Based on wave radiation transmission theory in random medium and Monte-Carlo method,the transmission characteristic of external mixture of aerosol which is composed of water soluble and soot with lognormal distribution is studied.The dependence of extinction coefficients of urban aerosol on incident wavelength is numerically simulated,which is compared with reference data.The accuracy of the discrete sampling Monte-Carlo simulation method is proved.The effect of incident wavelength,the cosine of incident angle,and optical thickness on the transmittance and reflectivity of laser in mixture aerosol is analyzed.Comparison is given between the external mixtures of aerosol with different mixing ratio.The numerical results show that the decrease of wavelength will lead to reduce transmission characteristic of external mixture aerosols and increase reflectivity.And the total transmission characteristic of external mixture aerosol is sensitive to its composition.

Based on the fact that the light from laser diode is partially coherent,a novel theoretical model is proposed using partially coherent light theory.This model can describe the close relation between the parameters of diode laser and its far-field.The different experimental far-field distribution patterns of laser diodes also can be well described by this model.This work provides a theoretical basis for the studying the laser diode output beam characteristics and its beam shaping technology.

A system of phase stabilized distribution of millimeter wave local oscillator is proposed,which is based on the principle of Michelson interferometer.In the system,the signal phase drift during transition is modulated on the reflected optical signal,which is later coherent heterodyne with reference signal to control the fiber stretcher.Then system phase can be corrected and the phase of output millimeter wave can keep stable.Based on the theoretical model and experimental system,the relationship of phase drift of local oscillator,the length drift of optical fiber and coherent heterodyne output signal are measured.The experimental results agree with the theoretical model,which indicates that the proposed system is feasible.

The resonant wavelength of long-period fiber grating (LPFG) coated with sensitive film,whose refractive index varies with the surrounding medium,changes with the film refractive index.When the coupling strength of LPFG with non-absorbing film coating is π/2,the loss peak corresponding to the resonance wavelength gets to zero.However,it is not the case for the LPFG coated with complex refractive index film.When the coupling strength of LPFG with complex refractive index film is π/2,the loss peak is not zero.While the resonant wavelength is sensitive to the film refractive index,imaginary part of propagation constant of clad mode becomes larger,which causes reduction or even disappearance of the loss peak.It is not conducive to the measurement of resonant wavelength.Analytical solution of the value of the loss peak is obtained by solving the coupled-mode equations for LPFG with complex refractive index film.The condition under which loss peak gets to zero is found.Designing LPFG according this principle,the unfavorable factor mentioned above can be effectively avoided.

The available resources of fiber bragg grating (FBG) sensor network is extremely rich in the frequency and time domain.A network employing single multiplexing technology can only use the resources on the one hand and the utilization ratio of network resources is low.In order to improve the efficiency of sensor network,a new type of FBG sensor network based on wavelength-division multiplexing/time-division multiplexing (WDM/TDM) techniques is designed.The fiber bandwidth is employed to WDM with arrayed waveguide grating (AWG),and then to TDM on each WDM channel.The analysis results show that the system performance is affected by shot noise and crosstalk.Making full use of optical wavelength and time domain information,the system shows the potentialities of interrogating and demodulating signals from several hundreds of FBG sensors.The sensor network can achieve a large capacity,increase bandwidth utilization ratio,reduce costs and have a good application prospects in the future.

An in-line all-fiber etalon,formed by a self-enclosed Fabry-Pérot (F-P) cavity inside an optical fiber fabricated by using 157 nm laser micromachining,is demonstrated.The strain and temperature characteristics of the etalon sensor are investigated.The results show that the strain sensitivity is 1 mrad/μm and 5.2 pm/μm,and the linearity is 99.92% with two fixed point at a distance of 1 m.Furthermore,the temperature sensitivity is 0.13 mrad/℃ and 0.64 pm/℃ at the range of 18 ℃ to 500 ℃.Experimental results show that the etalon can meet versatile applications for stain measurement because of its perfect sensor characteristics,such as excellent interferometric fringe contrast of up to 30 dB,low thermal cross-sensitivity,great potential to realize mass-production,low cost,and super capability to operate in harsh environments.

The feasibility for the applying of multimode fiber (MMF) in the future long haul,high bit-rate,and large capacity PON is analyzed,and the strengths and weakness of MMF are summarized.Then,initiating from the waveguide theory in the weakly guiding fiber and neglecting the intra-modal dispersion as well as nonlinearity,a simple model for multimode fiber is built,based on which analysis,research and comparison through simulation experiments on some performance improving techniques of MMF are made:offset launching,mode size changing,ring launching and feedback equalization.The simulation results demonstrated that the combination of field shaping (mainly ring launching) and feedback equalization can obviously improve the transmission properties of MMF,because of which,the 10 Gb/s data can travel in the MMF for more than 1 km.

