The solid-state lasers in the yellow-orange region of the spectrum have a variety of promising applications in biomedical diagnostic (based on fluorescence detection) and display. Operation of a high efficient 599 nm yellow-orange Raman laser with a Ba(NO3)2 crystal in the external Raman cavity pumped by the harmonic of Nd∶ YAG laser (532 nm) was reported. Barium nitrate crystal was grown by the aquasolution cooling method with the length of 48 mm long. To achieve conversion efficiency about the theoretical limit,the parameters of pump laser and external Raman cavity were optimized. The Raman cavity was composed of diachronic mirrors with optimal reflectivity for the second Stokes wavelength. The use of the external cavity with optimal reflectivity output coupler reduced the threshold pump intensity and increased overall efficiency with respect to single pass cell. The second Stokes Raman laser' s pulse compression phenomenon and two little peaks temporal behaviour were recorded and analysed. When the pump laser was operated at laser power of 4.1 W,the maximum second Stokes Raman output power of 710mW was obtained with FWHM of 1.1 nm at output wavelength of 599.38 nm,and the maximum conversion efficiency of 17.5% was observed. The slope efficiency was calculated as 24.8%.

A method for controlling the optical cavity length of ring laser is presented. The control of optical cavity length of ring laser is realized by controling the refractive index of dry air in capillary of ring laser by using of piezoelectric ceramics. The method has few influences on performance of ring laser. It has advantages of high speed of response,high sensitivity,and low power consumption. It can be applied to frequency stabilizing systems of ring laser with reflector and ring laser with total reflection prism. This method has important purposes in laser gyro and laser measure.

The laser diode which is the key of external cavity laser diode (ECLD) is a very tender part. It is easily damaged by the impact of the voltage,current and static when its assembly and running. To avoid the damage,the feedback constant current theory,low startup theory,low close up theory and MOS effect transistor speciality are applied to realize a new method of high-resolution constant current circuit,after some traditional methods used for reference. The new method is applied for the high resolutional external cavity semiconducter laser diode of the 1550nm wavelength to drive the current constantly. The resolution of drive circuit can be achieve in high level and be above 0.01%. The project is simulated by Protel DXP tool,designed by the PCB circuit,and applied to the laser driver circuit system,which has proved the constant current model can avoid the damage for drive current fluctuation availably.

A method for the calculation of optical modes in quadrupolar-shaped resonant cavities,is presented. The eigenvalue equation for resonant wavelength and optical field distribution is established. Numerical calculations are carried out for some deformation factor quadrupolar-shaped microlases. The theoretical analyses and numerical results show that the optical modes in quadrupolar-shaped microlases is typical for bow-tie mode with highly directional emission at a far-field angle Φ=45°,135°,225°,315°. This method can apply to other arbitrary cross section electromagnetic scattering and transmitting problems.

A compact diamond window cooled Yb3+/SUP> ∶ YAG disk laser has been demonstrated. In this cooling scheme,the rear face of disk is cooled directly by water while the front face of disk is applied in good thermal contact to a thin plate of chemical vapor deposition diamond window. The exceptionally good heat conduction properties of diamond can eliminate the temperature gradients perpendicular to laser beam thus previous difficulties with high average power pumping and efficient cooling are resolved. Simulation results show that with a pump intensity of 20 kW/ cm2 and repetition rate of 10 Hz,to keep the maximum temperature of the gain disk below a reasonable value,e. g.,less than 320K,the heat exchange coefficient of water should be about 4000 W/m2 K.

To the nano-position measurement of imprint lithography process,when the Michelson interference theory is used in laser interferometer measuring system in common environment conditions,it is difficult to avoid the disturbing error,which is fatal to measuring result. Through analyzing and calculating the Edlen formula,not only the influence from changes of temperature,humidity,and atmospheric pressure in measuring environment to laser interferometer measurement accuracy is theoretically revealed,but also the most serious disturbance coming from the flowing air is proved. By adopting the isolating mask of air flow and compensating feedback controller in measuring system,the phase-shift error between two laser interference signals can be compensated in real-time. At last,the measuring drifting error can be reduced from 13 nm to 5 nm in 10 minutes and this optimized measuring system can be used in the imprint lithography and match to the needs of 20 nm positioning accuracy in 100 mm motion range.

