operating wavelengths and their bandwidths are determined by optimal parameter selection. After least square fitting, the related linear regression coefficient of the experimental result is 98.35%. The experimental results show that the method can satisfy the demands of sensitivity, response speed and stability at the same time.

Under the assumption of weakly graded, the dependences of cut-off frequency of guided modes in graded parabolic index optical fibers on refractive indexes of fiber are investigated. The eigenvalue equation and approximate formula for cut-off frequencies of guided modes are obtained by vector-field-method. A parameter γ, called “permittivity ratio”, is defined, which is a constant determined by three refractive indexes of a fiber. It is shown that the normalized cut-off frequencies depend on γ merely. Actual cut-off frequencies of a parabolic index fiber can be obtained with normalized cut-off frequencies by γ simply, and consequently the definite relations between actual frequencies and normalized ones of the graded index fibers are obtained. The curves of normalized cut-off frequencies varying with γ for several modes are displayed. It is shown that the cut-off frequencies increase with γ monotonously, and the rule of increase of HElm modes is different from that of other modes.

Clock extration experiment based on the injection mode-locking laser is conducted. 40 GHz optical clock pulses are extracted from 40 Gb/s pseudo-random codes using injection mode-locked fiber laser. In the experiment, the injection signals pass through a Mach-Zehnder (M-Z) interferometer before going into ring cavity, so that the clock component of the injection signals increases relatively and it is beneficial to clock recovery. 10 GHz clock signal with perfect waveform from 10 Gb/s pseudo-random code, and then 40 GHz clock signal is extracted is firstly obtained from 40 Gb/s pseudo-random code after multiplexing.

The design project of a diffractive-refractive hybrid acoustic lens based on binary acoustical principle is presented. In photoacoustic imaging, the diffractive-refractive hybrid acoustic lens, comparing with single acoustic lens, has many advantages including real-time imaging, long imaging focal depth, using time-delay to realize tomographic imaging and especially its achromatization merit to increase imaging resolution. It is simulated that point spread function received after point acoustic source with band width passes through the diffractive-refractive hybrid acoustic lens. Compared with that through single acoustic lens, point spread function is greatly improved in the simulated figure and the influence of axial chromatism on imaging quality is partly eliminated.

A novel three-dimensional (3-D) imaging method based on position-shift point array projection is presented. A point-array structure light is projected sequentially onto the reference plane and the object surface, and then, a pair of point-array images form. By analyzing imaging process of the both point-arrays, a mathematical model that is able to express the relationship between height of the object and the lateral displacement of point is established. Based on this model, the 3-D digital image can be calculated by computing the lateral displacement of the same point on the two point-array images. In order to fill up the lost spatial information caused by discrete processing, the point-array can be moved along both lateral and axial direction step by step to achieve high spatial resolution. Experimental results are presented to show the theoretical predictions. This method is qualified for implementing 3-D profilometry of objects with complex topology or large height discontinuities.

A new method for determining the grating parameters with the transmission spectrum and the optimized algorithm is described. In order to decrease the difference and ensure the precision of the calculation result, the symmetric-order efficiency ratio m=±1 is employed. Firstly, several points from the simulated experimental curve are selected, which is attained by adding the Gauss noises on the transmission spectrum, submit to the optimization methodNormal simple algorithm to calculation the optical parameters of the grating. The result is very near to the true value. Secondly, the volume phase holographic grating parameters are calculated with this metrology, the result is perfect, its relaive error is less than 2%. This demonstrated the reliability and the credibility of the metrology. It has some advantages such as no damage, facility of manipulation, repeat, easy generalized and low cost.

