Dec 10 (Fri) @ 1:00pm: "Precision Optical Phase Synchronization Over Fiber Links Using Spectrally Pure, Chip-scale Lasers," Grant Brodnik, ECE PhD Defense

Date and Time
Henley Hall, Room 1010

Zoom Meeting: Meeting ID – 893 4020 6400 | Passcode – 764345


Ultra-narrow linewidth, stable lasers are instrumental in precision scientific applications spanning optical metrology and spectroscopy, low phase noise optoelectronic microwave generation, comparison of atomic clocks, and sophisticated laser ranging systems. In these application spaces, the low-phase noise and frequency stability afforded by spectrally pure lasers is paramount, enabling distribution of precise optical frequency and phase references to remote locations. The most exquisite of these optical sources typically employ sophisticated, highly engineered environmental isolation systems, often relegating their use to tabletop and laboratory-based implementations and limiting their scope to large-scale experiments. Porting these systems to the chip-scale via photonic integration, while maintaining a tolerable trade-off in performance, can provide innovation across previously independent scientific communities and potentially enable entirely new applications that require compact, low-power operation of spectrally pure optical sources.

This dissertation investigates these chip-scale, ultra-narrow linewidth, frequency stabilized laser systems and demonstrates their use in high performance optical phase synchronization. To realize such sources, techniques common in atomic clock systems and precision metrology are employed to achieve optical sources with simultaneous 1 Hz fundamental linewidths, 30 Hz integral linewidths, and carrier instability better than 2x10-13 at 50 ms. In addition to realizing these chip-scale sources, experimental efforts involve precision characterization techniques that required development of suitable in-house systems due to the achieved ultra-low-noise performance that limited the use of commercial instrumentation. Next, two independent sources operated together in a fiber-interconnected pair demonstrate the benefits of employing mutually coherent lasers in the context of distributed optical phase synchronization. This approach, termed an optical-frequency-stabilized phase-locked-loop,is demonstrated with a low residual phase error variance of 3x10-4 rad2 using only simple, low bandwidth and low power feedback electronics. Finally, this system is employed for carrier phase synchronization in a high modulation order quadrature-amplitude-modulated (QAM) coherent link. These efforts align with the Frequency Stabilized Coherent Optical (FRESCO) link for low-energy data center interconnects (DCIs) and demonstrate the promise of employing chip-scale, spectrally pure sources in tomorrow’s low power, high capacity optical communications.


Grant received his B.S. in Optical Engineering in 2014 from Rose-Hulman Institute of Technology and a dual-degree M.Sc. at Rose-Hulman and Seoul National University of Science and Technology, conducting research involving high-power diode laser characterization and performance metrics. He is currently pursuing an ECE Ph.D. in the OCPI Group, advised by Prof. Daniel J. Blumenthal. His research efforts involve system-level integration of narrow linewidth, frequency stabilized lasers for applications that require precision optical phase synchronization such as high modulation order coherent communications.

Hosted by: Professor Daniel J. Blumenthal

Submitted by: Grant Brodnik <>