A high-accuracy rotational Raman lidar system has been designed for daytime temperature profiling of atmospheric boundary layer. An ultraviolet laser with wavelength at 355 nm is selected as light source. A high-resolution grating is employed to separate scattering signals that the lidar receives and solar background signals according to wavelength spatially, and an edge mirror is then used to reflect the rotational Raman signal and block the majority of interference signals including solar background and Mie-scattering and Rayleigh-scattering signals. Two signal, whose central wavelengths are located at 353.9 nm and 353.1 nm, respectively, are filtered by two narrowband interference filters. The two filters also block the leakage of interference signal accurately, which ensures the requirement of daytime measurement. The lidar system is simulated by using a numerical calculation, and the result shows that the system is capable of measuring temperature profile of atmospheric boundary layer in daytime with a temperature errors of less than 1 K up to a height of 2.5 km under conditions of laser energy of 300 mJ, 25 cm diameter telescope, observation time of 10 min, solar radiance of 3×108 W/(m2·sr·nm) and atmospheric backscattering ratio less than 2.5.

There is a significant fluctuation in the light field under water caused by surface wave of water, to which the photosynthesis of phytoplankton in water responses. As a result, the phenomenon is attracting more and more attentions. Based on the data of light field under water in Meiliang Bay of Taihu Lake, the variation of light field under water with depth was calculated and the fluctuant characteristics of light field under water were analyzed. The results show that significant fluctuation in light field under water is resulted from surface wave of water. The maximal fluctuation depth in aptitude is approximately smaller than 20 cm, which is much smaller than that in ocean. The decrease of the fluctuation varies with depth is exponential. The larger is the diffuse attenuation coefficient, the faster is the attenuation of magnitude of the light field under water. The fluctuation will almost disappear when the depth is larger than 30 cm. In addition, the effect of boat on the measured light field under water was investigated. If the direct sunlight isn't blocked by the boat the larger proportion of the skylight in the incident light, the more relative errors just beneath the surface of water caused by the shelter of boat will be.

A new method is proposed for determination of three-dimensional orientation of the transition dipoles of single molecules. Water layer is added upon the immersion mirror objective on the total internal reflection fluorescence microscopy. The different indices of refraction between water and oil can lead to optical path difference resulting in defocused imaging. A polarization-displacement prism was added before CCD. Beam was split according to the polarization-displacement prism. The field distribution on the CCD includes the information about the orientation of single molecules. Exact field distribution excited by evanescent waves in CCD was considered. The three-dimensional orientation of single molecule was obtained by analyzing the different images of the orthogonal polarization of light.

Three-dimensional (3D) intensity distribution of double zero-order Bessel beams is theoretically analyzed and simulated in computer. It is found that a chain of three-dimensional localized hollow beams can be generated by interference of the double zero-order Bessel beams. Dependence of the size, the spatial period and the quality of these localized hollow beams on the parameters of the double zero-order Bessel beams are discussed quantitatively. The condition for zero intensity at the central points of the localized hollow beams is given. We also found that the optimal localized hollow beams can be generated only when the radial ratio of the inner to outer rings is taken as a special value. This research is significant for design of new diffractive optical elements to generate localized hollow beams based on interference of the double zero-order Bessel beams.

In order to realize the quasi-distributed measurement for Fabry-Pérot (F-P) sensors, a multiplexing scheme of optical fiber microelectromechanical system (MEMS) Fabry-Pérot pressure sensors with arrayed waveguide grating is presented. Based on Fabry-Pérot interferometry, the sensors are fabricated with microelectromechanical system techniques and interrogated with the dual-wavelength method. In this method, the single-valued relation between ratio of sensor reflectance at two different wavelengths and the calibrated pressure are used to determine the pressure. The arrayed waveguide grating (AWG) is used to multiplex the sensors. The demodulation and multiplexing principles are theoretically analyzed and experimentally verified. The experimental results demonstrate that in the linear measurement range of pressure (0～1.5 MPa), the sensitivity (ratio of sensor reflectivity/pressure) of the system achieves 0.02026 MPa-1, the measured ratio has a good linearity with the pressure, and the standard deviation of the reflectance ratio is less than 3×10-4. The system can eliminate errors resulted from wavelength-independent variations in the fiber interconnection to the sensor,and has reasonable linearity, sensitivity and precision. Many sensors can be multiplexed in this system and there is no observable crosstalk among them.

