Phase retrieval technique using the directly measured intensity distribution to recover phase information and reconstruct the wave function is an important research area of optics and image processing. A new setup for structured illuminations in diffraction imaging is proposed. In the new setup, the object is placed against the mask, and mutual position can be interchanged. Multiple structured illuminations are used to collect several diffraction patterns. In the absence of extra information of the signal, the phase information is obtained. Simulation results show that the new setup is simple, and can achieve the success of phase retrieval. In addition, the Toeplitz mask and circulant mask are used to collect diffraction patterns for phase retrieval. The two masks need to collect fewer diffraction patterns than binary mask does and need to collect diffraction patterns as many as Gaussian mask does. Compared with Gaussian mask, the two masks are easy to realize in physics.

The point diffraction interferometer is a common instrument used in modern ultra-precision surface testing. It can be used in the sub-nanometer measurement because its reference wave is produced by pinhole diffraction instead of optic surface, which dramatically limits the measurement accuracy. A new calibration system, which can reduce the alignment difficulty and a new method that takes advantage of the background intensity of the interferogram to locate the CCD senser have been proposed. The experimental result indicates that the system error is 0.009λ, when the pinhole has a diameter of 3 μm.

Optical data collected in the 17 cruise surveys in the Yellow Sea, the East China Sea and the Pearl River Estuary are used to establish new retrieval algorithms to evaluate diffuse attenuation coefficient Kd at 490 nm by using the relationship between remote sensing reflectance and Kd. Compared with in situ observation, the retrieval from the empirical algorithm shows that the correlation coefficient is 0.91, the root mean square error is 0.35 and the average relative error is 28.27%. And comparison between retrieval from the semi-analytical method and in situ observation shows that the correlation coefficient, root-mean-square error, average relative error of the results obtained are 0.83, 0.48, 31.53% respectively. Furthermore, both the empirical algorithm and the semi-analytical method can attain better performance than the existing algorithms by comparing retrieval with in situ observation. Although the empirical algorithm shows more precise than the semi-analytical method, the semi-analytical method is more independent to the in situ observation than the empirical algorithm during the process of algorithm establishment. Therefore, the semi-analytical method is more suitable in retrieving Kd in the Yellow Sea, the East China Sea and the Pearl River Estuary.

Hollow fiber has been successfully used in infrared wavelength regions for energy delivery and gas sensing. Metallic hollow fiber is used in spectroscopic sensing system for colored solutions owing to its low-loss property in visible light regions. A stable and practical sensing system is established for detecting the concentration of colored solutions based on spectroscopic absorption. The system sensing characterizations are analysed by theoretical analysis and computational simulation. Experiments on measuring the concentration of CoCl2 water solution are conducted. The experimental results show that the system has the advantages of rapid response, easy operation and high sensitivity. The possibilities of miniaturization and on-line measurement make the system a potential candidate for promising applications in the environment monitoring, chemical process control and medicine fabrication processing etc.

The optical modulation format conversion is a key technique in the future all-optical communication. An optical modulation format conversion technique from non-return-to-zero (NRZ) signal to return-to-zero (RZ) signal is presented, based on the cross-phase modulation (XPM) effect in a silicon micro-ring resonator. When a NRZ signal acting as the probe and a periodic pulse train as the pump are launched into the silicon micro-ring resonator synchronously, the power change of the pump corresponding to the rising or falling edge leads to negative or positive chirp of the probe frequency caused by XPM. The converted RZ signal can be extracted by utilizing appropriate optical band pass filters (OBPFs). The dependence of the quality of converted RZ signal on the power and pulse-width of pump is studied, as well as that on the wavelength detuning of an OBPF to the probe. It is shown that the optical modulation format conversion can be achieved in a chip by the XPM nonlinear effect of the silicon micro-ring resonator.

Based on the coupled-mode theory, the mode transition in absorption film coated long-period fiber grating (LPFG) and response characteristics of refractive index are studied. The response characteristics of effective index of cladding mode for coated LPFG with overlay thickness are discussed, and the mode jump and mode transition are unified in mode field distribution and the essence of waveguide transmission. Based on this result, the change in absorption film coated of real and imaginary of effective index of cladding mode for LPFG coating absorption film with different overlay thicknesses and overlay refractive indexes is analyzed. The one step and two step of mode transition of the high order and low order cladding mode are given and explained. The effect of film extinction coefficient to mode transition zone is further investigated. The results show that the film extinction coefficient has little influence on the mode transition zone. Finally, the response characteristics of refractive index in LPFG coated absorption film are investigated in the mode transition zone and near the mode transition zone. The results indicate that resolution of film refractive index in mode transition is one order larger than that in vicinity of mode transition, and the resolution can be also available to 10-5 in mode transition detected by transmittance change.