High temperature fast annealing behavior of CO2 laser pulse induced long-period fiber grating (LPFG) in an endless single-mode photonic crystal fiber (ESM-PCF) was studied.The experiment shows that the turning temperature is about 600 ℃.When the annealing temperature is lower than 600 ℃,the annealed ESM-PCF LPFG′s temperature resporse and tensile strain response are both unstable when the ambient temperature is lower than the anneaing temperature.And both the linearity and the repeatability of the responses are poor.When the annealing temperature is between 600 ℃ and 700 ℃,the annealed ESM-PCF LPFG′s temperaure response and tensile strain response are both stable with good linearity and repeatability when the ambient temperature is lower then the annealing temperature.When the temperature goes higher,the grating will be gradually and partly erased.This can be explained by the releasing stress induced in the grating writing process and fused silica structure change when heated.

The filtering demodulation is realized by using the good linear sideband near 1530 nm of the super-fluorescent fiber source.The light source of system adopts double-pass backward configuration,because the detecting sensitivity of light source decides the whole system′s sensitivity.When the linear sideband is 2.5 nm,the sensitivity of power is -14.7 μW/nm,and the degree of fitting is 0.9995.The system uses all-optical structure to improve the demodulation speed.By the way of computer simulation,its detection sensitivity for the wavelength and strain separately are -1.27 pm/mV and 1.06 με.The results show that this demodulation system has high sensitivity,good stability,quick demodulation speed,and it can realize real-time detection of seismic wave.

After deterministic error compensation,various random noises become the main error sources of fiber optic gyro (FOG).To reduce the random errors of FOG,the denoising method based on wavelet packet filtering is studied,including the principle of wavelet packet filtering and the selection of threshold and thresholding operator,which is modified.The Allan variance method and power spectrum density (PSD) are adopted to analyze the random error characteristics before and after filtering,and the theoretical analysis of filtering effect can be realized.At last,simulation is carried out based on the drift data of FOG VG951,it is proved that the proposed method can decrease the random error of FOG effectively.

Ad Hoc network technology can significantly extend the effective range of ultraviolet scattering communication.So it is important to discuss the coverage of communication nodes.Based on solar-blind ultraviolet (200-280 nm) communication features and the inherent characteristics of Ad Hoc network,three types of UV non-line-of-sight (NLOS) communication system are analyzed.Atmosphere transmission attenuation,effective scattering volume and received power in single scattering channel are discussed.The node communication distance is calculated and the coverage model of a UV communication network node is established according to the different focal angles of transmitter and receiver.At last,the formulas and calculation method of the coverage area are given.

Both theoretical and experimental researches on light-emitting diode (LED)-based digital holography are carried out.The propagation of the mutual intensity of the system is investigated under the premise that the LED is spatially incoherent and temporally quasi-coherent.A simple formula describing holographic fringe formation process with partially coherent illumination is found.The formula shows that the hologram fringe formation process can be presented as a linear space-invariant filtering operation.The filtering operation suppresses speckle noises and is also expected to experience a loss of resolution.The bandwidth of the filter is determined by the bandwidth of the secondary light source as well as diffraction distances of the object.Some methods are proposed to improve the resolution according to the theoretical analysis.Corresponding experiments are conducted and the results demonstrate the validity of the theoretical analysis.

In order to overcome the discontinuous phase unwrapping in three-dimensional (3D) shape measurements of discontinuous objects and improve measurement precision,a two-dimensional Gabor wavelet transform profilometry(2D-WTP) using a grid fringe pattern is presented.Compared with the profilometry using one-dimensional single frequency fringe pattern,double measurement informations can be obtained from the method and they can reach the same precision.It is unnecessary to utilize bandpass filters in the method for extracting two modulation phases from the grid fringe pattern.Through detecting the ridge,two wrapped phases along the x- and y- axis directions are directly extracted using 2D Gabor wavelet transform from the deformed grid fringe pattern respectively,and the corresponding unwrapped phases are obtained by use of a lookup table method.The detailed theoretical analysis is given and the experimental results show that the above method is valid.

In order to improve the precision of the space target optical characteristic calculation method,a verification and validation method for parameters of optical characteristic calculation model based on the target scale-model experiments is proposed.Firstly,the main influencing factors of the optical characteristics are analyzed,and the verification and validation scheme of the calculation model is proposed.Secondly,the experimental system is designed and the optical characteristics of two kind of targets are gained.Finally,the verification and validation algorithm is built up and parameters of the target surface materials and the geometryical construction are verified and validated step by step.It is showed that the results gained by the calculation model after verification and validation are close to the experimental results statistically.This verification and validation method can meet the requirement of short-range optical navigation.

Low-coherence dynamic light scattering (DLS) technique can be used to obtain dynamic characteristics of particles from dense suspensions,in which the multiple scattered light can be effectively suppressed by use of low-coherence interferometer.Based on the single-scattering theory,the measurement region is usually limited to the vicinity of solid-liquid interface.Influences of wall-drag effect close to the interface on particle sizing in low-coherence DLS are investigated.Particle sizes are measured for polystyrene latex particles volume fraction of 10％ with different radii using the phase modulated low-coherence dynamic light scattering measurement.The results are corrected by considering wall drag effects.It is found that the measured values of particle radii agree to the given values for different samples with the standard deviations within 5％ in the region of 10-30 μm close to the interface.As a result,considering the wall-drag effect close to the interface,the accurate particle size information can be obtained near the interface region in the path-length resolved measurement of low-coherence DLS.