In terms of the theory of diffraction and nonlinear small-scale self-focusing,the analytical expression which described ripples of different spatial frequencies' passing through nonlinear media was induced. By analytical method,the nonlinear-gain characteristics of different spatial frequencies'wavefront distortions were obtained. The division method of the wavefront-distortion's spatial frequency was developed according to the requirements for the focal spot in drivers and the separation points between the higher,middle and lower frequencies which were assured according to the characteristics of domestic driver.

The properties of Highly Birefringent Microstructured Optical Fiber (HB-MOF) were studied by using a Finite-difference Frequency-domain method with Uniaxial Anisotropic Perfectly Matched Layer boundary condition (UPML-FDFD). Based on the numerical results,the influence of air-hole size and pitch length upon the birefringence,confinement loss and single-mode properties was analyzed. The properties of HB-MOF and the influence between them were considered synthetically. The mode-cutoff properties were studied using the effective area for the first time,and the wavelength range for single-mode operation can be obtained from this. The investigation is important to the design of HB-MOF with good performance.

A racetrack resonator filter is fabricated by Ag+-Na+ ion-exchange technique in K9 glass. The free spectrum rang (FSR) and contrast ratio (Cr) of the resonator are tested to be 0.177 nm and 7.5 dB. With fitted results,the coupling ratio is κ=0.916,the loss factors of the coupler and the resonator are δ = 0.55 and γ = 0.48,respectively. The relative large losses of the waveguide device are due to the almost connection of the coupler waveguides,irregularity of the strip waveguide side and flaw of waveguide surface after one-step ion-exchange. By decreasing loss,this integrated waveguide resonator filter may be used in optics communications or sensing fields and can be combined with other waveguide structures to perform further functions.

Based on the eigen mode field distribution of single mode waveguide,the RayleighSommerfeld diffraction integral formula and the reciprocal theorem of antenna theory,the coupling characteristic between two non-contact single mode planar waveguides in the coupler are presented. As the optical field superposition theorem of multiple beam interference with equal optical path difference and unequal amplitudes is engaged,the original analytic function expression of spectral response efficiency of arrayed waveguide grating multi/demultiplexer is deduced. This expression affords the theoretical basis for analyzing the characteristics of arrayed waveguide grating multi/demultiplexer accurately and quickly. An example of computing the spectral responsivity and crosstalk of arrayed waveguide grating multi/demultiplexer is presented.

The transfer matrix of the slab waveguide made up of a negative-refractive-index material is solved using the rigorous electromagnetic wave theory. The characters and application of the transfer matrix were also discussed. The dispersion relations of the three-layer symmetric slab waveguide possessing a negative-refractive-index guiding layer and positive-refractive-index surrounding medium are investigated by the transfer matrix method. The exotic properties of guided transverse electric(TE) waves in a left-handed waveguide were investigated graphically. There are no fundamental modes in a left-handed waveguide. The lowest mode was the first-order mode which had cutoff frequency. The first-order mode exits only when the parameters of the left-handed waveguide satisfied certain terms. Guided modes existed both for imaginary transverse wave numbers and real transverse wave numbers in a left-handed waveguide,while guided modes only exist only for real transverse wave numbers in a right-handed waveguide.

A novel design of micro-machined variable optical attenuator (VOA) with a packaged size as small as 25 × 10 × 7 mm3 is presented. Attenuation was introduced by a rotatable miniature silicon mirror,with its orientation finely adjusted through the balance between a pair of electromagnetic forces. The design is free of conventional spring restoring force for attenuation reset and therefore ensures a high stability. The realizing structure was fabricated by EDM micro-machining as well as laser spot welding. VOA prototypes exhibit a wide attenuation range of 40 dB with an insertion loss of 0.8 dB and backreflection of －50 dB. The measured result was compared with that of an FEA model using ANSYS software package and a good agreement was obtained. The VOA can be arrayed for effective signal balancing and device protection in WDM/DWDM network systems.

According to the analysis of collimating misalignment of optic-fiber collimator,that is the coupling efficiencies in abaxial,angular shift,distance coupling and angular shift have the most effect in coupling efficiency. Spot position varied regularly as long as the temperature varied periodically during the experiment. Figured out by the position shifts of light spot in experiments,the angular shifts of saddle and arch clips during temperature cycles were 519 μrad and 395 μrad,and thus led to coupling lost of 0.944 dB and 0.718 dB;the angular shifts of saddle and arch clips during temperature shocks were 986 μrad and 138 μrad,and thus led to coupling lost of 1.793 dB and 0.251 dB. The result of the experiments demonstrated that arch clip is better than saddle clip in both situations of temperature variation.

