Novel Modulation and Detection Mechanisms in Silicon Nanophotonics

Citation

Baehr-Jones, Tom Wetteland (2006) Novel Modulation and Detection Mechanisms in Silicon Nanophotonics. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/SRA3-F079. https://resolver.caltech.edu/CaltechETD:etd-05052006-225043

Abstract

A number of nanophotonic integrated circuits are presented, which take advantage of the unique properties that light has when guided in very small waveguides to achieve novel functionality. The devices studied are designed to operate with light in the 1400-1600 nm range.

Nanophotonic integrated circuits are tiny waveguides and other optical devices that are fabricated on the nanometer (10-9 meter) scale. These waveguides are often two orders of magnitude smaller than more conventional optical waveguides, such as a fiber optical cable. This reduction in size is interesting because it opens the possibility that expensive optical components might be integrated in very small areas on a chip, and also because the concentrated fields that result from this compression can be used to produce new optical functionality.

First, the techniques used to design passive optical structures, and the methods used to test them, are discussed. Most of the waveguides studied are fabricated from 110 nm thick layers of silicon from silicon-on-insulator wafers. The best waveguide loss achieved was -2.8 dB/cm. Also described are waveguides based on utilizing surface plasmon waves to guide light.

The use of second order nonlinear optical polymers for modulation is also discussed. These polymers are integrated into Silicon slot waveguides, where the Silicon itself serves as the electrode. Modulation is achieved via the Pockels effect. The modulation figure of merit obtained for the device is superior to the contemporary state of the art, an improvement due to the nanoscale nature of the waveguide. Additionally, detectors based on these same polymers and waveguide geometry are presented. Though the detection efficiency is not very high, the detectors are interesting because they do not require any external power supply, and because they have virtually no speed ceiling.

Finally, the use of third order nonlinear optical polymers for all-optical modulation is discussed. When integrated with ridge waveguides, such polymers enable all-optical modulation. Several experiments are described that demonstrate that all-optical modulation has been achieved.

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