The propagation characteristics of optical pulses in the variable dispersion fiber is analyzed by numerically solving the nonlinear Schrdinger equation. The optical pulses compression factor and compressed pulses quality in different dispersion decreasing fibers are compared. It is calculated the compression factor of the pulses in comb like dispersion fiber instead of dispersion decreasing fiber. To optimize the picosecond optical pulses compression, a novel method of combining of high order soliton pulse compression and dispersion decreasing fiber compression is proposed.

The dual overwritten fiber Bragg gratings have significant applications in telecommunications and fiber sensors. The perturbation to the refractive index by dual overwritten fiber Bragg grating is analyzed, and the coupled mode equations are obtained. The spectral characteristics of dual overwritten fiber gratings are discussed and investigated by numerical simulation. The method described is conducive to the fabrication and applications of dual overwritten fiber Bragg grating.

The experimental results on high power Yb doped double cladding fiber broadband superflurescent source pumped by a 976 nm laser diode are reported. The maximum superfluorescent output power is 54.11 mW, while the slope efficiency is 69.35%, central wavelength of superfluorescent spectrum is 1082 nm with a 17.2 nm 3dB bandwidth.

The chiral optical fiber with liquid core is manufactured successfully. An experimental investigation is made on its polarity response. It is found that the polarization ratio and the extinction axes of output light is changed as compared with the bulk chiral medium.

The effect of intensity on the recording sensitivity and saturation diffraction efficiency was studied experimentally in holographic recording of (Cu,Ce):LiNbO 3 crystal by use of a red beam for recording and a blue for sensitizing. The sensitizing light increases the recording sensitivity, and the saturation behavior will appear with enough high intensity of sensitizing light. The recording light increases the recording slope defined as the initial time derivative of the square root of the diffraction efficiency by sublinear relation I x r (x<1) and thus the recording light decreases the recording sensitivity. Dependences of the saturation diffraction efficiency on the intensities of the recording and sensitizing light show that there is the maximum saturation diffraction efficiency.

The self enhancement and self depletion phenomena originated from the beam coupling effect are observed in photochromic (Fe,Mn):LiNbO 3 nonvolatile holographic storage experiments. Based on this self diffraction effect,four kinds of recording and optical fixing procedures are set up. The experimental results show that the highest diffraction efficiency available from the self enhancement may be twice of the lowest one from the self depletion,both during the recording and fixing phases. Therefore,the use of the self enhancement is necessary for the practical applications.

In study of ultraweak luminescence (wuch as bioluminescence) the weakness of luminescence or the lack of samples (photons) and the influence of system dark noise causes low SNR in photon images acquired by image intensifier. It is proposed that a photon image correlation integral method based on statistics and a photon image processing method based on correlation processing. The method accumulates photon image to get enhanced SNR grey scale image. A computer simulation method is developed to illustrate the process. This method also illustrates the SNR relation between photon image and traditional grey scale image and provides an effective way for detecting ultraweak bioluminescence.

A method of image reconstruction with attenuation correction for laser produced plasma is presented. The principle of the maximum entropy is used to derive reconstruction algorithm suited for reconstruction with absorption. The algorithm is used to simulate two images model. The results show that the reconstruction accuracy with attenuation correction is dramatically improved compared to the accuracy without correction.

When the speckle interferometry or the electronic speckle pattern interferometry (ESPI) is applied to measure the continuous movement or the deformation of an object, the temporal speckle patterns can be recorded. By analyzing these time-sequence speckle patterns, the continual deformation of the tested object is obtained. A new method is proposed for measuring the object deformation based on analysis the fluctuation of time sequence speckle patterns. Two experiments have been conducted to demonstrate the performance of the method.

A new method of three dimension shape measurement is presented. The random digital speckles are projected on the reference plane, which is moved by equal distance in the direction of depth. Temporal sequence speckle images are acquired with CCD as reference set R(t). Replace the reference plane by object, the speckle image O modulated by the object, is also grasped with CCD. The correlation value between any subimage O(x,y) in O and the corresponding subimages R(x,y;t) in R is approximately quadratic curve distribution. The position of the curve peak, is the height value of the object point. The method goes out of the limit of original horizontal correlation in previous method and is a true temporal sequence correlation method. It is a simple principle and higher measurement precision without complicated phase unwrapping and calibration procession, and can be used to measure the discontinuous and spatial isolation shape. According to the characteristic of error, a new interpolation method bas oncorrelation weight is presented. It has better result than normalinter polation method.

