A new scheme to trap cold atoms (or cold molecules) by an improved blue-detuned hollow optical trap is proposed,which is formed by an optical system composed of a binary phase plate and a circular aperture illuminated by a plane light wave. The dependence of the relative intensity of the optical trap and its well depth on the phase φ of the binary phase plate is studied,and some analytical relations between the geometric parameters of the optical trap and the parameters of the optical system are derived. It is found that the binary phase plate can be used to improve the intensity profile and produce a hollow optical trap with higher effective intensity and larger trapping volume. In particular,when a 100 W frequency-doubled Ytterbium fiber laser with a wavelength of 540 nm is used to illuminate the optical system composed of the π phase plate and the circular aperture,the optical trapping potential for 87Rb is about 80.2 μK. So this scheme is not only simple and convenient in the manipulation and control of cold atoms (or cold molecules) but also has wide potential applications in the fields of cold atomic and molecular physics,atom and molecule trap,life science,and so on.

The characteristics of grating structure in magnetic field measurements based on differential group delay of fiber Bragg gratings (FBG) are analyzed. Theoretical simulations are realized using the coupled-mode theory and transfer matrix method. The effects of grating parameters (physical length,index modulation) of uniform FBG on measurement range and sensitivity are analyzed. The impacts of chirped,phase-shifted and apodized gratings on the wavelength dependency of differential group delay are also monitored. The experimental measurements are conducted on FBG inscribed by means of the phase mask technique. The experiments demonstrate that the phase-shifted gratings can obviously improve the sensitivity of sensor system which match well with the simulations.

Phase noise mainly comes from laser linewidth,laser phase offset,in/quadrature (I/Q) phase mismatch,90° hybrid phase imbalance,fiber channel and component in optical quadrature phase shift keyed (QPSK) transmission system. Those phase noise can affect system performance of coherent optical communication system seriously. To compensate the impairments introduced by these phase noise,a novel feed forward phase estimation techniques with n-th power operation and logarithm operation are proposed. The simulation results shown the new solution can eliminate bit error rate (BER) deteriorating due to 7.5 MHz laser linewidth,30° laser phase offset,20° I/Q phase mismatch of transmitter,or 20° of 90° hybrid phase imbalance,and can improve the optical signal to noise ratio requirements 1 dB,significantly improve system performance.

Based on the nonlinear Schrdinger equation,transmission of the Gauss type chirped-pulse of nanosecond in width in single-mode fiber is discussed. The effects of aberration and nonlinear effects on both spectrum and waveform of the chirped-pulse are numerically simulated with split-step Fourier method and the contrast of the compressed pulse is analyzed in detail. The results show that for the input chirped-pulse of peak power smaller than 30 mW and of center wavelength at 1053 nm,after the transmission in 200 m single-mode fiber,the contrast of the compressed pulse is up to 1025 in 3 ps time window.

The application of low-cost optical pulse source will redound to the practical development of optical code-division multiple-access (OCDMA) system. The application of practical chirped optical pulse source in OCDMA system is improved. The effect of chirp elimination on decoding performance is investigated;The half-side bandwidth of encoding spectrum is utilized for encoding and decoding in order to improve the decoding performance in terms of the fact that the spectrum of common practical chirped pulse source is not wide enough to cover the whole encoding spectrum. The simulation and experimental measured data show that the decoding peformance can be improved via chirp elimination and further optimized by the full utilization of laser source spectrum due to the half-side bandwidth encoding and decoding. The results indicate that the application of chirped optical pulse source in OCDM can be optimized and improved effectively by chirp elimination and half-side bandwidth.

A novel method for measuring refractive index of liquids based on a liquid drop formed at the end of fiber sensing probe is reported. The effect of the drop is like a plane-convex lens whose refractive index equals to that of the tested liquid. The light from transmitting fiber successively experiences refraction of the liquid drop to air interface,the air to liquid drop plane interface and the air to liquid drop,and is finally collected by the receiving fiber. According to Fresnel′s formula,the transmission coefficient and reflection coefficient at these interfaces dependes on the refractive index of the tested liquid. Based on spherical refraction imaging and reflective intensity modulation,the light transmission path is analyzed,and the mathematical mode between the intensity of the collected light and refractive index is set up. NaCl solutions with different concentrations are tested. The experimental results indicate that the method can be used for measuring the refractive index of the liquid.

The optical pulse trains with multiplied repetition frequency is generated by fractional Talbot effect in optical fiber. The principles of Talbot and fractional Talbot effects in fiber are analyzed. The 20,40 and 50 GHz optical pulse trains are obtained from the original pulse with 2.8 ps width at 10 GHz repetition frequency. An optical pulse at 40 GHz repetition frequency is also produced by upshifting the repetition frequency of 5 GHz pulse. The degradation of 40 GHz and 50 GHz pulse trains is discussed by spectrum analysis of pulse and some improvement methods are proposed.

The delay characteristic of the Brillouin slow light using broadband pump with rectangular spectrum is analyzed. Analytical expressions of the time delay,the pulse-width broadening ratio and the gain of a Gaussian pulse are deduced under small-signal gain approximation. Calculated results show that the analytical solution and the numerical solution agree well and the Gaussian signal pulse can achieve zero-broadening delay,when its 10 dB bandwidth is not greater than 0.357-fold pump bandwidth. The maximum Brillouin gain bandwidth for a broadband pump with single rectangular spectrum is 20 GHz,indicating that zero-broadening delay of the Gaussian pulse with full-width at half maximum of about 100 ps can be achieved. Broadband pump light with rectangular spectrum is more favorable for reducing the pulse distortion than that with Gaussian spectrum.

