About

Shyamsunder Erramilli is a Professor and Chair in the Department of Physics at Boston University. His research interests encompass Biological Physics, Quantum non-linear vibrational spectroscopy, and mid-infrared photo thermal spectroscopy. His group combines femtosecond lasers with nanoparticle systems to enhance electromagnetic fields for studying biological systems. He exploits nonlinear physics to generate nanoscale shockwaves capable of inactivating viruses and pathogens without collateral damage, employing an interdisciplinary approach spanning Physics, Chemistry, Engineering, and Biomedical Science. Dr. Erramilli has contributed to the development of label-free imaging techniques, vibrational infrared photothermal and phase signals, and ultrafast spectroscopy methods, advancing understanding in these fields. He holds an M.Sc. in Physics from the Indian Institute of Technology and a Ph.D. in Physics from the University of Illinois. Recognized for his contributions, he received the duPont Young Professor Award in 1996.

Research topics

• Materials science
• Optoelectronics
• Nanotechnology
• Computer Science
• Biochemistry
• Optics
• Chemistry
• Biology
• Internal medicine
• Chromatography
• Composite material
• Microbiology
• Medicine
• Biophysics
• Electrical engineering

Selected publications

• Widefield pump-probe microscopy with coherent background subtraction by angle-compensated temporal shearing

  Optics Express · 2026-02-16

  articleOpen access

  Pump-probe microscopy enables label-free imaging of structural and chemical features of samples. However, signals in pump-probe microscopy are typically small and often must be measured in the presence of large backgrounds. As a result, achieving measurements with a high signal-to-noise ratio is challenging, particularly when using sensors that are easily saturated, such as CMOS cameras. We present a method for enhancing signal-to-noise ratio while avoiding detector saturation. In this approach, temporally separated (sheared) reference and probe pulses transmit through a sample before and after the arrival of a pump pulse. The probe and reference pulses are then temporally recombined with opposing phases and nearly matched amplitudes, resulting in interferometric background subtraction. This recombining operation is performed by a novel common-path interferometer. Unlike previous techniques for temporal shearing, this interferometer demonstrates negligible phase and group delay dispersion with angle of incidence, allowing convenient widefield imaging. To our knowledge, this is the first common-path interferometer with such a property. We demonstrate the technique by measuring transient absorption signals in gold nanorod films with a signal-to-background ratio enhanced by over 100% and a signal-to-noise ratio enhanced by about 70%.

  PublisherDOI

• Unraveling Plasmon-Enhanced Reactive Oxygen Species Generation through Ultrafast Light

  The Journal of Physical Chemistry C · 2025-02-11 · 1 citations

  articleOpen accessCorresponding

  Reactive oxygen species (ROS) generation through gold nanorods (AuNRs) excited by 812 nm centered, 85 fs (fs)-pulsed laser irradiation was investigated through a rhodamine B degradation assay. The initial rate of rhodamine B fluorescence intensity degradation is determined by the rate of ROS generation, but at later time points, the laser irradiation-induced deformation of AuNRs reduces the rate of rhodamine B degradation. For different AuNR preparations that all had a localized surface plasmon resonance (LSPR) mode at around 800 nm but differed in size, the initial rate of rhodamine B fluorescence intensity decrease follows a trend predicted by the simulated peak near-field intensities and absorption efficiencies, except for the smallest AuNRs with dimensions of 30 nm × 7 nm. The initial rate of ROS generation exhibits a power law dependence on the fluence. The reshaping of the AuNRs on longer time scales also depends on the fluence. For 2.3 mJ/cm2, the establishment of a stable regime is observed, where an initial reshaping of the AuNRs decreases the spectral overlap between longitudinal plasmon resonance and excitation wavelength so that the absorbed energy is insufficient to induce further structural changes but still allows for ROS generation. For a fluence of 3.9 mJ/cm2, the AuNR plasmon spectrum almost completely detunes from the excitation wavelength, resulting in a further reduction of ROS generation. AuNR reshaping and ROS generation also depend on the surface passivation of the AuNRs. Intriguingly, a lipid coating was observed to provide a relative stabilization of the AuNRs when compared with poly(ethylene glycol) (PEG) or cetyltrimethylammonium (CTAB) surface chemistries and still allow for ROS generation.

