The focusingcharacteristics of an achromatic atomic lens, composed of two laser beams oblique to thesodium atomic beams are studied. It is shown by numerical calculations that the fringewidth of the channeled Na atoms is reduced by a factor of two, and the ratio of signal tonoise can be significantly enhanced due to the correction of chromatic aberration tocertain extend.

This paper gives asimple formula for calculating the roughness of multilayer by using the small angle X-raydiffraction curves of the samples. The differences of the calculated values of roughnessfrom the formula for the different pairs of peaks of a diffraction curve of the sample ordifferent samples are very little, but these differences from B. Abples′ formula are considerably large.The calculated results are also in good conformity with the measured values reported.

Frequency-scanningnon-linearity influences range-detection accuracy of optical fiber sensors. In this paper,the influence is analyzed and a recovering technique is proposed. Non-linearity isrecovered through the learning process of backpropagation neural network. Simulationresults show that very accurate estimation is achieved even under severe non-linearity ofthe scanning source. The on-line learning of neural network is also investigated to makethis method more practical.

The influence of thewavelength variation of the input beam on the ring-shaped output is numericaly simulatedin this paper. The semiconductor laser with a wavelength of 660 nm is shapedexperimentally. The experiments conform with the simulations.

A newly developed GRINlens interferometer was employed to detect the quality of optical fiber faces. This paperintroduces the principle of GRIN lens interferometer and exhibits some experimentalresults, which shows the qualitative discrepancy of fiber faces treated with differentmethods.

The data density of thenear-field optical recording is mainly determined by near-field electromagneticdistribution of probe fiber such as transmission efficiency, near-field light spot size,polarization keeping and the grade of the electromagnetic field. The optical charactersand light wave propagation of various fiber probes for near-field optical recording arenumerically simulated using 3D finite-difference time-domain (3D-FDTD) method in thispaper. The possible application in near-field optical recording with these probes isdiscussed. The entirely metal coat probe is pointed out to have an extremely smallnear-field spot size about 10 nm, which is far less than that of the conventional probe.

This paper describes thepreparation of AlN films using pulsed laser deposition. Smooth and highly transparent AlNfilms were deposited on Si (100) substrates. The gap of the films was determined to be 5.7eV. The effects of substrate temperature and annealing temperature were also examined.

The clad coating ofNiCrBSi-TiC metal-ceramic powders on the surface of TC4 alloy was performed by CO2laser. By means of SEM and XRD, microstructure of the coating was investigated, andmicrohardness was measured. The experimental results show that the clad coating iscontinuous, homogeneous, poreless and crackless by optimizing the technical parameters.The phases of coating are composed of TiC, γ-Ni, M23(CB)6, CrB, Ni3B et al..The edges of TiC particles were dissoloved during laser heating, and the tiny dendrites ofTiC precipitated during cooling. The average hardness of coating is Hv980.

A real-time fingerprintidentification system using binary joint transform correlator with a single space lightmodulator and a single CCD has been developed successfully. A discrete cosine transformalgorithm was used to process the joint power spectrum in order to enhance thecross-correlator term and eliminate the auto-correlator term in the joint power spectrumand improve the discriminability of the system.The light energy passing through the systemwas controlled by adjusting the gray-value range of the space light modulator at Fourierplane, as a result the system could execute real-time fingerprint identification. A newtwo-parameter decision method was used to decide the correlator signal, and the decidingveracity was improved. Real-time tests yielded a false rejection rate of 0.47% and a falseacceptance rate of zero.

The AE(acousticemission) signals emitting from laser welding were sensed with an electrit condensermicrophone and analyzed with wavelet analysis to characterize their time-frequencydistributions. Based on the detail signals which were extracted from AE signals viawavelet analysis, a signal Intensity-Moving-Average(IMA) curve was defined in this paper.It was shown that the IMA curve of good-quality, full penetration welds was different fromthat of poor-quality welds, defined as either welds with misalignment problem or weldshaving a gap between the sheets being joined. According to the curve which shown to becapable of recognizing the transformation of welding states commendably, defects can bedetected quickly and exactly. With the help of IMA curve, it′s possible to realize the process control of laserwelding.

Using cw-Ti:sapphire laser as pumping source,the self-Q-switched Cr,Yb:YAG laser has been demonstrated at room temperature. An averageoutput power as much as 35 mW at 1.03 μm with a pulse width (FWHM) as short as 0.4 μs was abtained. The laser experiment demonstrated that theCr, Yb:YAG crystalexactly combines the Cr4+ saturable absorber and Yb3+ gain mediuminto one. And Cr, Yb:YAGcrystal can be a most promising self-Q-switched laser crystal for compact, efficientsolid-state lasers.

The mode-cleanerconsisting of a ring cavity with three mirrors was designed based on the theoreticalanalyses and experimental measurements to the intensity noise spectra of anall-solid-state laser. The intensity noise of a homemade single-frequency Nd:YVO4 laser has beensignificantly decreased by using the mode-cleaner with the characteristic of filteringhigh frequency noise. The noise frequency to reach the shot-noise-limit has been reducedto 7 MHz from 30 MHz without the mode-cleaner. In design, the requirements of both narrowbandwidth and higher transitivity for the cavity were considered compatibly. Thetransitivity of mode-cleaner is 70%.

