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PhD Defense
Photonic Time-Stretch Enabled High Throughput Microwave and MM-Wave Interferometry Applied to Fibre Grating Sensors and Non-Contact Measurement


Mr Eamonn Jalal Ahmad - ETRO, VUB and Kent University [Email]


The research presented in this thesis is focused towards developing real-time, high-speed applications, employing ultrafast optical microwave generation and characterization techniques. This thesis presents a series of experiments wherein mode locked laser pulses are utilized. Photonics based microwave/mm-wave generation and detection is explored and employed for applications pertaining to fiber grating sensors and non-contact measurement. The application concepts leverages techniques from optical coherence tomography and non-destructive evaluation of turbid media. In particular, I use principle of broadband dispersive fiber optics based photonic time stretch to slow down high-speed waveforms to speeds usable by state-of-the-art electronic photo-detectors and signal processors. I also apply instantaneous frequency measurement mapping microwave frequency measured to time instant of signal, which in turn is related to spatial location as established by the dispersive Fourier transformation relation. The experimental methods applied throughout this thesis is based upon Michelson interferometer architecture.
My original contribution to knowledge is realization of photonics based high throughput single tone and chirped microwave/mm-wave pulse generation utilizing the principle of photonic time stretch at the Photonics lab in the University of Kent. The method basis for photonically generated high frequency microwave signals is applied to deciphering physical strain profile along the length of a chirped fiber Bragg grating employed in a Michelson interferometer configuration. This interrogation scheme allows intra-grating, high resolution and high speed, temperature independent strain measurement. This concept was further on extended to utilize photonic generation of microwave pulses to characterize surface profile information of thin film and thin plate infrared transparent slides of variable thickness setup in a Michelson interferometer architecture. In addition, the photonically generated microwave signal were up-converted to broadband chirped mm-wave pulses and utilized as a source for non-contact measurement of turbid media based on a mm-wave coherence tomography set-up implemented at Vrije Universiteit Brussel (VUB), department of Electronics and Informatics (ETRO).


Date: 29.05.2019

Time: 09:30

Location: Room D.2.01 Building D

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