Compared with gradient index (GRIN) gas cell,the sensitivity of prism gas cell is easy to be adjusted and the interference noise is apt to be suppressed. Based on the Beer-Lambert law,detection of various volume fraction (0-20 %) of methane is completed by subtraction of background and harmonic detection method,as the atmosphere surroundings is treated as background. The direct absorption spectra of various volume fraction are measured using GRIN gas cell,combined with available distributed feedback laser diode (DFB-LD),where the R5 line of the 2ν3 band of methane is selected as absorption peak. The system is tested online during gas mixing process and the linear relation between system indication and volume fraction variation is validated,also the stability and dynamic response characteristics is confirmed by experiments. The system sensitivity can be adjusted according to volume fraction level of various field environments by changing the prism distance and using step motor. The system can be applied to various fields and can be adopted as monitoring instrument for coal mine tunnel and natural gas pipeline.

Polarization beam splitters and 3 dB couplers are used to construct a home-made 90° optical hybrid,by which a polarization diversity optical coherent receiver is carried out with single-ended detection. A 10 Gb/s polarization multiplexed differential phase shift keying (DPSK) signal is transmitted through 280 km standard single-mode fiber (SSMF) using erbium-doped fiber amplifier (EDFA) amplification,and no error bits are measured in the result. The various digital signal processing algorithms in coherent detection are discussed. Carrier phase estimation,optical chromatic dispersion compensation and digital polarization demultiplexing are carried out. The phase error offset from the 90° of the optical hybrid is compensated by using statistical method. The algorithm is irrelevant with signal modulation format and fiber chromatic dispersion. Digital polarization demultiplexing is carried out by using constant modulus algorithm,and the convergence time of the algorithm is less than 0.5 μs

A wavelength division multiplexing radio-over-fiber (WDM-ROF) system to generate 58 GHz optical millimeter (mm)-wave with OFDM signal by using a Mach-Zehnder intensity modulator and an optical interleaver (IL) is experimentally investigated. In the central office,four channels continuous lightwaves are generated by a laser array,and they are modulated by a intensity modulator which is driven by a 29 GHz radio frequency (RF) signal to realize double sideband (DSB) modulation. 2.5 Gb/s OFDM signals are modulated on the DSB signals by another intensity modulator before they are transmitted to the base station over 20 km single mode fiber (SMF). In the base station,an optical IL is used to separated optical carriers and first order sidebands. The first sidebands of desired channel are selected by a tunable optical filter (TOF) and detected by a high speed optoelectronic detector to generate 58 GHz electrical mm-wave which is demodulated by coherent demodulation to retrieve downstream OFDM baseband signals. The experimental results show that the power penalty of the downstream OFDM signals transmitted over 20 km SMF-28 is less than 0.5 dB at the BER of 10-3 and without dispersion compensation,and the constellation figures are still clear.

An all-fiber optical pulse cleaner (OPC) is investigated based on nonlinear polarization rotation (NPR). The theoretical analysis of pulse contrast enhancement using NPR is detailed. The relation of transmittivity versus incident angle and fiber length is calculated. The change of pulse width and shape of the output pulse is investigated. And an OPC operating at 1053 nm with a hundred picoseconds pulse duration is demonstrated. The pulse contrast between main pulse and continuous wave background power is enhanced by more than 47.5 dB,and the contrast ratio between main pulse and prepulses is enhanced by more than 16.94 dB,which are both beyond the response limit of the detecting devises. The overall peak power transmittivity of the system is 28.05%,and the duration of the pulse is shortened from 92 to 64 ps,which is in agreement with the theoretical prediction. Efficiency measurements are realized using an optical-to-electrical converter and an attenuator,for the autocorrelator is not applicable to the measurement of the pulses with 1 Hz repetition rate . More enhancement of contrast ratio will be detected with precise detection.

In the applications of tomographic imaging,insufficient data reconstruction using few projections from limited angle is very important,because it would enable rapid scanning with reduced X-ray doses delivered to patients. The iterative image reconstruction algorithm based on the minimization of the image total variation (TV) works well for limited-angle reconstruction problem. However,the weighting parameter in the cost function can only be determined through considerable experimentation and the parameter attained is not always the optimum. An iterative image reconstruction algorithm based on multiplicative regularization method is introduced. The method obtains the advantages of the TV method by introducing the TV as a multiplicative factor in the cost function,and it can also self-adaptively adjust the regularization parameter during the iterative process. Simulation results show that the proposed algorithm works effectively.

Designing on effective observation model to discriminate object region from complex background is the core of robust tracking. A tracking approach based on multi-features observation has been proposed for infrared image sequences. Object appearance is represented by gray value,local standard deviation and gradient features in a unified histogram form;a scence-adaptive weighting scheme for these three features is used to construct the observation model,the selection of these multifeatures weights is towards the direction of maximizing discriminability between the target and its adjacent background. Experimental results on real complex situation demonstrate that the proposed algorithm tracks target well in highly appearance changes and severe clutter.

A rapid and high-precision camera calibration technique based on active vision is proposed. A camera model and detailed analysis on the solution algorithm of its parameter are established. By in-plane translational motion of the camera,images of a hollow target plate are collected to calculate locations of the circular center. Meanwhile,the exact displacements of the camera are recorded;therefore the needed coordinates of the feature points in the object plane and in the correlative image plane are gained. Using these feature points,the camera calibration parameters can be calculated with a precision of 0.005 mm. Finally,automatic calibration is realized by use of the custom calibration module. The proposed method with less limiting conditions of camera motion basically realizes linear solution of the parameters of camera model,and provides an effective solution of camera calibration for active vision systems.