A fiber gas sensing system using hollow-core photonic crystal fiber (HC-PCF) as gas cell is introduced.The gas cell is made by a HC-PCF with length of 40 cm and core diameter of 20 μm.The HC-PCF is connected with a single mode fiber (SMF) by a connector.There is a 50 μm gap on the connector,from which the environmental gas can diffuse into HC-PCF cell.Combining with wavelength tunable fiber ring laser technology,a compact and a real all-optical-fiber gas sensing system is proposed.Because of the characteristic of high power and narrow wavelength width of the probing light emitting from the fiber ring laser the system can detect gas with high sensing selectivity and thus the cross-effects usually encountered in the ordinary gas sensing method are reduced greatly.The properties of the system are demonstrated experimentally by detection of acetylene (C2H2).The experimental results demonstrate that the time for acetylene diffusing into the proposed HC-PCF gas chamber is proximately 6 min under natural free diffusion conditions.Approximate linear relation between the system responses and the acetylene volume fraction are experimentally demonstrated and the minimal detectable volume fraction of acetylene of 0.1% is also achieved by experiments.

A typical infrared detection system [Ritchey-Chretien (R-C) system] and its baffles are designed.Its structure model is established with the TracePro software.Stray lights caused by thermal radiation of critical inner surface are analyzed by a ray tracing program.The relation of photons of stray lights and temperature which varies from 250 K to 320 K is given.The stray light caused by sky background is calculated.The curve of increasing rate of photon number of stray lights received by single pixel versus temperature is given.The results show that an open telescope without main tube cannot do well obviously in reducing stray lights.The temperature of the inner baffle of main mirror should be less than 230 K in order to detect the background-limited target.

A new method to measure the refractive index and the inclination of the sample in collection-mode scanning near-field optical microscope is presented.In this method,the illumination intensity is controlled by a feedback loop,the vertical vibrating tip scans the sample with a constant distance and the sample is illuminated by two symmetry light beams.Altering of the illumination intensity and the sampling of the local intensity are controlled by digital signal processing to be synchronized with the vibration of the tip.A group of extreme values of the tunneling light are obtained in one oscillation period.In another oscillation period,changing of any illumination beam will modify the near field distribution.Then,another group of extreme values of the tunneling light will be obtained.The refractive index and the angle of inclination of the object can be computed from groups of extreme values that obtained from multi-oscillation periods.Grating as well as erythrocytes membrane was analyzed in our experiment.Topography images of the grating produced by our prototype instrument are shown to have a lateral resolution better than 400 nm.As for the erythrocytes membranes,the refractive index of it is about 1.4.It can be concluded that this method could not only measure samples′ refractive index effectively but also offer a new approach to rebuild samples′ topography image using optical information.

A reliable design and optimization of laser diode end-pumped Yb:YAG disk pulsed laser with high peak power and high efficiency is investigated.Based on discussion of the energy storage and extraction in the gain medium firstly,and theoretical analysis and modeling the gain performance and thermal effects of gain medium,the process of the amplifier gain medium design and optimization is discussed and analyzed systematically.According to the analysis,a resultant laser amplifier with high peak pulse power and high efficiency is obtained,which is able to suppress sufficiently the parasitic oscillation and thermal effects.

The influence of laser-conditioning scanning process on the damage threshold and the initiating defects of ZrO2-SiO2 1064 nm high reflective (HR) coatings is analyzed.The changes of initiating defects in films are investigated before and after laser-conditioning scanning process based on that defects damage and density are used to characterize the initiating defects.The relation between the laser-conditioning energy density and the laser-conditioning effect is also investigated.It is found that the defects with lower threshold can be removed by laser-conditioning process.However,the defects with higher threshold can be transformed to defects with lower threshold when the scanning energy density is higher.So the laser energy density used in the laser-conditioning scanning process should be relatively lower.

New dither parameters which consist of K coefficient and the noise intensity in the dither amplitude are proposed to replace the traditional ones which consist of oscillating bias amplitude and the noise intensity in the dither drive signal.The improvement provides a same criteria for laser gyros with different dither frequencies and injecting efficiencies to compare with each other.The effects of ditker parameters such as K coefficient and the noise intensity in the dither amplitude on the null-shift stability and the angle random walk of dithered laser gyro are disscussed in detail.Experiments show that the null-shift stability and the angle random walk can be reduced to a minimum and the laser gyro works in good condition when K choose the value between 600 and 650,and the noise intensity in the dither amplitude choose the value between two and three percent.

