Refractive index evaluation of porous silicon using Bragg reflectors

Authors

D. Estrada-Wiese Instituto de Investigación en Ciencias Básicas y Aplicadas, Universidad Autónoma del Estado de Morelos, Av. Universidad No. 1001 Col. Chamilpa, 62209, Cuernavaca Morelos México.
J.A. del Río Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Privada Xochicalco S/N, 62580 Temixco Morelos, México.

Refractive index, porous silicon, effective medium approximation, Bragg reflectors, photonic structures.

There are two main physical properties needed to fabricate 1D photonic structures and form perfect photonic bandgaps: the quality of the

thickness periodicity and the refractive index of their components. Porous silicon (PS) is a nano-structured material widely used to prepare 1D

photonic crystals due to the ease of tuning its porosity and its refractive index by changing the fabrication conditions. Since the morphology

of PS changes with porosity, the determination of PS’s refractive index is no easy task. To find the optical properties of PS we can use

different effective medium approximations (EMA). In this work we propose a method to evaluate the performance of the refractive index of

PS layers to build photonic Bragg reflectors. Through a quality factor we measure the agreement between theory and experiment and therein

propose a simple procedure to determine the usability of the refractive indices. We test the obtained refractive indices in more complicated

structures, such as a broadband Vis-NIR mirror, and by means of a Merit function we find a good agreement between theory and experiment.

With this study we have proposed quantitative parameters to evaluate the refractive index for PS Bragg reflectors. This procedure could have

an impact on the design and fabrication of 1D photonic structures for different applications.