The fluorescence lifetime detection technology which was the key technique for optical fiber fluorescence temperature sensor was studied. The method of Pulse modulated PLD with two references (PLD-PMTR) was adopted in this paper. And the lifetime of fluorescence fiber temperature sensor was detected. The mathematic model has been deduced. This method has a high signal to noise ratio and can restrain the excitation leakage. The measurement output of system can be transferred faithfully over long distance and it easy to interface with a computer. Through experiments the method is efficient and practical. It can attain the demand of the system.

Four structure types of two dimensional position sensitive detectors have been studied. There are the tetra-lateral PSD,the modified tetra-lateral PSD,the duo-lateral PSD and the resistance bordered PSD. The RC models of these four structure type PSDs have been developed and the linearity of them are emulated by the soft of the Multisim. The linearity position grid and the errors graphics show that the average error in the 40% centric sensitive area of the tetral-lateral PSD,the modified tetra-lateral PSD,the duo-lateral PSD and the resistance bordered are 10.05%,3.70%,0.29%and 0.12 % respectively. The result shows that the models can give a more exact analysis on different structure types of two dimensional position sensitive detectors than the analytic and numerical methods.

Poly (ρ-phenylene vinylene) (PPV) derivatives with symmetrical and asymmetrical alkoxyl substitutes including poly (2-methoxy-5-butoxy)-ρ-phenylene vinylene (PMOBOPV),poly (2-methoxy-5-hexyloxy)-ρ-phenylene vinylene (PMOHOPV),poly (2,5-dibutoxy)-ρ-phenylene vinylene (PDBOPV) and poly (2,5-dihexyloxy)-ρ-phenylene vinylene (PDHOPV) were prepared through bisetherification,chloromethylation and dehydrochlorination reaction and characterized by UV-Visible absorption spectrum. The results revealed that the conjugated absorption peak of PMOBOPV,PMOHOPV,PDBOPV and PDHOPV assigned to π→π* transition of π electrons were located at 491 nm,495 nm,504 nm and 510 nm and the optical bandgaps were also measured to be around 2.23 eV,2.18 eV,2.12 eV and 2.07 eV respectively. The third-order nonlinear optical susceptibilities (χ(3)) of PPV derivatives were studied by degenerate four-wave mixing technique and the effects of molecular structure on third-order optical nonlinearities of PPV derivatives were also investigated. The experimental results showed that the resonant χ(3) values at 532 nm of PMOBOPV,PMOHOPV,PDBOPV and PDHOPV were 3.45 × 10-10,5.13 × 10-10,7.15 × 10-10 and 9.61 × 10-10 esu,and the corresponding off-resonate χ(3) values at 1064 nm were 1.09 × 10-11,1.42 × 10-11,1.62 × 10-11 and 2.14 × 10-11 esu respectively.

The principle of recording and reconstructing volume gratings with front phase encoding was expounded. The diffraction selectivity of superimposed volume gratings,utilizing the coupled wave theory,is deduced from the first order differential equation of diffracted wave. A complex stochastic process function is proposed,with whose correlation function,the necessary and sufficient condition of random wave front phase encoding volume gratings reconstructing without crosstalk is obtained. A diffraction selectivity theoretical analysis method of volume gratings with wave front phase encoding is proposed.

In this paper,it is investigated the polarization and the dispersive properties of the elliptical highindex-core Bragg fibers via a powerful full-vector finite element method. The simulation results show that the modal birefringence of the elliptical high-index-core Bragg fibers is on the magnitude of 10-3,about one order magnitude larger than that of conventional polarization maintaining fibers. The dependence of the modal birefringence on the fiber structural parameters has been fully investigated. The modal birefringence decreases with the filling ratio of the low-refractive-index material and changes little with the variation of the period of the cladding layers. Larger ellipticity or higher index-contrast will result in enhanced modal birefringence. These results will be helpful to the design of high performance one-dimensional microstructured polarization maintaining fibers.

By combining shooting method with Runge-Kutta method for solving differential coupling equations of backward-pumped fiber Raman amplifier (FRA),the effects of fiber length,initial signal power,initial pump power,fiber efficient area,Raman gain coefficient,and fiber loss of signal and pump on gain of FRA have been detailedly investigated. Finally,several ways are suggested to improve the gain of backward-pumped FRA. Accurate and reasonable results have been gotten,and are helpful to the study of FRA.

