A porous silicon waveguide with integrated grating coupler is demonstrated as a new platform for portable detection of chemical and biological molecules. The two-layer porous silicon waveguide is formed by electrochemical etching and a photoresist grating is fabricated directly on the waveguide core by means of electron beam lithography. Angle-resolved reflectance measurements reveal distinct peaks corresponding to the guided mode. A 0.420° reflectance shift was observed upon 16-base DNA hybridization, which was more than a factor of 5 larger than the observed reflectance shift after exposure to a mismatched DNA sequence.
Photonic crystal microcavities with multi-hole defects were simulated using finite difference time domain (FDTD)
analysis. Subwavelength, multi-hole defects (MHD) offer a significant increase in defect surface area without
compromising the quality factor of the photonic crystal. Calculations of the increase in surface area compared to a
traditional, single hole defect are performed for MHD structures with varying subwavelength defect hole size,
subwavelength defect hole spacing, and effective defect radius. For active photonic crystal applications, the resonance
wavelength and quality factor of several different MHD photonic crystal structures was calculated as a function of the
dielectric constant of the defect. MHD photonic crystals can be designed to enable large changes in resonance
wavelength for small changes in defect dielectric constant. These structures would be advantageous for applications in
biosensing and optical switching.