A new method for fabricating apodised fiber Bragg gratings (FBG) without self induced chirp is proposed by adjusting the period with the depth of refractive index modulation, in which general coupling coefficient is kept nearly constant along the grating. And effective medium picture is used to analyse the mechanism why self-induced chirp is eliminated by this method. Compared with that with uniform period, the reflectivity of Gaussian profile grating with nonuniform period has almost no resonance side lobes at shorter wavelength. And the numerical simulation spectrum is provided.

The researchers generally studied one channel all fiber modulator. In order to develop the great capability of optical fiber, the multiple channel all fiber acousto optical modulator should be concerned. The multiple channel all fiber acousto optical modulator is studied theoretically. The perturbed coupled mode theory is used to discuss the solutions of coupled mode equations for optical fiber when there are multiple parts being perturbed, and the multiple channel modulation is analyzed. The results can be used as a basis of experimental research.

A method for designing optimized polarization independent and temperature insensitive optical waveguide couples using fluorinated polyimide is presented. Based on measured polarization, temperature and dispersion characteristics of fluorinated polyimide, a 3 dB waveguide coupler with 120 nm bandwidth with minimal polarization and temperature variance is designed and verified through simulation based on three dimensional beam propagation. The coupling ratio of the theoretical device is (50±0.8)% for two orthogonal polarization modes in the waveband 1490～1610 nm and the temperature range -10～40 ℃.

The delay ripple of chirped FBG is analyzed in detail. A simple physical model and function of filter are set up about chirped FBG (CFBG). A numerical simulation of grating delay ripple has been done using Schrodinger equation and compared with experiment. The research shows that the system degradation depends on the period and amplitude of delay ripple. The period of CFBGs′ delay ripple is 0.01～0.1 nm indicated through a lot of experiments. The amplitude of delay ripple must be less than 15 ps in order to assure eye opening penalty less than 0.5 dB.

Based on the theory of polarized light interference and multibeam interference, the transmission function of birefrigent Gires Tournois (BGT) interleaver is deduced. It is concluded that the higher the reflectivity is, the broader interleaver bandwidth and the lower contrast are whereas the narrower the bandwidth, the higher the contrast. Related experiments are designed and adjusted to verify the relationship between performance parameters of BGT interleaver. The structure parameters can be determined and tunable interleaver can be achieved by using the characteristics of BGT interleaver.

As a key device in ASON (automatic switched optical networks), the study on all optical wavelength converters is becoming a very important project. A theoretical model of wavelength conversion based on semiconductor laser is established. The frequency modulation response of wavelength conversion is discussed by using rate equation under the small signal analysis. The characteristics of wavelength conversion are analyzed in different optical parameters including the injection current, signal average power, gain coefficient and so on. Those results are useful to optimal design of the wavelength converter based on semiconductor laser.

An identification method for fire smoke based on a neural network is discussed. The neural network′s input used three couples of extinction coefficient ratio of three laser beams with wavelengths of 670 nm, 1060 nm and 1550 nm respectively. The network′s output used fire smoke and non fire smoke factors. Experiments of multi wavelength lasers attenuation by typical fire smoke and non fire smoke factors were conducted, resulting in twenty six network sample pattern definition tables acquired from selected data. Three hundred and ninety one times of simulation training resulted in an output error less than 0.0001. The verification experiments prove that this method is effective in distinguishing between fire smoke and non fire smoke factors. This identification method has practical application for solving fire smoke recognition and other similar non structural problems.

The conventional TbFeCo magneto optical medium has a relatively small Kerr rotation in blue region than in the red, consequently, intensive optimization of RE TM blue disk is needed. Optimization of magneto optical properties and optical properties is carried out, and good results are abtained. The temperature distribution of the recording layer is calculated, the results show that the newly designed structure is successful in temperature control and has better thermal response.

Based on the principle of volume holographic storage in Fe∶LiNbO 3 crystal and angle fractal multiplexing, using diode pumped solid state laser (DPL) instead of huge ionized argon laser, a compact volume holographic data storage and correlation system was designed and constructed. The correlation of 1000 human face images is realized, and by using of wavelet transform to extract the edge character of each image, comparatively exact identification results are obtained.

