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SUMMARY:IMX Colloquium - From Nanoscale Interfaces to Macroscale Devices: 
 Soft Photonics for Large Areas
DTSTART:20251117T131500
DTEND:20251117T141500
DTSTAMP:20260921T202710Z
UID:42b37b127ac34d1b98a60f193b1d14292e120cea1c053aefcb87b834
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Tapajyoti Das Gupta\, IISC Bangalore\, India\nModern dev
 ices require the tuning of the size\, shape and spatial arrangement of nan
 o- objects and their assemblies with nanometre scale precision\, over larg
 e-area and sometimes soft substrates. Such stringent multi-scale and mecha
 nical requirements are beyond the reach of conventional lithography techni
 ques or simpler self-assembly approaches.\n\nIn this talk\, at first\, we 
 will demonstrate an unprecedented control over the fluid instabilities of 
 thin optical-glass and polymer films as a simple approach for the self-ass
 embly of advanced all-dielectric metasurfaces. We show and model the tailo
 ring of the position\, shape\, size and inter-particle distance of nano-ob
 jects with feature sizes below ten nanometres. This simple and versatile a
 pproach can generate optical nanostructures over tens-of-centimetres sized
  rigid and soft substrates\, with better optical performance and a resolut
 ion on par with advanced lithography-based processes. By having unpreceden
 ted control over the lattice and particle size via a simple nanoimprinting
  process\, we demonstrate sharp Fano resonances with the highest Quality f
 actor of ~300 visible to date. We also observe high-purity structural colo
 rs covering an extended gamut of spectra.\n\nIn the second part\, we will 
 show a recent result from our lab\, whereby by tuning the thermal coeefici
 ent of expansion of the substrate and the thin film we obtain large area p
 eriodic structures whose optical properties can be tuned dynamically. As a
  proof of concept we show simple mechnaochromic devices as well as camoufl
 age effect with such materials.\n\nIn the third part of the talk I will di
 scuss how by exploiting fluidic interaction of liquid metals and uncured o
 ligomer in soft substrates\, we obtained structural colors with Gallium ba
 sed liquid metal nanospheres\, paving the way toward a novel paradigm in s
 oft photonics and large area reflective displays. By tuning and optimizing
  a range of experimental parameters\, and the choice of substrate material
  we obtain vibrant coloration encompassing a wide range of chromaticity co
 ordinates due to the varying size distribution of controlled Ga nanodrople
 ts.\n\nAs a proof-of-principle\, we show pallets of structural colors of t
 he films derived from this process. Reflective display technology can bene
 fit greatly by leveraging the advantages of structural colors over its pig
 mented counterparts. The application of the thus-fabricated device exhibit
 s mechanochromic sensing\, which has been characterized to be of high fide
 lity and reliability\, functionalized by exploiting the fluidic properties
  of Gallium. For at least 1000 cycles of uniaxial stretching and relaxing 
 with a periodicity of 50 seconds\, the reflectivity spectrum of the sample
  for a given strain was unchanged\, thus proving the reliable reconfigurat
 ion of sample response to the application and removal of mechanical strain
 . The reversible change in the reflectivity spectrum results in the chroma
 ticity coordinates of the sample\, hence a visible change in the sample co
 lor. Our results can offer opportunities to dynamically reconfigure thin-f
 ilm-based functional nanodevices in situ and process technology for high t
 hroughput fabrication to achieve the same in a single-step method.\nRef:\n
 1. Das Gupta\, T.\, Martin-Monier\, L.\, Yan\, W. et al. Self-assembly of 
 nanostructured glass metasurfaces via templated fluid instabilities. Nat. 
 Nanotechnol. 14\, 320–327 (2019). https://doi.org/10.1038/s41565-019-036
 2-9\n2. Sahu\, R.R.\, Ramasamy\, A.S.\, Bhonsle\, S. et al. Single-step fa
 brication of liquid gallium nanoparticles via capillary interaction for dy
 namic structural colours. Nat. Nanotechnol. 19\, 766–774 (2024). https:/
 /doi.org/10.1038/s41565-024-01625-1\n3. Das Gupta\, T.\, Martin-Monier\, L
 .\, Butet\, J. et al. Second harmonic generation in glass-based metasurfac
 es using tailored surface lattice resonances. Nanophotonics. 10 (2021). ht
 tps://doi/10.1515/nanoph-2021-0277\n4. Biswas\, S.\, Sahu\, R.R.\, Shinkre
 \, O.D.N. et al. Tailored Thin Films: Modulating Soft Photonics with Dynam
 ically Tunable Large Area Microstructures via Controlled Thermal Processin
 g. Arxiv. (2025). https://doi.org/10.48550/arXiv.2501.05736\n5. Sahu\, R.R
 .\, Das Gupta\, T. Real-time tuneable bright bonding plasmonic modes in Ga
  nanostructures. Arxiv (2025). https://doi.org/10.48550/arXiv.2504.04922\n
 \nBio: Tapajyoti Das Gupta obtained his BSc and Btech in Physics and Radi
 o physics respectively from University of Calcutta in 2006 and 2009. He th
 en moved to France where he obtained his MSc in nanoscience from École Po
 lytechnique (l’X) in 2012 and PhD in Condensed Matter Physics lab (PMC) 
 from the same institute in 2015 under Prof. Thierry GACOIN and Alistair RO
 WE. He then joined prof. Fabien Sorin’s lab of Fiber Optics and Photonic
 s Devices (FIMAP) in École Polytechnique Fédérale de Lausanne (EPFL) du
 ring 2015 December-2019 November. He is currently an assistant professor i
 n the Department of Instrumentation and Applied Physics in Indian Institut
 e of Science\, Bangalore from July 2020. His research interest includes fi
 nding solution to fabricate large area metasurfaces and photonic devices f
 or applications including displays\, holography\, instrumentation and imag
 e processing.
LOCATION:MXF 1 https://plan.epfl.ch/?room==MXF%201
STATUS:CONFIRMED
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