Monolithically integrated broad-band Mach-Zehnder interferometers for highly sensitive label-free detection of biomolecules through dual polarization optics.

Protein detection and characterization based on Broad-band Mach-Zehnder Interferometry is analytically outlined and demonstrated through a monolithic silicon microphotonic transducer. Arrays of silicon light emitting diodes and monomodal silicon nitride waveguides forming Mach-Zehnder interferometers were integrated on a silicon chip. Broad-band light enters the interferometers and exits sinusoidally modulated with two distinct spectral frequencies characteristic of the two polarizations. Deconvolution in the Fourier transform domain makes possible the separation of the two polarizations and the simultaneous monitoring of the TE and the TM signals. The dual polarization analysis over a broad spectral band makes possible the refractive index calculation of the binding adlayers as well as the distinction of effective medium changes into cover medium or adlayer ones. At the same time, multi-analyte detection at concentrations in the pM range is demonstrated.

All-silicon monolithic Mach-Zehnder interferometer as a refractive index and bio-chemical sensor.

A complete Mach-Zehnder interferometer monolithically integrated on silicon is presented and employed as a refractive index and bio-chemical sensor. The device consists of broad-band light sources optically coupled to photodetectors through monomodal waveguides forming arrays of Mach-Zehnder interferometers, all components being monolithically integrated on silicon through mainstream silicon technology. The interferometer is photonically engineered in a way that the phase difference of light travelling through the sensing and reference arms is approximately wavelength independent. Consequently, upon effective medium changes, it becomes feasible even with a broad-band source to induce sinusoidal-type of detector photocurrents similar to the classical monochromatic counterparts. The device is completed with its fluidic and interconnect components so that on chip interferometric measurements can be performed. Examples of refractive index and protein sensing are presented to establish the potential of the proposed device for real-time in situ monitoring applications. This is the only silicon device that has achieved complete on-chip interferometry.

Transformation of InAs islands to quantum ring structures by metalorganic vapor phase epitaxy.

The transformation of InAs islands to quantum rings (QRs) by metalorganic vapor phase epitaxy is investigated. After covering the InAs islands with a thin GaAs partial capping layer and annealing under tertiarybutylarsine (TBAs) flow, ring-shaped nanostructures with a density of 10(7)-10(9) cm(-2) are obtained at 500-600 °C. The effects of the growth temperature, annealing process and thickness of the partial capping layer are studied. Optimum values for the annealing time and the partial capping layer thickness were found to be 60-120 s and 0.5-2.0 nm, respectively. Low temperature photoluminescence (PL) emission peaks from islands and QRs grown at 500 °C are observed at 1.04 eV and 1.22 eV, respectively. The annealing temperature affected the QR evolution and the PL emission from the QRs due to the temperature dependence of the diffusion rate of indium atoms.