Laboratory for Laser Plasma Interaction
(LLPI)
For Discovering The Unknowns
What Is Laser-Plasma Physics?
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From the time of its invention, laser has always been a wonderful tool for probing matter. However, with its modern advancements, high-power short-pulse (of duration nanosecond to femtosecond) lasers are routinely used to create other extreme states of matter: The Plasma-A hot, ionized state of matter with special collective properties. Laser-Plasma physics, in our context of research, is the study of high-power short-pulse laser matter interaction in the plasma production regime. Naturally, these interactions are extreme in nature and involve many complex and exciting physics.
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Why Do We Study Laser-Plasma Interactions?
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About 99.9 % of the visible universe is made up of plasma and very little material in space is made of rock like the Earth. To understand our universe, therefore, it is fundamentally important that we study plasma. Besides, laser-plasma interaction is important for its relevance in Inertial Confinement Fusion (ICF) for alternate green energy production, Laser-plasma accelerators for fundamental study and biomedical applications, High Energy Density Science (HEDS) for experimentally creating miniature version of starts, core of planets, white dwarf sand other astrophysical objects on laboratory table-top for studying their scaled properties and dynamics (Our community calls it the laboratory astrophysics) , laser ablation dynamics for green synthesis of nanomaterials for biomedicine, bio-imaging and environmental applications, Laser Induced Breakdown Spectroscopy (LIBS) to detect and characterize traces of unknown materials, attosecond (10^-18 s) X-ray science by High Harmonic Generation (HHG) and so on.
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Prof. Amitava Adak,
Assistant Professor, Department of Physics,
IIT(ISM) Dhanbad.
PhD from TIFR Mumbai, 2016
Research Interests:
Extreme Laser-Plasma Interactions, High Harmonic Generation, X-ray Science, Attoscience and Ultrafast Optics.
Email: amitavaadak@iitism.ac.in
Office no: 0326-223-5382
Mob: +91 9800038463
Office Room: 608/B, Department of Physics, Academic Complex.
Google Scholar: https://scholar.google.com/citations?user=yCCQWlcAAAAJ&hl=en
ORCID: https://orcid.org/0000-0003-0687-2830
SCOPUS: https://www.scopus.com/authid/detail.uri?authorId=55279838700
IIT(ISM) Dhanbad faculty profile: https://iitism.irins.org/profile/156452
A Few Research Highlights
Nonclassical Plasmonic Response of Laser-Plasma-Engineered Ultrasmall Nearly-Monodispersed Clean Copper Nanoparticles
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"Non-hazardous, by-product-free, green nanoengineering has attracted significant attention due to its application in biomedicine such as nanoparticle-mediated drug delivery for fetal treatment. Here we demonstrate, for the first time, the optimized clean fabrication of nearly mono-dispersed, record small (dia ∼ 4 nm) plasmonic copper nanoparticles by pulsed laser ablation (PLA) of a highly pure and polished copper plate (1.5 mm thick) immersed inside deionized water following a nonlinear pathway of intense laser-plasma interaction. The intense pulsed laser (1064 nm, 7 ns, 10 Hz) was focused (1.3 mm spot) on a continuously rastered polished copper plate. Controlling the pulse energy (17–70 mJ), we have established unique quantitative correlation among the (i) the localized surface plasmon resonance (LSPR) from the absorption spectra, (ii) the particle size distributions from the TEM analysis, (iii) variation of the size distribution with laser fluence, (iv) the prepared nanocolloid concentration, (v) the nonlinear pump laser absorption, and (vi) the integrated plasma emission, for the first time in a laser synthesis process by novel imaging and spectroscopic techniques. We also present a new observation of a sudden transition in the behavior of LSPR peak, showing red shift to blue shift across the driving fluence of 3 J/cm2, indicating a possible transition between two ablation regimes of laser-plasma interaction. Furthermore, a hitherto unobserved nonlinear trend of the LSPR peak and copper nanoparticles size (< 10 nm regime) is established by the direct correlative study of absorption spectra and TEM analysis. The observed nonlinear trend indicates the quantum response of the electrons beyond classical limits, and it will attract new nonclassical models of plasmonic behavior for ultrasmall copper nanoparticles. Overall, our study will significantly impact biosensing and biomedical applications." This experiment was performed in our laboratory (LLPI), Department of Physics, IIT(ISM) Dhanbad.