A simple scheme using fiber Bragg gratings to realize dual-wavelength optical auto gain clamping erbium-doped fiber amplifier is proposed and demonstrated. It shows that in three kinds of different clamping wavelength combinations: 1535.64 nm and 1562.68 nm,1530.48 nm and 1562.68 nm,1530.48 nm and 1551.36 nm,the outputs gain and dynamic state scopes of 1540 nm signal are almost the same. For above three clamping wavelength combinations,loop loss is 14.7 dB,15 dB and 15 dB,respectively. For the same pump conditions and loop loss,these three kinds of clamping wavelength combinations lead to almost the same results,which is proved by experimental results. However,the result is very different from above under the condition of 1551.36 nm and 1562.68 nm clamping wavelength combinations. It is revealed that when designing a dual-wavelength optical auto gain clamping EDFA,to get high gain,the separation of two clamping wavelengths should be as big as possible.

Cu films of different thickness were deposited on K9 glass using ion beam sputtering. The reflectance and transmittance of Copper films in the wavelength range from 310 nm to 1300 nm have been measured by Lambda-900 spectrophotometer. Relationships between reflectance,transmittance,absorptance and thickness of Cu films in the wavelength selected 310,350,400,430,550,632,800,1200 nm have been discussed. The optical constants of Cu films have also been discussed. The results show that the optical properties of Cu films have obvious size effect. There is a point of intersection,which is located in the relationship curves of between reflectance,transmittance and thickness of Cu films at wavelength 550 nm. The corresponding thickness of this point of intersection can be thought of as the minimal continuous thickness of the growth of metallic films from discontinuous to continuous. According to this characteristic criterion,the minimal continuous thickness of Cu films prepared by ion beam sputtering is 33 nm. The topography images of Cu films near the minimal continuous thickness were observed by using atomic force microscopy (AFM).

In this paper,the wetting eroding properties of MgO films,used as sacrificial layer materials,was researched in H3 PO4 solution,including the transverse eroding speed and vertical eroding speed. The relationships between the eroding speed of MgO films in H3 PO4 solution and the temperature and concentration of H3PO4 solution were obtained,and the better technical parameters were obtained for the manufacturing of the MgO films graphs and the holding structure in which MgO is used as sacrificial layer materials.

TiO2-Nb2O5 mixed optical film has been deposited on BK-7 substrate by the reactive magnetron sputtering technique. The microstructure,morphology,composition and optical properties have been investigated by X-ray diffraction,scanning electron microscopy,atomic force microscopy,X-ray photoelectron spectroscopy and spectrophotometer. The results show that the TiO2-Nb2O5 mixed film is amorphous and has optically flat and uniform surface. The structure of the film is compact and not column structures or defects can be observed,and the stoichiometric ratio of Nb2O5 to TiO2 is about 1.54.Refractive index and extinction coefficient of the film are determined from the normal incidence transmittance,and refractive index is 2.34 and extinction coefficient is 2.0 × 10－4 at 550 nm wavelength.These results indicate that the mixed film has high quality for optical applications.

Photoluminescence properties are studied in Poly[(2-methoxy,5-octoxy) 1,4-phenylen evinylene] (MO-PPV) thin film,which are prepared from MO-PPV chloroform solutions of different concentrations. Photoluminescence,excitation photoluminescence and selective excitaton photoluminescence measurements at room temperature have been perfomed. A long wavelength emission component near 630nm has been observed and identified through the results of experiment associated with the curve fitting method. The analyses results show this long wavelength emission peak should be attribued not to the emission from aggregators or excimers in films but to the vibronic transition from S1 excited state to S0 ground state. The variation of the emission peaks in thin film samples of different concentrations would be another proof to this conclusion and be explained by means of the integral strength of the Frank-Condon factor.

Phase-shifting technique is commonly applied in surface measurement of three-dimensional object in recent years. In phase measuring profilometry detector nonlinearity is the main factor introducing the errors of the measurement . This paper gives the theoretical analysis and the computer simulation of this kind of error,and compares the ability of tolerance with the second and the third order nonlinearity of detector for N-frame phase shifting algorithms. Also,this paper gives several geometry diagram to show intensity of ray when there is the nonlinearty error. The results of numerical simulation and theoretical analysis are consistent and it offers a theoretical basis of selection of algorithms.

