Acoustic, microwave, and photonic devices in thin film LiNbO3

Orsel, Ogulcan Emre

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https://hdl.handle.net/2142/122265 Copy

Description

Title

Acoustic, microwave, and photonic devices in thin film LiNbO3

Author(s)

Orsel, Ogulcan Emre

Issue Date

2023-12-01

Director of Research (if dissertation) or Advisor (if thesis)

Bahl, Gaurav

Doctoral Committee Chair(s)

Bahl, Gaurav

Committee Member(s)

• Fang, Kejie
• Vlasov, Yurii
• Goddard, Lynford

Department of Study

Electrical & Computer Eng

Discipline

Electrical & Computer Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Photonics, acousto-optics, electro-optics, nanophotonics, Lithium Niobate

Abstract

Lithium niobate (LN) has been a subject of extensive study due to its exceptional electro-optic, nonlinear-optic, and acousto-optic properties while providing wide transparency range and high refractive index. For instance, LN electro-optic modulators play a crucial role in the optical communication industry, and periodically poled LN (PPLN) is used for tasks like wavelength conversion and generating pairs of photons. Despite these remarkable qualities, the LN platform has struggled to compete with other integrated photonics platforms because of challenges related to material processing and integration. One hindrance is that traditional LN devices are made using titanium diffusion, resulting in bulky structures. These devices lack strong optical confinement and exhibit reduced efficiency in nonlinear processes. As a result of these issues, previous LN devices remained cumbersome and failed to establish a significant presence among other integrated photonic platforms. Recently, high-quality thin-film LN wafers have become commercially accessible, opening up new possibilities for creating nanophotonic devices using this platform. In the course of my Ph.D. research, I leveraged these thin films to establish a nanophotonic LN platform at UIUC (University of Illinois Urbana-Champaign), achieving impressive Q factors of 3.5 million at 1550 nm and 5 million at 780 nm. Using the ultra-low propagation loss and remarkable material nonlinearities, I designed novel integrated electro-optic and acousto-optic devices that enable crucial functions like optical isolation, non-reciprocal polarization rotation, suppression of back-scattering, and optical gyration. Significantly, I achieved a groundbreaking feat: the creation of the world’s first on-chip optical isolator at 780 nm, complemented by the lowest insertion loss isolator at 1550 nm. These remarkable accomplishments were made possible by harnessing the strong acousto-optic interaction inherent in LN. Furthermore, I used the same acousto-optic interaction to suppress unwanted Rayleigh back-scattering in integrated resonators which usually manifests itself as a transformation of a simple Lorentzian mode to a doublet mode. By inducing a chiral dispersion through this acousto-optic interaction, I was able to demonstrate recovery of such resonator modes to their intrinsic state and reduce the reflected signal from the resonator. On the electro-optics side, I used LN to create non-reciprocal polarization rotation through synthetically generated traveling waves. This approach demonstrated a significantly improved rate of polarization rotation per unit of loss when compared to magneto-optic alternatives. Lastly, my attention turned to unlocking the capabilities of electro-optics within LN micro-resonators, aiming to create synthetic gauge fields. By engineering these fields, I successfully showcased remarkable achievements, including an impressive isolation contrast (reaching approximately 60 dB) and the realization of optical gyration.

Graduation Semester

2023-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Ogulcan Orsel

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