Absorption of High Intensity, High Contrast Femtosecond Laser Pulses by a Dielectric Solid
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The basic understanding of high-intensity femtosecond laser absorption in a solid is crucial for high-energy-density science. This multidimensional problem has many variables like laser parameters, solid target material, and geometry of the excitation. This is important for a basic understanding of intense laser-matter interaction as well for applications such as ‘plasma mirror’. Here, we have experimentally observed high-intensity, high-contrast femtosecond laser absorption by an optically polished fused silica target at near-relativistic laser intensities (∼10^18 W/cm^2 ). The laser absorption as a function of angle of incidence and incident energy is investigated for both p- and s-polarized pulses in detail, providing a strong indication of the presence of collisionless processes. At an optimum angle of incidence, almost as large as 80% of the laser (p-polarized) energy gets absorbed in the target. Such a high percentage of absorption at near-relativistic intensities has not been observed before. At smaller angles of incidence the high reflectivity (e.g. about 60 - 70% at 30 deg incidence) indicate that, this study is fundamentally relevant for plasma mirrors at near-relativistic intensities. This experiment was performed at TIFR, Mumbai in UPHILL Laboratory.
Measurement and control of optical nonlinearities in dispersive dielectric multilayers
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"In this work, we report the first observation of transient nonlinear effects in dispersive mirrors in the commonly used 800 nm spectral range. Such nonlinear effects can be observed at peak intensity as low as a few TW/cm2, an order of magnitude below the known damage threshold. These effects are peak intensity, not fluence, dependent. Time resolved observations indicate a defect-mediated direct multiphoton absorption, creating long-lived free carriers in the multilayer stack. This nonlinearity can be severe, >20% absorption, and alters both the spatial and the spectral profile of the light reflected from the mirror, with a minimal effect on the duration of the reflected ultrashort pulses. This nonlinearity is completely reversible and reproducible, with no permanent mirror damage. By taking nonlinear absorption into account in the layer stack design, these nonlinear effects can be suppressed by >∼2x, substantially increasing the pulse energy handling characteristics of the mirror. Our findings may have a significant impact on the interpretation of past experimental work, especially on time-resolved experiments that could be affected by the long relaxation time of the nonlinear response. In other cases, these nonlinear effects can be used or engineered for applications including direct beam shaping of ultrafast laser pulses in the spatial and spectral/temporal domains." This experiment was performed at KM group, JILA, CU Boulder, USA.
Star Trembles at THz on Laboratory-Table-top
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We create and monitor high energy density state (similar to many astrophysical objects like star, core of planet etc.) on laboratory table top via high intensity femtosecond laser-solid interaction. Ultrafast pump-probe diagnostics in an experimental study revealed generation of an acoustic motion at THz frequency inside the hot dense plasma created by an intense femtosemd laser (∼5×10^16 W/cm^2). This experiment was performed at TIFR, Mumbai in UPHILL laboratory.
Magnetic turbulence in a table-top laser-plasma relevant to astrophysical scenarios
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"Turbulent magnetic fields abound in nature, pervading astrophysical, solar, terrestrial and laboratory plasmas. Understanding the ubiquity of magnetic turbulence and its role in the universe is an outstanding scientific challenge. Here, we report on the transition of magnetic turbulence from an initially electron-driven regime to one dominated by ion-magnetization in a laboratory plasma produced by an intense, table-top laser. Our observations at the magnetized ion scale of the saturated turbulent spectrum bear a striking resemblance with spacecraft measurements of the solar wind magnetic-field spectrum, including the emergence of a spectral kink." This experiment was performed at TIFR, Mumbai.
We are here
Laboratory-608/A, 6th floor Academic Complex
Department of Physics, Indian Institute of Technology (Indian School of Mines) Dhanbad, Jharkhand-826004, India