Papers by Carlos H De Brito Cruz
Anais do Congresso de Iniciação Científica da Unicamp, Oct 21, 2017
Proceedings of SPIE, Aug 22, 1988
ABSTRACT ÅOptical second-harmonic studies show that the electronic structure in the top 75 - 130 ... more ABSTRACT ÅOptical second-harmonic studies show that the electronic structure in the top 75 - 130 A of a crystalline Si surface loses cubic order only 150 fsec after the Si is excited by an intense 100 fsec optical pulse. This suggests that atomic disorder can be induced directly by electronic excitation, before the material becomes vibrationally excited. In contrast, the electronic properties of the equilibrium molten phase are not obtained for several hundreds of fsec.
Proceedings of SPIE, Aug 19, 2010
The fabrication of small-core photonic crystal fibers and preliminary supercontinuum generation c... more The fabrication of small-core photonic crystal fibers and preliminary supercontinuum generation characterization are reported. In such non-linear experiments fs pulses from a Ti:Sapphire laser were coupled in the fiber core and the generated spectra recorded.
Routledge eBooks, Mar 15, 2019
Revista Brasileira De Epidemiologia, 2020
A modified Imacon type streak camera with temporal resolution of 1.5 psec was used for the measur... more A modified Imacon type streak camera with temporal resolution of 1.5 psec was used for the measurement of pulses generated by a mode locked Er fiber laser operating at 1.55 micron wavelength. The specially developed S1-PV001 image tube had an initial sensitivity of 26 ...
Optics Communications, Feb 1, 1986
Nucleation and Atmospheric Aerosols, 1988
Optics Communications, Nov 1, 1981
Optics Letters, Oct 15, 1991
A polarization-rotation switch is demonstrated that is based on semiconductor-doped glasses. The ... more A polarization-rotation switch is demonstrated that is based on semiconductor-doped glasses. The response time is shorter than 50 fs, and an on-off ratio of 38:1 which corresponds to an intensity of 10 MW/cm 2 . Semiconductor-doped glasses have been shown to exhibit large optical nonlinearities when excited close to the fundamental absorption edge and to be promising materials for applications in fast alloptical switching devices.`4 Both absorptive and dispersive nonlinearities have been demonstrated in CdS.Sel-. -doped glasses, which are readily available as sharp cutoff optical filters. A polarizationrotation switch has been recently described 5 with those glasses with a response time of 4 ps. In this Letter we describe a polarization-rotation switch based on such glasses that has a response time shorter than 50 fs. Both pump and probe
Revista brasileira de fisica, 1980
Quantum Electronics and Laser Science Conference, May 12, 1991
Journal of Chemical Physics, 1989
A dynamic hole-burning study of light-adapted bacteriorhodopsin (BR568) using 6 fs optical pulses... more A dynamic hole-burning study of light-adapted bacteriorhodopsin (BR568) using 6 fs optical pulses has recently been reported [R. A. Mathies, C. H. Brito Cruz, W. T. Pollard, and C. V. Shank, Science 240, 777 (1988)]. The temporal evolution of the excited state absorption and emission spectra after excitation with 60 fs pulses provides a direct observation of the C13=C14 torsional isomerization of the retinal chromophore on the excited state potential surface. Here, we present a more detailed discussion of these spectra. The transient hole line shapes are then calculated by solving the density matrix equations for the third-order susceptibility of a multilevel system. The resulting equations are written without reference to the individual vibronic transitions by using the absorption correlation function 〈i‖i(t)〉. The calculations show that the sharp features seen at short delays arise from coherence coupling effects which occur when the pump and probe pulses overlap in time. This analysis demonstrates that the hole seen at 60 fs is consistent with the broad homogeneous absorption line shape for BR568 originally predicted from resonance Raman intensities, and points out the utility of 〈i‖i(t)〉, derived from resonance Raman intensity analysis, in understanding femtosecond dynamic hole-burning experiments.
Revista USP, Dec 22, 2022
progresso do conhecimento requer comunicação entre os pesquisadores. A comunicação acontece de mu... more progresso do conhecimento requer comunicação entre os pesquisadores. A comunicação acontece de muitas formas, e uma das mais tradicionais e efetivas é a comunicação de resultados, ideias, hipóteses e seus testes em publicações científicas. Em geral se reconhece que a primeira implementação de um periódico científico com seleção de trabalhos submetidos por pesquisadores, usando o sistema de revisão por pares que se tornou o padrão em boas revistas científicas, aconteceu na Philosophical Transactions of the Royal Society, por ideia de seu editor Henry Oldenburg, em 1665 (National Research Council (US) & Committee on Responsibilities of Authorship in the Biological Sciences, 2003). A publicação de um trabalho científico, além de facilitar a comunicação com os pares, permite aos autores garantirem o reconhecimento da comunidade como cria-dores dos resultados apresentados. Autoria e primazia são elementos de alto valor na comunidade científica, tendo o potencial para gerar importantes benefícios aos autores. Estes vão desde o reconhecimento, a consideração e estima dos colegas, até o aumento das chances de obter financiamentos à pesquisa ou promoções na carreira. Os benefícios não são sem sentido, pois a qualidade das ideias que a pessoa teve no passado é um dos indicadores de que poderá ter outras boas ideias no futuro ou, no mínimo, indicação de que domina certas técnicas e métodos relevantes para a descoberta científica em sua área. Como em quase toda atividade humana, a existência de benefícios em potencial pode, em certos casos, influenciar o comportamento dos envolvidos, que perdem o foco no progresso da ciência e na objetividade do trabalho e de seu relato, para buscar mais visibili-CARLOS HENRIQUE DE BRITO CRUZ é Professor Emérito da Unicamp e vice-presidente sênior de Redes de Pesquisa da Elsevier.
Conference on Lasers and Electro-Optics, Apr 26, 1987
International Quantum Electronics Conference, Apr 26, 1987
Phase transitions induced by intense optical pulses have been a controversial topic because dynam... more Phase transitions induced by intense optical pulses have been a controversial topic because dynamic effects other than lattice heating can in principle drive the phase transition.1 However, even experimental work with 90-fs time resolution has been interpreted to be consistent with lattice heating.2
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Papers by Carlos H De Brito Cruz