Angle- and polarization-dependent optical switching in porous silicon-based coupled photonic microcavities

Porous silicon (pSi)-based coupled photonic microcavities (MCs) are highly desirable for tunable optical transmission. The coupled microcavities (CMCs) are designed by stacking three cavity layers with a reflection of above 60-70% at lambda(c) = 685 nm. The position of the cavity in transmission mode is found to shift towards shorter wavelength regions with an increase in the angle of incidence for s-, p- and un-polarizations, which might be due to a decrease in effective thickness of pSi layer subjected to oblique incident angles. The line-width and intensity of transmission modes are found to be highly polarization (i.e., s-, p- and un-polarizations) dependent at a higher angle of incidence. Further, similar to 100 nm shift in the transmission mode towards lower wavelength has been achieved by doping of Ag nanoparticles into MC. This is a feasible approach to tune the optical cavity mode to desired wavelengths for applications in optical switching.