Based on the dispersion characteristics of double metal cladding wave guides, a novel coupling method, which is free from using the prism, grating and other coupling elements, is developed. Experimental results agree well with the theoretical prediction.

doubly clad optical fiber with an inner cladding made of birefringent single crystal whose optical axis is parallel to the fiber axis is discussed. Exact characteristic equations are derived for vector modes. The influence of the ratio (KCl) of the ordinary ray refractive index to the extraordinary ray index upon the waveguide dispersion is analyzed in detail. It is impossible to deduce the expression of waveguide dispersion because of the complexity of the characteristic equations, a feasible approach to calculate the waveguide dispersion is presented. The results show that with the change of k cl , the value of waveguide dispersion changes correspondly as the geometrical and optical parameters (S and R) keeping invariable. The influences made by k cl , S and R on the propagation and cutoff characteristics of low order modes are also analysed. The result provide a significant reference for designs of new types of dispersion flattened fiber, dispersion shift fiber and passive optical devices

Numerical simulations have been used to compare the transmission performance between low duty cycle RZ format with and without prechirping. It is shown that, pulse prechirping will act accompany with the second-order dispersion of the fiber and enhanced their effect to transmission performance. After slope compensation, prechirping of pulses is demonstrated to be helpful both in reducing pulse distortion and nonlinear interaction, and the transmission characteristic of the properly prechirped pulse with certain power level is better than that of non prechirping pulses. Moreover, the prechirping can be optimized to obtain the best transmission performance.

The effects of queuing delay of output buffer on the property of crosstalk in optical packet switching nodes are investigated. The analytical relationship between crosstalk and buffer length is derived. It is concluded that the crosstalk increases with the increase of buffer length. Among the crosstalk sources, the most of them are incoherent, and the probability of coherent crosstalk decreases with the increase of buffer length significantly, and if the buffer length is longer enough, the coherent crosstalk could be neglectable.

A new method of recording multiple fractional Fourier transform hologram with holographic lens is presented. With this method, images of several recorded objects can be reconstructed in different positions and directions in three dimension space. The theory and characteristics of the multiple fractional Fourier transform hologram recorded with holographic lens are analyzed. A multiple fractional Fourier transform hologram is fabricated and satisfying reconstruction results are obtained.

A robust filtering method based on Bayesian estimation rule and statistical signal processing technique is presented. The new method can efficiently reduce the noise of speckle fringe pattern, and rather accurately perform phase recovery from a single fringe pattern. Experiment on the test image is presented to illustrate the validity and processing of the new method.

A new type of 3 D digital imaging system is proposed. Using this system, the shape of an object can be digitized and the texture of this object can be obtained simultaneously. The hardware design and software framework design of the system are described in detail. Two methods to get the color texture of object are introduced. One is to extract from the coded fringe pattern; the other is directly to capture the texture of the object without fringe pattern. The 3 D digital image made on a human face as an experimental result is given. The system has great a potential in many industrial applications such as reverse engineering, film making, CAD/CAM, virtual reality, biomedical imaging, etc.

A fiber Bragg grating (FBG) is bonded to the side of the isosceles triangle cantilever beam with a determinate angle along the beam axis. Using the effect of FBG′s chirp, the sensing of many parameters about dynamics has been studied through measuring the FBG′s bandwidth. It is demonstrated in theory and experiment that this sensor can be automatically perform compensation for the FBG′s wavelength shift induced by temperature. In the experiments of displacement and stress, a good linear response has been obtained, the sensitivities of displacement and stress are 2.47 nm/mm and 2.26 nm/N, respectively, and the FBG′s bandwidth can be changed to 15.5 nm.

A method of writing fiber Bragg grating into the birefringent fiber is presented. The beat length of the birefringent fiber is easily obtained. It is found that there are actually two gratings respectively writen on the axises of the birefringent fiber. These two gratings act selectivity on the polarization states and these two polarization states are vertical to each other. A better polarization splitting device can be made by using this character.

A new microfabrication method--electron beam scanning exposure and fast atom beam etching--to fabricate sub wavelength gratings is described. 100 nm line width period structures and gratings can be obtained by this process. It can be applied in the devices with sub microns structures such as Bragg gratings, semiconductor laser and anti reflection surfaces.

A lasing wavelength red shift from the reflection center of fiber Bragg grating in a Yb doped fiber laser has been observed. The wavelength shift is about half of the grating bandwidth and it is not depend on the temperature or the reflection of fiber Bragg grating. Theory of lasing gain profile is used to explore this wavelength shift and it is well coincided with the experimental results.