An optical device designed to measure the phases of cells was introduced,which was made up of objective,PZT,CCD and computer. The phase reconstruction method and related analysis were presented,which was based on the phase shifting technique. The experiment of phase reconstruction of cells using this optical system was done. The results prove that the resolution of this system is higher then 1 μm and reconstructed phase of cells is well.

The secondary spectrum is a main factor debasing image quality in telescope objectives that have long focal length and large relative aperture. Recently,the special dispersion character of the diffractive structure has been applied to correct secondary spectrum with ordinary material and simple construction. In this paper,a diffractive optical element is equivalent to a thin lens with infinite refractive index. Based on this ultra-high index model,the PWC method has been investigated to design hybrid diffractiverefractive (HDR) apochromatic telescope objectives. A HDR doublet apochromatic telescope objective with a focal length of 2000 mm and a relative aperture of 1/15 has been designed. Compared with conventional triplet design,it is shown that hybrid objective is better to correct secondary spectrum and spherochromatic aberration,so has better image quality.

A general study of the Seidel aberration properties of the flat slab lens systems made from left-handed materials was presented according to the primary aberration theory. Seidel aberration sums of such a system were derived based on the addition theorem. The way to find a flat slab lens system free from all five Seidel aberrations was described accordingly. Finally,two special examples of the singlet and doublet LHM slab lens systems without Seidel aberrations were given and discussed respectively.

A new compression scheme of interferential multispectral images is proposed based on the analyses of the large aperture static imaging spectrometry. There are two novelties in the scheme. One is that a three-dimension wavelet with special motion compensation is proposed. The other is that a new method of three-dimensional asymmetric zerotree coding (AT-3DSPIHT) is put forward. This AT3DSPIHT can make a longer tree in fewer images,which increases the probability of a coefficient value being zero when moving from root to leaves. Moreover,this method needs lower memory and shorter time delay than 3DSPIHT. Experimental results show that the scheme provides a better protection of the spectrum curve and a better performance on the compression.

A new target detection method in hyperspectral images based on projection pursuit (PP) and genetic algorithm was introduced. First,skewness and kurtosis which were susceptible to outliers were chosen as the projection index (PI). Then,Real coding based Accelerating Genetic Algorithm (RAGA) was used to find optimal solutions for a selected PI. The proposed method was studied using real hyperspectral data. Experimental results show that the method can effectively and reliably detect the target from hyperspectral images.

Terbium-doped zinc oxide nanocrystalline are successfully prepared by Sol-Gel process.Photoluminescence spectrum (PL) and Photoluminescence spectrum excitation (PLE) of nanocrystalline ZnO: Tb3+ with excitation wavelength 368 nm are measured at room temperature. The luminescence process of Tb3+-doped zinc oxide nanocrystalline has been investigated by using PL and PLE. Emission of 5D4→7F6(485 nm),5D4→7F5(544 nm),5D4→7F4(584 nm) and5D4 →7F3(620 nm) of Tb3+ ions,and weak and wide visible band of ZnO were observed. An energy transfer from excited states of ZnO hosts to doped Tb3+ ions centers is disclosed by the fact that Photoluminescence intensity of the maximum of nanocrystalline ZnO : Tb3+ on doping concentration of Tb3+ ions increases.

A series of rare earth complexes with salicylate were synthesized and studied by infrared spectrum,ultraviolet spectrum,fluorescence spectrum. The results of infrared spectrum indicates that the rare earth ions coordinated with salicylate by carboxyl. As for ultraviolet spectrum of the complexes,energy transfer between salicylate and rare earth ions is the primary process;fluorescence spectrum,as a comparison,the complexes salicylate gadolinium (Ⅲ),salicylate terbium (Ⅲ),salicylate. dysprosium (Ⅲ)have higher efficiency of intermolecular energy transfer and stronger fluorescence character.

In this paper,the diffraction-enhanced imaging method was applied to the non-destructive testing of computed-tomography. With this technique,the 2-D cross-section image of the self-designed sample was reconstructed. The reconstructed images depict clearly the inner structures of the sample. By comparing these images with the reconstructed image obtained by the absorption imaging computedtomography,the result indicates that the technique of diffraction-enhanced computed-tomography can acquire better boundary among these elements that their absorption coefficients are very close in the object.

