Fabry-Perot waveguide modulator with nano-photonic distributed mirrors

Walter J. Zubrzycki

doi:10.17918/00008707

The next step towards photonic integration will require miniaturization of components and devices. The work presented in this thesis is directed towards developing a technology to realize nano-structure reflective components for a Fabry-Perot modulator device application. Included is the design of the modulator, analysis of nano-structure etch dynamics, and experimental evaluation of the grating devices. Components, such as periodic nano-photonic reflecting structures will assist in reducing the size of devices, such as lasers, filters, couplers, and modulators. Existing integrated-optic mirror technology employs shallow-etched distributed Bragg reflectors embedded in the semiconductor structure, requiring epitaxial regrowth to complete the structure. This approach typically results in long grating regions to attain high reflectivity. The Fabry-Perot modulator is designed to maintain single-mode performance from a ridge waveguide 2.0 [mu]m wide and 0.78 [mu]m tall. The overall device length is less than 435 [mu]m, which includes two 80% reflective-150 [mu]m long grating regions and a 135 [mu]m long cavity. Electric-field induced phase modulation changes the state of the resonant cavity, resulting in an intensity modulated optical output. The gratings are designed to eliminate epitaxial regrowth by etching deep trenches into the waveguide. The critical geometry required a squarewave profile, with vertical sidewalls, flat bottoms, and squared corners. The grating trench etch measured 100 nm wide across a 2.0 [mu]m wide ridge waveguide with a maximum depth of 800 nm. The modulator device was realized following successful grating fabrication development. The Fabry-Perot concept was verified with a modulation bandwidth less than 100 kHz, limited by excessive parasitics from a large probe pad and test instrumentation. The etch technology developed to fabricate the gratings was extended to two-dimensional nano-photonic post realization. Although high aspect-ratio etches have been performed in an Ion Beam Assisted Etching system, this is the first known analysis of Reactive Ion Beam Etching directed towards nano-photonic post applications. This work contributed to the development of next generation nano-photonic reflecting components which are expected to make the current distributed Bragg reflector technology obsolete.

Fabry-Perot waveguide modulator with nano-photonic distributed mirrors

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Fabry-Perot waveguide modulator with nano-photonic distributed mirrors

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