Considering pump depletion, walk-off effect, dispersion and nonlinear effect on pulses propagating inside optical fibers, amplification of intense pulse signal in fiber optical parametric amplifiers (FOPA) are numerically studied by solving the coupled nonlinear Schrdinger equations with split-step Fourier method. Calculation results showed that, except amplitude amplification and temporal width broadening, a very interesting phenomenon occurred that is one signal pulse splitting into two sub-pulses. Further, even if in the case of continous wave pumped, walk-off does have distinct effect on the amplification of strong pulse signal, leading to amplitude difference for two sub-pulses and pulse shift. At last, the unique strong pulse signal amplification characteristics are finely explained by saturated gain properties of FOPA, and the potential applications of pulse splitting phenomenon in pulse compression, signal sampling and time-division multiplex system are pointed out as well.

In order to obtain the droplet diameter and spatial distribution and velocity of gas-liquid flow, interferometric laser imaging droplet sizing technique (ILIDS) is studied. ILIDS is a novel planar measurement technique for droplet size and velocity vector for spray measurement that has high precision for droplet sizing and localizing. An automatic analysis method, which bases on image convolution localizing, Fourier transform and concise cross correlation algorithm, is developed for obtaining droplets' diameters and velocity of spray by using PIV setup. The method is experimentally tested on the water spray generated by an injector, and the different region of the spray is measured. The velocity field obtained by the method is calibrated by the normal particle image velocimetry (PIV) method, the result shows that the difference between velocity vector by two methods is only 0.38%.

It is proposed and demonstrated that the fiber-optic Mach-Zehnder (M-Z) interferometer measures accurately the electro-optic (EO) coefficients of, not only the polymer thin film, but also the polymer waveguide. Furthermore, the tensor components, r13 and r33, of EO coefficient can be measured simultaneously. In contrast with the free space M-Z interferometer, the fiber-optic M-Z interferometer has some advantages, such as compact devices, simple experimental configuration, easy operation, and good stability. The outstanding advantage is that the second electrode need not be fabricated on the top of the polymer thin film. So, the measurement system is especially suitable to measure EO coefficients of the polymer samples on trial. In the measurement system, the interference output is fed back and controls the phase bias of the interferometer to decrease the requirement of the environmental stability and increase the measurement precision. The EO coefficient measurements of the PMMA-DR1 sample are r13=8.3 pm/V and r33=25.7 pm/V.

A kind of dynamic tracking system for conducting high-precious measurement of transparent liquid concentration is designed. In accordance with the relations between liquid concentration and refractive index as well as the relations among refractive index, interference light wavelength of optical-fiber Fabry-Pérot (F-P) interferometer and grade orders, the liquid concentration variable quantity is obtained by measuring the variable quantity of fringe interference order. In this system, light source is He-Ne laser. Wavelength is 632.8 nm. Output poweris 2 mW. Reflectance of interference cavities is 0.90～0.95, the plane degrees of two reflective surfaces are 1/20～1/100 wavelength, and their parallel degrees are 1/10～1/20 wavelength. Linear charge coupled device (CCD) receives interference frings. When the output signals by linear CCD are processed in two-valuation, the threshold floating measures adopted can eliminate measurement error. The detecting system can recognize or detect concentration variations of 0.01% via measuring a group of alcohol.

A novel data processing method for demodulating the information from the interference spectrum of a white light extrinsic Fabry-Prot interferometer (EFPI) sensor system is presented. In the white light EFPI sensor system, an 850 nm LED is used as the broadband light source and a HR2000 high resolution miniature spectrometer is used to measure the interference spectrum. Through tracing a special peak point in the interference spectrum, the air gap value of the EFPI sensor can be demodulated. The order ambiguity problem of single peak tracing method is solved through the application of BP neural networks. As the BP neural networks can distinguish the interference orders of the peaks in the interference spectrum, many peaks can be traced continuously. Both high precision and large dynamic range are achieved. The data processing method is demonstrated on a white light EFPI strain sensor system. 0.1 με precision and 500 με measurement range are achieved with this system.

