一种新型的二元光学器件——多位相光束分束器的制作

本文报道了用于多光束分束器的反射式16位相值二元光学器件的制作。该二元光学器件把一束光束分成5×5光束阵列。测量的衍射效率为76.16%,接近理论设计值79.68%。该二元光学器件的有效孔径为10mm×10mm。     

Shape transition from InAs quantum dash to quantum dot on InP(3 1 1)A

We report on the shape transition from InAs quantum dashes to quantum dots (QDs) on lattice-matched GaInAsP on InP(3 1 1)A substrates. InAs quantum dashes develop during chemical-beam epitaxy of 3.2 monolayers InAs, which transform into round InAs QDs by introducing a growth interruption without arsenic flux after InAs deposition. The shape transition is solely attributed to surface properties, i.e., increase of the surface energy and symmetry under arsenic deficient conditions. The round QD shape is maintained during subsequent GaInAsP overgrowth because the reversed shape transition from dot to dash is kinetically hindered by the decreased ad-atom diffusion under arsenic flux.     

Long-wavelength GaInAsSb/AlGaAsSb DFB lasers emitting near 2.6 μm

We have successfully fabricated and characterized room temperature continuous wave (cw) GaInAsSb/AlGaAsSb distributed feedback lasers emitting in the wavelength region between 2.499 and 2.573 μm. To the best of our knowledge, this is the longest emission wavelength realized with a GaSb-based DFB laser diode. The laser structure used for DFB processing was grown by solid source molecular beam epitaxy. A DFB concept requiring no subsequent overgrowth step was used by defining first-order Cr-Bragg gratings laterally patterned to a ridge waveguide. Threshold currents smaller than 60 mA and room temperature cw output powers up to 6.5 mW were obtained. The laser diodes show single mode emission with side mode suppression ratios (SMSR) of up to 32 dB.     

Multiple doubly periodic solutions of semi-linear damped beam equations

The purpose of this work is to investigate the weakened Ambrosetti–Prodi type multiplicity results for weak doubly periodic solutions of damped beam equations. By using the topological degree theory, the author obtains a result which is similar to the result for damped wave equations in the literature.     

用于光控相控阵雷达的空间光调制器

空间光调制器是光信息处理机的基本结构单元,它能根据电驱动信号或光驱动信号,随时修正与空间和时间有关的读出光束的偏振、相位和幅度.介绍了适用于光控相控阵雷达系统的空间光调制器,包括它们的结构、原理和性能.     

Study on the possibilities of controlling the laser output beam properties by an intracavity deformable mirror

The possibilities of controlling the laser beam properties by a deformable mirror introduced into the laser optical cavity were studied theoretically and experimentally. The experiments were performed under conditions of an industrial high power transverse flow cw CO₂ laser operating with a stable resonator of a folded configuration. A deformable bimorph mirror of a surface profile controlled by the voltage applied to the mirror electrodes is implemented to the laser system as a back cavity mirror or as a one of the inner folding mirrors. The near-and far-field characteristics of the laser beam versus the resonator configuration controlled by the changes of the focal length of the deformable mirror are discussed in the paper. The analysis reveals that the resonator with an inner deformable mirror is much more sensitive to the mirror curvature variations than the resonator in which the deformable mirror is used as a back cavity mirror. The presented results show that dynamic and controllable changes in the resonator properties result in the controlled modification and optimisation of the laser output power and spatial parameters of the laser radiation.     

Structure and magnetism of bcc(1 1 0)-like Fe films grown on Cu(0 0 1) via ion beam triangulation and spin-polarized electron capture

The structure and magnetism of thin epitaxial Fe layers grown on Cu(0 0 1) is investigated by grazing scattering of fast H and He atoms. Information on the atomic structure of the film and substrate surfaces is obtained by making use of ion beam triangulation with protons. The magnetic behavior is studied via the polarization of light emitted after capture of spin-polarized electrons into excited atomic terms during scattering of He atoms. For the formation of bcc(1 1 0)-like Fe films at higher coverages, we detect differences in structural and magnetic properties for room and low temperature growth. We suggest that the crystalline structure depends on the film morphology and that Cu impurities affect the magnetic properties.     

Changes in the spectrum of Gaussian Schell-model beams propagating through turbulent atmosphere

Based on the extended Huygens-Fresnel principle, the spectrum of Gaussian Schell-model (GSM) beams propagating through turbulent atmosphere is derived analytically. It is shown that, if the scaling law is valid, the normalized spectrum S(ω) of GSM beams propagating through turbulent atmosphere is the same as the normalized source spectrum S⁽⁰⁾(ω), whether GSM source is quasi-homogenous or not. On the other hand, if the scaling law fails, S(ω) of GSM is different from S⁽⁰⁾(ω). The structure constant of the refractive index, transverse coordinate of observation point and spatial correlation length of the source affect the spectrum, which is illustrated numerically.     

Tesla变压器型电子束加速器初步实验

 介绍了一种Tesla变压器型的强流电子束加速器。当变压器初级输入20kV左右的电压时，加速器二极管输出电压500kV，电流9kA，信号脉宽大约50ns，该装置具有结构简单，安装方便，运行可靠等特点。