In this work, form birefringence physics and the mechanisms of Si/SiO2 dielectric concentric optical rings are investigated. The optical rings are modeled by means of a Bragg reflector. Similarly to a negative uniaxial crystal, the dielectric concentric pattern admits two preferred propagation directions defined by an extraordinary and an ordinary refractive index representing two field polarizations. The circular grating profile splits the electromagnetic field into a radial (extraordinary field) and a tangential (ordinary field) component which represent two modes of the periodic structure. These two modes are characterized by the refractive index ellipse obtained by the Huygens principle. The model is developed through the wave front propagation inside the anisotropic structure. The Bragg theory and conservation of momentum vectors provide the Bragg angles of the ordinary and extraordinary rays for different optical wavelengths. The Bragg theoretical model is validated by the finite difference time domain (FDTD) approach for a wavelength of λ = 0.98 μ m.
Bragg reflector by means of the form birefringence effect in dielectric rings
CINGOLANI, Roberto;DE VITTORIO, Massimo;
2010-01-01
Abstract
In this work, form birefringence physics and the mechanisms of Si/SiO2 dielectric concentric optical rings are investigated. The optical rings are modeled by means of a Bragg reflector. Similarly to a negative uniaxial crystal, the dielectric concentric pattern admits two preferred propagation directions defined by an extraordinary and an ordinary refractive index representing two field polarizations. The circular grating profile splits the electromagnetic field into a radial (extraordinary field) and a tangential (ordinary field) component which represent two modes of the periodic structure. These two modes are characterized by the refractive index ellipse obtained by the Huygens principle. The model is developed through the wave front propagation inside the anisotropic structure. The Bragg theory and conservation of momentum vectors provide the Bragg angles of the ordinary and extraordinary rays for different optical wavelengths. The Bragg theoretical model is validated by the finite difference time domain (FDTD) approach for a wavelength of λ = 0.98 μ m.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