Using a new poly(vinylidene fluoride) (PVDF) piezoelectricity gauge, the real-time measurement of pressure of the laser-induced shock wave is realized. The attenuation of peak pressure of the laser-induced shock wave in aluminum is an exponential function. Laser-induced shock waves on surface of aluminum targets different in confining materials are observed, and the effects of different confining materials are studied. At last, the 7050-T7451 aerial aluminum alloy material is shock-strengthened by laser shock-strengthening processing (LSP) technique with the device which is developed by authors, and the residual compressive stress and dislocation density of LSP area are tested, the test results show that test piece will have very high residual compressive stress after LSP, the residual compressive stress can exceed -200 MPa. There is a distinct increase in the dislocation density of aluminum alloy, the fatigue life is improved by 175%～428%. These experiments have guide meaning to the practical engineering applications of LSP technique.

The maximal visual range of low light level (LLL) imaging apparatus is a basic guideline in system's design. Based on the early work, the visual range equation of LLL imaging system has been summarized. The laser aids system is used in order to improve its watching ability in bad weather. If so, there would be changed in the equation of visual range, especially the spectral matching factor. What's more, the illumination, contrast, reflectivity and so on would be changed. The changes about these factors after the adding of the laser are discussed, which can help choosing the lasers. The visual range of the super second generation image intensifiers under the laser aids is estimated, which proved the laser (λ=850 nm) is reasonable.

In order to study the optical properties which are sensitive to the lattice structures for the PbWO4 (PWO) crystal, the electronic structure, dielectric function, complex refractive index and absorption spectra of the perfect scheelite- and raspite-structured PWO crystal have been calculated using linearized augmented plane wave+local obitals (LAPW+lo) method. The peaks of the absorption spectra corresponding to electronic transition and polarization of optical properties have been studied. The optical properties of PWO occur anisotropy. It may be caused by the anisotropy of lattice structure of PWO crystal. The differences of physical property between raspite-structured PWO and scheelite-structured PWO are remarkable. This indicates that the physical properties of PWO crystal are sensitive to the lattice structures. The calculated results provide a theoretical base for further studying the relationship between the optical properties and structures.

Calculation of reflectivities is foundation of computer simulation of X-ray rocking curve. The effect of HgCdTe composition ununiformity on X-ray reflectivities is studied. The results show that X-ray reflectivity rocking curves of HgCdTe materials are affected by transverse composition ununiformity. As composition ununiformity increases, peak value and full width at half maximum (FWHM) of X-ray reflectivity decrease and increase respectively in the exponential function of mean square deviation of composition ununiformity, but a integral reflectivities keep constant. The X-ray reflectivities of HgCdTe materials with a longitudinal linear composition gradient are calculated by using multilayer model. It is found that reflectivity peak values decrease and FWHM of the reflectivities increases as the increase of composition gradients. Besides of these, longitudinal composition gradients will induce some interference peaks at single side of the reflectivity curves. The interference wavelengths increase with the increase of composition gradient. And variation of interference wavelengths with interference period number also increases.

ZnO thin films were grown on Si(111) substrates by pulsed laser deposition (PLD). The optical properties of the films were studied by photoluminescence (PL) spectra using a 325 nm He-Cd laser. The structural and morphological properties of the films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements, respectively. Through controlling those growth paramters, oxygen pressure, laser repetition rate, growth temperature and laser intensity, their influence on the characteristics of light emission of the ZnO thin films was studied. The optimized parameters were obtained. ZnO films with narrow full width at half maximum (FWHM) and strong ultraviolet (UV) PL peaks were acquired under conditions of about 650 ℃, 50 Pa and 5 Hz. Further more, it was suggested that UV PL peaks were due to excitonics combination, the green bands were due to the replacing of Zn in the crystal lattice for O and the blue bands were due to the O vacancies.

