A method to couple high power laser diode array (LDA) beams into a single multi-mode fiber which includs collimating, shaping, focusing and coupling is present based on the beam parameter product (BPP) of laser beam. The orthogonal surface equation of the collimating micro-lenses array is derived, the divergence angles after collimating and the parameters of the focused lens are calculated. As a example, a high power fiber coupled LDA module with the core diameter of 800 μm and numerical aperture of 0.37 is gotten and the coupling efficiency is more than 53%.

Elaborate theory analysis has been done for the modulation characteristics of semiconductor 1aser and analytical expression has been deduced through the research of rate equation of semiconductor 1aser. By using the general regression neural network, a neural network model of the modulation characteristics of semiconductor laser is developed. Then, the modulation characteristics of semiconductor laser are analyzed and a semiconductor 1aser is designed through the trained neural network model. The simulation results are well agreed with the theoretical analysis results. Furthermore, this method has the advantages of high speed, high accuracy, good repeatability, etc. The results of research show that the characteristics of semiconductor laser can be analyzed and the some dimensions of semiconductor laser structure can be obtained using the neural network model.

According to the basic principle of light-ray propagation, the collimating characteristic, the intensity distribution, the transfer efficiency of light energy and the transport coefficient for the laser diode ray in the fast axis direction passing through a cylindrical lens are analytically calculated and discussed. Based on analyzing a few of adjustable parameters, such as the radius of cylindrical lens, media index, media loss, lens location, and interface reflection, some conclusions are deduced that the location of cylindric lens directly influence the collimating effect of diode rays; lens radius, media index, and media loss not only influence spot size, intensity distribution, and energy transport, but also newly polarization distribution. That is to say, the cylindrical lens must be set out of focus slightly and the every parameter including the optical coating of transform system must be optimized. Above consequences are usefull to design a collimating system with micro-cylindrical lens that can considerably decrease the diverging angle of laser diode in fast axis and improve beam quality.

S-shaped bend waveguide is indispensable to realize the lateral displacement and connections in the integrated optical devices, such as the optical switch matrix, star coupler and arrayed waveguide grating (AWG). Even when various optical devices are integrated onto one chip, S-bend also plays important roles. Its size and optical loss directly influences the integration dense and loss of whole device. The insertion loss (except the dispersion loss produced by the configuration defection) of S-bend includes two parts

For the conventional unstable resonator, the output laser is deteriorated by the hard-edge diaphragm diffraction. Using variable reflective mirror, as a soft-edge diaphragm, the intensity distributions of output laser are improved. Gaussian mirror has been used widely, and the super-Gaussian mirror is a development for variable reflective mirror. The fast Fourier-transform (FFT) algorithm is a convenient method for simulating the intensity distribution of resonator. In this paper, the three-dimensional intracavity distribution of super-Gaussian mirror resonator is analyzed, and the intensity distributions are simulated when the thermal focal length changes. Then the output intensity distributions are simulated with or without considering the thermal lens effect. And the influence of the thermal lens effect is discussed.

The complex refractive index distribution of photonic crystal fibers makes a numerical algorithm necessary. An effective index method based on weak-guidance approximation is often used to study the modal properties of such fibers including their dispersion properties. In this paper, a fully vectorial effective index method is formulated for photonic crystal fibers based on the solution of the vectorial characteristic equation and is used to compute the dispersion parameters of photonic crystal fibers. In analogy with step-index fibers, the effective index of the photonic crystal fiber cladding can be calculated simply by substituting the appropriate Bessel functions of the electromagnetic field into the vectorial characteristic equation for step-index fibers. The result obtained by the vectorial effective index method is in better agreement with those by the finite element methods and measured data.

The guiding problem in microstructure fiber with 780 nm zero dispersion wavelength is accurately analyzed through a reduced vector wave equation, using a novel finite element method (FEM). The two-dimensional transverse intensity distribution of the fundamental mode, the effective refractive index, dispersion curves of guided modes for different fiber structural parameters are calculated. The results match those achieved in recent experiments in which the feasibility of this type of fiber was shown. Furthermore, this method is used for simulating the random distributed microstructure fiber, and a reasonable result is gotten rapidly and accurately.

Bragg fibers are a kind of fiber formed by multilayer concentric cylinders with period index distribution in the radial. Since Bragg fibers have multilayer geometric characteristics, their dispersion properties are special. The effective index method (EIM) combined with multilayer waveguide theory is introduced to analyze the dispersion properties in detail, and also the scaling properties for Bragg fiber′s waveguide dispersion are gotten here. Examples are shown at last to illustrate how to design the chromatic dispersion through adjusting the Bragg fibers′ structure parameters based on the relations between the waveguide dispersion and the structure parameters.

