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DTSTART:20250101T000000
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DTSTART;TZID=Asia/Kolkata:20260521T090000
DTEND;TZID=Asia/Kolkata:20260603T170000
DTSTAMP:20260526T112657
CREATED:20260317T060029Z
LAST-MODIFIED:20260317T060144Z
UID:10126-1779354000-1780506000@www.cense.iisc.ac.in
SUMMARY:Advanced workshop on Semiconductor Manufacturing
DESCRIPTION:
URL:https://www.cense.iisc.ac.in/advanced-workshop-on-semiconductor-manufacturing/#new_tab
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260527T160000
DTEND;TZID=Asia/Kolkata:20260527T170000
DTSTAMP:20260526T112657
CREATED:20260525T092606Z
LAST-MODIFIED:20260525T092647Z
UID:10514-1779897600-1779901200@www.cense.iisc.ac.in
SUMMARY:[Thesis Defense] : Dispersion in Silicon-on-Insulator Micro-ring resonator
DESCRIPTION:Thesis Title             : "Dispersion in Silicon-on-Insulator Micro-ring resonator"\n\nName of the Student     :  Mr. Sudipta Nayak\n\nDegree Registered       : Ph.D. Engineering \n\nAdvisor                : Prof. Akshay Naik\, CeNSE\n\nDate                     : 27th May 2026\, (Wednesday)\n\nTime                    : 4 :00 PM\n\nVenue                 : CeNSE Seminar Hall (Hybrid):\n\nAbstract\n\nSilicon photonics underpins a wide range of applications spanning sensing\, communication\, \ncomputation\, and emerging quantum technologies. A common thread across these platforms \nis their strong sensitivity to refractive index\, with many applications critically relying \non its dynamic modulation. Achieving reliable and predictable device operation\, therefore\, \nrequires accurate characterization of refractive index changes and a clear understanding of \nthe underlying physical mechanisms. In silicon\, refractive index modulation arises from \nmultiple contributions\, including thermal effects\, free-carrier dispersion\, and the Kerr \nnonlinearity. While several techniques have been developed to probe these mechanisms\, \nthey are often limited in the quantities they measure\, restricting their broader applicability.\n\nCavity-enhanced photothermal spectroscopy is a widely used method to characterize Kerr nonlinearity. \nIt employs a pump tone and a probe tone\, both tuned to different resonances of the same optical cavity. \nThe pump intensity is harmonically modulated\, and the resulting oscillations in the probe intensity \nare monitored. Different dispersion mechanisms are studied through the strength of oscillation transfer. \nTypically\, probe amplitude data are analyzed using numerical fits; however\, these fits can be \nnon-unique and can be contaminated by experimental artifacts. Phase data\, a complementary observable\, \nare often affected by phase artifacts.\n\nWe present a method to remove these experimental artifacts and extract the oscillation-transfer phase \ndifference. An Erbium-Doped Fiber Amplifier (EDFA) is introduced before the pump intensity modulator. \nThe amplified spontaneous emission (ASE) passes through the intensity modulator and experiences the \nsame envelope modulation as the pump. A fraction of this ASE propagates through the probe path. Since \nthis ASE leakage undergoes the same experimental artifacts as the probe\, its phase is measured. \nThe intrinsic phase information of oscillation transfer is then obtained by subtracting the leakage \nphase from the probe phase. Using this\n\napproach\, we confirm the presence of free-carrier dispersion in a silicon-on-insulator ring resonator cavity. \nThis method provides a complementary extension to an established technique and remains applicable in regimes \nwhere conventional pump-based phase extraction fails.\n\nNext\, we investigate the nonlinear properties of ReS₂ by studying its effects on SoI ring resonators. \nAll-optical resonance shift measurements and cavity-enhanced photothermal spectroscopy are performed \nbefore and after transferring ReS₂ onto the resonator. Significant inter-device variability is observed \nin both resonance shift and photothermal response. Intra-device variability is also seen when the same \ndevice undergoes different surface processes. A possible explanation is proposed based on existing literature \non linear absorption loss in silicon\, its surface-dominated nature\, and its sensitivity to surface chemistry.\n\nAdditionally\, we study on-chip metal–semiconductor–metal (MSM) and graphene photodetectors. \nFor MSM devices\, current–voltage characteristics and photo-response are measured. \nThe responsivity and dynamic range of photoresponse are characterized. We show that these MSM \ndevices are suitable for integration with optomechanical systems. For graphene photoconductors\, \nwe demonstrate successful fabrication and performance comparable to that reported in the literature. \nFinally\, we suggest a direction for further exploration through the fabrication of \nMSM graphene–silicon–graphene devices using atomic force microscope lithography.\n\nThis work extends a well-established technique and improves its robustness. It provides new \ninsights into dispersion in silicon-on-insulator microring resonators\, highlighting the sensitivity \nof micro-cavity behavior to surface effects. Finally\, it validates multiple directions for future \nexploration of MSM and graphene photodetectors.
URL:https://www.cense.iisc.ac.in/event/thesis-defense-dispersion-in-silicon-on-insulator-micro-ring-resonator/
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