In order to study the effect on scenery radiation energy acquisition and signal-to-noise ratio of short-wave infrared (1.0-2.5 μm) imaging spectrometer caused by prism nonlinear dispersion,the expressions of radiation energy collection and spectrum sampling calculation are deduced,which are calculated and analyzed in the range of short-wave infrared spectrum. It is indicated that when the number of spectral channels is same,compared to equal interval spectral sampling method,the scenery radiation energy collected by a single prism dispersive imaging spectrometer detector is relatively higher in the 1.0-1.85 μm range,but it is relatively lower in the 1.85-2.5 μm range,and the signal-to-noise ratio has similar characteristics. The weak absorption feature of atmosphere is more and more clearly apparent,when the number of spectral sampling channels increases.

A camera calibration technique based on controllable rotation for active vision system is proposed. The camera is controlled to rotate a known angle around (or around nearby) the optical center to calculate the accurate equivalent focus length departed from other parameters. This method needs two rotations to get the equivalent focus lengths along two axes. Using the simplified imaging model,that two equivalent focus lengths are set to equal and the principal point is on image center,only one rotation is required to get the linear camera parameters. And then a camera calibration method combined by controllable rotation and traditional two steps calibration is put forward to get all parameters including the distortion coefficients. Experiments show that the use of camera parameters obtained by calibration method based on the controlled rotation has a high accuracy for pose measurement.

A new absolute method of radiance calibration was introduced,including the principle and its experimental setup. An ultraviolet laser (355 nm) was used to pump the nonlinear crystal BBO (β-BaB2O4),producing two correlated-photons whose wavelengths were 532.75 nm and 1064 nm,respectively. The under-calibrated laser was injected along the propagation of the infrared down-converted photons. With the high correlativity of the two VIS-IR correlated photons,through the measurement of the visible down-converted photons,the radiance of the injected laser source can be calculated,allowing the radiance of an infrared source can be measured with the high-quality visible detectors. The measurement result shows good linearity at different power of injected laser. At last,based on the estimate of the efficiency factor of the system,the radiance at a fixed power of 3.39 mW was calibrated,with the result 4.09×1017 W/(m2·sr) and its relative uncertainty 4.78%.

Spatially modulated imaging Fourier transform spectrometer (SMIFTS) is an instrument that depended on interference,it can obtain interferential information and achieve spectral information by Fourier transform. The lamp-house of outdoor calibration is sun,which can offset effective lamp-house of laboratory calibration (sun simulation)′s disadvantage of low shortwave radiation and signal to noise ratio (SNR),also simulate sun reflection spectrum speciality availably of SMIFTS object,obtained interferential information exactly,result of laboratory radiation calibration is validated. Principle,method and result of the experiment are shown,used sun-aerosphere-diffuse reflection method and standard-radiation-transfer method to accomplish outfield calibration in Dali. The results indicated that the uncertainty of sun-aerosphere-diffuse reflection method is 6.3%,uncertainty of sun-aerosphere-diffuse reflection method is 6.0%.

The technique of measuring the shock wave velocity directly in the transparent material under the ultra-high pressure is introduced. The preheat effect on shock wave velecity calculation in the indirect driven experiment is studied with imaging velocity interferometer system for any reflector (IVISAR). After analyzing the beginning time of preheat effect,it is found that the shock wave velocity cannot be deduced directly from the experimental data when the radiation temperature is higher than 160 eV with IVISAR. From the experimental data,the starting point of preheat effect is consistent with the laser pulse,and it is found that the preheat effect is the worst when the intensity of laser pulse is the highest. The preheat effect recovers after the intensity of laser pulse decreases. For the experimental data above 160 eV,the shock velocity curve can be calculated by extrapolating the background stripe to the jumping edge. This method is suitable for processing experimental data gotten from the indirectly driven square wave laser and the inorganic transparent window.

A triple Fabry-Prot etalon for wind lidar is developed. The relative thicknesses of the etalon measured by using the interference fringe with the He-Ne laser are 74.70±2.24 nm and 27.16±1.90 nm. The corresponding separation of two edges etalon and that between edge1 etalon and locking etalon are 5.05±0.07 GHz and 1.79±0.70 GHz,respectively. The etalon as a frequency discriminator,a laser with the push energy of 350 mJ at wavelength 355 nm,repetition frequency of 30 Hz and a telescope with the diameter of 450 mm are used) to simulate the wind lidar. As a result,the actual line-of-sight wind speed error is lower than 2.53 m/s,the accuracy of line-of-sight wind is improved by 14.1% compared with the theoretical value of 2.94 m/s at the altitude of 0-40 km.

A CIMEL CE318 is calibrated by using a new tunable laser-based facility for spectral radiance responsivity with combined standard uncertainties lower than 1%. The same CE318 is also calibrated by using a NASA lamp-illuminated integrating sphere source. Relative deviations between NASA and our calibration coefficients are within ±1.4%;which indicates that the proposed method is accurate.

Calibration is the estimation of the internal parameters of star sensor,which can decrease the system error and improve the pointing precision. Based on the different calibration method between coefficients to be determined and internal parameters,the calibration models are established. The different approaches of ground calibration and data processing are summarized according to different calibration models. The on orbit calibration method of focal length and optical center offset is analyzed,and the on orbit star images are processed with extended Kalman filter. The simulation results indicate that the new method can converge more quickly and eliminate the random centroiding measurement errors more efficiently than the nonlinear least squares estimation.