The effects of phase fluctuation on absorption,dispersion and population difference in an open four-Level atomic system have been analyzed by using the numerical simulation from the steady analytical solution. It is shown that variation of the linewidth cannot change the property of the inversionless lasing of the system;increasing RL reduces the magnitude of the gain and requires a larger Ω value for the onset of the gain;when the exit rate is small,effects of the finite linewidth RL,on the gain,dispersion and population difference is very weak;the system can still get a high refractive index without absorption when the linewidth does not equal to zero.

A two-step alignment,coarse-fine alignment,is proposed for obtaining high alignment accuracy in room-temperature imprint lithography process. A pair of special slant gratings are used as alignment marks. Coarse alignment was realized by observing the borderlines of the superposed marks through object lens,and alignment accuracy is within the capture range of fine alignment. The Moiré signals in the linear region for fine alignment generated by the alignment marks were detected by a photo-detector array and used to estimate the fine alignment errors in x and y directions respectively. Since the linear region of moiré signal is very steep,the signals highly sensitive to alignment error can be obtained and used to control the alignment of a X-Y stage by fine positioning. The final alignment accuracy can reach ±21 nm in x direction and±24 nm in y direction.

Based on the hypothesis testing of the watermark bits,a model of the blind watermark extraction is presented and implemented in the wavelet domain,which can extract the watermark bit by bit. To balance the imperceptibility and robustness of the watermark,the wavelet features of the image and the context modeling method are utilized to determine the variable watermark amplitude for every high frequency wavelet coefficient. So the embedding density of the watermark is adaptive to the image features. The watermark extraction results are dramatically based on the distribution model of the image's wavelet coefficients,thereby the wavelet coefficients are modeled as a general gauss distribution,and the parameters are estimated by the maximum likelihood method. A series of experimental results show that the method is robust.

The electrically control of polarization-assisted transverse superresolution and axial focal shift utilizing electrically control radial birefringent pupil filter has been proposed in this paper. The structure of the filter consists of two parallel polarizers,an electrically controllable azimuth optical rotator including two quarter-wave plates and one liquid crystal or electro-optical variable wave plate and a symmetric birefringent element. Variation of light polarization caused by electro-optical effect provides the feasibility controlling the superresolution and focal capability. Polarization states transformation on the Poincaré Sphere and Jones calculus for transmitted intensity are involved in this system. The most interesting and useful advantage of such a structure is that its transverse superresolution and axial focal shift quality can be changed merely controlling the applied-voltage on the electro-optical element. So no mechanic rotation is involved such as applied in the former design,and the vibration noise can also be avoided. Different structure parameters for obtained double effect such as azimuth angles of radial birefringent element and electro-optical modulation range are also given.

Experimental and theoretical analysis results show that there is an optimal Cs/O ratio for GaAs photocathode to activate successfully. In order to change Cs/O ratio of GaAs photocathode,the method applied is to regulate theheat currents of Cs resource and O resource in experiment. Activation experiment results show that the samples activated on appropriate Cs/O current ratio can achieve the optimal results,their photocurrent ascent rate is the largest during the first addition of O,quantum efficiency is the highest and stability is also very well. When deviation the appropriate Cs/O current ratio,activation experiment results are not as good as the former. Along with the increase of Cs/O current ratio,the total times of (Cs,O) alteration decrease. The Cs/O current ratio during the first (Cs,O) alternation should be regulated well,the Cs/O current ratio which can achieve the largest ascent rate is the optimal Cs/O current ratio. When regulated well the ratio should be maintained during activation process.

Based on the production and transportation of the fluorescence in wavelength-shifting fibers (WSFs) coupled to YAP scintillation crystal,a simulation model has been setup using the GEANT4 codes for a small gamma camera with WSFs coupled to a YAP scintillation crystal. An advantage of this technique over direct readout with a position-sensitive photo-sensor is small amount of readout channel could be used for the same image area. Simulation results show that at least 15 photons on average for 59.5 keV gamma ray (241Am). A spatial resolution of 1.28 mm FWHM is obtained when silicone grease is used to couple to the fibers to the crystal. The factors affecting the number of photons and the spatial resolution are discussed.

The authers have developed avalanche transisitors based pulser for use as a electro-optical switch driver. These transistors are mounted on microwave structure board. The circuit can generate a electrical pulse with peak voltage of 6.4 kV,peak current of 128A,voltage amplitude of 5 kV,fall time of 990 ps,in 50Ω load. The trig jitter is less than ±15 ps;trig delay is about 30 ns.