A combination of differential phase-shift keying (DPSK) modulation format with dispersion managed soliton (DMS) transmission technique can depress the noise and nonlinear damage, and gives additional innovative advantage in densely spaced channels at high bit rates (40 Gbit/s and more) systems. The phase jitter of root of mean square induced by multi-perturbations is analyzed by variational method in differential phase-shift keying dispersion managed solition system, which includes the amplifier spontaneous emission (ASE) noise, intra-symbol interference (ISI) between the channels. The effect area and magnitudes of multi-perturbations are given. The results declare that phase jitter induced by amplifier spontaneous emission noise is almost cubic relationship with transmission distance and phase jitter induced by cross phase modulation (XPM) is nearly linear with transmission distance. With the optimal dispersion management map strength S from 1.5 to 3.5, the perturbations are restrained. The phase jitter of amplifier spontaneous emission noise which is far below XPM's now is most decreased than the XPM-ASE and XPM. Then wave division multiplexing system is restricted by the external factor of the channel numbers increasing.

There is a strain transferring ratio between structure and fiber Bragg grating sensor for the existence of sensor’s interlayer. A strain transfer model is developed based on shear-lag theory for evaluating the interaction between the surrounding host material and a length of fiber Bragg grating sensor embedded in it, when there is an angle existence between the sensor axis and the external principal stress direction of the host material. And the general formula of average strain transfer rate is deduced at the same time. The fiber Bragg grating sensors were used to verify the theoretical results. When the angle α is 30.72°, the wavelength changes ratios of experimental results are 0.727,0.738,0.746 respectively; and the theoretical result is 0.739, the errors are less than 2%. At last, strain measured error which are induced by sensor location angle deviation is discussed. The result indicates that the strain transfer models that the fiber Bragg grating sensor under non-axial stress and axial stress are greatly different, and the measured results have some errors because of the angle location error of fiber Bragg sensors.

RF-TV overlay EPON technique is investaged. First, the interference problems between 1550 nm CATV path and 1490 nm data path are described and then the theoretic formula of the nonlinear crosstalk from 1490 nm to 1550 nm lightwave via stimulated Raman scattering effect in the optical fiber and the linear crosstalk from 1550 nm to 1490 nm lightwave caused by in-sufficient wavelength isolation of the CWDM coupler are presented, based on which the quantitative analyses and computation examples are given. The results show 9 dB carrier-noise-ratio degradation at the low end of CATV band due to the nonlinear crosstalk from data and 2.5 dB optical power penalty for data receiver due to the linear crosstalk from CATV in the case of conventional taper-fused CWDM. At last proposals to solve the crosstalk problems are offered including Ethernet idle scrambling, high isolation CWDM etc..

A novel 40 Gb/s all optical 3R regenerator was proposed. High finesse Fabry-Pérot (F-P) filter was used in clock recovery. Before clock recovery, a stable laser was used in wavelength conversion to aim the wavelength of input signal at the window of F-P filter. After clock recovery, the low frequency noise in the recovery clock was suppressed using semiconductor optical amplifier (SOA). In the all optical decision gate, dual SOAs in series were used to lengthen active region of SOA and to rise the optical switching speed. The pattern effect of the output of decision gate was eliminated by using narrow band filter. In experimental study, new 40Gb/s optical signal was regenerated from degraded optical signal using this 3R regenerator. The timing jitter and pulse width of the degraded signal were larger than 5 ps and 16 ps. Compared with these, the timing jitter of the regenerated pulse was 1.5 ps. The signal noise ratio improved 14 dB. This regenerator was recorded to work continually more than 15 h. This experiment testified that the new scheme of regenerator can work successfully in 40 Gb/s all optical 3R pulse regeneration.