An all-fiber temperature sensor based on reduced graphene oxide (rGO) is studied. Such a sensor consists of two key parts, including a section of side polished fiber (SPF) as a substrate and rGO film as temperature sensitive material which is deposited onto the SPF by spontaneous evaporation. Experimental results show that temperature change can affect the interaction between rGO film and propagation mode in SPF, and change the transmitting optical power through rGO-based SPF sensor. When temperature changes from -7.8 ℃~77 ℃, the transmitting optical power of the sensors spans over 11.3 dB. The sensitivity and temperature measurement accuracy of the rGO-based SPF sensor are measured to be 0.134 dB/℃ and 0.03 ℃, respectively. The linear correlation of the sensor between temperature and transmission optical power is 99.4% and response rate is at least 0.0228 ℃/s.

A distributed vibration sensor based on two-beam interference is proposed and experimentally demonstrated. Optical pulses are launched into two distributed fibers. With the interference effect of two channel Rayleigh scattering signals and the positioning principle of conventional optical time domain reflectometer (OTDR), detection and location of vibration events along sensing fibers can be achieved. A new signal processing method is subsequently utilized to improve the signal-to-noise ratio (SNR) of the signal and reduce the system computation. Experimental results show that the system can effectively detect and precisely positioning the external vibration events with high sensitivity. A validated optimal spatial resolution of 20 m is acquired under testing fiber length of 5 km and the SNR of the differential signal can be as high as 8.5 dB. This new interferometer can be used for long distance monitoring such as pipeline security pre-warning as well as any vibration monitoring.

According to the filter response analysis of the all-pass waveguide micro-ring, the notch filtering function can be achieved when the relationship between the coupling coefficient and the round trip loss meets the critical coupling condition. The micro-ring resonator based on polymer polysiloxane-liquid (PSQ-L) racetrack waveguide is designed and fabricated. With its notch filtering function, the power fading effect induced by the dispersion is suppressed effectively and the quasi-single sideband light-wave carried radio frequency (RF) signal of 14.35 GHz is transmitted through 25 km single mode fiber successively. To improve the flexibility of notch filtering, the conventional direction coupler is substituted with a Mach-Zehnder interferometer (MZI). The micro-ring coupling states, such as over, critical, and under coupling, and the resonant wavelength are tuned agilely by altering the power applied to the heating electrodes on the arm of MZI and the ring waveguide. The maximum notch depth is 12 dB, and the wavelength tuning efficiency is 8.2 pm/mW.

A low-loss, compact, miniaturized and stable low-pressure CO2 cell is proposed based on hollow-core photonic crystal fiber (HC-PCF). In order to ensure the gas purity, the HC-PCF is firstly flushed with high-pressure high-purity CO2, and then connected with conventional optical fibers under the high-pressure environment. The insertion loss of HC-PCF gas cell is reduced efficiently by splicing one end of the HC-PCF to single-mode fiber (SMF) and connecting the other end of HC-PCF to multi-mode fiber with ceramic ferrule sleeve. By placing the HC-PCF into a vacuum chamber to decompress its pressure and subsequent sealing process, a HC-PCF low-pressure CO2 gas cell with the pressure less than 10 kPa is obtained. The insertion loss of this gas cell is approximately 3.5 dB, and the good air-tightness and long-term stability are observed. This kind of low-pressure HC-PCF gas cell may find broad applications in optical fiber gas sensing, laser frequency stabilization, and high resolution spectroscopy.

An optical single sideband modulation radio over fiber (RoF) system with tunable carrier-to-sideband ratio (CSR) based on long period fiber grating (LPFG) is presented. The system mainly consists of five polarization controllers (PC), a polarization beam splitter (PBS), two parallelized long period fiber gratings (LPFG), and a polarization beam combiner (PBC). By tuning the polarization controller placed in front of the polarization beam splitter, continuously tunable carrier-to-sideband ratio can be obtained. The impacts of modulation index, transmission peak value of LPFG, and extinction ratio of the Mach-Zehnder modulator on CSR are discussed. Simulated results for transmission over 40-km single mode fiber (SMF) show that the receiving sensitivity increases by 5.7 dB when CSR changes from 13.22 dB to 5.4 dB which matches well with theoretical analysis.

A fiber Bragg grating (FBG) fabrication method with phase mask to achieve accurate control of Bragg wavelength by measuring and adjusting the pulling force applied on a straightened fiber is introduced. The fabrication error of FBG Bragg wavelength is hold within ±0.05 nm, and FBGs with central wavelengths covering 5 nm range can be fabricated by using the same phase mask, which improves the efficiency and flexibility of the phase mask fabrication method greatly. Meantime, a novel chirped-FBG fabrication method with scanning exposure technology is put forward by varying the fiber tension during the fabrication procedure.