In order to get photodisruption threshold of porcine nasopharynx tissue in nasopharynged carcinoma optical biopsy, temperature distributions in the porcine nasopharynx tissue were measured under irradiation of argon ion laser at the wavelength of 488 nm and 514.5 nm, respectively. The dependence of the temperature distribution on the measuring position and irradiation power density, as well as wavelength was studied in detail. Experimental results show that the temperature distributions in the porcine nasopharynx tissue were significantly affected by measuring position and the power density, as well as wavelength of irradiation laser. The temperature in the porcine nasopharynx tissue is increased with the increasing of the power density of irradiation laser, and the maximal temperature can be higher than 41.5℃ when the power density reaches 1.85 W/cm2. The optical-thermal effect at the wavelength of 514.5 nm is more remarkable than that of 488 nm under the irradiation of same power density.

This paper reports the generation of high power quasi-continuous wave (Q-CW) red laser radiation by frequency-doubling a Nd∶YAG (Nd∶Y3Al5O12) laser operating at wavelength near 1.3 μm with a KTP (KTiPO4) crystal (type Ⅱ phase match, θ=59.9°, φ=0°). The laser, with plane-concave cavity structure, is employing a high power CW pump module comprised a Nd∶YAG rod side-pumped by thirty 20 W laser diode arrays (LDAs) of a triangle radial geometry, and an acousto-optic Q-switch which results in the laser high repeated Q-CW output. The laser output characteristics of fundamental and frequency-doubled wavelengths involving powers and spectra have been studied. The highest power of the quasi-CW red laser is 8.1 W, achieved at 453 W pump power of LD. The value of M2 and the distribution figure of red beam at 8.1 W output power are given in the paper.

A laser diode (LD) end-pumped Yb∶YAG (Yb∶Y3Al5O12) chip laser has been demonstrated. The pumping source is a fiber coupled laser diode array with maximum output power of 13.56 W at 940 nm. The diameter of the fiber is 800 μm. Two lenses with focal length ratio of 30∶12 have been used to compress the pumping light into the laser crystal. 3.06 W continuous wave (CW) output power was obtained from the 8 at.-% doped, 1.6 mm thick Yb∶YAG crystal, the whole experiment set was cooled by thermoelectric cooler (TEC) and cooling water, slope efficiency was 33.1%, the M2 values were measured to be 1.54 and 1.73 in the x and y directions respectively.

A novel Smith-Purcell tunable radiation source with relativistic electron beam of middle energy and a quasi-optical resonator composed of diffraction grating and three-mirror reflector is reported. The well-known Smith-Purcell free electronic laser (FEL) experiment takes on a good future for developing submillimeter and far-infrared wave source. The novel scheme has considerable advantages as follows

A method for realizing a stable multiwavelength erbium-doped fiber laser at room temperature is analyzed theoretically and obtained experimentally. A sinusoidal phase modulation is inserted in the linear cavity, which suppresses the mode competition owing to the homogeneous broaden line in eribum-doped fiber and eliminates the unstable single-wavelength lasing at room temperature. What′s more, the spatial hole burning in linear cavity is propitious to suppress the homogeneous broaden line. Simultaneous five-wavelength lasing is obtained with 0.8 nm intervals defined by the sampled fiber Bragg grating, which is anchored on the ITU frequency grid.

The charge flux of plasma, the delay time of laser ignition and the absorbability of laser by plasma were tested to study the effects of plasma and ablation on laser ignition processes of energetic materials. Tested energetic material is B/KNO3 (m(B)∶m(KNO3)=40∶60)+additional 5% phenolic resin, 20 mg, under 37.92 MPa pressure. Laser set is a Nd∶YAG laser with 680 μs pulsed width. The density of plasma rises with increase of laser energy, and the charge flux of plasma is larger than that of combustion flow. The delay time of ignition is shorted with the rise of the energy density of laser linearly, but when the energy density increases over a critical value, the delay time keeps constant. The plasma do not almost absorb incident laser beam in the testing conditions, but experimental results of the delay time of ignition show that the ablation of laser prevents laser energy from depositing in energetic materials.

