Vertical multilayer structures based on porous silicon layers for mid-infrared applications

Maxime Duris,Mohammed Guendouz,Warda Raiah,Nathalie Lorrain,Vincent Thomy,Joël Charrier,Yannick Coffinier,Loïc Bodiou,Parastesh Pirasteh

doi:10.1364/ome.396343

Abstract

In this work, the fabrication of a porous silicon Bragg reflector and vertical cavity on P+ silicon substrate is investigated for applications in spectroscopic sensing in the mid-infrared (Mid-IR) wavelength range. The complex refractive index of porous silicon layers is measured. Optical vertical devices are then fabricated and characterized by Fourier transform infrared (FTIR) spectrophotometry. This work demonstrates the use of electrochemically prepared Bragg reflectors with reflectance as high as 99% and vertical cavity based on porous silicon layers operating in the mid-IR spectral region (up to 8 µm). Experimental reflectance spectra of the vertical cavity structures are recorded as a function of air exposure duration after thermal annealing under nitrogen flux (N2) and results demonstrate that these structures could be used for spectroscopic sensing applications in the mid-IR (2-8 µm) by grafting specific biomolecules on the porous silicon internal surface.

Highlights

Sensitive optical integrated sensors have received great interest during these last years [1,2,3,4,5,6,7,8,9]
Experimental reflectance spectra of the vertical cavity structures are recorded as a function of air exposure duration after thermal annealing under nitrogen flux (N2) and results demonstrate that these structures could be used for spectroscopic sensing applications in the Mid Infrared (Mid-IR) field (2-8 μm) by grafting specific biomolecules on the porous silicon internal surface
This paper demonstrates the fabrication of vertical Porous Silicon multilayer structures on Si substrates and their potential in the Mid-IR wavelength range notably near the cut-off band of Si due to its absorption at 8 μm

Summary

Introduction

Sensitive optical integrated sensors have received great interest during these last years [1,2,3,4,5,6,7,8,9]. The ability to tailor Porous Silicon (PSi) refractive index and layer thickness by controlling porosity and anodization etching time [22,23,24] makes it especially attractive for optical applications. Optical multilayer devices such as Bragg reflectors or micro-cavities have already been implemented from PSi layers notably for Visible and Near Infra-Red (NIR) wavelength ranges [25,26,27,28,29]. That is why the fabrication of Bragg reflector and vertical cavity on P+ silicon substrate is investigated for applications in spectroscopic sensing in the (Mid-IR) wavelength range

Experimental conditions

Results and discussion

Conclusions