The near field distribution of uncoated and metal coated fiber optic probes were characterized by the method of three dimensional finite difference time domain (FDTD). The result reveals that, for an uncoated probe, propagating wave emitting from the conic side dominates the near field distribution, while a film of metal is coated, the coated probe can confine the wave more strictly inside it. Second, the polarized incident wave becomes depolarized after emitting from the small aperture of two kinds of probes. In other words, there are two electric field components whose polarization direction is perpendicular to that of the incident one. Accordingly, the image contrast can be improved if the polarized components instead of the total field are detected. The relationship between the distribution characteristics of near field distribution and the phenomenon of depolarization is analyzed in detail.

A new structure to 3 D measurement is developed based on projection Moiré. The method of changing lights is used instead of using mechanical structure for phase shift. It improves the speed greatly (The speed is 4 s～8 s). Two CCD are used to eliminate the reflection and the structure of vertical projecting and incline imaging are used to get the better light field. The system can measure big area (300 mm×300 mm). The precision of system is 40 μm. Experiment shows that the method is effective and satisfying.

An automatic method of measuring optical fiber geometric parameters is described. The end face of the fiber is imaged by a microscope and recorded by a CCD camera, and then the image is transferred to a image grabber plugged in a microcomputer for further analysis. Several digital image processing methods are used to remove the noise in fiber image. The image segment algorithm is used to extract feature datapoints. The data is analyzed by using different algorithms to give the geometry parameters of the fiber. Sophisticated software is programmed. An instrument developed based on the hardware and software described above can be operated conveniently with high accuracy.

How to enhance the efficiency of high order harmonic generation is an important topic in high field physics. Many ways including two color laser field, phase matched in a gas filled hollow fiber and adding a magnetic field, etc. are adopted. In the investigation of two color field high order harmonic generation, it is found that the atomic energy level structure greatly affects the high order harmonic generation. For a certain level structure, a specially chosen high frequency additional driving field can greatly enhance the efficiency of high order harmonic generation.

The interaction between a femtosecond laser pulse and Ar atomic clusters is studied, and a simple model is established to calculate the energy spectrum of ions emitted from the exploded clusters. The calculated spectrum is very similar to an experimental one, and it can explain the characters of energy peaks in the experimental energy spectrum.

BBO I noncollinear optics parametric chirped pulse amplification pumped by a Q switched and frequency doubled Nd∶YAG laser is studied experimentally. The signal is a chirped pulse at wavelength of 800 nm, which is obtained from a self mode locked Ti∶sapphire laser and then is stretched by a grating pairs. The result shows that variation of the noncollinear angle can affect the gain spectrum significantly.

For the case of a Q switched Nd∶YAG laser with a KTP parametric oscillator inside the laser cavity, the temporal evolutions of the population inversion and of the pump and signal intracavity power are discussed by using the simple model of coupled equations. The results show that the optical parametric oscillator can produce single or multi pulses, depending on the signal cavity finesse and the pumping level. The single and multi pulses were obtained by the different signal cavity reflectivity experimentally. The theoretical calculation was coincident with experiment results well. The characteristics of intracavity optical parametric oscillator are analyzed.

The absorption spectra and fluorescence lifetime of high quality and highly doped Nd∶YAG crystals, grown by the temperature gradient technique in our laboratory were measured. The main absorption peak of Nd∶YAG crystal was 808 nm. The absorption coefficient of Nd∶YAG crystal with 0.030 mole fraction of Nd ion concentration was up to 20.7 cm -1 . The fluorescence lifetime was found to be 150 μs, and concentration quenching was shown. The laser characteristics comparative experiments of highly doped Nd∶YAG and Nd∶YVO 4 crystals pumped by a Ti∶sapphire laser were demonstrated. The mole fractions of concentration of Nd doped YAG crystals were 0.020 and 0.025, and the laser slope efficiency was 29.7% and 32% respectively. The mole fraction of concentraction of Nd doped YVO 4 was 0.030, and its laser slope efficiency was 34.7%. It suggested that high doped Nd∶YAG crystal was comparable in laser characteristics to high doped Nd∶YVO 4 crystal.

Some factors affecting the temperature of laser crystal in Yb∶YAG thin disk lasers are studied. The theoretical and experimental results show that reducing thickness of the crystal and increasing the number of pump passes simultaneously are effective to reduce the temperature of crystal and to improve the output power and efficiency of the lasers. As a result, 15 W output power at 1.03 μm with a slope efficiency over 40% from a 0.35 mm thick Yb∶YAG disk laser is obtained.

A scheme using anisotropic diffraction to implement the 2×2 switching element in a one block Fe∶LiNbO 3 photorefractive crystal is suggested. To decrease the crosstalk among the four individual photorefractive holograms, a thermal fixing scheme by a CO 2 laser is quoted. Based on Kogelnik diffraction efficiency equation, the relation between the optimal incident intensity ratio and the writing angles is analyzed. It is shown that the switch proposed has the properties of normal input, output and miniaturization.