  PublisherOA PDFDOI

• Heat Transport in Photothermal Microscopy: Newton vs Fourier

  The Journal of Physical Chemistry C · 2024-01-04 · 8 citations

  articleCorresponding

  Technological breakthroughs in photothermal microscopy have led to new discoveries in thermal transport at the cellular level. In the linear regime, heat transport is governed by the well-understood parabolic partial differential heat equation and its many extensions, with antecedents dating back to Fourier. The relaxation of the temperature from a point impulsive source of heat in a homogeneous medium in d dimensions is scale free and asymptotically follows a power law decay in time ∼t–d/2. It is therefore interesting that many recent experiments have used Newton’s law of cooling, an ordinary differential equation that yields exponential decays with a single time constant. We show that the observed apparent exponential decays in photothermal microscopy are set by externalities such as the sample cell design, experimental finite excitation pulse width, and spatial resolution and should still contain a power law prefactor. Combining analytical methods that include exact results and asymptotic analysis with experiments and numerical simulations, we show that the conditions for the emergence of Newton’s law of cooling are often not satisfied in experiments. These need to be reinterpreted to be consistent with the underlying Fourier theory at the microscopic subcellular length scales, taking into consideration the interfacial thermal conductance or equivalently the inverse Kapitza resistance at interfaces.

  PublisherDOI

• Molecular-Level Understanding of the Ro-vibrational Spectra of N$_2$O in Gaseous, Supercritical and Liquid SF$_6$ and Xe

  arXiv (Cornell University) · 2023-02-14

  preprintOpen access

  The transition between the gas-, supercritical-, and liquid-phase behaviour is a fascinating topic which still lacks molecular-level understanding. Recent ultrafast two-dimensional infrared spectroscopy experiments suggested that the vibrational spectroscopy of N$_2$O embedded in xenon and SF$_6$ as solvents provides an avenue to characterize the transitions between different phases as the concentration (or density) of the solvent increases. The present work demonstrates that classical molecular dynamics simulations together with accurate interaction potentials allows to (semi-)quantitatively describe the transition in rotational vibrational infrared spectra from the P-/R-branch lineshape for the stretch vibrations of N$_2$O at low solvent densities to the Q-branch-like lineshapes at high densities. The results are interpreted within the classical theory of rigid-body rotation in more/less constraining environments at high/low solvent densities or based on phenomenological models for the orientational relaxation of rotational motion. It is concluded that classical MD simulations provide a powerful approach to characterize and interpret the ultrafast motion of solutes in low to high density solvents at a molecular level.

  PublisherOA PDFDOI

• Molecular-level understanding of the rovibrational spectra of N2O in gaseous, supercritical, and liquid SF6 and Xe

  The Journal of Chemical Physics · 2023-03-15 · 9 citations

  articleOpen access

  The transition between the gas-, supercritical-, and liquid-phase behavior is a fascinating topic, which still lacks molecular-level understanding. Recent ultrafast two-dimensional infrared spectroscopy experiments suggested that the vibrational spectroscopy of N2O embedded in xenon and SF6 as solvents provides an avenue to characterize the transitions between different phases as the concentration (or density) of the solvent increases. The present work demonstrates that classical molecular dynamics (MD) simulations together with accurate interaction potentials allows us to (semi-)quantitatively describe the transition in rotational vibrational infrared spectra from the P-/R-branch line shape for the stretch vibrations of N2O at low solvent densities to the Q-branch-like line shapes at high densities. The results are interpreted within the classical theory of rigid-body rotation in more/less constraining environments at high/low solvent densities or based on phenomenological models for the orientational relaxation of rotational motion. It is concluded that classical MD simulations provide a powerful approach to characterize and interpret the ultrafast motion of solutes in low to high density solvents at a molecular level.

  PublisherOA PDFDOI

• Alanine aminotransferase assay biosensor platform using silicon nanowire field effect transistors

  Communications Engineering · 2023 · 11 citations

  • Materials science
  • Nanotechnology
  • Optoelectronics

  Abstract Frequent monitoring of serum alanine aminotransferase (ALT) activity is essential to prevent drug-induced liver injury (DILI). Current ALT assays are restricted to centralized clinical laboratories, making frequent patient monitoring logistically difficult. To address this, we demonstrated the capability of commercial foundry manufactured silicon nanowire field effect transistor (SiNW-FET) biosensors in a form factor that enables frequent near-patient monitoring. Here, we designed an ALT assay, by coupling the ALT-catalyzed production of pyruvate to the reduction of ferricyanide, enabling both spectrophotometric and electrical measurement of ALT activity. The two methods yield comparable ALT activity detection across a dynamic range wide enough to monitor patients at risk for DILI. This study demonstrates kinetic activity measurement of an endogenous enzyme using uncoupled SiNW-FETs, and commercial manufacturing of SiNW-FET sensor arrays for use in a portable biosensor platform.

