The adjustment of the position of the optical trap is of great importance for its practical application. In this paper, the imaging regularity of the laser waist through an inverted microscope is analysed. A method is advanced to observe the position of the waist and to measure its deviation (d) from the objective plane with an object plate. Furthermore, based on the transformation of the Gaussian beam, the position of the laser trap can be easily adjusted by regulating the collimating lens for the semiconductor-laser (the sourse of the laser teap). This meyhod is simple and adapts to various biological specimens.

An analytic expression is obtained for the chirp induced by the dispersion in the stepwise decreasing dispersion fiber. Using numerical method, we simulate the evolution of chirp in the stepwise decreasing dispersion fiber. The results show that the chirp in the stepwise decreasing dispersion fiber varies jumply taking the chirp in the fiber of slowly decreasing dispersion as the centre at the beginning, then the chirps coincide gradually with each other. However the chirp in the stepwise-descreasing-despersion fiber is smaller than the chirp in the conventional fiber.

A new method for reconstructing ordinary three dimension diffusion holograms with a white light source is described. In the method, a wave guided hologram (WGH) illuminator is used. It takes advantages of wavelength selection of the reflection holograms and the dispersion compensation of the WGH illuminator. A clear and quasi monochromatic reconstruction image is obtained through white light illuminating.

Photonic signals can be multiplexed independently in the space, time and wavelength domains. In this paper a new method using connection logical maps to describe the alteration of network structure from the space division switching network to the photonic switching network in three divisions is proposed for the first time. As an example, a multistage photonic switching network with 8 input ports and 8 output ports in the space only division, which matches Benes structure, is converted to another network in three divisions with the asme connection structure by this method.

Imaging of an absorbing object hidden in highly scattering random media is achieved with a CW broadband light from a luminous diode. A new image processing algorithm is developed to restore the image covered by the diffuse light. Submilimeter spatial resolution is achieved. This method may find the important potential application in medical imaging.

The characterization of the saturated gain spectrum of an EDFA in a WDM system was investigated experimentally. It is proposed that the gain of a single channel is higher than that of each channel when multi channels exsist simultaneously if the input power is the same; when saturated, the gain of the EDFA shows that the longer the wavelength, the higher the gain.

In this paper, the roles of nonlinear polarization rotation in an actively mode locked fiber ring laser were discussed. Both qualitative analysis and experimental results indicate that there is a special state at appropriate conditions in the ring cavity. In this state, both pulse compression and stability improvement can be achieved.

A continuously tunable ring laser of repetition operation is successfully made. The range of the tunable wavelength is 1535~1565 nm. The range of the repetition rates is 2.4~2.6 GHz. The time bandwidth product is close to the transform limit. Optical pulses with a repetition rate of 5 GHz are obtained by changing the direct current bias voltage, and the relative experimental principle is analyzed.

By tilting a pump beam quickly, a fast tuning optical parametric oscillator (OPO) was realized. The widely tunable spectral range of the OPO has been obtained by a piece of type I BBO crystal.

The performance of a wide stripe InGaAsSb/AlGaAsSb MQW diode laser grown by MBE is reported. Output pulse power of the laser diode at room temperature is 83 mW, the threshold current is 250 mA, and the typical peak wavelength is about 2.00 μm.

Spectral characteristics of a high power laser diode with external fiber grating feedback are investigated both theoretically and experimentally. The theoretical results show that the spectral linewidth can be narrowed or broadened according to different external cavity parameters. The change of spectral linewidth is more sensitive to the effect of external reflection coefficient than the external cavity length. The reduction of spectral linewidth from 6 nm to 0.8 nm is achieved in our experiments. The external cavity with fiber grating feedback not only improves the spectral characteristics but also increases the repression ratio of dominant modes to subordinate modes.

This paper reports the experimental researches on impurity free vacancy disordering (IFVD) of the InGaAs/GaAs strained quantum well capped by a SiO 2 film and the suppression effect on IFVD with a SrF 2 film. This technology was applied to ridge waveguide InGaAs/GaAs/AlGaAs strained quantum well lasers and fabricated window structure lasers with nonabsorbing mirrors. The maximum output power is 340 mW for 3 μm width ridge waveguide lasers with windows. Compared with that of the conventional quantum well lasers, this maximum output power has an increase of 36%. The emission wavelength is 978 nm and FWHM is 1.2 nm at 100 mW. The far-field angles are 7.2° and 30° in junction-parallel and perpendicular directions, respectively.

In this paper, with a Q switched Nd:YAG laser, the optical limiting in PDABS 1/CCl 3 and HDABS 1/CCl 3 solutions for ps and ns pulses is studied and proved to be resulted from single photon absorption.

In this paper, the statistical behabiors are analysed for an arbitrary paraxial beam with two dimentional distribution in the transverse section, and the propagation parameters are obtained for the equivalent Gaussian beam which can describe the statistical behaviors of the paraxial beam. The results in reference can be derived from the conclusions in this paper by using the concept of “embedded Gaussian beam”. This results can be used in the geometrical description for the propagation of a paraxial beam.

When a Q switched YAG laser pulse radiation produces SHG in a LiIO 3 crystal, due to converting part of the fundamental radiation into the SHG radiation, the optoacoustic signals in the SHG crystal induced by the laser radiation will be enhanced, and vary with the SHG phase mismatching angle of the crystal. This paper reports experimental results and gives an analysis.

Different concentrations of Pr 3+ /Yb 3+ codoped ZBLAN glasses were made. The absorption spectra were measured. The fluorescent properties were calculated by using the Judd Ofelt theory. The energy transfer rates between Pr 3+ and Yb 3+ were calculated. It is shown that the use of Yb 3+ intensifies the absorption of Pr 3+.

The unpolarized and polarized fluorescence spectra of Nd:YVO 4 crystal excited by π and σ polarized lights respectively are measured and compared. The characteristics of the Nd:YVO 4 laser pumped by a laser diode are studied. A 1064 nm laser with a maximum output power of 1012 mW and a slope efficiency of 53.6% is obtained at the incident pump power of 1900 mW.