ELEE Oral Comprehensive Exam for Doctoral Candidacy by Michael Benker-ECE
Topic: Linearized Optical Modulator Topologies for High Dynamic Range Integrated RF Photonics
Abstract:
This dissertation proposal presents a novel integrated photonics approach towards linearizing electro-optic modulators. Integrated photonics are crucial for various rapidly growing industries; however, optical links requiring high dynamic range (in excess of 60dBHz^(2/3) for a 1GHz bandwidth) often face limitations due to the optical modulator. Specifically, the inherent non-linearity of the Mach-Zehnder electro-optic modulator limits the spurious-free dynamic range (SFDR).
This work addresses this limitation by mathematically linearizing the Mach Zehnder intensity modulator's transfer function and implementing it in a photonic integrated circuit layout using fundamental building blocks such as optical waveguides, phase modulators, and couplers. This integrated photonics approach aims to create a linearized integrated modulator (LIM) as a single device, overcoming the SWaP (size, weight, and power) requirements of previous modulator linearization techniques using concatenated bulk modulators.
Preliminary results include modeling of linearized Mach-Zehnder modulators for the elimination of up to third, fifth, and seventh-order intermodulation distortion. The dissertation employs the thin-film lithium niobate (TFLN) platform for its compactness, low loss, and ease of fabrication compared to AlGaAs. Furthermore, the proposal includes modeling of LIM fabrication tolerance to directional coupler ratio errors, indicating a range of acceptable deviations that still improve dynamic range. Fabrication of a simple Mach-Zehnder modulator on the TFLN platform using Harvard’s CNS and UMassL’s CRF cleanroom facilities has also been conducted, achieving an optical loss of 1.2dB/cm and a V_pi of 1.9V*cm.
The proposed scope and directions involve the optimization and fabrication of the designed linearized modulators. Electron-beam lithography will be employed for its improved photolithography precision. Testing of devices will be performed at UMass Dartmouth’s RF Photonics Lab. This research aims to contribute to the advancement of high dynamic range optical links through a novel integrated photonics solution.
Co-Advisor(s): Dr. Yifei Li, Professor, Dept. of Electrical & Computer Engineering, UMass Dartmouth
Committee Members:
Dr. Mohammad Karim, Professor, Dept. of Electrical & Computer Engineering, UMass Dartmouth;
Dr. Dayalan P. Kasilingam, Professor, Dept. of Electrical & Computer Engineering, UMass Dartmouth;
Dr. Tariq Manzur, Adjunct Professor, Department of Electrical & Computer Engineering, UMass Dartmouth and Scientist & Engineer, Naval Undersea Warfare Center (NUWC);
Dr. Xuejun Lu, Professor, Dept. of Electrical & Computer Engineering, UMass Lowell
NOTE: All ECE Graduate Students are ENCOURAGED to attend. All interested parties are invited to attend. Open to the public.
*For further information, please contact Dr. Yifei Li
Claire T. Carney Library, Room 314
: 285 Old Westport Road, North Dartmouth, MA 02747
Yifei Li
508.999.8841
yifei.li@umassd.edu