Sub-femtosecond optical timing distribution for next-generation light sources
Author(s)Peng, Michael Yung
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science.
Franz X. Kärtner and Erich P. Ippen.
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Precise timing distribution is critical for realizing a new regime of light control in next-generation X-ray free-electron lasers. These facilities aim to generate sub-femtosecond (fs) X-ray pulses with unprecedented brightness to realize the long-standing scientific dream to capture chemical and physical reactions with atomic-level spatiotemporal resolution. To achieve this, a high-precision timing system is required to synchronize dozens of radio frequency (RF) and optical sources across kilometer distances with sub-fs precision. Since conventional RF timing systems have already reached a practical limit of 50 fs, next-generation systems are adopting optical technology to achieve superior performance. In this thesis, an optical timing distribution system (TDS) is developed using ultrafast mode-locked laser technology to deliver sub-fs timing stability. Optical domain components of the TDS are first presented. The timing jitter of commercial mode-locked lasers is characterized to confirm their viability as optical master oscillators for timing distribution. Stabilization of a 1.2-km dispersion-compensated polarization-maintaining fiber link is demonstrated as a proof-of-concept for eliminating polarization-induced timing drifts. The link is then enhanced to achieve state-of-the-art timing distribution across a 4.7-km fiber network with 0.58 fs RMS residual drift for over 52 hours. For a complete end-to-end TDS, a remote laser is stabilized at the output of a 3.5 km fiber link with 0.2 fs RMS residual drift. All demonstrations depend critically on the balanced optical cross-correlator for high-precision optical timing measurements. Second, the coverage of the TDS is extended into the RF domain using balanced optical-microwave phase detectors (BOMPD). Two generations of BOMPDs are developed to achieve sub-fs noise performance with MHz-level bandwidth capabilities and robust AM-PM suppression ratios (>50 dB). Optical-to-RF synchronization is demonstrated with 0.98 fs RMS drift for over 24 hours, while RF-to-optical synchronization is demonstrated with 0.5 fs RMS. Lastly, an Erbium Silicon Photonics Integrated OscillatoR (ESPIOR) based on optical frequency division (OFD) is developed for ultralow-noise microwave generation. Since f-2f interferometry is unavailable on-chip, an alternative fCEO control scheme called quasi-OFD is proposed to improve stabilization of an integrated frequency comb. The ESPIOR concept is demonstrated in a discrete testbed to achieve low-noise RF generation with -63 dBc/Hz phase noise at 10 Hz offset for a 6-GHz carrier frequency. This corresponds to an OFD ratio of 85 dB, which is close to the ideal OFD ratio of 90 dB.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 150-154).
DepartmentMassachusetts Institute of Technology. Department of Electrical Engineering and Computer Science.
Massachusetts Institute of Technology
Electrical Engineering and Computer Science.