A design for a novel broadband directional coupler (1×3) based on an asymmetric three-core photonic crystal fiber (PCF) is proposed. The asymmetry core in the fiber is introduced by the enlargement of air holes in three-core PCF. Numerical investigations demonstrate that the operating wavelengths of the novel broadband coupler range from 1530.9 to 1644.8 nm. The uniformity is less than 0.4 dB and polarization-dependent loss is less than 0.2 dB. In addition, the proposed coupler shows large tolerance to the fiber parameters. In particular, the coupler with at least ±4% derivation of the fiber length (20.9 mm) can ensure that the work bandwidth is not less than 80 nm.

A programmable bandwidth-tunable and wavelength-variable fiber grating filter based on a linearly chirped fiber Bragg grating (LCFBG) and thermal-optical phase shift technique is proposed. The number of transmission peaks, filter bandwidth, central wavelength and wavelength spacing can be adjusted independently. Due to the thermo-optical effect, a phase shift can be induced along the LCFBG by heating a small portion of the LCFBG, then a transmission peak can be obtained within the stop band. The specific location of fiber grating is accurately heated by using a thermal printer head as a digital heating unit. The number of the transmission peaks and the wavelength spacing can be set by changing the number and the spacing of the heating points, respectively. And the peak′s bandwidth can be tuned by changing the width of the heating region. Tunable bandwidth of transmission peak between 0.07 nm and 1.55 nm, central wavelength of transmission peak ranging from 1547.16 nm to 1558.64 nm and the minimum wavelength spacing of 0.95 nm can be achieved using this filter.

With the configuration of double-grating and two-stage amplifying, the optical fiber amplifier realizes high gain-clamped and high output power, controlled by two controlling lasers of different wavelengths. As input power ranging from -5.1 dBm to 2 dBm with the power attenuations of optical attenuators as 33.2 dB and 3.8 dB, the maximum output power comes to 1.55 W, while the average gain and noise figure of the gain-clamped fiber amplifier are approximately 30.3 dB and 6.4 dB, respectively. Furthermore, the gain′s excursion is limited in 0.27 dB. The range of clamped gain can be 24.5 dB~31.3 dB, while the gain′s excursion is less than 0.3 dB. As the powers of remaining channels are 0.74 mW and 1.57 mW respectively, the ranges of excursions are less than 0.08 dB and 0.16 dB with double channels existing in the gain-clamped amplifier.

Based on a semiconductor saturable absorber mirror (SESAM), an all-normal-dispersion ring cavity, tunable, ytterbium-doped passively mode-locked fiber ring laser is reported. Pumped by a 976 nm semiconductor laser, when the pumping power is more than 16 dBm, the fiber laser can realize tunnable output from 1033 nm to 1069 nm smoothly at a repetition rate of 25.4 MHz, and a regularly rectangular spectrum is produced. The dependence of output power, bandwidth, and domain pulse-width on wavelength is analyzed in detail at a fixed pumping power. The experimental setup is compact and self-started. In addition, the output pulse, with a spectrum width of 1.745 nm and time domain width of 34.85 ps at 1064 nm, is compressed to 15.45 ps by using single-channel grating pairs.

A new method is proposed to measure the modulation coefficient of the optical phase modulator based on piezoelectric ceramic (PZT). The modulation coefficient of the optical phase modulator based on PZT can be calculated by 3×3 demodulation algorithm, which utilizes the functional relationship between the output optical intensity and the phase difference between the two arms of the Mach-Zehnder (M-Z) interferometer. A second phase modulator is placed on another arm of the M-Z interferometer to decrease the influence of the system noise, and used as the interference source for the next experiment. We finally use the phase generated carrier (PGC) algorithm to demodulate an interfered signal of the M-Z interferometer to test the result. The whole scheme is successfully demonstrated both by numerical simulation and experimental results.

A model of describing optical discharge effect of double cladding fiber is proposed. The simulation results show that the velocity of optical discharge of double cladding fiber nonlinearly increases with the increase of power density in the fiber core and the velocity slowly increases at a higher power density. The threshold of optical discharge depends on the initial heated temperature. When the initial temperature is fixed, the threshold decreases with the increase of the diameter of fiber core. The thresholds of double cladding fiber with different core diameters are compared expenmentally, which are consistent with the model. Moreover, the comprison of different inner cladding diameters with the same core diameter shows that the threshold of larger inner cladding fiber is relatively high while the relationship between propagation velocity and power density is the same, which indicates that the core diameter is the main factor affecting optical discharge velocity.

A new optoelectronic oscillator with switchable frequency and high performance, based on multiple long fiber loops, is demonstrated. This oscillator can simultaneously obtain low phase noise and high side mode suppression ratio, and provide different output frequencies by selecting narrow bandpass filters. In the experiment, the optoelectronic oscillator can operate at 8, 9, 10, 12 GHz by switching the filter frequency. For each frequency, the output power higher than 10 dBm and side mode suppression ratio more than 60 dBc can be realized. The phase noise lower than -130 dBc/Hz at 10 kHz offset can be obtained. The experimental results agree with the theoretical analysis, which proves the correctness of the method.

