Specific detection of proteins is demonstrated using planar photonic crystal waveguides. Using immobilized biotin as probe, streptavidin was captured, causing the waveguide mode cut-off to red-shift. The device was shown to detect a 2.5 nm streptavidin film with a 0.86 nm cut-off red-shift. An improved photonic crystal waveguide sensor design is also described and shown to have a 40% improved bulk refractive index response.
The development of both "soft" and "hard" fabrication techniques for the patterning of nonlinear photonic devices in ionically selfassembled monolayer ͑ISAM͒ films is reported. A combination of electron beam lithography and reactive ion etching was used to pattern twodimensional holes with a lattice of 710 nm and diameters ranging from 550 to 650 nm. A soft alternative to this fabrication was also demonstrated. Nanoimprint lithography was successfully employed to pattern similar photonic structures with average hole diameters of 490 nm and a lattice spacing of 750 nm, as well as Bragg gratings with a period of 620 nm. Potential impact of this fabrication process on the chemical composition and nonlinear properties of the ISAM films was assessed using Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, and second harmonic generation. The spectroscopy techniques confirmed that the chemical composition and bonding of the ISAM films was not adversely affected by the thermal cycles required for nanoimprinting. Second harmonic generation analysis also confirmed that the nanoimprinting process did not affect the nonlinear properties of the material, PCBS/PAH ISAM films, further indicating the suitability of such materials for the nanoimprinting of nonlinear optical photonic structures.
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