Because of the specular reflection of the object,there must be many hight-light areas in the image. The intensity of the specular reflection is relatively strong,so phase information of structured optical field is inevitably covered up by specular reflection. If the reflected light field of the surface with specular reflection by general Fourier transform profilometry is directly measured,wrong 3D surface data must occur. According to polarization properties of the light field,using light-filtering function of optical components,and combining Fourier transform profilometry with Phong illumination model,3D surface of the object with specular reflection can be correctly measured. Both theoretical analysis and experimental results not only prove that specular reflection will affect the modulation field of the surface,but also prove that the proposed measurement method can measure the surface with specular reflection. So application fields of Fourier transform profilometry could be greatly expanded.

In the traditional prism surface plasmon resonance (SPR) sensor system,the resonance trough is shallow and the valley is smooth,which causes the resonant wavelength difficult to determine. A novel detecting system is built which added a polarized beam splitter (PBS) based on traditional prism SPR sensor system. In the experiment of alcohol detection,when the S polarized light is filtered,the resonance radius of curvature decreases from 86.2394 to 39.3990,similar to the S polarized light presenced′s 50%,which coincides with the theoretical analysis. Traditional and novel prism SPR sensor system is used to measure 6 kinds of liquid whose refractive index is 1.32-1.39. The resolution ranges from 1.62×10－4 to 1.55×10－4. The detecting system with filter S polarized light that doesn′t excite SPR effect,which making a more acute resonance trough,thus detecting system has been improved.

A new miniature extrinsic Fabry-Pérot (F-P) fiber optical pressure sensor based on fiber fusion and F-P interference is developed. It is made of commercial single-mode fiber and graded-index multimode fiber. Its all-silica structure has good stability for long-term use. The sensor is fabricated by simple techniques involving only cleaving,wet chemical etching and fusion splicing. The relation among the diaphragm thickness,the different cavity radius and the sensitivity is simulated,and the diaphragm thickness and the cavity depth are obtained. The processing step is designed. The key technologies,fiber etching and fiber splicing are discussed. By tracing a peak point in the interference spectrum,the gap length of the sensor can be demodulated. The demodulation system is set up. Experimental results demonstrate that a high linear response in the range of 0 to 0.1 MPa is obtained in this sensor.

Tunable diode laser absorption spectroscopy (TDLAS) is a detective technology with high sensitivity,high resolution and rapid response ,which has been used abroad for the measurement of trace gas in atmosphere and the diagnosis of toxic and harmful gas in the industry process,and the detection of nature gas leakage. Due to the features of tunability and narrow linewidth,the distributed feedback (DFB) diode laser can tune the laser output wavelength to a single absorption line of the gas precisely,which makes the TDLAS technique can be utilized to measure gas concentration with high sensitivity. A brief description of on-line gas monitors using wavelength modulation spectroscopy with second-harmonic (WMS-SH) detection is presented. A discussion of feasibility of the gas detection based on the least squares method is also presented. After the application of the modification-weighted moving average filter,the system response time is not more than 1 s. Both the signal to noise ratio and the detection sensitivity have been improved. The detective approach has been applied in the real-time detection of hydrogen sulfide in natural gas treatment factory.

Difficulties of phase unwrapping caused by the intense height discontinuity of the tested object exist in the traditional Fourier transform profilometry (FTP) when the single frequency sinusoidal fringe pattern is projected. The hybrid encoding method based on digital point array and sinusoidal fringe pattern projection can solve the problem of the phase ambiguity and error propagation effectively. But a point array pattern and a sinusoidal fringe pattern are demanded to be projected respectively,and it can seriously reduce the measuring efficiency. A new method of colorful composite grating is proposed. It is possible to get a point array pattern and a sinusoidal fringe pattern from only one frame of image. The wrapped phase can be exactly unwrapped according to the point array pattern. Theoretical analysis and experimental results show that the proposed method can be used to solve the profilometry of objects surface with large height discontinuities. Besides that,the novel method has a strong capability of anti-error-propagation and high efficiency in the measurement.

In order to realize on any direction of laser detection in a big field of view,and guarantee the stable structure,sensitive response,the low cost and so on,two-dimensional overlapping mask encoding method is proposed. The laser direction detection system uses six flat-window detectors,and it is constituted with two-dimensional separated mask in the horizontal plane. Using the mask and the detection angle,the field of view of the two-dimensional overlapping encoding can be calculated,and thus to realize the laser direction. According to the experiment,the laser direction can be calculated by the coding method with six detectors,and the accuracy of angle can reach 30°. The experiment of laser with incline incidence to the detectors shows that,under the most tilted angle of laser the response voltage of the detector is more than 40 mV,which is greater than the voltage arising from noise. Therefore,the field of view of the system is in the rotating area from 18° to 162°.

The amplification and nonlinear effects of 100 ps pulse in the diode-pumped Yb-doped double-clad fiber amplifier (YDDCFA) is investigated. The YDDCFA is seeded with 100 ps pulses with a spectrum centered at 1053 nm at repetition rate of 70 MHz and 1 Hz,respectively. The saturated gain of the quasi-continuous pulse input signal with average power of 55 mW,spectral width of 0.016 nm,is 7.02 dB. And the spectrum broadening caused by SPM is 0.01 nm,measured with F-P interferometer. The SRS is observed when the peak power of the single-shot pulse is amplified to 6950 W corresponding to a gain of 29.3 dB. Novel methods are devised to detect the spectrum of single shot. The change of spectrum caused by SPM and SRS is measured using a stretched fiber Bragg grating;and the Stocks pulse and signal pulse are separated using the dispersion of long sing mode fiber,revealing the SRS effect. Experimental results show that the SRS is the main limit of amplification of 100 ps pulse.