In the satellite-to-ground laser communication, atmospheric turbulence influences the wave-front and increases bit error rate. The data information is got by an unequal arm-length interferometer based on differential phase shift key (DPSK), with the interference between the former code and the latter code of signal light. Generally, atmospheric turbulence makes the same influence on the wave-fronts of the front and rear codes in high speed rate communication, so differential information is obtained by the subtraction of the two successive wave-front phases when interference occurs. On the basis of theoretical foundation above, the diffraction propagation of incident signal light in the structure of the free-space differential interference is analyzed with Fresnel diffraction theory. In numerical simulation, the impact of detected optical wave aberrations on the performance of differential interference system is discussed. It is proved that free-space differential interference structure can overcome the disturbance of optical phase information of atmospheric turbulence effects. In addition, the applications and conclusions of optical signal demodulation with free-space differential interference structures are given.

In order to effectively reduce the peak-to-average power ratio (PAPR) of orthogonal frequency-division multiplexing (OFDM) signals, an improved precoding algorithm based on square root Better-Than Nyquist pulse is proposed. A 60 GHz radio-over-fiber (RoF) system with precoded 5 Gb/s 4-order quadrature amplitude modulation (4QAM) OFDM downstream signals is demonstrated by simulation so as to evaluate the effectiveness of the proposed algorithm. The simulation results show that, compared with existing precoding method, the improved algorithm further improves the PAPR reduction performance by 0.3 dB. However, considering the balance between bandwidth sacrificed and PAPR reduction performance, the data redundancy no more than 20% is recommended. Meanwhile, the obtained maximum PAPR of the signals is independent of the number of subcarriers. Moreover, for both back to back and transmission cases, the receiver sensitivity can also be improved by 0.4 dBm by using the proposed precoding algorithm. Better bit error rate (BER) performance can be achieved by high-level modulation. Hence, it is suitable for future 60 GHz OFDM-RoF system applications.

A new all-optical buffer array scheme with dynamic configurable delay time is proposed, in which the dual-loop optical buffer (DLOB) based on 3×3 collinear fiber couplers is the main part and the nonlinear optical loop mirror (NOLM) or Mach-Zehnder interferometer (MZI) is the optical controllable optical switch. Its operation principle is analyzed. The theoretical analysis and experiment demonstrate that delay time can be configurated flexibly, and the signals from the buffer can satisfy the transmission requirement.The proposed optical buffer can eliminate network congestion, and reduce packet loss rate effectively.

Optical orthogonal frequency division multiplexing (O-OFDM) is an efficient modulation technology for reduction of intersymbol interference. There is a strict requirement for the linear characteristics of amplifiers in transmitters and receivers if the peak to average power ratio (PAPR) is high in the implementation of O-OFDM modulation technology, which limits the practical employment of O-OFDM. Various techniques on reducing the PAPR are summarized, and the definition and distribution of PAPR are introduced. In order to contain the PAPR in O-OFDM systems, a new scheme for optical OFDM system PAPR reduction using dummy subcarrier is presented, which does not need to send sideband information in the transmitter and does not need additional treatment in the receiver. The experimental results show that the method can not only reduce the PAPR and the complexity of the calculation, but also improve the bit error rate (BER) of the system when the O-OFDM signals transmits over 200 km standard single-mode fiber (SSMF).

Coherent optical orthogonal frequency division multiplexing (CO-OFDM) system is considered as a promising technology for high speed optical transmission. Polarization dependent loss (PDL) and polarization mode dispersion (PMD) influence system performance seriously in high speed transmission. The mathematical model and mechanism of transmission affected by first-order and second-order PMD and PDL are presented. Analysis and simulation results show that first-order PMD adds cosine factors for different OFDM subcarriers and in second-order PMD, CO-OFDM system performance is mainly influenced by depolarization rate which can moderate phase noise induced by chromatic dispersion. In addition, PMD can not only make subcarrier polarization strengthen with the increase of frequency, but also moderate noise induced by PDL. At the fiber link of 720 km, loss factor of 0.5 and without chromatic dispersion consideration, system Q value is improved about 2 dB over the case of no second-order PMD.

The premise of all literatures about manycast routing and wavelength assignment problem in wavelength division multiplexing (WDM) networks is that all nodes are either split-capable or split-incapable. Sparse splitting network is a more realistic assumption considering network performance and cost. Manycast routing problem over sparse splitting optical networks with respect to several target functions is studied. The concept of light track and a trail-based tabu search (TTS) are proposed. Manycast member only algorithm (MOM) is an algorithm slightly adapted from the member only algorithm which is known as the best algorithm for sparse splitting multicast routing.Simulation results show that TTS algorithm performs well in comparison with MOM algorithm and is more suitable for sparse splitting networks.