  PublisherOA PDFDOI

• Thermal transport across membranes and the Kapitza length from photothermal microscopy

  Journal of Biological Physics · 2023-07-21 · 3 citations

  articleOpen accessCorresponding
  PublisherOA PDFDOI

• Ultrafast 2DIR comparison of rotational energy transfer, isolated binary collision breakdown, and near critical fluctuations in Xe and SF6 solutions

  The Journal of Chemical Physics · 2022-10-14 · 2 citations

  article

  The density dependence of rotational and vibrational energy relaxation (RER and VER) of the N2O ν3 asymmetric stretch in dense gas and supercritical Xe and SF6 solutions for near critical isotherms is measured by ultrafast 2DIR and infrared pump–probe spectroscopy. 2DIR analysis provides precise measurements of RER at all gas and supercritical solvent densities. An isolated binary collision (IBC) model is sufficient to describe RER for solvent densities ≤ ∼4M where rotational equilibrium is re-established in ∼1.5–2.5 collisions. N2O RER is ∼30% more efficient in SF6 than in Xe due to additional relaxation pathways in SF6 and electronic factor differences. 2DIR analysis revealed that N2O RER exhibits a critical slowing effect in SF6 at near critical density (ρ* ∼ 0.8) where the IBC model breaks down. This is attributable to the coupling of critical long-range density fluctuations to the local N2O free rotor environment. No such RER critical slowing is observed in Xe because IBC break down occurs much further from the Xe critical point. Many body interactions effectively shield N2O from these near critical Xe density fluctuations. The N2O ν3 VER density dependence in SF6 is different than that seen for RER, indicating a different coupling to the near critical environment than RER. N2O ν3 VER is only about ∼7 times slower than RER in SF6. In contrast, almost no VER decay is observed in Xe over 200 ps. This VER solvent difference is due to a vibrationally resonant energy transfer pathway in SF6 that is not possible for Xe.

  PublisherDOI

• Flatfield ultrafast imaging with single-shot non-synchronous array photography

  2022-04-01

  article

  We present a method for acquiring a sequence of time-resolved images in a single shot, termed Single-Shot Non-Synchronous Array Photography (SNAP). In SNAP, a diffractive optical element is used to create an array of angled probe beams. Each of these sub-pulses then transmit through an echelon to impart unique time delays, creating an angled pulse train. After probing a scene, the sub-pulses can be differentiated with techniques from light field microscopy. Temporal resolution in SNAP is fundamentally limited only by the probe pulse duration. We demonstrate SNAP by capturing the evolution of a laser initiated plasma at an average framerate of 4.2 Tfps.

  PublisherDOI

• Flatfield Ultrafast Imaging with Single-Shot Non-Synchronous Array Photography

  The International Conference on Ultrafast Phenomena (UP) 2022 · 2022-01-01

  articleCorresponding

  A diffractive optical element, custom echelon, and microlens array are used to achieve ultrafast imaging of at upwards of 4.2 trillion frames per second. We term this new technique Single-Shot Non-Synchronous Array Photography (SNAP).

  PublisherDOI

Recent grants

• Development of Infrared Spectroscope for Microfabricated Proteome Chips

  NSF · $598k · 2003–2007

• Plasmonic Inactivation of Virus and Mycoplasma Contaminants

  NIH · $1.3M · 2021–2025

Frequent coauthors

• Mi K. Hong

  Boston University

  32 shared

• L. D. Ziegler

  28 shared

• Pritiraj Mohanty

  23 shared

• Michelle Y. Sander

  Université de franche-comté

  18 shared

• Alket Mërtiri

  Draper Laboratory

  13 shared

• Atcha Totachawattana

  12 shared

• Xihua Wang

  10 shared

• M. K. Hong

  10 shared

Awards & honors

• duPont Young Professor Award (1996)