Omnidirectional photonic bandgaps in porous silicon based mirrors with a Gaussian profile refractive index

Abstract

We have designed and fabricated one dimensional photonic bandgap (PBG) structures from dielectric multilayers of porous silicon, with a periodic repetition of a unit cell consisting of 21 layers (95%) with the refractive index varying according to the envelope of a Gaussian function and another layer (5%) with a fixed refractive index. The structures can be designed to demonstrate the wavelength scalability within the visible as well as near infrared region. Three different structures have been stacked together to enhance the width of the PBG. The omnidirectional nature of the PBG was verified experimentally and theoretically up to 68° and 89° angles of incidence, respectively.