Optical response of porus silicon and porous alumina hybrid structures

LUISINA FORZANI; RAÚL URTEAGA; LUISA CENCHA; R.R. KOROPECKI

Tarragona

Conferencia; 10 International Conference PSST; 2016

In this work, we evaluate theoretically and experimentally the optical response of structures that integrate porous silicon and porous alumina to form a multilayered hybrid structure. We perform a rational design of the optimal sequence necessary to produce a high transmission and selective filter. The combination of these two porous materials can be used to exploit the distinguishing features of each material, i.e. high transparency of the alumina and high refractive index contrast that can be achieved with porous silicon. We build hybrid microcavities with a central defect of porous alumina which is placed between two porous silicon distributed Bragg reflectors. In this way we construct a Fabry-Perot resonator with high reflectivity and low absorption that improves the finesse of the filter respect to a microcavity constructed only with porous silicon. We also explore a simpler design in which one of the Bragg reflectors is replaced by the aluminium that remains bound to the alumina after its fabrication. We theoretically explore the potential of the proposal and its limitations when considering a possible roughness of the layers. We found that a microcavity made completely in porous silicon shows a limit in the finesse that can be achieved in the visible range mainly because its absorption. This limitation is overcome in the hybrid scheme, be-ing the roughness of the layers the factor that determines the ultimate finesse. Q factors of 180 are obtained for microcavities supported on aluminum and Q =240 for microcavities with double Bragg reflectors in 700nm.