A low cost curvature optical fiber sensor that can detect curvature directly is developed in recent years; its curvature measurement sensitivity is improved using bend enhanced method and the sensor can distinguish between positive bending and negative bending. This sensor has a wide linear range and is suitable for measuring large curvature deformation. It meets the demand for embedded measuring in structure. With transfering strain to curvature, it can also measure axial strain. Nevertheless, the operation principle of this sensor is still under exploration. Through analyzing radiation law of cosines,whisper gallery ray and groove angle theories, the operation principle of this intensity modulated macro-bend curvature optical fiber senor is presented based on light scattering theory: bending of sensitive zone bring about mode coupling and lead to the variation of surface scattering loss. The mathematic model of relationship among light loss, bending curvature, surface roughness and parameters of the fiber’s configuration is also presented. Experimental results have demonstrated the proposed model.

A soft-lithography based optical interconnection circuit for inter-chip communications on printed circuit board (PCB) was designed, fabricated and characterized. A novel circuit termination coupler was proposed, capable of easing the coupling between transceiver and waveguide significantly and reducing the demand for installing precision, and it was found that an optimum coupling was achieved at a ratio of 12∶1 between the lengths of beam duct and entrance/exit window. The fundamental circuit layout criteria were analyzed for waveguide intersections, and the crosstalks between crossed waveguides were calculated as a function of both various waveguide cross-sections and crossing angles. It was found that cross-talk would be lower than -30 dB for crossing angles greater than 54° in the case of strong bounding. Polymer devices for optical intercomnection circuit are fabricated experimentally. Experimental measurement for both coupling structure and cross-over circuit elements were compared with calculated results and a reasonably good agreement was obtained. In contrast with traditional lithography or laser direct writing, soft lithography features a simple fabrication process and high-precision duplication of polymer three-dimensional structure in quantity.

It is spontaneous scattering light that the optical time domain reflector (OTDR) based on Brillouin scattering distributed optical fiber sensor detects, which is very weak, and has a frequency width of several decades megahertz, so it is difficult to perform traditional coherent demodulation. A novel optical coherent detection based on Morlet wavelet transform is presented according to the signal's characteristic. Firstly, the spontaneous Brillouin back-scattering light is coherently detected with the frequency-shifted light modulated by a microwave electric optical modulator as the reference light. Secondly, the detected photocurrent signal is processed with amplitude demodulation by Morlet wavelet transform. Finally, the distributed sensing signal with improved signal-noise ratio is gained. The simulation and experimental results of the detection method are given, and the proposed method can process the Brillouin optical time domain reflector signal quite well. The methods based on Morlet wavelet transform and Hilbert transform respectively are compared, and it is found that the former is better for Brillouin optical time domain reflector.

In the field of optical information security, the most attractive work is the so-called double random phase encoding encryption scheme. This encryption method is based on the principle of Fourier transform algorithm and its linearity opens avenues of attacks. Double random phase encoding encryption can be implemented optically or digitally. We demonstrate a new approach to chosen-plaintext attack on double-phase encoding encryption system implemented digitally. With this attack an opponent can access both random phase keys with the help of impulse functions. The expressions of retrieved keys are also given. One of the most apparent advantage of proposed approach is that the decryption process is lossless. Numerical simulations show a good agreement with theoretical analysis.

In order to solve non-consistence color appearance between different viewpoint images, a multi-view video automatic color correction system is proposed. Global correction matrix is first obtained between target image and source image, then estimate whether global correction is satisfied. If no global correction is satisfied, image segmentation and Karhunen-Loeve transform are performed. Then local mapping relations between target image and source image segmentation regions can be established. And preferred region color mapping is performed to correct source image. Finally video tracking technique is used to correct video images. For the standard multi-view images, compared with histogram matching and global one dimension correction algorithms, experimental results show that the proposed algorithm can effectively eliminate the influence of matching distortion, and achieve good correction result. The studies indicate that the system can apropos reveal color change relation existing in images, has capability of showing content adaptivity, and also is important method of color correction.