The characteristic of scattering and three kinds of inter-link interferences of wireless ultraviolet non-line-of-sight (NLOS) communication are studied. The wireless ultraviolet NLOS single scattering communication simulation model based on Monte Carlo method is established. The correctness of the model is verified by the theoretical formula. Using this model the non-coplanar inter-link interference in wireless ultraviolet communication is simulated. The results show that adjusting the receiving elevation and field angle of the working link receiver reasonably can reduce the inter-link interference and improve the performance of communication system.

From the optical principle of spatial light mixer which is the core-block of the free space coherent laser communication receiver, based on it′s importance in the coherent receiver system, a structure model of the spatial light mixer is established by dielectric film polarization beam splitting (PBS) cross-spectral. Meanwhile, the mathematical relationship of optical signal and local oscillator laser effected by each optical component in the structure model is studied and the spatial light mixer mathematical model is established finally. With the mathematical model evoluted to the specific structure, the correctness and rationality of mathematical model of the spatial light mixer are evidenced by experiment. The mathematical model of spatial light mixer points out not only the relative placement of various optical components, their relative angles, but also the compensating scope of crystal phase compensation and its adjustment method, which has a great guiding significance for the development and improvement of high-performance spatial light mixer in the future.

A burst-segmentation-based and path-correlation-considered controlled retransmission scheme in optical burst smtching (OBS) core nodes is proposed. The improvements compared with previous researches are that the performance of several times retransmission under the same transmission probability and the different transmission probability situations are evaluated when the values of retransmission probability are different. The number of times for retransmission is limited to realize the controllability for both retransmission probability and retransmission times. In addition, the impact of path correlation on the proposed burst-segmentation-based controlled retransmission scheme is considered to overcome the limitation of previous researches that only refer to single path and cannot capture the effect of network topology. Path blocking probability and byte loss probability are used to evaluate the performance of proposed method, and an extensive simulation is used to validate it. From the results it can be seen that, compared with the conventional retransmission scheme, path blocking probability reduces by 13%, 24%, 16%, 6% with every decrement of 0.2 for retransmission probability respectively from 1.

For sweeping aerial remote sensor using linear array time delay integration charge-coupled device (TDI-CCD) as an imaging detector, the moving target imaging, integral time, flight and TDI scan two-dimensional space all suffer from streaking phenomenon. This reduces the sensing system modulation transfer function (MTF), and leads to the decrease of the image resolution. For the above phenomenon, we analyze the causes of image smear and establish a mathematical model for the quantitative analysis of the influence of image smear on the MTF. Mapping of the image smear to the image resolution is then founded through the relation between MTF and image resolution. Active compensation is performed on the image smear. Flight environment is simulated by use of dynamic target generator, parallel light pipe and three-axis turntable, through which the theoretical analysis results are verified experimentally. The experimental results show that when the control accuracy in a theoretically allowable error range, image smear phenomenon can be compansated and image resolution can be improved obviously.

All kinds of factors which affect the non-uniformity of a large area array color CCD aerial mapping camera are presented through analyzing the process of camera imaging. According to the analysis results, the differences in illumination of optical system are the main causes for the non-uniformity of camera imaging. The detections and measurements of the dark current noise, imaging non-uniformity and the pixel response are completed through the laboratory radiometric calibration method. The non-uniformity measurement results show that the non-uniformity of each color pixel is serious, especially that of the red pixel reaches 17%, which must be corrected. The detection results of responsivity indicates that the radiometric responsivity of each pixel for R, G and B color channel varies linearly in working spectral range, but the responsivity of pixel in the central area is significantly higher than that of the edge region. By analyzing the distribution of each pixel response characteristics, the non-uniformity correction method based on radiation response characteristic is put forward. Retrieval radiance of each pixel is computed, and according to the variation of radiance, assemblage of pixels which are used to fit the correction curve are selected sub-regionally. The calibration curve is required by using the method of least squares fitting, then the image taken on the ground by area array color CCD camera is corrected, and the correction is better than the traditional two-point calibration method. The measurement results of the non-uniformity show that, after correction, the non-uniformity of integrating sphere image decreases to 4.3% or less, wherein the non-uniformity for red channel pixel is reduced to 1.79%, which can meet the requirements of engineering practice.

In order to improve the subdivision accuracy of photoelectric rotary encoder, the method of automatic compensation of sine deviation for the grating fringe photoelectric signal is proposed. According to square wave information from precise code conversion, adaptive sampling of precise code signal is realized. The transformation process of precise code time domain signal to equal interval spatial domain signal is completed. Periodic grating fringe photoelectric signal of 24 bit photoelectric encoder is actually collected and frequency spectral analysis of discrete amplitude sequence for photoelectric signal is completed. The main harmonic components of sine deviation for high precision photoelectric encoder signal are revealed and waveform equation is established. Based on the mathematical model of grating fringe photoelectric signal and amplitude subdivision principle, compensation model of subdivision error is established. Seven undefined parameters of signal model are identified using particle swam optimization (PSO) and the signal is corrected. Uncompensated and compensated subdivision error are analyzed using subdivision error compensation model. The experimental results show that the peak value of subdivision error is reduced from 0.923″ to 0.316″. This method can actually be used in encoder system, which improves environmental adaptability and angle measurement reliability of the encoder.

