998 resultados para moving mirror


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A novel type of interferometer, the moving-mirror-pair interferometer, is presented, and its principle and properties are studied. The new interferometer is built with three flat mirrors, which include two flat moving mirrors fixed as a single moving part by a rigid structure and one flat fixed mirror. The optical path difference (OPD) is obtained by the straight reciprocating motion of the double moving mirror, and the OPD value is four times the physical shift value of the double moving mirror. The tilt tolerance of the double moving mirror of the novel interferometer is systematically analyzed by means of modulation depth and phase error. Where the square aperture is concerned, the formulas of the tilt tolerance were derived. Due to the novel interferometer's large OPD value and low cost, it is very applicable to the high-spectral-resolution Fourier-transform spectrometers for any wavenumber region from the far infrared to the ultraviolet. (C) 2008 Optical Society of America.

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Single photon Sagnac interferometry as a probe to macroscopic quantum mechanics is considered at the theoretical level. For a freely moving macroscopic quantum mirror susceptible to radiation pressure force inside a Sagnac interferometer, a careful analysis of the input-output relation reveals that the particle spectrum readout at the bright and dark ports encode information concerning the noncommutativity of position and momentum of the macroscopic mirror. A feasible experimental scheme to probe the commutation relation of a macroscopic quantum mirror is outlined to explore the possible frontier between classical and quantum regimes. In the Appendix, the case of Michelson interferometry as a feasible probe is also sketched.

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飞秒激光脉冲通过时空变换技术将时域信息变换到空域,通过空域的处理再返回到时域,是实现飞秒激光脉冲整形、测量和控制的一项重要技术。在应用方面,可产生各种所需要的波形.已广泛应用在飞秒化学、信号处理、安全通信、生物学和医学成像等方面。介绍了飞秒时空变换脉冲整形的几种方法。

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We present a one-dimensional scattering theory which enables us to describe a wealth of effects arising from the coupling of the motional degree of freedom of scatterers to the electromagnetic field. Multiple scattering to all orders is taken into account. The theory is applied to describe the scheme of a Fabry-Perot resonator with one of its mirrors moving. The friction force, as well as the diffusion, acting on the moving mirror is derived. In the limit of a small reflection coefficient, the same model provides for the description of the mechanical effect of light on an atom moving in front of a mirror.

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No presente trabalho foi considerado um campo escalar real não massivo em um espaço-tempo bidimensional, satisfazendo à condição de fronteira Dirichlet ou Neumann na posição instantânea de uma fronteira em movimento. Para uma lei de movimento relativística, foi mostrado que as condiçõoes de fronteira Dirichlet e Neumann produzem a mesma força de radiação sobre um espelho em movimento quando o estado inicial do campo é invariante sobre translações temporais. Obtemos as fórmulas exatas para a densidade de energia do campo e da força de radiação na fronteira para os estados de vácuo, coerente e comprimido. No limite não-relativistico, os resultados obtidos coincidem com os encontrados na literatura. Também foi investigado o campo dentro de uma cavidade oscilante. Considerando as condiçõoes de fronteira Neumann e Dirichlet, escreveu-se a fórmulas exata para a densidade de energia dentro de uma cavidade não-estática, para um estado inicial arbitrário do campo. Tomando como base a equação de Moore, nós calculamos recursivamente a densidade de energia e investigamos a evolução temporal da densidade de energia para o estado coerente do campo.

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The posterior inferior frontal gyrus (pIFG) and anterior inferior parietal lobule (aIPL) form the core regions of the human “mirror neuron system” that matches an observed movement onto its internal motor representation. We used event-related functional MRI to examine whether simple intransitive finger movements evoke “mirror activity” in the pIFG and aIPL. In separate sessions, participants either merely observed visuospatial stimuli or responded to them as quickly as possible with a spatially compatible finger movement. A picture of a relaxed hand with static dots on the tip of the index and little finger was continuously presented as high-level baseline. Four types of stimuli were presented in a pseudorandom order: a color change of a dot, a moving finger, a moving dot, or a simultaneous finger-dot movement. Dot movements were spatially and kinematically matched to finger movements. Participants were faster at imitating a finger movement than performing the same movement in response to a moving dot or a color change of a dot. Though imitative responses were facilitated, fMRI revealed no additional “mirror activity” in the pIFG and aIPL during the observation or imitation of finger movements as opposed to observing or responding to a moving dot. Mere observation of a finger movement alone failed to induce significant activation of the pIFG and aIPL. The lack of a signature of “mirror neuron activity” in the inferior frontoparietal cortex is presumably due to specific features of the task which may have favored stimulus–response mapping based on common spatial coding. We propose that the responsiveness of human frontoparietal mirror neuron areas to simple intransitive movements critically depends on the experimental context.