A novel all-optical switching structure based on a photonic crystal directional coupler is proposed and analyzed. Efficient optical switching is achieved by modifying the refractive index of the coupling region between the coupled waveguides by means of an optical control signal that is confined in the central region. Small length (around 1.1 mm) and low optical power consumption (over 1.5 W) are the main features estimated for this switching structure.
Slot and sandwiched waveguides with silicon nanocrystals were fabricated by means of industrial microelectronic tools, including DUV lithography. Low loss of 4 dB/cm will pave the way to compact all-optical XOR logic gates.
IntroductionUsing silicon, oxides, nitrides and other Si-based materials as active means for photonic functionalities is of great interest since it would allow a potential monolithic integration of electrical and optical circuits in a fully compatible CMOS processing. For example, optical interconnects, optical amplifiers and switches integrated in CMOS photonic chips would make it possible to develop low cost and all-optical communication networks without bottlenecks induced by electrical/optical converters. Passive devices (filters, couplers, multiplexers...) that make use of silicon-based waveguides and materials exhibiting non-linear optical properties have already been demonstrated. Nevertheless they use Si thermo-optic effects or refractive index variation due to the free carrier concentration in Si, as bulk Si is a very poor material for non-linear optics. Notwithstanding, nanostructured Si, due to quantum confinement effects, and particularly silicon nanoclusters (Si-nc) embedded in SiO2 (Si-nc/SiO2) are considered very promising materials due to extraordinarily enhanced nonlinear properties in comparison to bulk Si, as its Kerr coefficient is reported in the range
Coupled-cavity waveguides (CCWs) allow light propagation with strong field confinement in the cavities and small group velocity, which greatly enhances the efficiency of nonlinear effects. In addition, guided modes have zero dispersion at the central region of the transmission miniband. We show that CCWs created in planar photonic crystals, in which index guiding is required in some spatial dimensions, are intrinsically lossy in the region of zero dispersion, which strongly limits their use in nonlinear applications and devices.
Combining photonic integrated circuits with a biologically based sensing approach has the ability to provide a new generation of portable and low-cost sensor devices with a high specificity and sensitivity for a number of applications in environmental monitoring, defense, and homeland security. We report herein on the specific biosensing under continuous air flow of DMMP, which is commonly used as a simulant and a precursor for the synthesis of Sarin. The proposed technology is based on the selective recognition of the targeted DMMP molecule by specifically modified proteins immobilized on photonic structures. The response of the biophotonic structures shows a high stability and accuracy over 3 months, allowing for the detection in diluted air of DMMP at concentration as low as 35 μg/m(3) (6.8 ppb) in less than 15 min. The performance of the developed technology satisfies most current homeland and military security requirements.
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