Radiance detector (RD) is composed of trap detector, interference filter and precision stops. Its radiance responsivity can be traced from the cryogenic absolute radiometer. The absolute spectral responsivity of RD is obtained by measuring absolute responsivity of trap detector, spectral transmittance of filter, gain of trans-impedance amplifier, diameters of field stop and aperture stop and the distance between them, accurately. The overall performance is measured and the uncertainties are evaluated in detail. The combined standard uncertainty in the absolute spectral radiance responsivity calibration is less than 1.26% (confidence probability coefficient k=1), which can meet the high-precision calibration requirement of remote sensors.

To meet the radiometric calibration requirements of optical remote sensor with large aperture and wide viewing field, a spectrally tunable reference light source with 3-m diameter integrating sphere and 1-m diameter exit port is designed. By incorporating multi-wavelength light-emitting diode (LED) modules and tungsten-halogen lamps modules, both absolute radiance and spectral distribution of the light source can be adjustable within 400~2500 nm. A spectral auto-match algorithm is developed to generate solar, ocean, vegetation, desert and other typical target spectrum. LED modules are cooled by water circulating system with high temperature stability and driven by high precision programmable direct current power supplies, which ensures the stability of exit radiation. The test results show that the planar uniformity of the source is better than 99.5% at the exit port, the angular uniformity is better than 99.4% within ±60° to the exit normal, and the stability of source is better than 99.8% within 2 hours.

We design an optical phase locked loop (OPLL) whose bandwidth is 1~7 GHz with ADF4107. Through a fast photo-detector, we can obtain a beat signal of two external cavity diode lasers. Then, two kinds of error signal are generated while passing OPLL, which are respectively loaded into the grating piezolectric ceramics and feedback current of semiconductor lasers to reduce the noise of the beat signal from MHz to Hz. The system is successfully used in electromagnetically induced transparency (EIT) spectral experiment. This method can be also applied to the Raman spectroscopy experiments of ultra-cold atoms.

The upper limit of output power for single-mode laser from a single ytterbium-doped fiber can be reached using a tandem pumping configuration. Ytterbium-doped fiber laser is difficult to operate below 1030 nm due to the relatively large absorption cross sections. In order to get highly efficient ytterbium-doped fiber laser, the most basic method is to regulate the fluorescence properties of fiber and make the emission subpeak approach 1018 nm. The mechanism of how Yb3+ ions fluorescence properties change in silica fiber is studied and a 1018 nm ytterbium-doped fiber is obtained by co-doped method. The emission subpeaks of the preform and fiber are at 1008 nm and 1021 nm, respectively. The emission subpeak of the fiber is 18 nm, which is shorter than that of normal Yb-doped fiber, and the difference of emission cross sections is larger. Its optical-optical convertion efficiency at 1018 nm is up to 68%.

A new method of non-metric camera distortion calibration is proposed, independent of the known imaging center, which is fit for the second order polynomial distortion calibration model. This method is made up of the following two steps. First, the curves distorted from straight lines are closed by adding straight-line segments, and areas of those curves are computed. Sencond, the relationship between these areas with ends and the distortion parameters with center are elicited, thus the approximate values of parameters are resolved. The above relationship is iteratively modified by the reference values according to the distortion model, based on the endpoints of these curves and the current calibration. Therefore, the distortion parameters and center are iteratively approaching the real values. Moreover, a target function of distortion calibration is designed, with local nonlinear optimization method, so as to reduce the image noise′s effect on calibration. Both simulations and real image tests show that this method can implement exact calibration with fast convergence.

As the development of machine vision technology, the color line-scan system is widely applied in the on-line inspection. Due to the non-uniform distribution of optical intensity, the vignetting of optical lens and the different responsivities of charge coupled device (CCD) camera, non-uniform and color distorted image, which induces the problem of image processing and the stability system, could be output from the color line-scan system. A method used in image correction for color line-scan machine vision system is presented. Compared with the polynomial fittings, the mean and variance result of uniform object obtained by this method is better and closer to the real gray of object. The method has been used in the automatic optical inspection of prited circuit board (PCB).