Laser cooling of solid material is also called anti-Stokes fluorescent cooling, and it is a developing all-optical cooling technology in recent years. The key question of this cooling technique is to choose suitable materials. Taking Tm3+ ion as an example, relationship between the minimum energy gap and the laser pumping rate is analyzed, and the relationship between the energy gap and the cooling power as well as the relationship between the energy gap and the heat-light converting efficiency under the different pumping rate is studied, then the relationship between the optimal heat-light converting efficiency and the pumping rate is obtained. It is found that energy gap required in the cooling cycle should be at least 4500 cm-1. It is more appropriate to choose the energy gap at 5000～6000 cm-1. Finally, the feasibility of laser cooling of thulium-doped material and the choice of host material are briefly discussed.

The linear absorption, single-photon fluorescence and three-photon absorption properties of two novel fluorene-based derivatives (4-(7-(4-(dimethylamino) phenyl)-9, 9-bis (2-ethylhexyl)-9H-fluorenee-2-yl)-N, N-dimethylbenzenamine (abbreviated as B(DMAP)F) and 4-(2-(7-(4-aminostyryl)-9, 9-bis(2-ethylhexyl)-9H-fluoren-2-yl) vinyl) benzenamino (abbreviated as BASF) with D-π-D structural motifs were reported in THF and DMF solvents. The results show that the absorption peaks and emission peaks of two compounds all have red shift induced by solvent effect. It was found that the three-photon absorption cross-section becomes larger in the more polarity solvent and maximal cross-section is in the order of 10-76 cm6 s2. Large optical power limiting induced by three-photon absorption has also been demonstrated for both dyes. When the incident irradiance reaches 8 GW/cm2, the limiting nonlinear transmissions of B(DMAP)F and BASF can reach 35% and 39%, respectively.

Three kinds of polymeric films with different rigidity, poly (methyl methacrylate) (PMMA), poly (N-vinylcarbazole) (PVK) and polystyrene (PS), which were doped with same concentration (mass fraction 0.003) of azo-dye 4'-[[2-(acryloyloxy)ethyl]ethylamino]-2-chloro-4-nitroazobenzene (disperse red 13, DR13), were prepared. The photoinduced birefringence effect of these three kinds of samples were studied by using a linearly polarized control beam from an Ar+ laser (514 nm) and a linearly polarized probe beam from a He-Ne laser (632.8 nm). It was found that under the same control beam power (15 mW) and with the same sample’s thickness, the PVK with large matrix rigidity showed small birefringence effect while polystyrene with small matrix rigidity showed large birefringence effect. Based on the four-energy-level model of photoisomerization of azo chromophores, a phenomenological model, in which a parameter s was introduced to describe the rigidity of polymer matrices, was presented to simulate the photoisomerization and orientation of the azo chromophores in polymeric matrices with different rigidity. The influence of the matrix rigidity parameter s on the photoinduced anisotropy of the azo-dye containing samples was investigated by numerical calculation. The computed results showed that large rigidity samples present small birefringence effect and the experimental results could be explained qualitatively by the theoretical simulation results.

Electric field applied to silicon, which is a kind of centrosymmetric materials, induces effective even-order nonlinear susceptibilities for silicon due to the vanishing of its inversion symmetry. The tensors of effective second-order susceptibilities of silicon are systematically studied according to the theories of χ(2)eff=χ(3)·E and tensor transformation when the directions of the applied electric fields or the built-in fields in the bulk of silicon crystal are along the crystal orientations of [111], [110] and [001], respectively. The results show that the forms of effective second-order susceptibilities agree with those of point groups of C3v, C2v and C4v, respectively, which indicates that silicon single crystal should belong to C3v, C2v or C4v group instead of Oh group under corresponding electric field, and thus, it should possess second-order nonlinear optical properties corresponding to related symmetric crystal. Also, a general deduction of χ(2)eff for silicon under an arbitrary applied electric field E is proposed, which can provide theoretical fundamentals for electric field-induced second-order nonlinear optical experiments of silicon and for those of other centrosymmetric materials.

