Roy Davidson

Fully programmable ring-resonator-based integrated photonic circuit for phase coherent applications

A novel ring-resonator-based integrated photonic chip with ultrafine frequency resolution, providing programmable, stable, and accurate optical-phase control is demonstrated. The ability to manipulate the optical phase of the individual frequency components of a signal is a powerful tool for optical communications, signal processing, and RF photonics applications. As a demonstration of the power of these components, we report their use as programmable spectral-phase encoders (SPEs) and decoders for wavelength-division-multiplexing (WDM)-compatible optical code-division multiple access (OCDMA). Most important for the application here, the high resolution of these ring-resonator circuits makes possible the independent control of the optical phase of the individual tightly spaced frequency lines of a mode-locked laser (MLL). This unique approach allows us to limit the coded signals spectral bandwidth, thereby allowing for high spectral efficiency (compared to other OCDMA systems) and compatibility with existing WDM systems with a rapidly reconfigurable set of codes. A four-user OCDMA system using polarization multiplexing is shown to operate at data rates of 2.5 Gb/s within a 40-GHz transparent optical window with a bit error rate (BER) better than 10/sup -9/ and a spectral efficiency of 25%.

Broadband optical absorbance spectroscopy using a whispering gallery mode microsphere resonator

We demonstrate the ability to excite and monitor many whispering gallery modes (WGMs) of a microsphere resonator simultaneously in order to make broadband optical absorbance measurements. The 340 microm diameter microsphere is placed in a microfluidic channel. A hemispherical prism is used for coupling the WGMs into and out of the microsphere. The flat surface of the prism seals the microfluidic channel. The slight nonsphericity in the microsphere results in coupling to precessed modes whose emission is spatially separated from the reflected excitation light. The evanescent fields of the light trapped in WGMs interact with the surrounding environment. The change in transmission observed in the precessed modes is used to determine the absorbance of the surrounding environment. In contrast to our broadband optical absorbance measurements, previous WGM sensors have used only a single narrow mode to measure properties such as refractive index. With the microfluidic cell, we have measured the absorbance of solutions of dyes (lissamine green B, sunset yellow, orange G, and methylene blue), aromatic molecules (benzylamine and benzoic acid), and biological molecules (tryptophan, phenylalanine, tyrosine, and o-phospho-L-tyrosine) at visible and ultraviolet wavelengths. The microsphere surface was reacted with organosilane molecules to attach octadecyl groups, amino groups, and fluorogroups to the surface. Both electrostatic and hydrophobic interactions were observed between the analytes and the microsphere surface, as indicated by changes in the measured effective pathlength with different organosilanes. For a given analyte and coated microsphere, the pathlength measurement was repeatable within a few percent. Methylene blue dye had a very strong interaction with the surface and pathlengths of several centimeters were measured. Choosing an appropriate surface coating to interact with a specific analyte should result in the highest sensitivity detection.

Tunable bandwidth microring resonator filters

Tunable bandwidth, tunable line-shape filters are realized by incorporating Mach-Zehnder interferometers as directional coupler elements within higher order microring resonators. A flat-top bandwidth tuning range of 2.7 GHz to 21 GHz is demonstrated.

Advanced photonic integration and high-index-contrast circuit

We highlight recent advances in advanced photonic integration of reliable densely integrated photonic integrated circuits (PIC) and high-index-contrast photonic lightwave circuits (PLC). The applications and benefits of these devices will be presented.

Compact Optical Programmable Delay Lines with Fast Thermo-Optic Switching and Output Power Balancing

The authors demonstrate compact 8-bit programmable delay lines having an integrated VOA for output power balancing. Delays from picoseconds to several nanoseconds are feasible on a 1 cm-sq solid state chip. Thermo-optic switches with 45 musec switching are incorporated

Large-scale high-index-contrast planar lightwave circuits

Large scale optical integration is enabled by high index contrast materials and building blocks. We highlight recent advances in the miniaturization of optical elements and of dense integration of planar lightwave circuits for telecommunications and RF photonic applications.

Advanced Ring Resonator Based PLCs

Microring resonators are finding increasing use in commercial applications. We highlight the theory of microrings, their fabrication, and a summary of microrings in commercial use, including tunable filters, dispersion compensators, and OCDMA coders

Tunable Narrow Band Filters for RF Photonics

We demonstrate compact, narrowband and tunable high-order microring resonator filters suitable for RF photonic applications. Sixth order filters having bandwidths of 1.5 GHz, out-of-band optical rejection ratios > 60 dB, and on-chip losses < 2 dB are highlighted

Integrated polarimeter assisted ring scanning spectrometer

Three-stage Vernier, 3rd order lattice ring filters are implemented to realize a full C-band spectrometer. A polarization controller is also integrated for ldquosplit and fliprdquo operation.

Ultra-compact low loss array waveguide grating

We have demonstrated an ultra-compact low loss AWG, which is fabricated on 17% index-contrast Hydex material by Little Optics. The device offers good performance and Integrate-ability. It can serve as a key wavelength selective component in a large-scale planar lightwave circuit for WDM applications.