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DTSTART:20250101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260116T110000
DTEND;TZID=Asia/Kolkata:20260116T120000
DTSTAMP:20260514T154813
CREATED:20260106T065244Z
LAST-MODIFIED:20260106T065615Z
UID:9840-1768561200-1768564800@www.cense.iisc.ac.in
SUMMARY:[Seminar] : Nano- and Micro-electromechanical mass sensor with sub-zeptogram resolution; Towards Single molecule protein sequencing and identification
DESCRIPTION:Speaker: Prof. Sang Wook LEE\, Department of Physics\, Ewha Womans University\, Seoul\, Korea.\n\nTitle: "Nano and Micro-electromechanical mass sensor with sub-zeptogram resolution; \nTowards Single molecule protein sequencing and identification"\n\nDate: Friday\, January 16\, 2026 - Time: 11 AM\nTea & Coffee: 10:30 AM\nVenue: CeNSE Seminar Hall\n\nAbstract:\nIn this presentation\, we will show a electro-mechanical resonant mass sensor utilizing a graphene \nand quartz crystal microbalance\, which achieves sub-zeptogram resolution and a single nano \nparticle detection under room temperature conditions. Our research indicates that by employing \nJoule heating\, the graphene membrane surface can be effectively cleaned\, leading to a considerable \nenhancement in the stability of the resonance frequency. By combining machine learning algorithm to\ntaking frequency shift signal out of thermal fluctuation-oriented noise environment\, we could persue \neven higher mass change detection resolution so that it would be possible to recognizing small \nparticles\, including large proteins and protein complexes by mass detection. We recently developed \na new idea to detect a single nanoparticle detection out of micro-mechanical system by utilizing \na complete non-linear resonant state. The ultra-small mass change detection is also performed in \nliquid environment so that this technique can be directly applied to detect a single biomolecule.\n\nBiography:\n\nProf. Sang Wook Lee received his B.S. degree in 1999 from the Department of Physics at Seoul National \nUniversity\, Korea. He subsequently earned his M.S. degree in 2001 and his Ph.D. degree in 2005 from \nthe School of Physics\, Seoul National University\, Seoul\, Korea. His research interests include \nnano-transport\, nano-electromechanical systems\, ultra-sensitive mass and force detection \nusing nanomechanical devices\, single-molecule protein sequencing\, and in-situ electromechanical \nmeasurements of semiconductor nanowires.\n\nHost Faculty:  Prof. Vini Gautam
URL:https://www.cense.iisc.ac.in/event/seminar-nano-and-micro-electromechanical-mass-sensor-with-sub-zeptogram-resolution-towards-single-molecule-protein-sequencing-and-identification/
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260116T160000
DTEND;TZID=Asia/Kolkata:20260116T170000
DTSTAMP:20260514T154813
CREATED:20260105T090119Z
LAST-MODIFIED:20260105T090405Z
UID:9814-1768579200-1768582800@www.cense.iisc.ac.in
SUMMARY:[Seminar] : Light-Matter Interaction at Nanoscale
DESCRIPTION:Speaker: Dr Vibhuti N. Rai\, Fachbereich Physik\, Freie Universität Berlin\, Berlin\, Germany.\nTitle: "Light-Matter Interaction at Nanoscale"\nDate: Friday\, January 16\, 2026 - Time: 4 PM\nTea & Coffee: 5 PM\nVenue: CeNSE Seminar Hall\n\nAbstract:\n\nControlling the optical response of individual quantum systems\, such as molecules and atomic-scale \ndefects\, by minimising the effects of the local environment is essential for next-generation \noptoelectronic and quantum devices. In device geometries\, the emission of an emitter is dictated \nnot only by the intrinsic structure but is also influenced by its coupling to metallic electrodes\, \norientation\, and any external perturbations. To fully access their inherent properties\, we must (i) \ncontrol the emitter’s coupling and alignment with respect to its local environment and \n(ii) understand the