Steve Zamek

Processing advantages of linear chirped fiber Bragg gratings in the time domain realization of optical frequency-domain reflectometry.

The inclusion of a linear chirped fiber Bragg grating for short pulse dispersion is shown to enhance the time domain realization of optical frequency-domain reflectometry. A low resolution demonstrator is constructed with single surface scans containing 140 resolvable spots. The system dynamic range meets that shown in earlier demonstrations without digital post-processing for signal linearization. Using a conjugate pair of chirped pulses created by the fiber grating, ranging is performed with position and velocity information decoupled. Additionally, by probing the target with short pulses and introducing grating dispersion just before photodetection, velocity immune ranging is demonstrated.

Metamaterials for enhanced polarization conversion in plasmonic excitation.

Surface plasmons efficient excitation is typically expected to be strongly constrained to transverse magnetic (TM) polarized incidence, as demonstrated so far, due to its intrinsic TM polarization. We report a designer plasmonic metamaterial that is engineered in a deep subwavelength scale in visible optical frequencies to overcome this fundamental limitation, and allows transverse electric (TE) polarized incidence to be strongly coupled to surface plasmons. The experimental verification, which is consistent with the analytical and numerical models, demonstrates this enhanced TE-to-plasmon coupling with efficiency close to 100%, which is far from what is possible through naturally available materials. This discovery will help to efficiently utilize the energy fallen into TE polarization and drastically increase overall excitation efficiency of future plasmonic devices.

Optical Bistability in a Silicon Waveguide Distributed Bragg Reflector Fabry–Pérot Resonator

We demonstrate optical bistability in a silicon waveguide Fabry-Pérot resonator formed by a pair of distributed Bragg reflectors. In the bistable regime, the output power of the resonator ceases to be uniquely determined by the input power because multiple powers within the cavity satisfy the resonance condition. Pulsating behavior is observed within the resonator output, and is attributed to noise within the experimental setup driving the resonator between the multiple allowed output powers.

Compact chip-scale filter based on curved waveguide Bragg gratings

We propose a method for miniaturization of filters based on curved waveguide Bragg gratings, so that long structures can be packed into a small area on a chip. This eliminates the stitching errors introduced in the fabrication process, which compromise the performance of long Bragg gratings. Our approach relies on cascading curved waveguide Bragg gratings with the same radius of curvature. An analytical model for the analysis of these devices was developed, and a filter based on this model was designed and fabricated in a silicon on insulator platform. The filter had a total length of 920μm, occupied an area of 190μm×114μm, and exhibited a stop band of 1.7nm at 1.55μm and an extinction ratio larger than 23dB.

Micro-resonator with metallic mirrors coupled to a bus waveguide

We demonstrate a micro-resonator based on a channel waveguide terminated with metallic mirrors side coupled to a bus waveguide. Transmission through such a resonant structure implemented in a silicon-on-insulator platform is investigated theoretically and demonstrated experimentally. The resonator is 13.4 μm long, exhibits an unloaded Q-factor of ~2100, and a free spectral range of 21 nm around the wavelength of 1.55 μm.

Near-field measurement of amplitude and phase in silicon waveguides with liquid cladding

In recent years Near-Field Scanning Optical Microscopy (NSOM) has emerged as an important characterization tool for guided-wave photonic devices. The NSOM uses a subwavelength aperture probe to couple evanescent waves to the far-field, allowing subdiffraction-limited imaging and measurement of local properties of photonic structures. By integrating the NSOM into one of the arms of a heterodyne interferometer, we may image near-field phase as well as amplitude. However, on-chip guided-wave devices are typically coated with a solid overcladding. Heterodyne NSOM (H-NSOM) characterization of these devices has typically been limited to similar devices without cladding since the probe cannot penetrate the solid cladding layer to access the evanescent fields contained within. Here we demonstrate a technique that allows optical near-field characterization of devices while preserving their optical properties. To do so, a liquid overcladding is introduced to emulate the actual overcladding of the final operational device while allowing the probe to sample the evanescent field at the core-cladding interface for analysis by the NSOM. This technique enables metrology on the actual rather than duplicate device and preserves the dispersion of the optical structures to replicate the designed structure. To our best knowledge this is the only H-NSOM technique allowing characterization of photonic circuits in their final form.

Wide bandwidth, low loss 1 by 4 wavelength division multiplexer on silicon for optical interconnects

We demonstrate an add/drop filter based on coupled vertical gratings on silicon. The concept is extended to implement a 1 by 4 wavelength division multiplexer with 3nm bandwidth, 1dB insertion loss and 16dB crosstalk suppression.

On-chip waveguide resonator with metallic mirrors

We introduce an optical microresonator consisting of a planar waveguide terminated by metallic mirrors. The resonator was fabricated on a silicon-on-insulator platform, and its optical performance was theoretically and experimentally investigated. The demonstrated device had dimensions of 200 mumx40 mum and exhibited a quality factor of about 1000 and a free-spectral range of about 8 nm. Application to high-throughput, label-free biochemical sensing is considered, and optimization with respect to the surface sensitivity is carried out. The optimized sensitivity makes it possible to detect subnanometer layers of molecules adsorbing to the surface of the resonator.

Fabrication approaches for metallo-dielectric plasmonic waveguides

Different techniques for fabricating long-range plasmonic metallo-dielectric waveguides are discussed. The approaches depend strongly on the material system in use. Specific results are presented for SU8 and PDMS.

Active and passive nanophotonics for information systems applications

This paper explores the role of nanotechnology with focus on nanophotonics in dielectric, metal, and semiconductor inhomogeneous metamaterials and devices for optical communications, information and signal processing, and sensing.