High power laser diode arrays (LDA) have been used widely. A nondestructive and effective method is desired to evaluate the quality of LDA. The parameter h is the sinkage at the threshold in the electric derivative curve,and the parameter Q is the ratio of the height to the width of the peak sharp in the second optical derivative curve at the threshold in the presented derivative technique. The dependence of the value of h and Q on the uniformity and quality of the laser diode bars is analyzed. By using the equations derived from the equivalent circuits of the bars,the influence of the bar uniformity on the behavior of the value of h is investigated in theory under certain conditions. Compared the compute results with the experiment results,for the same kind devices,it shows that h and Q are both sensitive parameter about the cell uniformity.

Output characteristics of laser diodes (LDs) emitting at 808 nm with 3 different thicknesses of waveguide-layer made from Al0.65Ga0.35As (0.4,0.5 and 0.6 μm) and 3 different AlGaAs-based large optical cavities (LOC) (Al0.65Ga0.35As-1 μm,Al0.6Ga0.4As-1.5 μm and Al0.45Ga0.55As-2 μm) were studied. P-I curves of these different structures were simulated,threshold currents were computed by the means of linear fitting,and characteristic temperatures of these devices was calculated. The experimental results authenticated the theoretical calculation results. The research of different waveguide-layer thickness showed that when thickness of single quantum well was fixed,the thicker the waveguide layer was,the higher the characteristic temperature was,and the better the device performance. The study of different large optical cavity indicated LD with 2 μm-LOC was the best of those three as a result of an aluminum content of x=0.45 yielding an effective vertical spot size of 1.0 μm and a lower electrical resistance.

Although adaptive optics technique without a wave-front sensor can get rid of the restriction of the terms of wave-front aberrations and is an effective way to compensate the wave-front distortion of the high power laser beam to improve the beam quality,the laser intensity fluctuation and the circuit noise will make the performance of the system deteriorate. The influence of intensity fluctuation and the circuit noise on the results of the beam cleanup system based on stochastic parallel gradient descent (SPGD) algorithm is analyzed,corresponding experiments is done. Result shows that when the frequency of the laser intensity fluctuation is faster than or equal to the disturbance rate,the performance of the system decreases quickly with an increasing amplitude of intensity fluctuation. In the case of low intensity fluctuation rate,the capability of anti-jamming of the SPGD algorithm is excellent. To avoid the influence of the intensity fluctuation and the circuit noise on beam cleanup system,beam cleanup technology based on normalized performance evaluation function:power-in-bucket (PIB) is proposed. Both theoretical and experimental results show that this technology is an effective way to avoid the influence of intensity fluctuation and the circuit noise on beam cleanup system,ideal results approaching the correction limit of the system can be obtained.

Using rare earth oxides as raw materials,YAG:Ce phosphors are prepared by solid-state reaction which dopes with praseodymium,gadolinium,as well as the praseodymium gadolinium altogether. The excitation and emission spectra of the phosphors are tested by fluorescence spectrophotometer. The results indicates that these phosphors can be excited by blue (455-470 nm) light effectively. The center wavelength of theYAG:(Ce,Gd) emission spectra occurs red shift differently by justing the mol density of doping Gd3+ions,there is a new emission wave crest at about 610 nm in the YAG:(Ce,Pr) emission spectra;not only a new emission wave crest at about 610 nm but also the center wavelength occurs red shift existed in the YAG:(Ce,Pr,Gd) emission spectra. So the flaw of the traditional light emitting diode,lacking of red emitting in the spectra,can be effectively improved. It will be very important for light emitting diode to apply in high colour rendering required field.

Geometrical structure of CdS with vacancy was optimized by using density functional theory (DFT) based on first-principle ultrasoft pseudopotential method. Optimized results showed that the vacancy resulted in local lattice distortion and the relaxation of neighboring atoms. Then vacancy effects on electronic structure (energy-band structure and electron-state density) of CdS were analyzed. The results revealed that S vacancy made the band gap narrower and Cd vacancy made it wider,but CdS with S and Cd vacancy were direct band gap semiconductor. The optical properties of CdS with vacancies were investigated. The results indicated that changes on optical properties mainly focused on low-energy region because of the change of electronic structure of atom neighbor vacancy.

Research on laser-induced damage of silicon-on-insulator (SOI) material is quite important for applications of optical devices based on this material. Irradiation experiment is performed on SOI material with 1064 nm pulsed laser. For pulse width of 190 ps and 280 μs,the laser-induced damage threshold values are measured to be 2.5 and 19.8 J/cm2,respectively. Damage patterns induced by the two pulse lasers are also different from each other. According to the experimental results,the temperature distributions in the SOI material after laser pulse duration are simulated by a finite element analysis method with the ANSYS heat analysis module. Based on observation to the damage morphologies,the laser-induced damage mechanism of SOI material is discussed.

The geometry,electronic absorption spectra and second-order nonlinear optical properties of unsymmetrical liquid crystalline dimmers with imine and cholesteryl moieties were studied at the level of B3LYP/6-31G. The results showed that the maximum absorption electronic transition of the title compounds were from the highest occupied molecular orbital to the lowest unoccupied molecular orbital (π→π*),and the maximum absorption wavelength was in 337-349 nm,belonging to the UV. Decrease of central soft spacer length and increase of the attraction electron capacity of the terminal substituent group can enhance the second-order optical properties of the title compounds.