It has been proved by experiments that multi-level optical storage can be achieved by photochromic media. A theoretical model of optical crosstalk in photochromic multi-level storage is proposed, which is the basic of compensation and equalization in subsequent electrical system. This model is based on the normalized coordinates presented by Hopkins in the classical scalar diffraction theory and the superposition of Fourier optics and photochromic marks. The results of numerical simulation show that the crosstalk will decrease if the center distance increases, hence the crosstalk of adjacent track could be neglected if no track error. The cross term of the adjacent mark and unwritten disk is the main component of crosstalk. The crosstalk rate is approximately a proportion function of writing power, that is, crosstalk caused by high level photochromic mark is much higher than low level one. The experiment has well certified the theoretical model.

Based on the objective lens and voice coil motor of the current DVD pickup head,according to photobleaching three-dimensional (3D) optical information storage's theory of two-photon absorption,the Ti∶sapphire femtosecond pulse laser was used as written optical beam and reading optical beam of two-photon three-dimensional optical storage voice coil motor was carried through multiplayer choice, and the storage and readout experimental study of binary format code with two-photon photobleaching in the new photobleaching material consisting of stilbene derivant was conducted. Three layers optical data storage was realized,the two adjacent bits distance in each layer was 4 μm and the two adjacent layers interval was 15 μm. The signal intensity of the written information was readout and identified with Matlab software,and the identified result matchesd with the written binary format code。The experiment proved that proceeding two-photon three-dimensional optical data storage with DVD pickup head was feasible, which indicated that two-photon photobleaching technology combined with the current CD/DVD and provided a base for realization of high density and super high density optical data storage.

Based on the quantum-confined Stark effect, a novel multimode interference 1×3 splitter incorporated with functions of electroabsorption modulator is proposed. The operating principle of the devices is analyzed in detail. On the basis of predefined ridge waveguide parameters which are length of 275 μm, width of 10 μm and thickness of 0.2 μm, a GaAs/AlGaAs multiple quantum well multimode interference 1×3 splitter is fabricated, coplanar waveguide structure is applied for electrode. The wave propagation characteristics of the splitter are numerically simulated by the finite difference beam propagation method and experimentally investigated. The static modulation characteristic of the device is also tested. When the applied direct current voltage is 3 V, Gauss beam with wavelength of 0.86 μm is symmetrically incident to the center of multimode waveguide, electroabsorption modulation depth is upto 90%, and bandwidth is 2 GHz.

To achieve high quantum efficiency and good stability has been a main direction to develop GaAs photocathode recently. For a molecular beam epitaxy grown, (100) wafer, Be doping and 1 μm thickness reflection-mode GaAs emission layer, a new-type gradient doping structure, in which from GaAs bulk to surface doping concentrations are distributed gradiently from 1×1019 cm-3 to 1×1018 cm-3, was designed. And the new-type GaAs emission layer was prepared into photocathode by (Cs,O) activation technique. The spectral response curves show that compared to common uniform doping GaAs photocathode, the quantum efficiency of gradient doping GaAs photocathode is increased within whole response waveband, with integral sensitivity of 1580 μA/lm, and the photocathode also behaves more stable, which proved that the new-type gradient doping structure is executable and practical, has great potential, and the development of it provides an important approach to development of the national GaAs photocathode with high performance. The inherent reasons why the new-type GaAs photocathode obtained higher quantum efficiency were also discussed.

The finite-difference time-domain (FDTD) method is developed for analyzing the photonic crystals in the non-inertial frame. The difference equations and the perfectly matched layer absorbing boundary condition equations in the non-inertial frame are given. Designing a photonic crystal structure with a ring cavity and a directional coupler. The length of directional coupler is 43a, which keep the high quality factor and necessary frequency resolution. The theoretical results indicate that there is frequency tolerance between wave propagating along the clockwise and counter-clockwise in the ring cavity. The frequency tolerance depends on the rotational speed.

