Ryan Aguinaldo

Large Dispersion of Silicon Directional Couplers Obtained via Wideband Microring Parametric Characterization

Using the measured transmission spectrum of a waveguide-coupled silicon microring, we develop an algorithm for determining the wavelength dependencies (i.e., the dispersions) of the coupling coefficients and loss of the ring. Our analysis reconstructs the measured spectrum without use of Lorentzian fitting, covers 15 free spectral ranges (FSR), and was performed from ~ 1520 to 1570 nm, covering all of and extending past the C-band. We demonstrate that the dispersion of the coupling coefficient of a silicon-waveguide directional coupler considerably exceeds (by a factor of ~ 10) the modal refractive-index dispersions of its constituent waveguides.

Efficient CW Four-Wave Mixing in Silicon-on-Insulator Micro-Rings With Active Carrier Removal

Silicon-on-insulator rib waveguides with passive loss of -0.74 dB/cm and free-carrier lifetime reduction via reverse biased p-i-n diodes are used to show efficient continuous wave four-wave mixing with 2 × reduction in required pump power for comparably high conversion efficiency of -8.2 dB, similar to best reports. A conversion efficiency of -13.4 dB is also subsequently achieved using 20 μm radius micro-ring resonators at significantly reduced pump power.

Wideband silicon-photonic thermo-optic switch in a wavelength-division multiplexed ring network

Using a compact (0.03 mm(2)) silicon-photonic bias-free thermo-optic cross-bar switch, we demonstrate microsecond-scale switching of twenty wavelength channels of a C-band wavelength-division multiplexed optical ring network, each carrying 10 Gbit/second data concurrently, with 15 mW electrical power consumption (no temperature control required). A convenient pulsed driving scheme is demonstrated and eye patterns and bit-error rate measurements are shown. An algorithm is developed to measure the power-division ratio between the two output ports, the insertion and switching losses, and non-ideal phase deviations.

Loss-Tolerant Allpass-Based Filter Bank Design Suitable for Integrated Optics

This paper presents a novel design algorithm for a filter bank structure that is suitable for photonic integrated circuits. The proposed design is entirely based on the principle of loss-exhibiting allpass filtering, which is a behavior naturally observed in a variety of microscale optical components. The setup and mathematical optimization of the system is explored in detail from a signal processing perspective, and an algorithm based on convex and nonlinear optimization techniques is subsequently presented. The algorithm methodologically utilizes the otherwise-undesirable effect of waveguide loss to derive an allpass-based filter bank structure that is amenable to photonic implementation. The proposed structure is ideal for applications in time-stretched analog-to-digital converters, WDM network channelizers, and general optical signal multiplexers.

Realistic Photonic Filter Design Based on Allpass Substructures With Waveguide Loss Compensation

We present a lowpass design algorithm targeted specifically for photonic implementation. Allpass filter based systems are ideal for photonic realizations because they can be naturally realized using a variety of nanoscale dielectric components. The allpass filters based lowpass system is a particularly noteworthy example of advanced usages of allpass sub-structures. While the structure is excellent for implementation using photonic components, practical considerations about its suboptimal performance are yet to be considered. Realistic optical filters are subject to the imperfections of photonic materials and limitations from current fabrication capability. The waveguide power loss is an unavoidable source of performance degradation that arises when realizing photonic filters. In this paper, we consider the derivation of allpass filters based lowpass structures that can minimize the loss effect. The proposed algorithm will enable the utilization of low cost photonic devices for stringent design requirements, and also improve the performance of high end photonic devices.

High performance silicon multi-ring filters

The paper demonstrated a compact (0.5 mm x 0.05 mm) cascaded silicon multi-ring resonator filters operating at the wavelength range near 1.5 μm which exhibit high contrast (>;60 dB) simultaneously with wide passbands. The flat top transmission characteristic may be useful to lessen performance degradation of conventional single-ring filters due to thermal or wavelength fluctuation effects, and the high dynamic range contrast may be useful in band-rejection of strong jamming signals e.g., in photo-detector front-ends, or in microwave applications.

Compact silicon photonic resonance-assisted variable optical attenuator

A two-part silicon photonic variable optical attenuator is demonstrated in a compact footprint which can provide a high extinction ratio at wavelengths between 1520 nm and 1620 nm. The device was made by following the conventional p-i-n waveguide section by a high-extinction-ratio second-order microring filter section. The rings provide additional on-off contrast by utilizing a thermal resonance shift, which harvested the heat dissipated by current injection in the p-i-n junction. We derive and discuss a simple thermal-resistance model in explanation of these effects.

Characterization of a silicon-photonic multi-wavelength power monitor

We describe the design and operation of a silicon-photonic device for monitoring power variations of individual channels in a multi-wavelength DWDM network. Amplitude variations of ~20 dB, for channels spaced by 100 GHz, are measured.

Characterization of a silicon-photonic wideband switch in UCSD's MORDIA ring network

We demonstrate and investigate concurrent switching of twenty 10-Gbps channels using a silicon Mach-Zehnder interferometer switching structure with low on-state loss, low power, and microsecond-scale switching time.

Localized surface plasmon assisted contrast microscopy for ultrathin transparent specimens

We demonstrate a high contrast imaging technique, termed localized surface plasmon assisted contrast microscopy, by combining localized surface plasmon resonances (LSPR) and dark-field microscopy technique. Due to the sensitive response of LSPR to the refractive index of the surrounding media, this technique is capable of converting a small refractive index difference to a change in scattering intensity, resulting in a high-contrast, diffraction limited image of a thin unstained specimen with small, gradual refractive-index variation.