United States

AIPP Photonics in Chemical Physics

Effects of electron-vibrational interaction in equilibrium and hot polariton luminescence in microcavities

fano resonances

electron-vibrational interaction

exciton-polariton

luminescence

## Dr. Nishikant (Nish) Sonwalkar: Academician, Scientist, Musician

![](https://assets.underline.io/uploads/markdown_image/1/image/0f9b63a0b3deba4a355d98e2c87af68a.png)

Dr. Sonwalkar is regarded as a leading expert in the application of computers in education. He has extensive research and development experience in hypermedia authoring, mobile learning, adaptive learning, and brain-based synaptic learning, advanced scientific visualization, database management systems, and computer simulation.

After receiving doctoral degree from MIT in the area of Molecular Dynamics of Nano-interfaces, he joined MIT as faculty in Mechanical Engineering, but his passion for technology enabled education led him become the founding director of Hypermedia Teaching Facility (Hypermedia Lab) at MIT and later he was appointed as the Principal Educational Architect of MIT.

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NISH 2021

poster

The field of photonics, broadly defined, ranges from basic physical work on lasers and ultrashort laser pulses to applications in healthcare, communications, and materials. With its increasingly diverse disciplines and subdisciplines, photonics has become a key component in modern society. The scientific program consists of cross-disciplinary researchers, including chemists, physicists, and engineers, in both theory and experimentation. These researchers will discuss this rapidly expanding field and cover topics that address the latest advances in photonics related research and debate the current needs and priorities, as well as the emerging areas.

To access the AIPP Photonics in Chemical Physics conference, [please remember to register.  ](https://services.aip.org/AIPPHorizons/?confID=3351210)

The field of photonics, broadly defined, ranges from basic physical work on lasers and ultrashort laser pulses to applications in healthcare, communications, and materials. With its increasingly diverse disciplines and subdisciplines, photonics has become a key component in modern society. 

Controlling light-matter interaction with molecular vibrations in mid-infrared resonators offers exciting new research opportunities in chemistry and physics [1]. Laboratory implementations use standard materials, operate at room temperature, and use traditional fabrication and detection techniques, yet they have deeply challenged our fundamental understanding on the connections between cavity quantum electrodynamics and chemistry. We have developed rigorous microscopic quantum theory to describe the optical and chemical properties of realistic molecular vibrations in infrared cavity resonators with non-perturbative light-matter interaction [2,3]. We can successfully describe the linear and nonlinear spectra of vibrational polaritons [4]—hybrid vibration-cavity eigenstates– and realistically study the dissociation dynamics of cavity-coupled molecular bonds under non-adiabatic conditions [5]. The role of symmetry of the ground state electronic density with respect to nuclear displacements in the dynamics of vibrational polaritons is discussed, and future applications of these systems for the generation of THz quantum light are suggested.

Strong light-matter coupling with molecular vibrations in infrared resonators

Donor-bridge-acceptor systems based on boron dipyrromethene (BODIPY) are attractive candidates for bio-imagining and sensing applications because of their sensitivity to temperature, micro-viscosity and solvent polarity. The optimization of the properties of such molecular sensors requires detailed knowledge of the relation between the structure and the photophysical behavior in different environments. In this work, we have investigated the excited-state dynamics of three acceptor-donor-acceptor molecules based on benzodithiophene and BODIPY in solvents of different polarities using a combination of ultrafast spectroscopy and DFT-based electronic structure calculations. Transient absorption spectra show that upon photoexcitation an initial excited species with an induced absorption band in the near-infrared regime is formed independently of the solvent polarity. The subsequent photophysical processes strongly depend on the solvent polarity. In non-polar toluene, this initial excited state undergoes a structural relaxation leading to a delocalized state with partial charge transfer character, while in the more polar tetrahydrofuran a fully charge-separated state is formed. The results clearly show how factors such as donor-acceptor distance and restricted rotational motion by steric hindrance can be used to tune the excited state photophysics to optimize such systems for specific applications.

Excited state dynamics of BODIPY-based acceptor–donor–acceptor systems: a combined experimental and computational study


In this study, optical deep-level transient spectroscopy (O-DLTS) has been employed to investigate trap properties in the p-GaN/AlGaN heterostructure, the key part of such a normally-off enhancement-mode III-N transistors. Three electron traps labeled as E1, E2, and E3 were extracted by O-DLTS. The temperature-enhanced emission process of E3 has been studied by isothermal mode O-DLTS.



Study of Traps in p-GaN Gate HEMT by Optical DLTS

The new trends in biosensing field involves fast and real-time identification of biomarkers for rapid diagnosis with less-invasive methods by means of low-cost miniaturized and portable point of care devices. The ability of plasmonic systems to confine the light at nanometer dimension and manipulate the light with size, shape and material features, makes these systems promising candidates for biomedical devices. In this work we demonstrate the sensing capability of compact arrays of 3D metal dielectric core-shell chiral nano helices-based metamaterial enabled by the engineering of many technological elements. On one hand, the intrinsic chiral geometry of these structures, realized by Focused Ion Beam Induced Deposition technology, makes the system unaffected by background interferences, allowing to work even in optically dense environments like body fluids. Moreover, the metal-dielectric architecture realized through a conformal coating of a functional polymeric layer, enhance the chiroptical plasmonic properties of the chiral metamaterial in the far and near- field, and offers a large surface to suitable for molecular immobilization, together with the extrusion along the third dimension. We recorded refractive index sensitivity of about 800nm/RIU and FOM= 1276 RIU-1 for different concentration of glycerol-water solution. We also demonstrated the detection abilities to surface-specific binding event with the Tar-Dna binding protein, TDP-43, currently under study as biomarker for early-stage detection of neurodegenerative diseases. We successfully tested the sensor at different molar concentrations ranging from 1pM down to 10 fM, and in different environment, like human serum. We believe that our finding provides new perspectives for novel diagnostic tools.

3D Helix-based Metamaterial Arrays for Femtomolar Biodetection

Stepwise two-photon absorption (2PA) processes are becoming an important technique because it can achieve high reductive photochemical reactions with visible and near infrared light and intensity-gated high spatiotemporal selectivity with much lower power thresholds than those of the simultaneous 2PA. However, excited states generated by stepwise 2PA (higher excited states and excited states of transient species) are so short-lived that the efficiency for the stepwise 2PA induced photochemical reactions is usually quite low, which limits the versatility for this technique. Here, we demonstrated that the electron of the higher excited state can be efficiently extracted in a nanohybrid of organic molecules and wide bandgap semiconductor nanocrystals (NCs).1 Using perylene bisimide (PBI)-coordinated CdS NCs as a model compound, we demonstrated that the electron of the higher excited state of PBI generated by stepwise 2PA can be extracted to the conduction band of CdS NCs with a quantum yield of ∼0.5–0.7. Moreover, the extracted electron survives at the conduction band of CdS NCs over nanoseconds, which is more than hundred times longer than the lifetime of the higher excited state of PBI. This method can be applied to other organic molecules and larger wide bandgap semiconductors, and therefore, will expand the versatility for the photochemical reactions utilizing the short-lived excited states.

Green and far-red-light induced electron injection from perylene bisimide to wide-bandgap semiconductor nanocrystals with stepwise two-photon absorption process

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