Non-resonant third-order non-linear optical properties of amorphous GeSe2 film

The real and imaginary parts of third-order susceptibility of amorphous GeSe2 film were measured by the method of the femtosecond optical heterodyne detection of optical Kerr effect at 805 nm with the 80 fs ultra fast pulses. The results indicated that the values of real and imaginary parts were 8.8 x 10(-12) esu and -3.0 x 10(-12) esu, respectively. An amorphous GeSe2 film also showed a very fast response within 200 fs. The ultra fast response and large third-order non-linearity are attributed to the ultra fast distortion of the electron orbits surrounding the average positions of the nucleus of Ge and Se atoms. (c) 2005 Elsevier B.V. All rights reserved.

Super-resolution scanning laser microscopy with a third-order optical nonlinear thin film

In a configuration of optical far-field scanning microscopy, super-resolution achieved by inserting a third-order optical nonlinear thin film is demonstrated and analyzed in terms of the frequency response function. Without the thin film the microscopy is diffraction limited; thus, subwavelength features cannot be resolved. With the nonlinear thin film inserted, the resolution is dramatically improved and thus the microscopy resolves features significantly smaller than the smallest spacing allowed by the diffraction limit. A theoretical model is established and the device is analyzed for the frequency response function. The results show that the frequency response function exceeds the cutoff spatial frequency of the microscopy defined by the laser wavelength and the numerical aperture of the convergent lens. The main contribution to the improvement of the cutoff spatial frequency is from the phase change induced by the complex transmission of the nonlinear thin film. Experimental results are presented and are shown to be consistent with the results of theoretical simulations.

Propagation properties of off-axis Hermite-cosh-Gaussian beam combinations through a first-order optical system

Based on the Collins integral formula, the analytic expressions of propagation of the coherent and the incoherent off-axis Hermite-cosh-Gaussian (HChG) beam combinations with rectangular symmetry passing through a paraxial first-order optical system are derived, and corresponding numerical examples are given and analysed. The resulting beam quality is discussed in terms of power in the bucket (PIB). The study suggests that the resulting beam cannot keep the initial intensity shape during the propagation and the beam quality for coherent mode is not always better than that for incoherent mode. Reviewing the numerical simulations of Gaussian, Hermite-Gaussian (HG) and cosh Gaussian (ChG) beam combinations indicates that the Hermite polynomial exerts a chief influence on the irradiance profile of composite beam and far field power concentration.

Spectral anomalies of focused hollow Gaussian beams at the geometrical focal plane

On the basis of diffraction integral and the expansion of the hard-aperture function into a finite series of complex Gaussian functions, an approximate expression for spatially fully coherent polychromatic hollow Gaussian beams passing through aperture lens is obtained. Detailed numerical results indicate that remarkable spectral changes always occurs near the points where the field amplitude has zero value. The effects of truncation parameter, Fresnel number and the beam order on spectral shifts and spectral switches are investigated numerically. (C) 2008 Elsevier B.V. All rights reserved.

Creche Odetinha: um estudo de caso

Esta Pesquisa, de natureza qualitativa, teve por objetivo, descrever e analisar o processo de formação (2009) de um grupo de educadores os Agentes Auxiliares de Creche1 (AAC)-, recém concursados, através de um Estudo de Caso. Para tanto, fez parte das análises as recentes mudanças nas políticas de educação infantil do município do Rio de Janeiro (1997-2010) e o percurso de constituição da unidade de educação infantil -Creche Municipal Odetinha Vidal de Oliveira, através do relato de alguns de seus líderes comunitários. No município do Rio de Janeiro, as creches públicas resultaram da transferência das instituições que pertenciam à antiga Secretaria de Desenvolvimento Social (SMDS), atual Secretaria Municipal de Assistência Social (SMAS), para a Secretaria Municipal de Educação (SME). Atualmente, a rede municipal de ensino totaliza 255 creches municipais, com 33.348 alunos, em horário integral (7h -17h). No ano de 2005, o poder executivo do município do Rio de Janeiro, através da Lei 3985 de 08 de abril, criou a categoria funcional de Agente Auxiliar de Creche, que passou a integrar o Quadro de Pessoal de Apoio à Educação. O ingresso ao cargo deu-se através de concurso público, realizado em 2007, constituído de provas e provas de títulos, sendo exigida, a formação mínima em nível fundamental (o que fere a LDBEN 9394/96) e carga horária de 40 horas semanais. A seleção ocorreu regionalmente, isto é, por CRE. Em junho de 2008, o quadro de pessoal das creches públicas do município do Rio de Janeiro passou a contar em sua estrutura, com os novos profissionais egressos do concurso, marcando uma nova trajetória na história dessas instituições. A partir da análise do perfil destes educadores, meu objetivo foi refletir sobre a formação em serviço necessária para atender às especificidades de trabalho com criança de zero a três anos. Estaremos assim, co-participando na implementação de políticas públicas de Educação Infantil da prefeitura quanto à formação em serviço dos agentes auxiliares de creche. Para tanto, propomos três temas comuns e complementares de pesquisa: Inserção das crianças e famílias à creche; Brincar/Brincadeira; Arranjo espacial. Os instrumentos utilizados na pesquisa foram: observação participativa, questionários, e entrevistas. Foram também desenvolvidas, com os educadores, atividades de formação e sessões reflexivas que proporcionem o pleno desenvolvimento profissional desses sujeitos.

Microwave Resonant and Zero-Field Absorption Study of Doped Magnetite Prepared by a Co-Precipitation Method

Fe3O4 and ZnxFe3-xO4 pure and doped magnetite magnetic nanoparticles (NPs) were prepared in aqueous solution (Series A) or in a water-ethyl alcohol mixture (Series B) by the co-precipitation method. Only one ferromagnetic resonance line was observed in all cases under consideration indicating that the materials are magnetically uniform. The shortfall in the resonance fields from 3.27 kOe (for the frequency of 9.5 GHz) expected for spheres can be understood taking into account the dipolar forces, magnetoelasticity, or magnetocrystalline anisotropy. All samples show non-zero low field absorption. For Series A samples the grain size decreases with an increase of the Zn content. In this case zero field absorption does not correlate with the changes of the grain size. For Series B samples the grain size and zero field absorption behavior correlate with each other. The highest zero-field absorption corresponded to 0.2 zinc concentration in both A and B series. High zero-field absorption of Fe3O4 ferrite magnetic NPs can be interesting for biomedical applications.

加速度对激光双频干涉仪测量误差的影响

为了减少由于加速度所导致的激光双频干涉仪测量误差,引入二阶多普勒频移,建立了由被测物体加速度所引起的测量误差的理论模型。仿真结果表明,在0.4s时间内0.6g加速度所引起的累积误差可达2.5 nm左右,这对于纳米精度的测量是不应忽视的; 初速度不为零时加速运动会引起更大的误差,而减速运动所引起的误差则相对小。通过实验验证,所测的误差变化趋势与理论模拟比较吻合。