mechanisms of different excitations\, such as excitons and vibrational \nmodes\, within that environment. To address these two aspects\, I studied the electroluminescence \nof tailor-made single molecules and excitation dynamics at defects in (quasi-)two-dimensional \ntransition-metal dichalcogenides (TMDCs) with ultrafast temporal resolution. Scanning tunnelling \nmicroscopy (STM)-induced luminescence is a unique tool for probing the op tical properties of \nemitters with atomic-scale spatial resolution. We achieved a molecular design by mounting a \nchromophore on a tripodal platform connected via a linker\, exhibiting a high degree of \nelectronic and mechanical decoupling\, reflected in its high emission yield (10⁻³ ph/e⁻) and \nclear hot luminescence [1\, 2]. This approach provides a route toward engineering emitter \narchitectures with tailored optical properties for optoelectronic components. While such control \nis highly promising\, conventional STM experiments lack the temporal resolution (ms to μs) required \nto understand fundamental excitation and relaxation processes\, such as excitons or phonons\, which \noccur at nanosecond to picosecond timescales and are strongly influenced by the local environment\, \nultimately limiting device performance [3]. To overcome this limitation\, I efficiently coupled \noptical and THz radiation into an STM junction [4] to probe picosecond dynamics. I investigated \n(quasi-)two-dimensional materials such as TMDCs\, which exhibit strong light-matter interactions and an \ninterplay between electronic and structural degrees of freedom\, i.e.\, electron-phonon coupling. These \nmaterials host various structural defects that significantly modify their physical properties and can \npotentially act as quantum dot-like single-photon sources. Compared to single-molecule emitters\, \nthese defects are more stable and provide an ideal platform for studying interactions with the environment\, \nsuch as lattice vibrations. I probed the phonon dynamics of bulk 2H-MoTe₂ in a THz pump-THz probe scheme \nand was able to excite and detect long-range coherent phonon modes. We find that defects modulate the \nrelative excitation efficiency of different modes due to local tip-induced band bending [5]. With access \nto ultrafast timescales and atomic-scale spatial resolution\, we can directly unravel how a quantum system \ncouples to its environment. This capability opens the door to probing charge-transfer mechanisms in hybrid \nsystems\, tracking the evolution of coherent states\, and guiding the design of efficient optoelectronic devices. \n\n[1] V. N. Rai et al. Nat. Commun. 14 (1)\, 8253 (2023) Link \n\n[2] V. N. Rai et al. Phys. Rev. Lett. 130\, 036201 (2023) Link \n\n[3] K. Kaiser et al. Nat. Commun 14\, 4988 (2023) Link \n\n[4] T. Cocker et al. Nat. Photon. 7\, 620-625 (2013) Link \n\n[5] V. N. Rai et al. Sci. Adv. 11\, eadz6549 (2025) Link.\n\nBiography:\n\nI (Vibhuti Rai) completed my schooling in my hometown of Azamgarh. Thereafter\, I attended Ramjas \nCollege\, University of Delhi\, where I pursued a Bachelor of Science (Honours in Physics) from 2009 to 2012. \nAfter that\, I was admitted to the S. N. Bose National Centre for Basic Sciences\, Kolkata as an integrated \nPhD student. After completing my master’s degree\, I continued there as a Junior Research Fellow. In 2016\, \nI was selected for two PhD scholarships: the Deutscher Akademischer Austauschdienst (DAAD\, Germany) and the \nMonbukagakusho (MEXT\, Japan). I pursued my PhD under the DAAD scholarship at the Karlsruhe Institute of Technology\, \nGermany\, from 2017 to 2021. The topic of my PhD was “Light Emission from Single Self-Decoupled Molecules in Scanning \nTunnelling Microscopy"\, under the supervision of Prof. Wulf Wulfhekel. Following my PhD\, I continued as a postdoctoral \nresearcher in the same group for two additional years. The topic of my research was “Single Molecules as Single Photon \nSources". Since 2023\, I have been working in the group of Prof. Katharina J. Franke\, where I use THz STM to probe \nultrafast processes with atomic-scale spatial resolution.\n\n\n\nHost Faculty:  Prof. Dhavala Suri
