Difracção espacial e dispersão temporal: estudo unificado

This Thesis presents a theoretical study of the electromagnetic radiation propagation in two distinct optical regimes; in the space diffraction regime of monochromatic light waves and in the dispersive media propagation regime of ultrashort optical pulses. The study is made under a unifying perspective, where it is demonstrated that the propagation in both regimes is formally equivalent, in other words, it is shown the existence of a perfect analogy between the propagation in the two regimes – space diffraction/time dispersion (SDTD) analogy. In this way, it is overtaken the limitation of the primitive SDTD analogy, which is only valid under the second order dispersion approximation. Related to the SDTD analogy, it is also made a study of the electro-optic time lens, where it is proposed a more realistic theoretical model relatively to the previously existing one. This last model is only valid for above 1 ps pulses and in the case of existence of a perfect match between the pulse group velocity and the micro-wave phase velocity. The proposed model is suitable for sub-picosecond pulses; it takes in account the possible velocities mismatch and it allows the apropriate function characterization of the lens, particularly the definition of the aberration coefficients. It is also demonstrated that the electro-optic time lens is formally equivalent, in the space diffraction regime, to the GRIN space lens (GRIN graded index). The study of the electro-optic time lens is complemented with the demonstration of its operation through numerical simulation. Trabalhos publicados Artigos em revistas cientificas internacionais: • Extended analogies between time-dispersion and space-diffraction propagations, Francisco J. Marinho, Luis M. Bernardo, J. Opt. Soc. Am. A 23(9), 2331-2334, Setembro 2006. • Graded-index time-lens implementation, Francisco J. Marinho, Luis M. Bernardo, Optics Letters 31(11), 1723-1725, Junho 2006. Apresentacoes orais em conferencias internacionais: • Electrooptic Time Lens Model for Femtosecond Pulses, Francisco J. Marinho, Luis M. Bernardo, aceite na Conferencia da SPIE Photonics Europe 2008. • Electro-optic graded-index time-lens, Francisco J. Marinho e Luis M. Bernardo, SEON 2006 IV Symposium on Enabling Optical Networks and Sensors, Faculdade de Engenharia da Universidade do Porto, Junho 2006. Apresentacao oral em conferencia nacional: • Estudo da analogia entre a difraccao espacial e a dispersao temporal, Francisco J. Marinho, Luis M. Bernardo, III Jornadas IFIMUP 2007 Instituto de Fisica dos Materiais da Universidade do Porto, Maio 2007. Poster em conferencia nacional: • Lente electro-optica temporal: modelo e caracteristicas, Francisco J. Marinho, Luis M. Bernardo, Conferencia Nacional de Fisica, Aveiro, Setembro 2006.