In high-low temperature experiments,the null shift of the four-mode laser gyro whose beam intensity is stablely controlled in two different modes is very different.The null shift vibrates in one mode but changes linearly with temperature in the other one.Aiming at this phenomenon,through the analysis based on the basic theory,the physical reason that the differential lose null shift and the constant magnetism biasing null shift change differently with temperature in different modes is found.If using temperature compensation to improve the precision of the four-mode laser gyro,the coefficient must be gotten in the same mode which is selected by actual use.

When operating at a high-power region,thermal lens effect of diode pump solid state laser is an important factor which must be considered to optimize the laser system.The Nd:YVO4 crystal is pumped by a fiber-coupled laser diode which is shaped and focused by a lens group.The focal length of thermal lens is measured by using stable cavity method.The mode distribution of three thermal stable resonators with the thermal focal length is simulated by LAS-CAD software.By using this results the LD dual-end-pumped Nd:YVO4 laser Z-folded resonator has been optimized,with total reflection mirror radius of curvature R1=300 mm,and output coupling mirror radius of curvature R2=100 mm,with length of the resonator Ltotal=280 mm,and transmisttance of the output coupling mirror T=50%.CW TEM00 mode output is 21.3 W when the pump power is 61 W,and beam quality factor M2 is less than 1.41.The experimental results on laser output characteristics are in good agreement with the theoretical ones.

A 3.09 W sodium guidestar laser with the sum frequency generation efficiency more than 35% is reported.The laser is based on the periodically poled stoichiometric lithium tantalite(PPSLT) crystal quasi-phase-matched sum frequency generation.Two acousto-optical (AO) Q-switched diode pumped Nd:YAG lasers of 1064 nm and 1319 nm are used as the fundamental-frequency lasers.To get the narrow linewidth output,the etalons with well temperature controlling are inserted into the cavities.The sodium guidestar laser is generated through an external-cavity quasi-phase-matched sum frequency PPSLT crystal.When the total power of 1064 nm and 1319 nm is 8.80 W,the output sodium guidestar laser′s power is 3.09 W with the highest sum frequency generation efficiency at the matching temperature of 68 ℃.The repetition frequency of the laser is 800 Hz and the width of pulse is about 60 ns.The linewidth is about 1.6 GHz.The central wavelength is locked to sodium D2a line 589.1591 nm (error less than ±0.2 pm) by tuning the angle and the temperature of the etalons.

The repair of the helicopter turbine oriented implement leaf blade was investigated by employing the laser repair technology.The fourth turbine oriented implement leaf blade of a helicopter and the Ni-base alloy were utilized as the substrate and layer cladding material,respectively.The surface figuration,microhardness and microstructure of the cladding layer were studied under laser power of 1-2 kW,scan velocity of 2-15 mm/s,facula diameter of 1-3 mm and thickness of 0.2-0.6 mm.The rigidity analysis,scanning electron microscope (SEM) observations and the macroscopical modality of the repaired leaf blade indicate that laser cladding layers of close organization and good metallurgy union were obtained.Therefore,it is feasible to employ the laser modification technology to repair the turbine oriented implement leaf blade shattered.

Covariance matrix is an excellent objet descriptor which can fuse multiple features and provide a global optimal resolution.Unfortunaely,it is hard for traditional covariance matching to track target when severe occlusion occurres.Further more,more similar background′s disturbances may be introduced by global search.In order to improve the performance of covariance tracking,a covariance tracking algorithm based on forgetting factor and Kalman filter is proposed.Multiple features can be skillfully fused using covariance matrix.In order to reduce the disturber from similar targets,weights on the distance function among covariance mattrixes is imposed using forgetting factor based on fuzzy membership.The Kalman filter is used to predict the trajectory of target and judge whether severe occlusions occurre which allow us to capture again when occlusions disappear.Experimental results show that the method can successfully cope with camera moving,clutter,occlusions,and target variations such as scale and rotation for tracking rigid and non-rigid targets.

Surface speckle pattern intensity distribution resulting from laser light scattering from a rough surface contains various information about the geometrical and physical properties of the surface.A texture analysis method based on spatial filtering is used to analyze speckle patterns of grinding surface.The feature parameters of speckle texture with a good monotonic relation related to the surface roughness (Ra) are extracted.The basic principle of the texture analysis is to extract three types of vectors based on fractional Brownian motion model of window speckle images,which are the normalized scale range vector,the normalized pixel pair number vector,and the normalized multiscale intensity difference (NMSID) vector,then to make a NMSID vector transformation for speckle patterns,and finally statistically to investigate both the transformed images with zero gray pixels and the transformed images without zero gray pixels.The analysis results show that both texture features energy and new entropy of the transformed images have a good monotonic relation with surface roughness value Ra.

A three-dimensional (3D) reconstruction measurement method based on depth candidates is proposed for online measurement of cement clinkers thickness.A line laser is projected from the top and stereo cameras are used to acquire images of clinker surface.Establishing the depth candidates on vertical plane in which the laser stripes looate in the world coordinate system,the depth is recovered according to intersection of the corresponding line on parallax image ofthe candidates and the laser stripe in the images.The experiment proves the validity,accuracy of the method and computing speed,and it can be applied to online 3D reconstruction of cement clinkers during transport.