The phenomenon of sensitized luminescence in the Ce3+:Eu3+:Cr3+:Sm3+:YAG layer grown by LPE is reported. With higher concentration of Ce 3+ ion doped into the layer, there are new lines observed in the blue and green band of the emission spectra of this layer. The analysis of those emission lines show that they can be assigned to the radiative transition from the 5D i(i=1,2,3) higher excited levels of Eu 3+ ion directly to the ground state levels 7F j(j=0,1,2,3) because of the sensitization and energy transfer from Ce3+ ion to Eu3+ ion in YAG lattice. And this Ce3+ :Eu3+:Cr3+:Sm3+:YAG epitaxially grown layer also turns out to be a new single crystal phosphor for white emission.

Nonlinear optical response of C 10 PPV solution was investigated by using the resonant femtosecond optical Kerr effect (OKE) method. The experimental results revealed that the OKE signal showed an ultrafast rising followed by a fast and a slow relaxation process with time constant of 200 fs and 400 ps, respectively. By analysing the photoluminescence spectra of C 10 PPV and C 10 PPV doped with C 60 , it is suggested that the 400 ps slow component can be assigned to the singlet exciton migration among different conjugated segments inside polymer.

The quasi phase matched second harmonic generation in periodically poled lithium niobate (PPLN) Z cut 0.5 mm thick annealed proton exchanged (APE) waveguide with fan grating was realized by applying an external field poling. The grating period ranges inverted from 5.8 μm～6.2 μm and the interaction length was 4 mm. Used a CW Nd:YAG laser as a fundamental beam source at 1.064 μm, input power in waveguide was 10 mW. The green SHG of 20 μW at 0.532 μm was achieved at 125%/(W·cm 2) normalized conversion efficiency in PPLN waveguide.

The bidirectional reflectance distribution function (BRDF) is simplefied and modelled according to the principles of simple geometry optics and statistical modeling. The model is fitted with experimental datum by the optimization of genetic algorithms in order to gain more light scattering information of the object rough surface. Other models are put forward to fitting the experimental datum and the results are good.

Acoustooptic tunable filter (AOTF) is one of the most important devices in the high densed WDM system. One significant limitation of AOTF′s performance is the presence of sidelobes in the transmission spectra. It is proposed that the apodization can be accomplished by use of the electrooptical effect of LiNbO 3 crystal based on the principle of the birefringence apodization. This method is analyzed and discussed theoretically. The experimental results are consistent with the theoretical results on the whole.

On the basis of coupled mode theory the linear dispersion relation in an infinite one dimensional periodic structure is given and then a class of slow Bragg soliton like solutions is found by introducing the nonlinearity. It is shown that an increase of intensity will lead to strengthen the effect of group velocity dispersion. Because of the nonlinearity, the width of stop band structure decreases, and the pulse attains an instantaneous frequency which depends on the detuned parameter, velocity, intensity and nonlinear coefficient.

The squeezing effect of two coupling atoms interacting with a single mode light field in Kerr medium is studied by means of the quantum theory. The influences of the Kerr medium on the squeezing effect are discussed. In particular, the effect of the excited field intensity and the coupling constants of two atoms on the squeezing effect are analyzed.

The evolution of the linear entropies of field, atom and field atom coupling system in the system of a two level atom inside a phase damping cavity interacting with a coherent field under large detuning are investigated. The effects of atomic initial state and the mean photon number of the field on the above linear entropies are discussed. The results show that the linear entropies of both the field and the atom are strongly dependent on atomic initial state, but the evolution of the linear entropy of the field atom coupling system is independent of the atomic initial preparation. With the increasing of the mean photon number, the linear entropies of field, atom and field atom increase.

It is shown that the idea of higher order amplitude squeezing can be applied to the q deformed light field. The orthonormalized eigenstates squeezing properties of the q deformed operator a N are determined by the even and odd structure of the states. Breaking such structure will get states with new squeezing properties.

A new type of green light sensitive photopolymer material is prepared. The photosensitive medium is composed of acrylamide monomer, photoinitiator, coinitiator and polymeric film forming binder. With holograms recorded in this material, the diffraction efficiency of the photopolymer as high as 55% is obtained. 10 holograms are stored in this medium using angular multiplexing technology and the SNR of the reconstruction images is high. It proves that the photopolymer is suitable for high density volume data storage.

The differential optical absorption spectroscopy (DOAS) has become a widely used method to measure the concentration of trace gases in the atmosphere. By using the least squares fits of reference spectra to the measurement spectra, it usually has a high measurement precision. But in order to determine the detection limit, the error must be considered seriously. The measurement error in DOAS is analyzed, it is caused mainly by noise, selection of waveband and interferences of other trace gases. The relationship between error and those factors is discussed.

The c axis oriented AlN films on Si (100) substrates diameter of 6.35 cm are prepared using N 2, Ar and AlCl 3 vapour via electron cyclotron resonance plasma enhanced chemical vapor deposition. The characterization of film is investigated by means of X ray diffraction (XRD), energy dispersive X ray analysis and scanning electron morphology. The dependences of the c axis orientation of the AlN film on the microwave power, substrate temperature and N 2 flow rate are studied. High quality AlN films of large area and c axis standard deviation less than 5° are obtained.