We present a multi-modality optical sensing platform employing integrated Vertical Cavity Surface Emitting Lasers
(VCSELs), photodetectors, and filters suitable for portable, real-time analyte detection in aqueous environments.
Fluorescence and refractive index sensors designed to utilize visible and near-infrared VCSELs for low background
absorption from analyte delivery fluids are described. We demonstrate in vitro fluorescence sensing of Cy5.5 dye with a
detection sensitivity of 5 nM and photonic crystal slab refractive index sensing with tunable GaAs-based 670 nm
VCSELs. This compact, parallel sensor architecture enables multiplexed, cost-effective on-chip biosensing.
We present the optical characterization of an all-dielectric photonic crystal (PC)-based guided resonance filter sensitive to index-of-refraction changes in aqueous solutions. Spectral peak width was found to be 9.8 and 4.4 nm around 816 nm (water media), corresponding to a quality factor Q of 83 and 181, respectively. A spectral shift of peak wavelength with index change of 130 nm/RIU was observed for bulk fluid experiments. Measured peak shift (&Dgr;&lgr;=0.2nm) corresponds to a detectable index change &Dgr;n=1.5×10-3.
We present the design, simulation, and fabrication of an all-dielectric photonic crystal-based nano-sensor that detects index of refraction changes in aqueous solutions. The photonic crystal structure is designed for incorporation with an optical readout module that includes a light source, detector, and micro-optics to form a miniature integrated nanosensor. This enables reduced cost, small sample volume, and increased speed and parallelism desirable for high throughput analysis in medical diagnostics.
For applications such as fiber optic networks, wavelength conversion, or extracting information from a predetermined channel, are required operations. All-optical systems, based on non-linear optical frequency conversion, offer advantages compared to present systems based on optical-electronic-optical (OEO) conversion. Thanks to the large nonlinear susceptibility of AlGaAs (d14 = 90pm/V) and mature device fabrication technologies, quasi-phasematched non-linear interactions in orientation-patterned AlGaAs waveguides for optical wavelength conversion have already been demonstrated. However, they require long interaction length (~ centimeters) and a complex fabrication process. Moreover, the conversion efficiency remains relatively low, due to losses and poor confinement. We present here the design and fabrication of a very compact (~ tens of microns long) device based on tightly confining waveguides and photonic crystal microcavities. Our device is inherently phase-matched due to the short length and should significantly increase the conversion efficiency due to tight confinement and high cavity-Q value. We characterized the waveguides, measuring the propagation loss by the Fabry-Perot method and by a variant of the cutback method, and both give a consistent loss value (~5 dB/mm for single-mode waveguides and ~3 dB/mm for multimode waveguide). We also characterized the microcavities measuring the transmission spectrum and the cavity-Q value, obtaining Q's as large as 700.