A novel LiAlO2:Fe single crystal with good quality was grown by Czochralski method.The spectroscopic characteristics and structure of the crystal were studied by absorption spectrum,photoexcitation and emission spectra,and X-ray excited luminescence (XEL) spectra.The results show that the crystal is transparent in the visible-infrared range,while has absorption band related to the Fe doping in deep ultraviolet range,and the crystal shows the 710 nm typical Fe3+ peak when it is exited by 266 nm light.For the similarity of excitation and emission spectra to LiAlO2:Fe phosphor,the Fe3+ ions occupied the octahedral sites of Li+ in γ-LiAlO2 crystal.The XEL spectra show a strong emission band peaked at 318 nm for γ-LiAlO2 cryatal.It was concluded that the emission band at 318 nm should be related to F+ centers resulted from the loss of Li2O,whereas the Fe doping could restrain the evaporation of Li2O and improve the thermal stability of γ-LiAlO2 crystal.

Au/Si/Au multilayer films have been prepared on n-Si(100) substrate using radio-frequency magnetron sputtering method,and then annealed in-situ at 300 ℃ for 30 min in vacuum environment.Based on results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM),it is observed that the smooth film transformes to uniformed nanoparticles after vacuum heat treatment.The average size and surface density of nanoparticles are 10-20 nm and 1×1011 cm-2 respectively.X-Ray photoelectron spectroscopy (XPS) measurements and TEM results confirm that Au element reacts with Si film and AuSix(x=1/2,1/7)nanoparticles with single crystallinity form.The photoluminescence (PL) properties of the sample after annealing have been analyzed at room temperature.Three peaks located at 580,628,700 nm are observed,which relate to SiO2 on the surface of the sample,defects around AuSix nanoparticles forming during annealing and non-bridging oxygen defects in SiO2 on the surface of sample.

The transparent geramanate glass ceramics with a mole composition ratio of x(GeO2):x(Al2O3):x(NaF):x(CaF2):x(ErF3)=54:20:6:20:2 have been prepared.The luminescence properties were studied.Using two-step heat treatment,the CaF2 crystals with nanometer size,could be formed in the matrix glass.Excitated by 980 nm LD,the upconversion luminescence intensities of Er3+ ions are significantly higher for the transparent glass ceramics than for the glass,whereas 1.5 μm emission is weaker.The transition is related to two-photon absorption for red (4F9/2→4I15/2) and green (4S3/2→4I15/2) luminescence,and three-photon absorption for blue (2H9/2→4I15/2) luminescence.The Er3+-doped transparent oxy-fluoride germanate glass ceramics is a kind of active optical material with excellent properties.

Steady-state luminescence spectra and transient luminescence dynamics process of 4 kinds of ruthenium complexes [Ru(bpy)3]2+,[Ru(bpy)2HPIP]2+,[Ru(dmb)2PIP]2+,[Ru(dmb)2DMNP]2+ are studied by using time-resolved luminescence spectroscopy.The results indicate that the luminescence intensity is enhanced,the shapes of the spectra are largely changed and the transient luminescence lifetime is prolonged when ruthenium complexes are in low temperature conditions comparing with room temperature.The solvent medium transforms from a fluid to a rigid glass when at 77 K.The electron transfer process in a rigid medium is quite different from that in a fluid media,which results in large changes in the shape of the spectra.The probability of intersystem crossing and amplitude of molecular vibration and thermal motion are all reduced at 77 K comparing with room temperature.Therefore,the phosphorescent quantum yield is highly raised,which leads to enhancement of luminescence and prolongation of lifetimes.

The 514 nm visible laser-induced preferential domain nucleation effect is investigated in the 3% mole fraction hafnium-doped lithium niobate crystal.The local variation of phase distribution during the laser-induced preferential domain nucleation is in-situ recorded and is reconstructed by the digital holographic interferometry.The nucleation field decreases exponentially with increase of irradiation intensity.The space-charge field along Z direction has an important influence on the laser-induced preferential domain nucleation.According to the experimental results,a qualitative model for the laser-induced preferential domain nucleation process in lithium niobate crystal is presented.This model not only provides the essential information for the future optimization of laser-induced domain engineering,but also supplies the new experimental evidences for the future mechanism investigation of laser-induced domain nucleation in LiNbO3.

A graded photonic crystal formed by the varying the high-refractive-index square dielectric rods is used as a structured lens to focus.This lens can realize high energy utilitzation and large numerical aperture.Otherwise,the energy utilization and the imaging quality can be greatly improved by adding thin dielectric films on the two sides of the lens,and the energy utilization increases as the fill factor increases.A lens with an aperture of 100 μm and a focal length of 50 μm is designed for the wavelength of 10.6 μm.The energy utilization reaches 48.5% in the case of filling factor as 44.7% by finite difference and time domain (FDTD) algorithm,and the spot size approaches to the diffraction limit.