A detailed theoretical study on the band structure, electronic density and optical properties of β-FeSi2 under the isotropic stress is performed based on the first-principles pseudopotential method. The results show that the lattice constants of β-FeSi2 change with different stress. With the compression stress increasing, the densities of Fe-d and Si-p states decrease, and the conduction bands move to higher energy while the valence bands have little change that makes the energy gap widened; when the lattice is stretched, the densities of Fe-d and Si-p states increase, and the conduction bands move to lower energy while the valence bands have little change which makes the energy gap narrow down. The valence and conduction bands are traversed by the Fermi energy when stretch stress is -25 GPa that means the semiconductor β-FeSi2 converts to the conductor. Compressing lattice will lead to the blue shift, increase the absorption index and photoconductivity, and decrease the reflectivity. While stretching will result in the red shift, increase the static dielectric constant, refractive index n0 and reflectivity, and decrease the absorption index. Applying stress can effectively regulate the electronic structure and optical properties of β-FeSi2, which is an effective way to change and control the photoelectric transmission performance of β-FeSi2.

Rare earth complex Tb(aca)3phen is synthesized and characterized by ultraviolet-visible absorption spectrum, and the absorption range is mainly from 250 nm to 355 nm, which has two absorption peaks located at 296 nm and 345 nm. The photoluminescence spectra of the material show bright green emission under the excitation of 345 nm light and four emission peaks are located at 487, 545, 585, 621 nm, which correspond to the 5D4→7F6, 5D4→7F5 , 5D4→7F4, 5D4→7F3 electron transitions. A series of organic light emitting diodes (OLEDs) based on Tb(aca)3phen as emission layer are fabricated, the devices′ structure is ITO/PEDOTPSS/Tb(aca)3phenPVK/Bphen(x nm)/Al. The effect of Bphen layer thickness on the performance of OLEDs is investigated. The recombination of hole and electrons can be increased when the thickness of Bphen is about 5 nm. The luminescent power of OLEDs is 2.4 times as large as that of OLEDs without Bphen buffer layer under 20 V driving voltage.

The ultrafast carrier dynamics and nonlinear optical properties in graphene oxide and reduced graphene oxide of different reduced time are investigated using pump-probe and Z-scan techniques with femtosecond laser pulses. Partially reduced graphene oxides are produced by expositing graphene oxide to the hydrazine vapor for different time. The extent of oxidation and contents of different functional groups in materials aremeasured by X-ray photoelectron spectroscopy. Results of pump-probe experiments show that the decay time of carrier relaxation of graphene oxide become shorter after being reduced. The amount of functional groups also affects the ultrafast dynamics process in reduced graphene oxide. For nonlinear optical properties, experiments of Z-scan results show that the saturable absorption property of graphene oxide is enhanced after being reduced. After reduction for a certain time, the enhancement of saturable absorption will not be changed visibly. It is greatly related to the extent of reduction.

An athermal optical design of a refractive/diffractive static infrared earth sensor, which meets the requirements such as portability, cheapness and reliability, is presented. The optical system has a wide-angle f-θ structure with a diffractive element introduced, which is beneficial to the correction of the monochromatic, chromatic and athermal aberrations. The inverse telephoto structure is adopted to achieve enough back-working distance. It is shown for the designed optical system that the f-θ linearity is less than 0.5% at 20 ℃, the field of view is 140°, the modulation transfer functions are greater than 0.52 at the spatial frequency of 20 lp/mm in the temperature range from -20 ℃ to 40 ℃ and the wave-front aberration is less than λ/4 for all situations, with a satisfactory back-working distance of 15 mm. These meet the requirements in the actual applications.

Through the study on the structural features and aberration characteristics of the off-axis three mirror optical system, a freeform surface is used in the appropriate location of the system. A broad width off-axis three mirror optical system is designed, with focal length of 1000 mm, F-number of 7, field of view of 20°×10°. The modulation transfer function of this optical system is higher than 0.49 at spatial frequency of 50 lp/mm. Compared with the previous pushbroom imaging model, this optical system realizes frame imaging model, so the choice of detector is more extensive. Compared with other three mirror optical systems, the main advantage of this broad width off-axis three mirror optical system is that it can obtain a wider imaging field of view, enhancing the quality of remote sensor imaging.

The quaternion method is introduced into the polarization optics systematically. Two quaternion representations of polarized light are presented which are based on the Poincare sphere representation and the Stokes parameters, respectively, and their equivalence relation is proved. The diversity of the quaternion representations of the polarized light is discussed. The quaternion representations of polarizing devices and systems are obtained. By using the quaternion representation, the equivalent theorem of polarizing system is proved, and the composition and the quaternion representations of the reduced equivalent system are deduced. The quaternion matrix calculation method for polarizing systems is presented, and the transform relations between the quaternion representations and the Mueller matrixes are obtained. Based on the conditional commutative low of the quaternion matrix multiplication, the optimization way of the quaternion matrix calculation method are discussed, and the application prospects of the algorithm are pointed.

