BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//132.216.98.100//NONSGML kigkonsult.se iCalcreator 2.20.4//
BEGIN:VEVENT
UID:20260804T121638EDT-9859VVC7Xd@132.216.98.100
DTSTAMP:20260804T161638Z
DESCRIPTION:                                                               
                                                                           
                                                                           
       Abstract\n\nIntegrated optical biosensors based on high-Q microcavit
 ies can achieve exceptionally low detection limits\; however\, their opera
 tion typically requires tracking narrow resonance features using highly st
 able\, tunable\, narrow-linewidth lasers. These coherence and wavelength-c
 ontrol requirements impose constraints on system cost\, footprint\, and po
 wer consumption\, and remain a primary barrier to full on-chip integration
 . A more scalable approach would enable accurate extraction of cavity loss
  without reliance on high-coherence sources or active wavelength tuning. P
 artially coherent phase-shift cavity ring-down spectroscopy (PS-CRDS)\, a 
 time-domain cavity interrogation technique\, addresses this need by determ
 ining photon lifetime from the phase response of an intensity-modulated op
 tical carrier. This approach enables the use of broadband\, partially cohe
 rent sources while still resolving cavity loss\, thereby supporting compac
 t\, low-cost\, and fully integrated microresonator-based biosensors suitab
 le for portable and point-of-care applications.\n\nThis thesis advances th
 e theoretical foundations required to realize such systems by developing t
 wo analytical frameworks that quantify coherence effects in cavity-based s
 ensing. The first contribution is a closed-form model describing how finit
 e optical coherence influences the temporal transfer function of optical c
 avities. Using a linear-systems formulation\, the model captures the impac
 t of source bandwidth on cavity buildup\, decay dynamics\, and transmitted
  intensity for both cavity-enhanced absorption spectroscopy (CEAS) and tra
 ditional cavity ring-down spectroscopy (CRDS) in standing- and traveling-w
 ave resonators. The results show that\, while intrinsic cavity loss remain
 s the dominant factor governing photon lifetime\, partial coherence introd
 uces measurable modifications to the cavity response that must be consider
 ed in accurate time-domain analysis.\n\nThe second contribution is a close
 d-form analytical model for partially coherent PS-CRDS\, which characteriz
 es the dependence of phase shift\, sensitivity\, and signal-to-noise ratio
  (SNR) on source linewidth and modulation frequency. This framework clarif
 ies the trade-offs associated with replacing narrow-linewidth lasers with 
 broader-bandwidth sources such as laser diodes or LEDs. The analysis shows
  that absorption-induced loss changes can be reliably detected using both 
 coherent and partially coherent sources\, with only moderate sensitivity r
 eduction when the source bandwidth remains within the cavity free spectral
  range (FSR). Beyond this regime\, performance saturates\, indicating that
  broadband sources can still be effectively used in integrated implementat
 ions. Experimental measurements using silicon-on-insulator (SOI) microring
  resonators are presented to validate these concepts under both narrow lin
 ewidth (tunable laser source\, TLS) and effectively broader-bandwidth (swe
 pt VCSEL) excitation. The measured phase response and analytical fitting s
 how good agreement with theoretical predictions\, confirming the feasibili
 ty of photon-lifetime extraction under partially coherent operation. While
  the TLS configuration achieves higher sensitivity and lower detection lim
 its\, the VCSEL-based implementation demonstrates competitive performance 
 while reducing the need for active resonance tracking.\n\nOverall\, this w
 ork establishes a comprehensive theoretical and experimental framework for
  partially coherent PS-CRDS\, providing a practical pathway toward integra
 ted\, low-cost\, and scalable microresonator biosensors. These results sup
 port the development of robust photonic sensing platforms capable of opera
 ting without highly stable narrow-linewidth lasers\, enabling compact lab-
 on-chip and point-of-care diagnostic systems.\n\n \n
DTSTART:20260727T150000Z
DTEND:20260727T170000Z
LOCATION:Room 603\, McConnell Engineering Building\, CA\, QC\, Montreal\, H
 3A 0E9\, 3480 rue University
SUMMARY:PhD defence of Motavas Mohammad – Microring resonator-based partial
 ly coherent phase-shift cavity ring-down spectroscopy for point of care se
 nsing
URL:/ece/channels/event/phd-defence-motavas-mohammad-m
 icroring-resonator-based-partially-coherent-phase-shift-cavity-ring-373610
END:VEVENT
END:VCALENDAR