2 μm emission properties of Tm3+ in fluorozirconate glass were reported. The Judd-Ofelt (J-O) intensity parameters Ωt (t=2,4,6),spontaneous emission probability,fluorescence branching ratio,and the radiative lifetime were calculated on the basis of Judd-Ofelt theory by measuring the absorption spectra of the glass. The effects of Tm3+ ion concentration on the optical parameters were discussed. From the measured emission spectra of glass,it was found that the peak wavelength of Tm3+:3F4→3H6 transition is located at 1.82 μm in the Tm3+-doped fluorozirconate glass. It was also found that the cross relaxation (3H4→3F4,3F4→3H6) between the Tm3+ ions occurred with the Tm3+ ion concentration increasing,which leads to the increasing magnitude of 3F4→3H6 transition. Due to the concentration quenching mechanism of three-energy level ions,the intensity of luminescence decreased obviously. The stimulated emission cross section of Tm3+:3F4→3H6 transition was calculated by using Mcumber theory. The results show that doping concentration has little effect on the emission cross section of Tm3+ in the present fluorozirconate glass.

A novel design approach of realizing flattened mode large mode area photonic crystal fibers (PCFs) is presented by introducing a depressed-index region in the core of 7-rod core triangular PCFs. The influences from structural parameters,such as the size of depressed inner core,air hole pitch and the relative size of air hole,on the refractive index of inner core and the fundamental mode area are calculated with full-vectorial finite-difference method. A flattened mode PCF with mode area as large as 2000 μm2 is given,which can be easily fabricated with present technique. In the simulation,it is also found that less higher order modes will be contained in the fiber by scaling the depressed inner core and light wavelength as well as decreasing the relative size of air hole.

Photonic crystal ring resonator can be constructed by putting ring resonators and the waveguides next together. The spectral transmittance and propagation of the optical field entering this system is analyzed numerically using the plane-wave expansion (PWE) method and finite-difference time-domain (FDTD) method. On the basis of this structure,ultracompact multiway beam splitter was designed and the ones with three and four output channels are discussed in details as examples. By simply tuning the radii of coupling dielectric rods in the ring resonators and inducing the redistribution of the optical field,equipartition of energy or free distribution can be achieved. Compared with the results of normal waveguides reported,the most important aspect is that a large separating angle can be obtained in this structure.

A numerical method to the inverse problem in shape-based diffusion optical tomography is proposed to simultaneously recover the smooth boundaries of the tissue regions and the optical properties. The regions of different tissues are assumed to have piecewise constant optical properties,thus the forward problem of the light propagation of diffuse optical tomography (DOT) can be modeled as a set of coupled Helmholtz equations,and solved by the boundary element method (BEM). Fourier series expansion is used for the representation of the smooth complicated boundaries. For inverse problem the Levenberg-Marquardt optimization process is implemented here. The performance of the proposed approach is evaluated by the measurements at different noise levels. The numerical results illuminate that the methodology has faster convergence speed and global convergence,and the boundaries and the optical coefficients can both be recovered with the good accuracy from the noisy measurements.

Cross-polarized wave (XPW) generation is a simple and flexible nonlinear filter for the contrast improvement of ultra-intense femtosecond laser pulse,which could enhance signal-to-noise ratio(SNR) efficiently. The principle of XPW filter is introduced briefly. The results from numerical simulation indicate that the XPW energy conversion efficiency is determined by the angle β between the input polarization direction and its [100] axis,phase modulation (PM),input intensity,crystal length and spatial shape. Among them,PM is the main cause of shorting saturation length and decreasing maximum conversion efficiency. It also reveals that initial quadratic and third-order spectral phase induced XPW pulse shape distortion,spectrum narrowing,central spectral shift of the center and efficiency decline,which provides the theoretical basis for XPW nonlinear filter to enhance ultra-intense and ultra-short pulse effectively.

The influence of driving field on dynamics characteristic in nondegenerate optical parametric oscillator (NOPO) is investigated. The Lyapunov exponents of nondegenerate optical parametric oscillator system are calculated,and also the steady state,periodic state,chaotic state and the hyperchaotic state with certain system parameters are obtained. The simulation results based on the Lyapunov exponent spectrum,phase diagrams as well as time series confirm our calculations. The results will be used in studying the anti-control of the nondegenerate optical parametric oscillator system.

A high-power mid-infrared laser is presented. The temperature-dependent tuning curve of the output wavelength of OPO is obtained through theoretical calculation,and the wavelength change with the effect of the crystal′s heat expansion is analyzed. The MgO doped periodically poled lithium niobate (MgO:PPLN) is pumped by an acoustic-optical Q-switched Nd:YAG laser. Using the optical parametric oscillator (OPO) configuration,an average power of 53.2 W for both 1.75 μm and 2.71 μm laser is obtained when the pump power is 104 W,at the repetition rate of 7 kHz,the conversion efficiency is 51%. The conversion curve doesn′t reach the saturated area,so the output power should increase with a higher pump power under the damage threshold of the crystal.

In order to increase the sensitivity of surface plasmon resonance sensors through planar metallic film closely coupled to nano- gratings and use grating period to adjust the wavelength of resonance reflection,sub-micron gratings is needed. The fabrication technique for sub-micro gratings structure is introduced. The sub-micron gratings are fabricated by synchrotron radiation (SR) lithography with SR source at Ritsumeikan University,Japan,and polymethylmethacrylate (PMMA) is used as X-ray resist. The 250 nm-width with 500 nm period pattern is successfully fabricated. The sub-micron grating with the aspect ratio of 8 is achieved. The lithography parameters such as proximity gap of exposure,the exposure dosage,and the development time influencing the structure are optimized to fabricate the gratings.

