Francisco Cuesta-Soto

All-optical switching structure based on a photonic crystal directional coupler

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.

Deep-UV Lithography Fabrication of Slot Waveguides and Sandwiched Waveguides for Nonlinear Applications

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 NOR logic gates.

Intrinsic losses of coupled-cavity waveguides in planar-photonic crystals

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.

Numerical analysis of all-optical switching based on a 2-D nonlinear photonic crystal directional coupler

A photonic crystal (PhC) all-optical switch based on a nonlinear directional coupler is presented and discussed. The coupling strength of the structure may be tuned by a high optical power control signal that propagates along the coupling region. Thus, the power ratio between the output ports of the device can be tuned and, hence, switching is accomplished. The study of the present structure is performed with a numerical tool based on the finite-element method. This tool allows to calculate the nonlinear band diagram of a two-dimensional PhC. The implementation and characteristics of this method are thoroughly addressed.

Biophotonic ring resonator for ultrasensitive detection of DMMP as a simulant for organophosphorus agents.

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.

Variable carrier reduction in radio-over-fiber systems for increased modulation efficiency using a Si 3 N 4 tunable extinction ratio ring resonator

Variable optical carrier reduction via the use of a Si(3)N(4) ring resonator notch filter with tunable extinction ratio is demonstrated in a 10 GHz radio-over-fiber system for improving the modulation efficiency. The extinction of the filter notch is tuned with micro-heaters, by setting the Mach-Zehnder coupler of the ring. Experimental results showing a modulation depth improvement of up to 20 dB are provided.

All-Optical MZI XOR Logic Gate based on Si Slot Waveguides Filled by Si-nc Embedded in SiO2

An all-optical XOR logic gate based on a Mach-Zehnder interferometer is proposed and analyzed. It is implemented with silicon slot waveguides filled with silicon nanocrystals embedded in silica, which show a high nonlinear Kerr effect

Compensating intermodal dispersion in photonic crystal directional couplers

Intermodal dispersion between the supermodes of a directional coupler may induce undesirable pulse breakup in a sufficiently large device. When this happens the device will no longer exchange power between its arms, and the extinction ratio is completely canceled. It is shown that, by carefully designing the coupling area of the directional coupler, one may compensate for intermodal dispersion. The compensating device should accomplish three basic requirements: inverse intermodal dispersion, balanced coupling of each supermode, and maximum power transfer while preserving the sign of the slope of the coupling coefficient with frequency for multiplexing-demultiplexing applications. This structure is designed and optimized with a genetic algorithm.

Numerical analysis of the performance of Mach-Zehnder interferometric logic gates enhanced with coupled nonlinear ring- resonators

In this paper, the implementation of an all-optical logic gate based on a Mach-Zehnder interferometer (MZI) configuration is addressed with underlying nonlinear slot-waveguides. In order to reduce power consumption requirements, different ring-resonator structures are introduced in the arms of the MZI. A nonlinear Transfer Matrix Method is developed and used to analyze the response of the nonlinear MZI in order to optimize power requirements with maximum bit rates. The numerical analysis shows that a reduction in the switching power from 2.5 W to less than 5 mW can be achieved by a proper design of the ring-resonator structures introduced in the MZI arms. In addition, it is shown that the logic gate can handle bit rates higher than 60 Gbit/s.

Experimental demonstration of adiabatic coupling into SOI photonic crystal coupled-cavity waveguides

The experimental demonstration of an adiabatic coupling technique between Silicon-on-insulator photonic crystal single-line defect waveguides and coupled-cavity waveguides is reported. Experimental results are compared with three dimensional finite-difference time-domain simulation results showing very good agreement.