In real-time vehicle type recognition, shadows interfere with moving vehicle extraction, location and recognition due to light. We propose a simple and effective method to segment moving vehicle cast shadow. The proposed method exploits spectral and geometrical properties of shadows and relationship between the point in shadow region and space position and shape of vehicle. Feature points of occluding function are detected using multi-resolution of wavelet transform and the boundary between self-shadow and cast shadow is detected. Firstly, the shadow can be coarsely segmented by the shadow spectral property, and then the feature points are extracted by multi-scale wavelet transform. The proposed method can effectively segment moving vehicle cast shadow. It needs not know in advance the information of the light direction, vehicle color and background texture. Our experimental results show that the proposed method is robust and effective in detecting shadows.

Automatic exposure control (AEC) is one of the indispensable functions of modern digital still cameras and video cameras. A new automatic exposure algorithm using luminance histogram of an image is proposed. According to the attention mechanism of human visual system (HVS), it is considered that peak regions in luminance histogram correspond to the regions of no interest in an image. The aim of the algorithm is to find the two largest peak regions in histogram and calculate the mean weighted luminance of entire image. The luminance weights of pixels in peak regions are decided by a set of quadratic curves, and the parameters of quadratic curves are affected by the brightness of image background, which can be obtained from parameters of the automatic exposure system. Fuzzy logic is applied to practical systems to determine the luminance weights of pixels in the two largest peak regions. Results show that the new automatic exposure algorithm gives efficient exposure control over various scene tests.

In order to obtain a correct phase unwrapping (PhU) result, as well as to alleviate the effect of noise, a phase unwrapping algorithmweighted discrete cosine transform (DCT) algorithm based on phase derivative variance quality weight is proposed. In testifying the validity of the proposed algorithm, the weighted and non-weighted discrete cosine transform algorithms are used to unwrap the simulated and experimental phase maps with artificial random and shot noise, respectively. The two results derived from the different ways are compared with the same unwrapping phase without artificial noise, respectively. It shows that the phase unwrapped by use of weighted discrete cosine transform method is closer to the ideal results. At the same time, the two algorithms are almost equal in computation time. All these prove that in recovering the true phase, our proposed method not only has high efficiency, but also keeps satisfactory noise robustness and reliability.

The problems arising in the computed tomography area are well known for their high dimensions and ill-posed. Tikhonov regularization method is developed to reconstruct temperature distribution from deflectometric projection data. Beam deflection angles obtained from moiré deflectograms are integrated to optical path length differences, and a modified regularization method is applied to the linear projection equations. The conjugate gradient method is used to compute the regularized solution for the least-square equations. In numerical simulation, the approach produced reliable reconstructions by computing underdetermined equations and overdetermined equations respectively for asymmetrical distribution. The average errors were 2.1% and the maximum value errors were 5.2% after 10 iterations, which provided a good indication of the precision and convergence of the method. The experimental results of reconstruction from real projection data were satisfactory when compared with the reconstruction results by deflection angle revision reconstruction technique (DARRT) and the direct thermocouple measurements.

Based on the characteristics of the color scanner, the spectral reconstruction of images was studied using the method combining the principal component analysis (PCA) and back-propagation (BP) artificial neural network. The IT8.7/2 standard color card was adopted as the training samples, and the different set of patches in this card was used as testing samples to discuss the effect of different structure networks, principal component numbers and training sample numbers on the spectral reconstruction; meanwhile the color patches of Natural Color System (NCS) were selected as testing samples to analyze the relationship between the performance of spectral reconstruction and the different types of training and testing samples. The experimental results showed that the back-propagation (BP) network structure of 3-14-6 and 6 principal components were the best choices. The consistency between training samples and scanned objects was important for the spectral reconstruction of images based on color scanner.

In electronic speckle pattern interferometry (ESPI), the saw-tooth phase map obtained by the phase-shifting technique is inherently full of speckle noise. Noise reduction must be carried out to suppress the high-level noise before it is unwrapped. In accordance with the feature of the saw-tooth phase maps, an adaptive filter is developed combining the classical sine/cosine filter and the fringe orientation information of the saw-tooth phase map. Fringe orientation map is firstly generated from the saw-tooth phase map, and then the fringe-contoured-window is derived accordingly. Finally, the filtering is carried out within the window. Comparing with existed filters, it has a better performance on phase jump information preservation and does not have any blurring effect on the phase distribution providing the filtering is implemented on the equal-phase window. Moreover, its capability of noise reduction is more powerful. The effectiveness and advantages of the novel filter have been verified by both simulated and real saw-tooth phase maps.