To improve the abilityof calibrating the nonlinearity error of nanometer interferometer by beatwave F-Pinterferometer, a method of using 633 nm external-cavity diode laser (ECL) as the slavelaser is presented in this paper. Based on an AR-coated 637 nm quantum well laser diode,using a diffraction grating in Littrow mount for wavelength selection and output coupling,a tunable 633 nm ECL is developed.The experiment results show that the linewidth isnarrower than 5MHz. A course tuning range of 4 nm around 633 nm is achieved throughtemperature control and grating rotation.By controlling the frequency-tuning device, acontinuous tuning range of 1.8 GHz, which is equivalent to a measurement range of 0.75λ of beatwave F-P interferometer,is realized.

A blue-green XeF(C-A)laser optically pumped by a sectioned surface discharge based on photodissociation of XeF2has been developed. The pump source is a single-channel sectioned discharge on the Teflonsurface with the average deposit power density of about 4.5 MW/cm in the first half periodof the discharge. The effective active length is 60 cm. The aperture of laser cell is 10cm×10 cm and fused silica window with Brewster angle is used. A stable resonator with thelength of 1.4 m consists of a spherical mirror of 5 m with the reflectivity of better than99% and a flat mirror with the transmission of 4% in the spectral range 450～500 nm. Laser energy of more than150 mJ in 600 ns is extracted from the medium with a gas mixture of 250 Pa XeF2,40 kPa N2, 60 kPa Ar, with the total stored energy of 5.4 kJ. The wavelength ofXeF(C-A) laser is in the range of 470～500 nm. The divergence angle was 1.7 mrad in horizontal and 3.7mrad in vertical.

An accurate model wasused to predict the gain, saturation and noise characteristics of ytterbium-doped fiberamplifiers (YDFA), pumped at λp=910 nm. It was shown that the strong backwardpropagating ASE around 975 nm could dramatically increase the NF and limit the gainavailable at longer wavelength.

This paper presents anexact method to calculate astigmatic Kerr-lens mode-locked cavity. The influence of cavityparameters on astigmatism, stability, beam parameters, self-focusing and Kerrself-focusing strength has been studied in the three-element cavity. The results provide atheoretical basis for the design and alignment of the cavity.

In this paper, the farfield distributions of some modes distorted by misalignment of resonators are calculatedand the influence of complex spatial coherence on the distributions is discussed.

The sound source whichis generated by laser in liquid is studied theoretically and experimentally on the basisof the thermoelastic equition. The influence of the optical penetration depth on theultrasonical sourse is considered. In two-dimensional model, the thermal diffusion effectis neglected. From the thermal diffusion equation and wave equation, the generalexpression of displacement is given. The influence of the optical penetration depth on thesound directivity is analyzed. The theoretical curve of the sound directivity vs theoptical penetration depth is drew. In the end, the experiments testify the theoreticalresults.

The characteristics ofRaman amplifier are investigated in a Raman cell without solid windows. The Raman mediumis a mixed gas with gas mixture and reflective index near that of air. The effects of gasflow on beam quality are also studied.

The three-energy modelsimulated with photocycle characteristics is used to explain bacteriorhodopsin’s 3-order nonlinearsusceptibility and its time response, which was measured with four-wave mixing technique.The saturation density and length of excitons in bacteriorhodopsin are obtained withfitting to the phase-space filling model. The possible mechanism for generating the 3rdnonlinear optical susceptibility χ(3) and response time are discussed.

Theoretical analysis onthe performance of OXC nodes in which SOA is used as power equalization device ispresented. The power penalty of link with SOA is simulated; and then the impact of somefactors on system, including extinction ratio of transmitter, bit rate of signal,spontaneous noise factor of SOA, is discussed; finally the BER performance of cascaded OXCnodes with SOA-based equalization module is given. All these provide the theoreticalfoundation for the design of OXC nodes and the optical network.

The wavelengthconversion by nondegenerate four-wave mixing in a tunable semiconductor-fiber ring laserusing the lasing beam as a pump beam is demonstrated. Because of the continuous tunableand high power of the ring laser, a wide range up-conversion of 13.8 nm has been abtainedat 2.5 Gbit/s.

In broadband (～35 nm) EDFAs, gain flatteningfilter can be inserted between the two stages of EDFs. In this paper, an iterationalgorithm for designing the filter′s transmission function is proposed. The principle of thisalgorithm is taking the advantages of homogeneous broadening and gain compensation betweentwo stages. In each iteration step, the average gain level is taken as reference, andwithin the wavelength range where the gain is higher than the reference, an inverse gainspectrum is used to modify the transmission function. Then the gain within otherwavelength range will be compensated automatically. Simulation results show that by usingthis iteration algorithm, the flattened gain can reach the possible highest value of theoriginal amplifier, and noise penalty is the minimum.