Sensitivity of the optical properties of porous silicon layers to the refractive index of liquid in the pores

• Published in: Physica status solidi. A, Applied research Applied research, 2003-05, Vol.197 (2), p.528-533
• Main Authors: Anderson, M. A., Tinsley-Bown, A., Allcock, P., Perkins, E. A., Snow, P., Hollings, M., Smith, R. G., Reeves, C., Squirrell, D. J., Nicklin, S., Cox, T. I.
• Format: Article
• Language: English
• Subjects: 07.07.Df; 78.40.Fy; 78.66.Db; Exact sciences and technology; General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Physics; Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
• ISSN: 0031-8965; 1521-396X
• DOI: 10.1002/pssa.200306558

The sensitivity of the optical reflectivity of porous silicon structures to the refractive index of liquid within the pores is studied for a single layer, a Bragg mirror and a microcavity. Sucrose solutions of concentration in the range 0.05 to 1.0% by weight are introduced into the pores within a flow cell in order to change the refractive index of the liquid in the pores from 1.3330 to 1.3344. Optimum wavelengths for detection via reflectivity changes are determined based on a signal to noise analysis. The optical thickness of the single layer is also monitored by measuring the fringe spacing via a Fourier transform technique. It is just possible to detect the effect of a change in refractive index of liquid in the pores of 0.00007 for both the reflectivity and optical thickness approaches.