In order to enhance the energy conversion efficiency and the power-load of two-cell stimulated Brillouin scattering (SBS) system, different liquid SBS mediums with almost similar Brillouin frequency shifts are used in the generator cell and the amplifier cell. The characteristics of the SBS system are investigated experimentally with Nd∶YAG Q-switched laser. Compared with two-cell SBS system with the same liquids, it can not only keep enough high-energy conversion efficiency, but also can effectively improve the system power-load ability and stability. The influences of the distance between the two cells on the SBS characteristics are analyzed in detail.

The optical system has been established in which the changes of polarization state for magneto-optic crystal can be measured. In this optical system, WGY model semiconductor laser is applied as the light source, and the tuning range of the intensity of magnetic field is 0～1500 mT. Depolarization effect in GdYBiIG crystal which often be used in optical isolator is measured in large variation range of adjustable magnetic field. The experiment result shows that polarization performance will be best in GdYBiIG crystal when it reaches saturated magnetization. And the depolarization effect occurs when the intensity of magnetic field increases over saturation intensity. The principle for magnetic depolarization effect is also given according to the experimental result. It presents that magnetic circle dichroism and magnetic linear birefringence are the reasons which cause depolarization effect. From these results, it is optimum to make sure that the magnetic field should be lager only a little than the saturation intensity of magnetic field.

The properties of blue-green laser induced crystallization for as-deposited Ag11In12Sb51Te26 phase change thin films irradiation are studied by measuring the reflectivity contrast at 500, 100 and 60 ns pulse duration. The results show that Ag11In12Sb51Te26 phase change thin films irradiated by blue-green laser have high crystallization speed. The reflectivity contrast of thermal treatment Ag11In12Sb51Te26 phase change thin films is also investigated, and the results show that there is a different in the reflectivity contrast, which is 8% and 19.2%, for laser-induced and thermal treatment films, respectively.

ZrO2 coatings were prepared by electron beam evaporation,while coating thickness and deposition rate were monitored and demonstrated by quartz crystal oscillation. The refractive index and thickness of ZrO2 coatings were measured by NKD7000 spectrophotometer. The surface morphology and root-mean-square (RMS) roughness had been characterized by atomic force microscopy (AFM). It was found that the refractive index and RMS roughness were decreasing as the working pressure was increasing; the refractive index and RMS roughness were also increasing as a result of increasing deposition rate. Which were agreed with the results of tooling factor. Proper process conditions had to be used in order to get optical coatings with better structures under proper RMS roughness.

The measurement of tiny force is an important function of the optical tweezers, for which the trap stiffness plays a key role in the measurement. In this paper, the results of the experimental study on the regulation are reported that the trap stiffness changes with experimental conditions. The results show that the trap stiffness is linearly dependent on the laser power and decreases with the trap height increasing of the bead. In addition, it decreases along with the diameter increase of the trapped bead. The results are qualitatively discussed. The accuracy and range of force measurement are also analyzed.

Based on the Kirchhoff law, a practical high-precision dual-wavelength fiber-optic temperature measuring system using LiTaO3 pyroelectric detector is presented. The structure and the principle of the system are described. According to the temperature resolving power of single detector, the linearity of R(T)-T curves, temperature measuring sensitivity in the measuring system as well as the relationship between the temperature measuring errors and the change of wavelength bandwidth, and after considering the minimal responsibility and the measuring resolution of a single detector, the optimization for its working wavelength bandwidth was done. The optimal result showed that the proper bandwidth of the working wavelength should be 20nm at 400～1300℃ and λ1=2.1 μm, λ2=2.3 μm.

This paper analyzes the self-mixing interference effect in the laser diode (LD) with multiple external reflectors and presents the analysis based on the compound cavity effect in lasers. Each external cavity is considered to be an optical thin film, and the reflectance ratio can be get from the theory of the thin film optics. The general expression of the threshold gain and frequency in the compound laser cavity are deduced and some simulation analysis is made at different conditions. A self-mixing interference experiment system is build with multiple external reflectors. And some experiment results are presented. It is found from the simulation and experiment that the output of the self-mixing interference system with multiple external reflectors is sinusiodal or saw-toothed waves which is similar with the three-mirror Fabry-Perot cavity system. The simulating and experimental results demonstrate the validity of the principle. This principle can be used to analyze the fiber-coupled self-mixing system and the simulation is accordant with experimental results.

The curves of free photoelectron and shallow-trapped photoelectron decaying with time in different doping method and doping amount of iodide are measured under the action of short-pulsed laser by using microwave absorption phase sensitive technique, which is used to measure faint signal. According to the curve, the lifetime values and the decay time values of free photoelectron and shallow-trapped photoelectron under different condition are obtained. By comparing these values, the work of iodide in AgBr-T grain and its influence on the photographic property of AgBr-T are analyzed. In addition, the absorbed and dispersive signals with the iodide amount less than, more than, and equal 3% are analyzed in detail, and the influencing factors on every section are discussed.