A frequency response measuring system of semiconductor optical amplifiers based on direct-subtracting method is proposed according to the definition of scattering parameters of optoelectronic devices. By subtracting the frequency response of laser-photodetector system, the frequency response of an semiconductor optical amplifier its own can be obtained. With this system an InGaAsP traveling-wave semiconductor optical amplifier is measured under different input optical powers and different bias currents, and the frequency response curves are calculated. These curves indicate the gain saturation effect and the noise characters of the semiconductor optical amplifier. Moreover, it is shown that the signal gain of lower frequencies is less than that of higher frequencies. The reason is the carrier lifetime of semiconductor optical amplifier is limited. Lower-frequency signals have longer period to deplete carriers continuously, therefore the number of carriers cannot resume in time.

In order to settle the problem of real-time and dynamic non-contact measuring the swing angle of scanning mirror, a method of laser dynamically measuring swing angle of scanning mirror for the infrared earth sensor based on laser measuring technology and CCD detecting technology is presented. System for dynamically measuring swing angle of scanning mirror is developed, which can accomplish the dynamic and static laser non-contact measurement for the parameters of scanning mirror which are swing frequency, angle of zero position, amplitude value, average of peak values, etc. The composition and overall structure of system is introduced. Emphasis on analyzing and discussing the theory of dynamically measuring swing angle of scanning mirror, the method of design for large field of view, large relative aperture and special linear scanning optical system, the problems of error correction for measured data and graph manipulation are settled by established mathematic model of the system. The accuracy of measurement system is verified by experiment, the results indicated that measurement range of system for swing angle is 0°～±12°, distinguishing ability of the system is 0.01°, accuracy of dynamic and static measurement is less than ±0.04°, this method of dynamically measuring swing angle is suitable.

Based on the principle of measurement of celetial body's brightness, the signal-noise ratio (SNR) of photon-multiplier-tube (PMT), common charge-coupled-device (CCD) and electron-multiplying CCD (EMCCD) was deduced, the performance of these three devices had been compared in theory and experiment. The results showed that the performance of EMCCD was the best in all situations. When the radiation was fairly weak, the dominating factor which had an effect on detection ability was readout noise of CCD, so the performance of PMT was better than CCD's. If the radiation is fairly strong, the limits detection ability was quantum efficiency, then the performance of common CCD was better than PMT's. Finally, sum of squared error and signal-noise ratio (SNR) were experimentally validated, it showed that experimental value was consistent with theoretical value.

Signal-noise ratio (SNR) is an important parameter for the performance of a heterodyne detection system. In order to make full use of the received signal, the signal-noise ratio should be analyzed.The principle of signal-noise ratio is discussed, and general equations for a shot noise limited operation are derived in terms of the distribution functions of the local oscillator and signal fields, the size and quantum efficiency of the detector. To obtain the maximum signal-noise ratio, the phase, amplitude and polarization of the local oscillator and the signal light should be matched strictly. Finally, the signal-noise ratio is discussed for Airy function distribution fields. Numerical simulations show that when the ratio of the size for Airy disks is controlled within 0.8～1.2, the bias x0 of Airy disk axis below 0.5, the size of detector in the range (0.6～0.8)λf/d, the signal-noise ratio is above 0.7ηPs/(hνB).

Besides defocus and astigmatism that can be corrected by wearing spectacles or contact lens, there are also higher-order aberrations in human eye which influence the visual function. By using adaptive optics technology, the system of higher-order aberrations correction and vision analysis for human eye has been developed. The principle of correcting high-order aberrations and vision analysis is presented, and key element technologies, such as wave-front corrector, Hartmann wave-front detector and control system, are explained, correct capability to Zernike modal aberrations are listed, most of aberrations that RMS error equals 0.5λ decreased below 0.2λ, the simulated result is shown to explain how the function of system is realized. It is an effective tool to study the influence of higher-order aberrations to vision function.

