Three-dimensional micro- and nano-fabrication in transparent materials by femtosecond laser

Femtosecond pulsed lasers have been widely used for materials microprocessing. Due to their ultrashort pulse width and ultrahigh light intensity, the process is generally characterized by the nonthermal diffusion process. We observed various induced microstructures such as refractive-index-changed structures, color center defects, microvoids and microcracks in transparent materials (e.g., glasses after the femtosecond laser irradiation), and discussed the possible applications of the microstructures in the fabrication of various micro optical devices [e.g., optical waveguides, microgratings, microlenses, fiber attenuators, and three-dimensional (3D) optical memory]. In this paper, we review our recent research developments on single femtosecond-laser-induced nanostructures. We introduce the space-selective valence state manipulation of active ions, precipitation and control of metal nanoparticles and light polarization-dependent permanent nanostructures, and discuss the mechanisms and possible applications of the observed phenomena.

Group delay dispersion measurement of Yb : Gd2SiO5, Yb : GdYSiO5 and Yb : LuYSiO5 crystal with white-light interferometry

We report the measured group delay dispersion (GDD) of new crystals Yb:Gd2SiO5 (Yb:GSO), Yb:GdYSiO5 (Yb:GYSO) and Yb:LuYSiO5 (Yb:LYSO) over wavelengths from 1000nm to 1200nm, with a white-light interferometer. Those GDD data should be useful for the dispersion compensation for femtosecond pulse generation in the lasers with these new crystals as the gain media. (C) 2007 Optical Society of America

Demonstration of GaN/InGaN light emitting diodes on (100) beta-Ga2O3 substrates by metalorganic chemical vapour deposition

The growth and fabrication of GaN/InGaN multiple quantum well (MQW) light emitting diodes ( LEDs) on ( 100) beta-Ga2O3 single crystal substrates by metal-organic chemical vapour deposition (MOCVD) technique are reported. x-ray diffraction (XRD) theta-2 theta. scan spectroscopy is carried out on the GaN buffer layer grown on a ( 100) beta-Ga2O3 substrate. The spectrum presents several sharp peaks corresponding to the ( 100) beta-Ga2O3 and ( 004) GaN. High-quality ( 0002) GaN material is obtained. The emission characteristics of the GaN/InGaN MQW LED are measurement. The first green LED on beta-Ga2O3 with vertical current injection is demonstrated.

Extended bidirectional reflectance distribution function for polarized light scattering from subsurface defects under a smooth surface

By introducing the scattering probability of a subsurface defect (SSD) and statistical distribution functions of SSD radius, refractive index, and position, we derive an extended bidirectional reflectance distribution function (BRDF) from the Jones scattering matrix. This function is applicable to the calculation for comparison with measurement of polarized light-scattering resulting from a SSD. A numerical calculation of the extended BRDF for the case of p-polarized incident light was performed by means of the Monte Carlo method. Our numerical results indicate that the extended BRDF strongly depends on the light incidence angle, the light scattering angle, and the out-of-plane azimuth angle. We observe a 180 degrees symmetry with respect to the azimuth angle. We further investigate the influence of the SSD density, the substrate refractive index, and the statistical distributions of the SSD radius and refractive index on the extended BRDF. For transparent substrates, we also find the dependence of the extended BRDF on the SSD positions. (c) 2006 Optical Society of America.

Measurements of light scattering from glass substrates by total integrated scattering

A total integrated scattering (TIS) measurement was performed to investigate the surface and volume scattering of K9 glass substrates with low reflectance. Ag layers with thicknesses of 60 nm were deposited on the front and back surfaces of the K9 glass substrates by the magnetron sputtering technique. Surface scattering of the K9 glass substrate was obtained by the TIS measurement of the Ag layers on the assumption that the Ag layers and the K9 substrate had the same surface profile. Volume scattering of the substrates was deduced by subtracting the front and back surface scattering from the total scattering of the substrates. (c) 2005 Optical Society of America.

光学薄膜中界面层和表面吸附层对相位延迟的影响

多层介质反射镜在非正入射的时候，两个不同的偏振态之间会产生不同的相移．根据空气与膜层、膜层之间的实际情况，建立了界面层和表面吸附层模型，并运用它分析相位延迟产生误差的原因．通过优化设计，入射角为54°，在1285～1345nm之间p，s波获得了270±1°的相移，同时也使反射率在99．5％以上．用离子束溅射技术制备相位延迟膜，用分光光度计测试了光谱特性和用椭偏仪测试了相位特性，在相应波段获得了262．4±1．8°的相移，同时也使反射率在99．6％以上．误差的主要来源是离子源工作特性会产生不均匀的过渡层和最

氧碘激光器相位延迟片的制备与性能研究

多层介质反射镜在非正入射的时候，两个不同的偏振态之间会产生不同的相移。利用矩阵法，根据菲涅耳公式和电磁场边界条件，推导出p，s波的相移。通过优化设计．入射角为54°，在1285～1345nm之间p，s波获得了270°±1°的相移，同时也使反射率在99．5％以上。用离子束溅射技术制备相位延迟膜，用分光光度计测试了光谱特性和用椭偏仪测试了相位特性，在相应波段获得了262．4°±1．8°的相移，同时也使反射率在99．6％以上。误差的主要来源是离子源工作特性会产生不均匀的过渡层和最外层会吸收一些水气、灰尘等也产生

反射式相位延迟器的性能研究

多层介质反射镜在非正入射的时候，两个不同的偏振态之间会产生不同的相移。通过优化设计，入射角为45°，在1285～1345nm之间p，s波获得了270°±0．15°的相移和99．5％以上的反射率。对使用的膜系进行了每层光学厚度的误差分析。用离子柬溅射技术制备相位延迟膜，在大气中对样品进行不同温度的退火，用分光光度计测试了光谱特性和用椭偏仪测试了相位特性。结果表明，未退火的样品在相应波段获得了267．5°±0．5°的相移和99．6％以上的反射率；根据拟合分析，最外层的误差和折射率与设计值的偏差是发生相移偏小的

Control of polarization for a broadband dichroic filter at 45 degrees incidence

A method for the control of polarization for a broadband dichroic filter was reported and some design examples were elaborated. This method could be applied over a wide range of wavelengths and a wide range of polarizations in the transmission region. A nonpolaiizing broadband dichroic filter and a broadband dichroic filter with certain polarization were designed and fabricated by electron beam evaporation with ion beam assisted deposition. The experimental spectral performances showed good agreement with their theoretical curves. In addition, the application of the method was discussed. (c) 2007 Optical Society of America

Propagation and polarization properties of hollow Gaussian beams in uniaxial crystals

Based on the paraxial vectorial theory of beams propagating in uniaxially anisotropic media, we have derived the analytical propagation equations of hollow Gaussian beams (HGBs) in uniaxial crystals, and given the typical numerical example to illustrate our analytical results. Due to the anisotropy crystals, the ordinary and extraordinary beams originated by incident HGBs propagate with different diffraction lengths, thus the linear polarization state and axial symmetry of incident HGBs do not remain during propagating in crystals. (c) 2007 Published by Elsevier B.V.