Air-guiding photonic bandgap fibers are developed into application in various areas.Microbending loss properties of fiber play an important role in practical application including optical communications and optical fiber senors.Microbending losses in air-guiding photonic bandgap (PBG) fiber are investigated experimentally.Transmission spectra of PBG fiber subjected to microbending under different pressure and conditions are measured.Various factors which affect the microbending loss,including wavelength,pressure,bending period,and diameter,are analyzed.An analysis of the losses associated with surface modes and mode coupling is presented.The results show that,as the existing of surface modes,spectral losses of PBG fiber increase with the wavelength in the band of 1520-1620 nm.Moreover,within the critical period,transmission loss increases with the microbending period.Additionally,as the diameter of the microbending increases,the fiber is found to be more sensitive to the bending loss.

There are important applications for stimulated Brillouin scattering slow light in all optical communications network.The conventional optical fibers used as slow light medium have low delay efficiency,so the demands of fiber length and pump power are higher.The delay efficiency can be improved by using highly nonlinear photonic crystal fibers.The Brillouin gain of 33 dB is achieved in a 70 m highly nonlinear photonic crystal fiber under the pump power 101 mW,which results in 30 ns time delay of 50 ns signal pulses.The delay efficiency of this kind fiber is 0.0046 ns/(mW·m),which is about 13.7 times larger than the single mode fiber.The demands of fiber length and pump power are effectively reduced when this kind of fiber is used,and the fiber has a large potential use in stimulated Brillouin scattering slow light system.

Optical tweezers were used to study the dynamic process and the changing rule of the activity of the red blood cells in vitro.Red blood cells irradiated by the Gaussian beam of LD laser were deformed and reversed in optical tweezers.When the LD laser was cut off,the free recovery time of blood cells was obtained,which was associated with the cells′ activity.By comparing the decay process of cells activity between irradiated the red blood cells by low-power He-Ne laser and static red blood cells,the results showed:the cells activity presented a changing rule that,after fluctuations,it gradually declined till cells died.Irradiated by low-power He-Ne laser,red blood cells activity decreased slowly,namely laser irradiation postponed some decay stages.The results can provide valuable reference for the study of cells viability and dynamic analysis.

The selective photothermolysis,induced by the interaction of pulsed laser and skin,has been widely used in laser medicine.The melanin content is mainly responsible for the surface temperature discrepancy in the individual skin irradiated by pulsed laser with the same parameters.The thermal responses of individual Asian skin melanin in vivo to 532 nm pulsed laser are experimentally studied.A method to ascertain the optical absorption coefficient of individual Asian skin epidermis is presented based on the pulsed photothermal radiometry,and the simulated and experimental surface temperatures of individual skin are compared.The results show that the simulated and experimental surface temperatures of individual skin are consistent,and the method presented is of significance for optimizing light treatment parameters of individual Asian skin lesion.

An idea is presented for the photorefractive spatial soliton,namely,screening-photovoltaic solitons pairs in a biased series two-photon photovoltaic photorefractive crystal circuit consisting of two photorefractive crystals connected electronically by electrode leads in a chain with a voltage source.A set of two coupled equations is derived under appropriate conditions for two-beam propagation in the crystal circuit.The existence of dark-dark,bright-dark and bright-bright two-photon screening-photovoltaic soliton pairs in such a circuit is proved.Studies on the interaction between two solitons in one soliton pair show that only the dark soliton can affect the other by light-induced current,whereas the bright one cannot.The asymmetry result comes from the limit in which the spatial extent of the optical beam is much less than the width of the crystal.

The evolution of the optical beam with initial phase-front curvature is studied in the strongly nonlocal nonlinear media with exponential-decay response.The analytical solutions are obtained by employing the variational approach.It is found that no matter how high the input power is,the beam is initially expanded for the positive phase-front curvature,and initially contracted for the negative phase-front curvature.For a fixed input power,the curves of the beam width with different initial phase-front curvatures intersect periodically,and interestingly,at these very cross points the optical beams with zero phase-front curvatures happen to either expand to its maximum or contract to its minimum,which do not exist in the Snyder-Mitchell linear model through the comparison between our model with Snyder′s strong nonlocal solitions model.

A Cassegrain optical system of infrared search and trace (IRST) working at 8-12 μm is introduced.After analyzing the characters of the IRST system,the compositions of the optical system are described.A diffractive optical element (DOE) is successfully introduced to the second imaging to correct ray aberrations,which makes the system working well at room temperature.In order to make the system work in a wide thermal environment,an electromechanical device is utilized to control the compensation lenses.To suppress the great amount of stray light,lens hood is set on the primary and secondary mirrors,which could eliminate stray light efficiently.Hence signal-to-noise ratio and contrast of the picture have been enhanced.The experiment shows that the system works well.