The experiment results of improved performance of all optical time division multiplexing to wavelength division multiplex conversion are reported. Demultiplexing of optical time division multiplexing is demonstrated based on the cross gain modulation (XGM) in a semiconductor optica amplifier (SOA). A 1.2 Gbit/s TDM bit stream at 1555 nm is converted to two 622 Mbit/s WDM bit stream at 1544 nm and 1536 nm respectively, in addition, α conversion from wavelength division multiplex (WDM) to optical time division multiplex (DTDM) is available.

Theoretical analysis and experimental study on noise characteristics in cross gain modulation (XGM) wavelength conversion based on the copropagating and the counterpropagating configuration are presented. Results show that amplified spontaneous emission noise in counterpropagating configuration is more serious than that in copropagating configuration. Carrier consumption induced by amplified spontaneous emission, gain dispersion and internal loss in active region are all taken into account in numerical calculation which is based on section amplifier model and transfer matrix method. It can be shown from theoretical calculation that the amplified spontaneous emission noise power is mainly related to the carrier density while the power difference between two operational configurations is mainly determined by the uniform spatial distribution of the carrier density.

It is proposed that using a optimized three protion phase shifting apodizer to increase the depth of focus of the next generation digital versatile disk (DVD) and at the same time minimize the spot size. It makes the depth of focus of next generation DVD comparable to current DVD. The simulation result shows that an optical system with this apodizer also has a good defocus characteristic.

The propagation of cosh Gaussian beams through a first order paraxial optical system with rectanglar hard aperture is studied. By using the expansion of the rectangle function into a finite sum of complex Gaussian functions a closed form propagation equation of cosh Gaussian beams is derived. As a special case, the propagation equation of unapertured cosh Gaussian beams is derived. Numerical calculation examples are given for the focusing of cosh Gaussian beams by an aperture lens. A comparison is made, which has shown the advantage of this method and the results are in good agreement with those obtained by the straight forward integration of Collins formula.

The transmission properties of femtosecond optical pulse are analyzed with the momentum method. The results show that the third order dispersion and self steep directly affect not only the property of symmetry of pulse, but also the width of it. The results are independent of the shape of pulse, and so it is of certain universalism. Using the pulse in the shape of sech 2, the approximate solution has been obtained and compared with the numerical simulation of evolution equation. This work will be helpful to the theory and experiment of 10 fs～100 fs optical pulse transmission within short distance.

Considering three two level atoms initially in the entangled state, then two atoms of the three atoms are put into two initially empty cavities respectively and made resonant interaction. It is shown that the emission properties of the two atoms respectively inside the cavities are much affected by manipulating the atom outside the cavities.

The precise location from the perturbanced ring image is an important step for hemispherical imaging and tracking (HIT) system targeting object. Conventional method could not satisfy the HIT system tracking object in real time. According to the feature of geometric symmetry of a circle, a new method of resisting light perturbace is presented. The experimental results show that the measurement error might be no more than 1 pixel for perturbance free images. In the meantime, by the proposed method the measurement error might be no more than 5 pixels for perturbanced images.

A novel and efficient method for chirping fiber grating is demonstrated. The fiber Bragg grating was attached slantwis on a side face of a flexible beam. When the beam is bending, a strain gradient formed along the grating produces a variable shift in the Bragg spacing, resulting in a chirp up to 11.32nm nearly without central wavelength shift.

Six novel pyrromethene BF 2 compounds, with peak absorption wavelength in the range of 517 nm～524 nm, were synthesized. The electronic absorption spectra were measured in their solution of absolute ethanol. Pumped with a frequency doubled pulsed Nd 3+ ∶YAG laser at 532 nm, they can lase more efficiently than rhodamine 6G and show wide tunability.

Monolayer TeO x thin film was deposited on K 9 glass substrates by vacuum evaporation. By adopting a specific locating method, atomic force microscope (AFM)could be used to analysis the structure of short wavelength laser static recording bits, which were recorded at different writing powers in TeO x thin film. It was found that the film had good writing sensitivity, the reflectivity contrast could reach to a high value at writing power 1.5 mW. The bits were characterized by obvious hollows and mounds. With the increase of writing power, the height of hollow and mound increased, so did the length of the recording bits. The present setup allows the correlation of the change in reflectivity contrast caused by a specific laser pulse to the bit topography. This establishes the use of the analytical power of AFM for dedicated efforts in improving the performance, e.g., signal to noise ratio and storage density of optical storage media.