The Portevin-Le Chatelier (PLC) effect associated with avalanching shearing deformation, will occur during a tensile test for many alloy materials. With the aid of the digital speckle metrology technique including digital speckle pattern interferometry (DSPI) and digital speckle correlation(DSC), an optical system was set up to measure the three-dimensional deformation on the specimen in real time during tensile test. The nucleation process of a shearing band in Al-Cu polycrystal was captured by using a high-speed digital photography (1000 frame/s). The quantitative results of the displacement field and axial strain field on the front and lateral surface are obtained by digital speckle correlation method and the propagation of the out-plane deformation of the band is vividly visualized by correlation fringes. By combining the in-plane and out-plane deformation results, a report of three-dimensional nucleation process for the shearing band is presented here.

Using the theory of electromagnetic field and Maxwell equations in medium, we derive the TM mode optical field distribution of resonators with arbitrary cross section. Moreover, taking quadrupolar-shaped microcavity as example, it deduces the eigenvalue equation which contains the propagation constant. Using the software Mathematica, it stimulates the optical field distribution of fundamental mode (m=1) and high-order mode with the different deformation factors, and it is found that the fundamental mode gets the maximum of light emission at φ=45°, 135°, 225°, 315°, it has the feature of “bow-tie” mode. Furthermore, when the deformation factor is 0.1～0.15, the effect is more obviously; however there is not the phenomenon of drawing out the light directionally in the microcavity when m≥2, and it does not form the stable “bow-tie” mode when the deformation factor gets any values. It provides a certain theoretical base for designing and making the quadrupolar-shaped microcavity lasers.

Stereo matching is currently one of the most active research topics in domain of computer vision. A sub-line segment match method based on the wavelet transformation is presented, in order to match feature points more accurately and efficiently. It is based on that the multi-scale local maxima of wavelet transform can obtain the locations of the signal sharp variation points at different scales for transformation coefficients of a quadratic spline wavelet. A from-coarse-to-fine matching algorithm is applied to match these feature points. Sub-line segment is structured by these feature points. The points between the two endpoints of the sub-line segment are matched quickly using acceleration way. This method proposes a good solution for balance problem between match precision and match speed. The thickness of cement clinker in the cooler is measured using this method. The experiment shows this method can obtain the bed of material distributed condition of the cement clinker precisely.

An optical engine of the mini-projector suitable for the personal use is designed. It is a single panel digital light processor (DLP) system by using LED as its illuminator and X prism as its mix-color device, which can provide a 38.1～50.8 cm color projection display. The theoretical analysis shows that the design can satisfy the need of the color projection display with the system efficiency 16.1%. The simulation by using the software is LightTools made. After three million rays are traced, it shows that the efficiency of the optical engine is 14.6% with flux 22.8 lm on the screen. The simulation results coincide with the theoretical analysis of the system efficiency. The ANSI nine-point uniformity of the screen is 91.55%, -93.36%, which can reach the specification of the design.

Utilizing polarizing beam splitter (PBS) and polarizing beam combiner (PBC), a dual-loop optoelectronic oscillator (OEO) is designed without adding any active device. This oscillator can simultaneously produce optical and electrical output. No additional electronic noise can be introduced because of avoiding additional active devices. Furthermore, there is no signal frequency fluctuation and beat noise caused by interference and beating due to optical carrier orthogonally coupled in optical domain. According to the analysis of optoelectronic oscillator, dual-loop is able to effectively suppress the side modes in each single loop. Through experimental comparison, the side mode suppression ratio is improved by 30～70 dB. Finally, we demonstrate the free-running experimental result, which has high quality spectrum at 12 GHz with side mode suppression ratio 50～70 dB, phase noise of -93 dBc/Hz at 10 kHz from carrier and Q value of 1010.