The filtering and tuning properties of birefringent laser crystal are theoretically investigated. Using a matrix method and the given reflectance, transmittance coefficients in Refs.[12~14] by author, Fresnel coefficients on two boundary surfaces of filter plate are found. Using phase shift formulas and the ray tracing formulas, the accurate phase shift of filter can be calculated from incident angle and azimuth of optical axis. The Fresnel coefficients and accurate phase shift formulas of birefregent filter are used on the Jones-vector formalism and the eigenfunction of transmittance is obtained. The eigevalue is the transmittance of the waveplate. And the main filtering properties, in particular the transmission bandwidth, are deduced. The influences of the system parameters (incident angle, azimuth of optical axis and thickness of filter) on the filtering properties are discussed. Tuning properties are discussed using the accurate phase shift formulas. Finally optimum value of the parameters are derived. The optimum parameters are that thickness is about 1500～2000 μm, azimuth  is greater than 45° for quartz filter, number of round trips r is as big as possible lager, and incident angle is small as gain of laser is larger.

Colloidal TiO2 was prepared by hydrolyzing tetra-n-butyl titanate. PSS/TiO2 composite films were fabricated through the electrostatic self-assembly multilayer process. Both the colloidal TiO2 and the composite films were characterized with a UV-vis spectrophotometer and a fluorescence spectrophotometer respectively. The ultraviolet-visible absorption spectrum of the colloidal TiO2 shows that the absorption onset shifts to blue and that quantum size effect can be observed. The photoluminescent spectrum of the colloid shows that the shortest luminescence wavelength is 371 nm and that the photoluminescence is within the blue part of the spectrum. The photoluminescence behavior of the PSS/TiO2 composite film is similar to that of colloidal TiO2, and the luminescence of thin films mainly results from TiO2. However, PSS in the films has some influence on the photoluminescence behavior of the films.

High efficiency CsI∶Tl crystal is used as X-ray converter in the detection system. The response characteristic of CsI∶Tl crystal to X-ray is very important in precision image processing. It is difficult to obtain a stabile H-D curve of X-ray film because of some uncontrollable factors in its processing. The response of CsI∶Tl crystal to X-ray has been theoretically proved to be linear. Some experiments on the 60Co X-ray source are performed to prove the linear of the response and the quantificational H-D curves of the CsI∶Tl crystal with different width are obtained. These H-D curves definitely show that the response is linear and that the linearity is very good. The linearity of less 0.15% is obtained from the experiment. This solves some unconquerable problems such as obtaining a stable, repetitive H-D curve which have existed for a long time in a X-ray film system.

A method of selecting and confirming materials with W and B4C for X-ray broadband multilayer film is presented. The minimum bilayers number of X-ray broadband multilayer film has been confirmed by using BERNING formula at the wavelength 0.154 nm. After introducing the suitable merit function, a broad angular broadband W/B4C multilayer film has been designed successfully by using genetic algorithm. The flat reflectance of broadband multilayer film is 40% in the wavelength 0.154 nm at the grazing incidence angel (θ) of 0.5°～0.9°. The multilayer film has been fabricated on the magnetron sputtering system. A flat relative reflectance spectrum curve has been measured at the grazing incidence angle (2θ) of 1.0°～1.8° by X-ray diffractometer.

Low power X-ray source and high count rate detector system are used to measure the space distribution of X-rays with different energies in the beam focused by the monolithic polycapillary X-ray lens, and the energy dependence of the focal spot size and transmission efficiency of the lens. The “halo” phenomenon can result in the increase of focal spot size and the measured transmission efficiency with higher energies. The focal spot size decreases with the increase of the energies. The transmission efficiency of the 04-5-10-5 lens increases with higher energies below about 5.8 keV and decreases with higher energies above about 5.8 keV. The axial scanning method is devised to find the energy function of the output focal distance. The output focal distance of the lens increases with the increase of the energies.