URL:https://www.cense.iisc.ac.in/event/seminar-light-matter-interaction-at-nanoscale/
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DTSTART;TZID=Asia/Kolkata:20260123T160000
DTEND;TZID=Asia/Kolkata:20260123T170000
DTSTAMP:20260514T154813
CREATED:20260116T054250Z
LAST-MODIFIED:20260116T054250Z
UID:9879-1769184000-1769187600@www.cense.iisc.ac.in
SUMMARY:[Thesis Colloquium] : Design and Fabrication of Nanofluidic Devices via Semiconductor Techniques for Single-Molecule Sensing and Computing
DESCRIPTION:Thesis Title: "Design and Fabrication of Nanofluidic Devices via Semiconductor Techniques for Single-Molecule Sensing and Computing "\n\nName of the Student: Mr. Muhammad Sajeer P\n\nDegree Registered: Ph.D. Engineering\n\nAdvisor: Prof. Manoj Varma\, CeNSE\n\nDate: 23rd January 2026\, (Friday)\, 4 PM\n\nVenue: CeNSE Seminar Hall \n\n\nAbstract\nNano- and angstrom-scale fluidic devices\, including nanopores (0D)\, nanotubes (1D)\, and nano-slits (2D)\, \nare pushing the fundamental limits of single-molecule sensing. These confinement regimes allow for the \nprecise investigation of ionic transport\, enabling applications that range from next-generation sequencing \nto novel computational applications. While biological alternatives of these devices have received significant\n attention and widely used for next generation sequencing applications\, their solid-state counterparts had \nlimited growth. There have been several practical and technical challenges hindering these including lack \nof scalability and limitations of ionic current based sensing technique itself. This thesis addresses several \nof these challenges through a four-phase framework: Building\, Improving\, Applying\, and Reflecting.\n\nPhase 1 (Building) establishes a robust and optimized protocol for solid-state nanopore fabrication \nand characterization. By standardizing fabrication workflows\, this work lowers the barrier to entry \nfor nanopore research and enables reliable in-house device development.\n\nPhase 2 (Improving) focuses on active control and advanced readout. On the device side\, we \ndemonstrate solid-state nanopores integrated with microheaters to achieve thermal modulation of \nionic conductance. On the measurement side\, we introduce "nanopore electrometry\," a self-referenced \nreadout technique. This method presents a robust alternative to traditional ionic current sensing and \nis validated through the discrimination of amino acids using Molecular Dynamics and Multiphysics simulations.\n\nPhase 3 (Applying) transitions to 2D material-based nanofluid devices such as nano-slits and nanochannels. \nWe establish ultramicrotomy as a scalable\, high-throughput technique for fabricating MoS2 nano-slits towards \nsingle-molecule DNA topology studies. Furthermore\, we utilize van der Waals (vdW) assembled hBN-MoS2 nanochannels \nto explore biomimetic protein dynamics and demonstrate their potential for computational applications.\n\nPhase 4 (Reflecting) situates these technological advances within a broader societal context by examining \nthe ethical\, legal\, and societal implications (ELSI) of nanopore sequencing technologies. This analysis highlights \nthe need for inclusive governance\, ethical foresight\, and responsible innovation as these technologies transition \nfrom laboratory research to widespread public use.\n\nTogether\, this work advances the scalability\, functionality\, and societal awareness of solid-state nanofluidic \ntechnologies\, contributing to their maturation as platforms for both fundamental research and real-world applications.