Ternary InGaAs bulk layer is used as active region. TM mode gain is enhanced by directly introducing 0.20% tensile strain into bulk InGaAs active layer so that a polarization insensitive semiconductor optical amplifier (SOA) for converter is fabricated. The desired tensile strain value is achieved by only changing the TMGa source flow during low-pressure metalorganic vapor-phase epitaxy (LP-MOVPE). At injection current of 200 mA, the fabricated SOA has a 3 dB optical bandwidth of 50 nm and the gain ripple is less than 0.5 dB. More important is that the polarization sensitivity of SOA is less than 1.1 dB over a wide current and wavelength range. Under bias of current of 200 mA, for λ=1.55 μm, the SOA shows less than 1 dB polarization sensitivity, 14 dB fiber to fiber gain, 3 dBm saturation output power and more than 30 dB chip gain. A high conversion efficiency can be obtained when SOA is used as wavelength converter. A better performance SOA will be achieved if the coupling loss between the SOA chip and the fiber is decreased further.

High speed and long wavelength photodetector is the key device for high-bit-rate optical fiber communication systems and optical networks that need wide frequency bandwidth and high external quantum efficiency simultaneously. It is well known that to increase the speed of PIN photodetector, the absorbing layer thickness should be reduced. The reduction of the absorbing layer thickness means a reduction in the quantum efficiency. So for conventional PIN photodetectors, there is a tradeoff between the quantum efficiency and the device frequency bandwidth through the absorbing layer thickness. One effective solution to this conflict is to use a resonant cavity enhanced (RCE) photodetector. In the RCE photodetector, the absorbing layer is put inside a Fabry-Perot cavity. This means a very thin absorbing layer thickness can be used to achieve a high quantum efficiency and wide frequency bandwidth. In this paper, analyses of light field distribution in the absorption layer of RCE photodetector based on practical design and manufacture are performed. The expression of light field distribution is used in the continuity equations to the frequency response of the RCE photodetector. The frequency response of long wavelength RCE photodetector is analyzed and calculated. The result of analyses and calculation is almost identical with the measuring result of the wide frequency bandwidth RCE photodetector manufactured. That device is an InP-based long wavelength resonant cavity enhanced photodetector with InP-Air gap reflectors and has 8 GHz frequency bandwidth and about 60% external quantum efficiency with the active area of 50 μm×50 μm.

An adaptive polarization mode dispersion (PMD) compensation experiment for 10 Gbit/s nonreturn-to-zero (NRZ) and return-to-zero (RZ) optical fiber communication systems with a two-stage compensator is successfully realized, in which degree of polarization (DOP) feedback signal is used as PMD monitor. The algorithm so-called particle swarm optimization (PSO) is used in optimum searching and tracking process. It was proved that in the optimum searching process, the PSO algorithm has the characteristics of rapid convergence to the global optimum rather than being trapped in local sub-optima and robust to noise. In the tracking process, the algorithm can track the random changed PMD with fast speed. The compensator shows its ability to compensating the first- and second-order PMD at same time. After compensation the eye diagrams can be well recovered both for NRZ and RZ formats. The searching process is finished within several hundreds of milliseconds and the response time of recovering to optimum for a sudden PMD disturbance is less than 20 milliseconds. The quasi-real time adaptive PMD compensation is realized.

A new type of double function optical circulator for double fibers is proposed in this paper. Two fiber tips and lens twice are employed in this kind of device. Because two fiber tips and lens twice are used, the function of optical circulator is duplicated in comparison with conventional optical circulator with single fiber tip. Thus the optical circulator has a low cost and a small volume comparatively. Typical insertion loss and isolation of the developed circulator are analyzed and discussed by using Jones-Matrix in theory. The analysis results show that the above two characteristics are as good as conventional optical circulator′s characteristics. The isolation is increasing with increment of extinction ratio. The surface reflectivity and material absorption are the main source of the insertion loss. The rotator errors of the rotators have an important effect on the isolation. The higher the errors, the lower the isolation. It′s very important for using optical material with high transmission and high extinction ratio to achieve low insertion loss and high isolation. Also the rotation error of the rotators must be reduced in assembly to win low insertion loss and high isolation. Details of design and high characteristics of this circulator are presented.