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Measurement of the beating force in a system of coupled waveguides

Grant number: 17/14920-5
Support type:Scholarships in Brazil - Master
Effective date (Start): March 01, 2018
Effective date (End): February 28, 2019
Field of knowledge:Physical Sciences and Mathematics - Physics
Cooperation agreement: Coordination of Improvement of Higher Education Personnel (CAPES)
Principal Investigator:Pierre Louis de Assis
Grantee:Cauê Moreno Kersul de Castro Carvalho
Home Institution: Instituto de Física Gleb Wataghin (IFGW). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Pairs of nanometric optical waveguides form a coupled system, in which the energy of propagating eigenmodes is distributed among waveguides. When light propagates in one of these eigenmodes, optical forces act on the dielectric material of the waveguides. The attractive or repulsive character of such forces depends on the parity of the electrical field and the separation between waveguides.Due to the quadratic dependence on the electromagnetic field, the optical force for a system excited in a superposition of modes will present beating terms, that are not observed when a single eigenmode is excited. We have recently shown, theoretically, that these additional beating terms are related to the oscillation of the center of energy of the propagating field. We predicted a beating force, which must act with the same direction and sign on both waveguides, in contrast to the eigenmode forces with have different signs for each waveguide.The objective of this Masters project is to use nanofabrication and optomechanical techniques that are already well established in the Department of Applied Physics to fabricate a pair of suspended waveguides and measure the amplitude of their oscillation when excited by a beating force modulated in resonance to their collective mechanical mode. From this measurement, the student Cauê Kersul will be able to verify the theoretical prediction that the beating force acts with the same sign on both waveguides, thus efficiently coupling to a mechanical mode of even parity, that eigenmode forces can only excite with a strength two orders of magnitude lower, according to finite element simulations. (AU)