A micro-electro-mechanical systems (MEMS) infrared (IR) emitter is presented. The IR emitters are fabricated on silicon-on-insulator (SOI) wafer,and the resistance heating film on the SOI wafer used boron-doped polysilicon by ion implantation technology. The single crystal silicon on SOI wafer is designed as a heavily-doped infrared absorption layer for realizing the self-heating effect. The light-emitting layer is fabricated by using deep reactive ion etching(DRIE)process on the backside of SOI wafer,and the buried SiO2 layer of the SOI wafer is used as etching stop layer to control the thickness of light-emitting layer. The surface temperature and emission spectrum of IR emitter are measured by thermal imaging system and spectroradiometer. The experimental results show that in the case of surface temperature of about 700 K,the energy conversion efficiency is about 5.58% in the spectrum range of 1.3-14.5 μm. The experiments also show that the modulation frequency can reach to 40 Hz at 50% modulation depth.

A novel probe is put forward based on the nano optical antenna which is added by a metallic dipole nano-antenna onto the tip of the ordinary probe. When the sample light arrives at the nano-antenna,the huge field enhancement will be obtained at the antenna feedback for the surface plasmon resonances produced on the surface of the metal. The light coupled into the probe and the signal-to-noise ratio is increased,and then the higher resolution is realized. Based on the FDTD algorithm the measure results are investigated numerically by different aperture probes for the same sample with the incident wavelength of 830 nm and the scan height of 10 nm.The results show that the the new probe resolution with aperture increass first and then decreases with the change of the aperture diameter and reaches the highest of 45 nm at 150 nm which is four times of the ordinary probe resolution. The optical fields on the probe with different diameter are analyzed. The results show that the change law of the new probe resolution is caused by the different efficient length of nano-antenna on the probe. The results also show that the new probe has higher sensitivity and contrast ratio.

Based on space-variant polarization manipulation and polarizing interference,a set of amplitude pupil filters is presented. The control of axial focal shift and extended focal depth can be realized when keeping the transverse superresolution. This filter consists of two parallel polarizers,an electro-optical crystal and a two-zone half-wave plate. The electro-optical tuning characteristic and modulated distribution of intensity in the focal region of the filtered optical system are analyzed. When the modulated phase delay varies from –π to π,the real-time control of the focal shift and transverse superresolution behavior can be obtained. Here this system can be realized as a lens having variable focus with transverse superresolution adjusted by external voltage. The ratio of the first zero position can be modulated by azimuth angle of the inner λ/2 plate when the electro-optical phase delay is chosen. The electro-optical phase delay to change the focal depth can be realized in real-time control when the azimuth angle of the inner λ/2 plate is chosen.

Here the performance dependence of the organic light-emitting devices (OLEDs) on the location of a 0.5 nm LiF interlayer had been investigated,of which the thin LiF layer was used as a hole blocking and exciton confining layer. It was found that all the OLEDs exhibited improved efficiency when the LiF interlayer was used. When the LiF interlayer located 20-40 nm distance to the interface of TPD/Alq3,OLEDs showed peak electroluminescence efficiencies of around 4.5 cd/A,which is around 1.8 times of that in control device without LiF layer. Meanwhile,the current density of the devices increased when reducing the distance between LiF interlayer and cathode interface. The LiF interlayer was used to block the unrecombined holes at the interface between the recombination region and LiF interlayer,so that the electric field inside electron transport region increased,leading to a better electron transport and injection,improved charge balance and recombination probability in the recombination region. LiF interlayer may also confine the excitons in the recombination region and suppress the exciton quenching by the metal cathode.

A novel optic accelerometer based on grating interference and phase generated carrier(PGC) modulation has been fabricated and tested. The reported prototype has sensitivity of above 4×10-5gn. Its dynamic range,which is relative with cantilevers of inertia system,is completely free from the limit of optical structure. In comparison with piezoelectricity and capacitive micro-electro-mechanical systems (MEMS) accelerometers,this device achieves an improvement both in resolution and dynamic range. Applying interference between ±1 refraction beams from a grating to acceleration sensing can also enhance stability and reduce the requirements on the installation of precision. The scheme proposed can also be applied to MEMS technique,which supplies a new thought for the design of high resolution and large dynamic range micro-opto-electromechanical systems (MOEMS) accelerometers.

Using the nondistortion transport property of optical fiber taper and taking it as the optical relay component,X-ray image intensifier and charge coupled device (CCD) are coupled into X-ray image device by photosensitive adhesive as the coupling medium. The influences on coupling efficiency of optical fiber taper and CCD coupled by the coupling medium of air and photosensitive adhesive are analyzed,the coupling crafts are discussed and the key coupling techniques are given out. Experiments show that the spatial resolution of X-ray image device can reach as high as 3.5 lp/mm,which has good perspective images of human body and can meet the demands of small medical imaging as well as nondestructive testing.

Thermal stability of polymer waveguide devices is a key issue for their commercialization. Thermal stability of device is decided by thermal stability of waveguide layer (polymer). The thermally stable modulators using side-chain polyurethane and cross-linked polyurethane with same electro-optic (EO) coefficient property at room temperature have been investigated. The thermal stability is studied by measuring the change of EO coefficient of polymer modulator during ascending the curing temperature rise. The experimental results show that the cross-linked polyurethane presents a remarkably controlled significant improvement of thermal stability.