In accordance with the characteristics of a high resolution space remote sensing camera, a focusing mechanism is designed to compensate for defocusing. The accuracy of focusing mechanism is analyzed from the transmission mechanism, the photoelectric encoder and the focusing control system. Before calculating the total errors of the focusing mechanism, all of the causes and values of error are discussed. After testing the accuracy of the focusing mechanism with closed-loop control mode, the data of the encoder codes and the focusing mirror displacements are processed respectively. Contrasting the results, the accuracy of the focusing mechanism is obtained, equal to ±3.1127 μm, which is in accordance with the theoretical value, and it proves that the design of the focusing mechanism is effective. Finally, the reason of differences between the accuracy results of the encoder codes and the focusing mirror displacements is obtained after analyzing the testing method. The experiments show that the accuracy of the focusing mechanism meets the camera′s accuracy requirement of ±10 μm.

The application of 4th radial order whispering-gallery mode (WGM) on refractometric sensor is investigated. A microcapillary resonator with 4.8 μm wall thickness is researched in experiment and the sensitivity difference among different modes is observed. The highest sensitivity of 48.74 nm/RIU (refractive index unit) and detection limit of 6.2×10-6 RIU are achieved. The 4th order WGM resonant spectrum can be picked out clearly by comparing with the simulation results, and it shows a significant advantage against other modes in sensor sensitivity. In addition, the temperature dependent resonant wavelength shifts of different orders WGM are calculated. The 4th order WGM shows a lower response to temperature fluctuations comparing with other low radial modes. This may provide a solid theoretical and experimental foundaiton to build practical refractometric sensors with high sensitivity and low noise.

Field of view (FOV) and effective aperture area are always limited by a reciprocal relationship in conventional heterodyne receiving antenna system of synthetic aperture imaging ladar, leading that the final signal-to-noise ratio (SNR) can't be improved via unilateral increasing one. From key aspects of receiving viewing angle, detectable ability of signal light and SNR, relative merits of three typical heterodyne receiving structures are discussed, which are telescope for heterodyne receiving, focusing lens for heterodyne receiving, and telescope for self-heterodyne receiving. Qualitative analysis results, compared with telescope receiving structure, show that the heterodyne receiver using a lens and a detector can expand the system′s receiving viewing angle and reduce the emission signal power, but can′t enhance the SNR actually, while the heterodyne receiver using a lens and an array detector with larger FOV and stronger detection ability has a reduction to 1/N in transmitting power and N times improvment in final SNR.The conculusions of this study meet with Siegman′s optical heterodyne receiving antenna theory and provide a certain reference to the parameter choosing of other heterodyne detection systems working in the photo-limited regime.

Based on the first-order Born approximation and scattering theory of non-stationary fields, the spectra and coherence properties of partially coherent pulse scattered by anisotropic media are studied and analyzed numerically. The dependences of medium parameters and pulse parameters on the spectral density and spectral degree of coherence of partially coherent pulse scattered by an anisotropic medium are given. Results show that, compared with the case of isotropic medium, the distributions of spectral density and spectral degree of coherence of partially coherent pulse scattered by an anisotropic medium are asymmetrical. Finally, physical interpretation of the main results is given.

According to the wave equation of the optical pulse propagating in the nonlinear fiber, the nonlinear coupled equations is deduced under the Raman effect and the parametric amplification in the low-birefringent fiber. The gain spectra is obtained from the coaction of Raman effect and parametric amplification when the pump linearly polarized along the fast axis of low-birefringent fiber. The results show that the Raman effect can lead to asymmetric of Stokes and anti-Stokes gain spectra. The maximum value and location of the gain spectra are different when power of input pulse and propagation constant are variable.

A plasma column with length of several decimeters is generated in the upstream region of flowing gas (argon and trace air）at atmospheric pressure by using dielectric barrier discharge device in coaxial configurations. The discharge mechanism of the plasma column is investigated by optical method. The result indicates that a moving layer of light emission propagates in the upstream region, which behaves like a plasma bullet with a velocity of about 0.8×105 m/s. It indicates that streamer breakdown mechanism is involved in the upstream discharge. Electron density in the order of 1015 cm-3 is also obtained by Stark broadening. Electron excited temperature can be calculated by Boltzmann plot. The results show that the excited electron temperature in the upstream region increases with the increasing of the peak value of the applied voltage.

A model for partially coherent light propagation suitable for synchrotron soft X-ray is established based on statistical optics theories. We use mutual optics intensity to describe the partially coherent light, and sum the discrete wavefront considering reasonable approximation. The coherent properties after propagating a distance are numerically analyzed with the model. The influences of propagation distance, coherent length of source and source size on the coherent properties at sample position are studied with the established model. Meanwhile, coherent diffraction experiments are carried out in the soft X-ray interference lithography branch beamline (BL08U1B). Simulations on the experimental results are performed according to the model. The results show that the simulations coincide with the experimental patterns. The model can be used for the design of the synchrotron beamlines with high coherent properties.