A novel 3 D temperature field reconstruction method is proposed, which is based on multi wavelength thermometry and optical computed tomography. A mathematical model of multi wavelength thermometry is founded, and a novel optical computed tomography based on changeable relaxation parameter technique is proposed. Through computer simulation and comparison with algebraic reconstruction technique and filter back projection algorithm, the reconstruction results of the new method are discussed in detail. The study shows that the new method always gives the best reconstruction results. As an example, temperature distribution of a profile of four peaks candle flame is reconstructed with multi wavelength radiation computed tomography.

The four beam laser tracking interferometer system for three-dimensional coordinate measurement is introduced including the principle of measuring system, the redundancy technique, laser tracking interferometer, a new type of target retroreflector, the optimal arrangement of system and the experimental results. The future work is also pointed out. The experimental results show that four beam laser tracking interferometer system has achieved an accuracy of 0.0620 mm on a 700 mm×600 mm plane located 800 mm away from the trackers.

A real-time measuring method based on the ATR technique is proposed. The experimental setup consists of a laser diode as the optical source, a spatial filter as a beam expander, a CCD detector as a camera and a coupling prism, when a converged light beam which is transmitted through the spatial filter incidents upon the hypotenuse face of the prism, the reflected divergence spot imaged by the CCD camera will embody a black line in the case of the angular width of the light beam contains a coupling angle corresponding to guided wave resonance, several dark lines corresponding to the guided-wave modes are demonstrated on the computer screen. The dark lines move when some parameter of guide wave change, according to the shift of the dark lines, the refractive index and the film thickness of the polymer can be determined. This experimental setting can be used widely such as the wave-guide fabricating, detecting the poling process etc.

Space selective gold nanoparticles were precipitated in silicate glasses containing gold ions by irradiation with Ti∶sapphire femtosecond pulsed laser and heat treatment. Absorption spectra measurements show that the plasmon absorption peak of the precipitated gold nanoparticles shift red slightly and their intensities increase with the increasing of treatment temperatures; Also, average size of nanoparticles increases along with increase in laser power density. This means that under the given laser irradiation and heat treatment conditions, gold ions inside the glass can be reduced to Au atoms and then accumulate to form gold nanoparticles with quantum size effect. According to the laser irradiation profiles, the sizes and multicolor display of gold nanoparticles can be controlled by changing the power density of irradiation. Au nanoparticles are stable, and their color is fadeless at room temperature.

In consideration the spectrum characteristics of the pump high power laser diode, a modified Fabry Perot fiber laser resonator is designed. And a fiber laser with more than 10 W output, near diffraction limited and operating in the 1110 nm region is developed.

By letting the pulses pass through an electrooptic intensity modulator twice, a simple method for the amplitude equalization of high repetition rate pulses generated from a p order rational harmonic mode locked fiber ring laser when p<5 was proposed. The modulator was used as both a mode locker and a pulse amplitude equalizer in the cavity. A theoretical explanation based on time domain analysis was used to find appropriate parameters to obtain equalized pulse train and the experimental results agree with the theory.

A revised plane wave expansion method for quickly calculating the band structure of photonic crystals of pixel type is used to design a photonic crystal of square lattice with a large absolute band gap at high frequency. The optimal GaAs photonic crystal structure has a large absolute band gap of Δ ω=0.0995ω e (where ω e=2π c/a, a is the lattice constant, c is light velocity) with a mid gap frequency of 1.2625ω e.

In a hybrid recording system, the coercivity is dependent on temperature, and an external laser can locally reduce its value to a point where the field from the magnetic head is sufficient to switch the magnetization and this occurs only where this area crosses the magnetic field from the head. The rectangle waveguide near field optical spot and the recording media heat effect have been studied. The results indicate that the rectangle waveguide near field heating technology can break superparamagnetic limit.

There are five parameters, i.e. the initial amplitudes of a pump beam and a signal beam, the ratio of the initial beam width of the pump to that of the signal, the initial separation between the two beams′ centers, and the wavelength ratio of the pump to the signal, which influence the induced focusing of the signal optical beam due to the cross phase modulation of the pump beam in self defocusing nonlinear media. The effect of the ratio of the initial beam width on the focusing of the signal beam is discussed under other different parameters. The numerical results show that there exists a pair of optimum values for the ratio of the initial beam width and the initial separation, which can result in the strongest focusing of the signal, and another pair of optimum values for the ratio and the separation, under which the optimum focusing can be obtained for the given length of the medium specimen. The detailed discussion about the effects of all five parameters on the induced focusing of the optical beam in self-defocusing nonlinear media can be used to design experiments leading to the best effect of the focusing.