The fabrication and characteristics of a polymeric electro-optic modulator with double channels in attenuated total reflection (ATR) configuration, made of a thermally crosslinkable polyurethane, has been investigated. The fabrication procedure of proposed double-channel ATR modulator is extremely simple, it can be implemented by replacing a single electrode with two discrete electrodes in a single channel ATR modulator. Working at 832 nm, a double polarization modulator is demonstrated with the electro-optical coefficient of 24.2 Pm/V, an independent operation modulation speed of 500 MHz and low insertion losses of below 1.5 dB by measuring polarization modulation of the poled devices. There is no measurable cross talks due to the large horizontal separation of two channels and the small vertical separation of the electrode pair. A long-term thermal stability of the fabrication modulator at an elevated temperature, 100 ℃, is obtained due to cross-linking polyurethane as the waveguide layer of the devices.

The rate equations of Er-doped and Yb-Er co-doped systems pumped at 0.98 μm are presented, considering the upconversion mechanisms, such as cooperative upconversion, cross relaxation, and excited state absorption. A multi-theoretical model is founded to analyze the gain characteristic of the waveguide amplifier, by two-dimensional waveguide finite element model and propagation equations with forward and backward amplified spontaneous emission. The dependences of the gain on waveguide length, pump power and doping concentration are obtained. The new theory is used to analyze the gain performance of a practical Yb-Er co-doped Al2O3 waveguide amplifier, and the analyzing results are in accordance with experimental data.

A new photonic crystal fiber (PCF) with composite hexagonal air hole lattice is proposed and analyzed using the full-vector finite difference frequency domain (FDFD) method with anisotropic perfect match layer (APML) absorbing boundaries. We numerically demonstrate that the flattened dispersion of different levels, even the nearly zero ultra-flattened dispersion characteristics can be achieved through optimizing three geometrical parameters, two for air-hole diameters and one for hole pitch. As an example, the dispersion is 0±0.545 ps/(km·nm) from 1.48 μm to 1.78 μm wavelength when Λ, d1 and d2 are 2.1 μm, 0.5 μm, 0.8 μm respectively. The flattened dispersion feature makes it suitable for the wavelength-division multiplexing communication systems and nonlinear optics.

Transmission spectrum of a one-dimensional photonic crystal micro-cavity containing dispersive medium are calculated by use of the finite-difference time-domain method, and frequency shift of defect modes is investigated. In comparison with photonic crystal without dispersive medium inside micro-cavity, we find the frequency shift phenomenon of defect modes which results from the medium dispersion. And then, the dependence of frequency shift of defect modes on dispersive medium parameters such as strength of dispersive, damping coefficient and centre frequency is analyzed in detail. The result shows that the above parameters of dispersive medium determine the resonant frequency of the defect modes. The frequency of the defect modes can be significantly tuned by adjusting carefully the dispersive medium parameters. Such phenomenon can be used to tune the resonant frequency, which has a great potential for a new generation of optical components.

Electromagnetically induced transparency (EIT) and slowing-down of group velocity (SGV) in Eu3+∶Y2SiO5 were investigated by using the density matrix equations of the interaction between the light and the matter and their numerical solutions. The relationship of the probe transmissivity with different probe detuning and coupling Rabi frequency was obtained. The influence of inhomogeneous line width on electromagnetically induced transparency and slowing-down of group velocity were analyzed. Electromagnetically induced transparency was restrained when increasing the inhomogeneous line width. The center transmission was not homogeneously change with the increase of ions-doped concentration. There is an optimal concentration which can make the electromagnetically induced transparent remarkable. It is evident that group velocity of the probe has a minimum value for a certain coupling field strength.

Calculating the transmitted light intensity of light scattering from random scatters is important for extracting information within the scatterers which is unable to be directly measured or observed. On the basis of analyzing the components of the transmitted light intensity from nano-particle random scatterers, it is pointed out that multiple scattering theory, first-order multiple scattering theory and Lambert-Beer law can be used to calculate the transmitted light intensity in relatively precise degree. The formula of the transmitted light intensity has been deduced too. For a given random system, the said three theories are used to numerically calculate the transmitted intensity and there exist four kinds of typical relationships between the three numerical results. Through analyzing the calculated relationships, the scattering processes within the random scatterers and their contribution to the transmitted light intensity have been analyzed.