URL:https://www.cense.iisc.ac.in/event/thesis-colloquium-design-and-fabrication-of-nanofluidic-devices-via-semiconductor-techniques-for-single-molecule-sensing-and-computing/
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260130T160000
DTEND;TZID=Asia/Kolkata:20260130T170000
DTSTAMP:20260514T154813
CREATED:20260122T051341Z
LAST-MODIFIED:20260122T051341Z
UID:9882-1769788800-1769792400@www.cense.iisc.ac.in
SUMMARY:[Thesis Colloquium] : 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: 30th January 2026\, Time : 4 PM\n\nVenue: CeNSE Seminar Hall : \n\nAbstract\nSilicon photonics underpins a wide range of applications spanning sensing\, communication\, computation\, and emerging quantum technologies. A common thread across these platforms is their strong sensitivity to refractive index\, with many applications critically relying on its dynamic modulation. Achieving reliable and predictable device operation\, therefore\, requires accurate characterization of refractive index changes and a clear understanding of the underlying physical mechanisms. In silicon\, refractive index modulation arises from multiple contributions\, including thermal effects\, free-carrier dispersion\, and the Kerr nonlinearity. While several techniques have been developed to probe these mechanisms\, they are often limited in the quantities they measure\, restricting their broader applicability.\nCavity-enhanced photothermal spectroscopy is a widely used method to characterize Kerr nonlinearity. It employs a pump tone and a probe tone\, both tuned to different resonances of the same optical cavity. The pump intensity is harmonically modulated\, and the resulting oscillations in the probe intensity are monitored. Different dispersion mechanisms are studied through the strength of oscillation transfer. Typically\, probe amplitude data are analyzed using numerical fits; however\, these fits can be non-unique and can be contaminated by experimental artifacts. Phase data\, a complementary observable\, are often affected by phase artifacts.\nWe present a method to remove these experimental artifacts and extract the oscillation-transfer phase difference. An Erbium-Doped Fiber Amplifier (EDFA) is introduced before the pump intensity modulator. The amplified spontaneous emission (ASE) passes through the intensity modulator and experiences the same envelope modulation as the pump. A fraction of this ASE propagates through the probe path. Since this ASE leakage undergoes the same experimental artifacts as the probe\, its phase is measured. The intrinsic phase information of oscillation transfer is then obtained by subtracting the leakage phase from the probe phase. Using this approach\, we confirm the presence of free-carrier dispersion in a silicon-on-insulator ring resonator cavity. This method provides a complementary extension to an established technique and remains applicable in regimes where conventional pump-based phase extraction fails.\nNext\, we investigate the nonlinear properties of ReS₂ by studying its effects on SoI ring resonators. All-optical resonance shift measurements and cavity-enhanced photothermal spectroscopy are performed before and after transferring ReS₂ onto the resonator. Significant inter-device variability is observed in both resonance shift and photothermal response. Intra-device variability is also seen when the same device undergoes different surface processes. A possible explanation is proposed based on existing literature on linear absorption loss in silicon\, its surface-dominated nature\, and its sensitivity to surface chemistry.\nAdditionally\, we study on-chip metal–semiconductor–metal (MSM) and graphene photodetectors. For MSM devices\, current–voltage characteristics and photo-response are measured. The responsivity and dynamic range of photoresponse are characterized. We show that these MSM devices are suitable for integration with optomechanical systems. For graphene photoconductors\, we demonstrate successful fabrication and performance comparable to that reported in the literature. Finally\, we suggest a direction for further exploration through the fabrication of MSM graphene–silicon–graphene devices using atomic force microscope lithography.\nThis work extends a well-established technique and improves its robustness. It provides new insights into dispersion in silicon-on-insulator microring resonators\, highlighting the sensitivity of micro-cavity behavior to surface effects. Finally\, it validates multiple directions for future exploration of MSM and graphene photodetectors.
URL:https://www.cense.iisc.ac.in/event/thesis-colloquium-dispersion-in-silicon-on-insulator-micro-ring-resonator/
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