A fiber optic switch based on a novel micro-electromechanical system (MEMS) technology is developed, allowing fast switch (50 dB) and wide bandwidth. Each switch module consists of an electromagnetically actuated gold coated silicon mirror rotating around a 100 μm diameter shaft and a miniature 5 V driven coil. Enabling technology is of precision EDM machining. The switch is scalable to 8×8 and allows the realization of high capacity cross connects.

A new photoacoustic tomographic imaging mode by using acoustic lens directly imaging is put forward, acoustic lens response is figured out and distribution of criterion sample at image plane in a known sound field is measured. Considering sound resource point of cylinder piston, a theoretical correction to sample imaging is carried out and the results are analysed. Investigation indicates that it is feasible for photoacoustic tomographic imaging by acoustic lens. By picture reconstruction, the images of eyewinker in tissue are obtained. The axial resolution and transverse resolution are very high.

The scattering medium consists of various volume fraction of particles which are either 0.22 μm or 0.494 μm in diameter and which are suspended in filtered distilled water. A comparision is made of the intensity distribution of the horizontally and vertically polarized radiation side-scattered from small particles. The experimental results indicate that the intensity of horizontal polarization for the small particles is much larger than that of the larger particles. This phenomenon is exactly the reverse of the vertical polarization cases.

Design theory of a new acceleration sensor is advanced. The acceleration sensor adopts a cube corner prism as inertia pendulum, and two dimensional acceleration measurement can be realized by using laser angle measurement principle. A systematic theoretical study, selection principle of the design parameters and preliminary experimental results are given.

A method is put forward for designing hyperboloidal catadioptric omnidirectional imaging system. The re projection formulae about this kind of system are derived,thereby the coordinate mapping between virtual image plane and real image plane is established, which offer a essential model and a calculational method to deal with video image. According to this omnidirectional imaging system design method, a hyperboloidal mirror is developed,and a hyperboloidal catadioptric omnidirectional imaging system is established.

The mathematic model of modal wavefront reconstruction using Hartmann Shack (H S) wavefront sensor is analysed. The effect of non orthogonalisty of the mode on the reconstrution precision is simulated, and it is indicated that the non orthogonality does not affect the use of modal algorithm. The conclusion is that the mode orthogonality is not a necessary condition in the course of wavefront measurement and correction using Hartmann Shack sensor, and the orthogonalizing algorithm cannot improve the measurement and correction precision in Hartmann Shack sensor and adaptive system.

Based on the modified effective Hamiltonian for the atom field system, the wave function of the system is derived by means of matrix forms. A feasible scheme is presented to generate the four photon coherent states via far off resonant interaction of a degenerate Λ type three level atom with coherent state cavity field. It is also proved that the superposition states of four photon coherent states with more than four component cannot be generated by using the above same method. That is, the four photon coherent states can remain unchanged in the cavity when the third atom with the same velocity as the second atom is injected into the cavity.

Two photon laser induced fluorescence spectrum (TP LIF) of NO in the wavelength range 220～350 nm is obtained by using optical parameter generator and amplifier pumped by Nd∶YAG laser as excitation source. A few stronger band can be attributed to A 2Σ(v′=0)→X 2Π(v″=1～8) transition. Some molecule constants about NO in the ground state are deduced by the spectrum. The Frank Condon factor and relative spectrum intensity are calculated. Compared with the results of experiment they are in accordance basically and a little difference is discussed. All of these can provide an important reference for monitoring of NO by the technique of laser induced fluorescence.

A reflective phase compensator (RPC) based on thin film interference theory is constructed. It can be used to compensate the group delay (GD) of an extra narrow band pass filter that cannot be compatible with the 40 Gb/s system. The group delay for an extra-narrow band filter with bandwidth of 0.2 nm is reduced from about 10 ps to <0.76 ps by means of combination of a 50 GHz narrow band thin film filter and RPC filter.