A 9.3× continuous zoom optical system with fixed finite conjugate distance was designed for E-vision aid device.By using optical design software,the configuration of the optical system and the evaluation of the optical performance including modulation transfer function,spot diagram and diffuse spot in diameter were investigated.The stability of the system performance was forecasted by using the tolerance sensitivity analysis and Monte Carlo method.This mechanically compensated zoom lens combines four group components including a fixed front element,moving variator,compensator,and a fixed rear element with a total of 11 pieces of lens.The optical system which has a tube length of 76 mm and a front intercept distance of 262 mm can realize continuous zoom from 8.8- 52 mm without any image vignetting or obvious fluctuation in image quality.

To meet the requirements of computed radiographic (CR) system,a new high-performance laser scanning optical system is designed.In view of differences in performances of scanning methods,a scanning arm which is composed of pentagonal prism and scanning object lens is designed.The scanning arm is used to replace the f-θ lens.To cooperate with scanning arm,a circular imaging plate transport mechanism is designed.The scanning arm also receives stimulation fluorescence as a receiving device.The performance of object lens is analyzed using the Zemax software.The performance of mechanical structure is simulated by using the finite element method and the rotational speed of scanning arm is confirmed.The influences of the following factors that the incident light out of vertial to the pentagonal prism and there is location error of the pentagonal prism on the system′s resolution are studied.The results reveal that the system is easily adaptive to the error and can be used widely.Experiments are carried out to verify the performance of the laser scanner.Moreover,the results indicate that the images have good visual effect and can meet requirements of industrial inspection.

Indium tin oxide(ITO) film is fabricated with vacuum electron-beam evaporation.A novel AlGaInP light-emitting diode (LED) with a 300 nm thickness transparent conducting indium tin oxide film as window layer is fabricated.LED chip was annealed rapidly in N2 atmosphere for 40 s .As the rapid thermal annealing (RTA) temperature increases,the luminous intensity increases at the beginning and then decreases while the voltage first decreases and then increases.And the optimal annealing temperature for the luminous intensity and voltage is 435 ℃.The result from Hall test of ITO film showed that the carrier concentration is the highest and the resistivity is the lowest when ITO is annealed in a RTA system at 435 ℃.The forward voltage of LED decreases due to the resistance of ITO and the Ohmic contact resistance decreased and the light output increases due to the better current-spreading effect of ITO as current-spreading layer

To improve the utilization efficiency of interleaver bandwidth in 10 Gb/s plus 40 Gb/s hybrid system,an all-fiber asymmetric bandwidth optical interleaver based on a cascaded Mach-Zehnder interferometer is proposed and discussed.Influences on its transmission characteristics by such factors as splitting ratio of the coupler of the directional fiber couplers and the physical length differences of the interferometer arms are numerically analyzed in detail.The preference condition of the interleaver which meets the maximal isolation and the characteristic of the output spectrum is obtained.One set of optimized data is validated in the experimental result.The results of numerical simulation and experiments show that all-fiber optical interleaver with -3 dB passband in odd channels and even channels could be obtained,which have more than 60 GHz passband and 30 GHz passband,for transmission speed of 40 Gb/s and 10 Gb/s,respectively.Experimental results are in good agreement with the simulation results.Comparing with the conventional interleaver with uniform bandwidth channel,the kind of interleaver with higher bandwidth utilization efficiency has more advantages as multiplexer/demultiplexer during upgrade from 10 Gb/s to 10 Gb/s+40 Gb/s.

Nonlinearity of photoelectric pyrometer is one of the main uncertainty sources for realization of international temperature scale.A novel nonlinearity measurement system based on light-emitting diode (LED) light sources and flux addition method is established.A high-brightness LED with nominal 645 nm peak wavelength is utilized as light source to substitute conventional tungsten lamp.The switch of power supply for LED can realize flux addition,and the abandonment of optical strobe can avoid the nonideal result from repeated reflection.The experimental research on the spectral radiation drift of LED under step-mode power supply is carried out to validate the end time of nonlinear drift stage.The pulse-mode power supply of fixed phase shift for double LEDs and beam splitter are combined to attain flux addition.The linear drift stage of LED is chosen to measure the nonlinearity of pyrometer.The linear drift effect on the nonlinearity measurement is eliminated by exchange the measurement turn and experiments are carried out to validate the method.The nonlinearity of the standard radiation thermometer (model RT9032) is experimentally studied.

A new type of optical element--combined axicon is proposed for generating non-diffracting Bessel beams.This element is designed with gluing positive and negative axicon.Its property is the same as single positive axicon for beam transformation,and equivalent conical angle is decided by the conical angle difference of positive and negative axicon.Therefore,we can get smaller conical angle by combining positive and negative axicon with comparatively large conical angle for each axicons,and also get non-diffracting beam with longer distance.The technical problem of the small conical angle which is hard to machining is solued.The ABCD matrix of the combined axicon is deduced.It shows that the combined axicon can transform plane wave to Bessel beam by numerical calculation.The optical field distribution behind combined axicon is also simulated by Zemax software,and compared with single positive axicon.Research results open a new way for generating non-diffracting Bessel beams.