To investigate the performance of a reflecting 256 pixel×256 pixels phase-only liquid crystal spatial light modulator (LC-SLM) and to improve the ability of wavefront correction,the Twyman-Green interferometer and the phase-shift point-diffraction interferometer are set-up to measure the phase-shift characteristic and the static distortion of this SLM individually,and then use the SLM to compensate the distortion from itself. Experimental results show that the peak-to-valley (PV) value and the root mean square (RMS) values of the wavefront are reduced from 0.39λ and 0.08λ to 0.23λ and 0.03λ (λ=632.8 nm) respectively after applying an appropriate mapping of phase to grayscale and adding static distortion compensation. In addition,the Strehl ratios of far-field point spread functions are increased from 0.82 to 0.98. Therefore,this SLM with compensation is an excellent candidate for applications,such as dynamic diffractive optical elements,wavefront generation,high-resolution and high-precision wavefront correction.

Built-in electronic field has important effect to improve the quantum efficiency of the photocathode. In order to get a stable electronic field,the exponential-doping method is applied in the active layer. Exponential doping actually is a special gradient doping,according to this consideration,a new quantum efficiency formula including uniform doping and exponential doping is brought forward. Four doping samples with concentration from 1019 to 1018 cm-3 are produced in the experiment,meanwhile their spectral response curves and quantum yield curves are detected. Through the data fitting analysis of the quantum yield curve with three methods which are uniformly-doping quantum yield formula fitting,exponential-doping quantum yield formula fitting and the new-built graded-doping quantum yield formula,the fitting precision of the new-built quantum yield formula is proved best.

Spherical particle model is often used to evaluate the attenuation of electromagnetic wave by sand and dust storm and retrieval of optical thickness with satellite reflectance sensing. Measurements in laboratory and in situ show that the shapes of natural sand and dust particles are nonspherical,thus suggesting that Mie theory may not be suitable for interpreting the scattering and attenuation properties of sand and dust storm,and it will cause large errors. A model big using shape distributions of polydisperse and randomly oriented spheroid particles was used to model the natural sand and dust particles. The rigorous T-matrix method was used to compute the single scattering of sand and dust storm,and the result was compared with the spherical model. The results show that the phase function averaged over a wide aspect-ratio distribution of spheroids is smooth,featureless and flat at the side-scattering angle and closely resembles those natural sand and dust particles. The multiple scattering characteristics of sand and dust storm were computed by the adding method,and the result indicated that significant errors will be caused with the application of any single shaped particles to compute the scattering characteristics of sand and dust particles.

Spatial heterodyne spectroscopy (SHS) experimental system based on 940 nm water vapor absorption band is introduced. According to analysis of spectral resolution and bandwidth for water vapor detection,the system parameters are designed and the experimental equipment is developed. The performance test using tunable laser and cathode hollow lamp,and water vapor detection in the clear weather is conducted. The results show that the experimental equipment′s practical capability is in agreement with theoretical index. Moreover,the observed and the theoretical water vapor spectrum are also coincident. Those demonstrate the superiority of SHS technique in water vapor detection and retrieval.

Limb imaging spectrometer is an important new remote sensor for research and application of atmospheric remote sensing. The principle of atmospheric sounding using limb imaging spectrometer is analyzed. The prototype of grating dispersion type UV/visible limb imaging spectrometer is designed and manufactured. It consists of a broad-band refractive achromatic fore telescope optical system and a modified Czerny-Turner spectral imaging system. The fore telescope system is telecentric in image space and the spectral imaging system is telecentric in object space. It works over the spectral range of 540-780 nm (1st order) and 270-390 nm (2nd order). It records images from 540-780 nm when the visible filter in place,and 270-390 nm when the UV filter in place. The volume of the prototype is about 450 mm×250 mm×200 mm,and the total mass is about 8 kg. The test result demonstrates that the spatial resolution is 0.45 mrad and the spectral resolution of the prototype is 1.3 nm. Both spatial and spectral resolution satisfy the design requirement. The volume of the prototype is small and the mass is light,so it is suitable for spatial remote sensing.

Vanadium dioxide undergoes a reversible phase transition at approximately 68 ℃,and it is accompanied with drastic changes in its electrical and optical properties. It is difficult to get the accurate analytic expression dependent on temperature and wavelength through theoretical derivation,because phase transition mechanism is complex. Dispersion theory for refractive index and extinction coefficient of the vanadium dioxide thin film is studied,and its temperature-dependence dispersion formula of optical constants is presented by numerical fitting with Sellmeier dispersion model. By film matrix theory,the optical transmittance and reflectivity at different temperatures and wavelengths are calculated. In the use of magnetron sputtering,vanadium dioxide thin films of different thicknesses are deposited on glass,sapphire and silicon dioxide substrates. The optical transmittance and reflectivity of the films are measured,and the experimental curve agrees well with that of simulation.

To conduct source apportionment of aerosol particles in the laboratory,we established an X-ray fluorescence (XRF) spectrometer based on polycapillary slightly focusing X-ray lens (PSFXRL) and laboratory X-ray source. The gain of power density of the PSFXRL used in the spectrometer was 450,and the focal spot size of the PSFXRL was 205 μm. The samples of receptors and sources with diameter of 1-2 μm were quantitatively analyzed by the XRF when the working voltage and current of X-ray source were 35 kV and 70 mA. On this basis,the chemical mass balance (CMB) model was employed to apportion source contribution and the source apportionment results indicated that the main pollution source of samples for receptor were vehicle exhaust and cement dust. The source apportionment results were ideal. The experimental results show the PSFXRL has potential application in source apportionment of aerosol particles.