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Arsenic Trisulfide on Lithium Niobate for Acousto-Optic Interactions

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posted on 10.06.2021, 20:42 by Md Shofiqul KhanMd Shofiqul Khan
Effective optical processing of information in the integrated photonic circuits requires strong light confinement and guiding of light at the micronanoscale using waveguide structures, as well as techniques to control its propagation. Optical confinement is stronger for a guiding medium with a
high refractive index and complex optical information processing is possible if this refractive index can be manipulated efficiently using multiple techniques. Refractive index manipulation is possible through various methods
such as electro-optic, thermo-optic, magneto-optic and acousto-optic modulation. Acousto-optic modulation technique uses strain induced by the acoustic wave to change the refractive index of the optical wave propagation
medium. Such modulators have successfully been demonstrated on material platforms such as aluminum nitride, gallium arsenide and lithium niobate. Despite having some of the highest electromechanical coupling
coefficients and strong acousto-optic coefficients, these material platforms cannot simultaneously exploit the best material properties because of their anisotropy. In other words, if both acoustic devices and the photonic devices
are built on one of these same material platforms, both devices may not be the most efficiently optimized because of the anisotropy of the material. We have studied lithium niobate as the piezoelectric substrate which is used to
generate the acoustic wave and incorporated arsenic trisulfide, an isotropic material, as the photonic material platform which enables decoupling of the acoustic device from the photonic device. We have demonstrated arsenic
trisulfide on oxide on lithium niobate as a material platform for low frequency (»MHz) modulator application through an acousto-optic modulator formed by an arsenic trisulfide Mach-Zehnder interferometer, operating in a push-pull configuration and placed inside a surface acoustic wave cavity on a Y-cut lithium niobate wafer. A comprehensive analytical modeling of the acousto-optic interaction is offered which enabled the first ever extraction of acousto-optic coefficients for the thin film arsenic trisulfide from an integrated device. First ever extraction of the thermal coefficients for waveguides on arsenic trisulfide, lithium niobate on insulator and arsenic trisulfide on lithium niobate on insulator using optical racetrack resonators is also demonstrated. Arsenic trisulfide on lithium niobate on insulator is discussed as a high frequency (»GHz) modulator platform which includes a qualitative study of this hybrid material platform. This hybrid material platform will pave new opportunities for microwave-to-optical conversion,
non-reciprocal devices, Brillouin scattering and beam steering applications.

History

Date

19/02/2021

Degree Type

Dissertation

Department

Electrical and Computer Engineering

Degree Name

  • Doctor of Philosophy (PhD)

Advisor(s)

Gianluca Piazza James A. Bain

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