An approach has been introduced called time reversal to coherently control the position in which the optical energy localizes in plasma nanosystems.This approach is based on the impulsive localized excitation of the nanosystem and time reversal of the generated far-zone field at a single point with one polarization.Despite strong interaction and significant dephasing and dissipation in metal plasma systems,and incompleteness of this time reversal,the proposed approach proves to be very efficient in controlling the nanoscale optical fields.The approach may be applied in nanoscales spectroscopy,optical modification,ultradensememory,and information processing on the nanoscale.

The resonance peak of long period fiber grating fabricated in twisted optical fiber by using high-frequency CO2 laser pulses could split into two peaks,after the twist applied to the fiber is removed.The splitting and the torsion characteristic of the special gratings are analyzed and explained by beat-frequency theory.As the temperature sensitivity of the two splitting peaks of the grating is almost the same,it is proposed that torsion can be measured by detecting the interval change between the two splitting peaks when torsion is applied.Besides,the torsion sensor can distinguish torsion direction as the distance of the two splitting peaks increases or decreases when different torsion is applied,therefore,this kind of torsion sensors has a great potential application in high sensibility torsion sensing.

A theory validation system of coherent lidar with balanced coherent detection and chirped amplitude modulation is built based on narrow line width diode laser,acousto-optic frequency shifter,Mach-Zehnder intensity modulator,and all-fiber coherent detection optics.The principle of the chirped amplitude modulation coherent lidar is introduced.The design of direct digital synthesis(DDS) based chirp signal generation and radio frequency signal processing circuits are also discussed.The measurement of time resolution and minimum detection power of the system is conducted and some phenomena in the experiment are analyzed.

The function relation between polarization and the density of seawater at the range of visible waveband can be established by index of refraction,but there is a great calculation error.In order to calculate the density of seawater more accurately,the best waveband of calculating the density of seawater was determined based on dispersion theory.Seawater from Dalian Bay and Yueya Bay was used as study objects,and USB2000 spectrometer was used to measure the polarized spectrum of seawater,and then its polarization was calculated.Iterative inversion was used to find out the waveband which has the smallest polarization errors that match along with the actual density,which means the optimal waveband of calculating the density of seawater.The results show that seawater with different densitis has different optimal wavebands to calculate the densities at different incident angles.That is to say,the calculation of density has a higher accuracy at the range of (650±2)-(670±2) nm waveband.A further step of using polarization information to calculate the density of seawater in the practical application of remote sensing technology is showed.

The infrared radiation could be effectively attenuated by the man-made water fog.For that the water fog particles have been greatly used in the fields of infrared stealth.Some radius distribution of the water fog particles could make the stealth effect be optimal,and that has become the emphasis and difficulty of studies.Based on Mie theory,the physical and mathematic models of the water fog particles extinction were given.Three qualifications used to ascertain optimal extinction radius of the man-made water fog were summed up.In the meantime,aimed at middle and far infrared bands the optimal extinction radius of water fog particles was calculated and analyzed by compiling Matlab programs in the method of scattering phase function and extinction factor.Explicit radius distribution of the water fog particles was got,and the rule of distribution of the optimal particles radius for middle and far infrared bands was given.This conclusion could offer references for studies such as stealth of warships and land targets and fire fighting.

Cross-linked azobenzene containing copolymer is synthesized and utilized to fabricate axially-symmetric phase retardation plate.Based on the photo-isomerization characteristics of azobenzene copolymer,a linearly polarized light inducing device is set up.Placed on a rotating stage,an azobenzene film is irradiated by a linearly polarized light to form molecule alignment with axially-symmetric distribution.The probe beam is used to detect in real time the phase retardation ofthe film under the effect of linearly polarized light.During the investigation,a particular software on the computer is used to record the intensity curve of the probe light which goes through the film placed in the group of orthogonal polarizer plate.After that,a measuring optical circuit is set up to measure the axial symmetry of the phase retardation plate and the measurement patterns are recorded with a CCD.The experimental results show that the induced birefringence is 0.0205,the thickness is 3 μm,and the phase retardation is 65°.

Using the glow discharge technology with acetylene reactive gas,the diamond-like carbon films with different nominal thicknesses are deposited on Si substrate with the identical process.Variable angle spectroscopic ellipsometry (VASE) is used to characterize the film optical constants at the wavelength range of 380-1700 nm.Given the various selected film thickness,the different optical constants of refractive index and extinction coefficient of sbsorbing films,showing good consistency between the calculated and experimental data,could be obtained based on single sample ellipsometric fitting method.This result indicates that it is generally rather difficult to determine the refractive index and extinction coefficient of absorbing films accurately and rapidly due to the strong correlations between thickness and optical constants.A new multiple sample analysis method is put forwarded to solve this problem.Assume that the optical properties are same for the used three samples of DLC films with various deposition time,the accurate optical constants and related thickness of each sample could be determined rapidly even without any predicted dispersion models.Meanwhile,this new method can be used both for the transparent substrate and non-transparent substrate with absorbing films.