Department of Physics
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Item Tailoring polarisation of attosecond pulses via co-rotating bicircular laser fields(Elsevier, 2024-01) Holkundkar, Amol R.The present work introduces a robust way to generate attosecond pulses with tunable ellipticity via high-order harmonic generation by co-rotating bicircular laser fields. The total electric field of the laser fields exhibits an absence of rotational symmetry, which leads to the generation of high harmonics of the same helicity across a broad range of spectral bandwidth. High-harmonics with the same helicity offer the opportunity to synthesize attosecond pulses with tunable ellipticity. The polarisation properties of the generated harmonics are robust against the variations in driving fields' parameters, such as wavelength, intensity ratio, and the sub-cycle phase between fields. Our work opens an avenue to study chiral-sensitive light-matter ultrafast processes on their intrinsic timescale.Item Controlling resonant enhancement in higher-order harmonic generation(ARXIV, 2021) Holkundkar, Amol R.; Bandyopadhyay, Jayendra N.We present a method to tune the resonantly enhanced harmonic emission from engineered potentials, which would be experimentally feasible in the purview of the recent advances in atomic and condensed matter physics. The recombination of the electron from the potential dependent excited state to the ground state causes the emission of photons with a specific energy. The energy of the emitted photons can be controlled by appropriately tweaking the potential parameters. The resonant enhancement in high-harmonic generation enables the emission of very intense extreme ultra-violet or soft x-ray radiations. The scaling law of the resonant harmonic emission with the model parameter of the potential is also obtained by numerically solving the time-dependent Schrödinger equation in two dimensions.Item High-order harmonic generation by sub-cycle laser pulses and associated scaling laws(Elsevier, 2023-02) Holkundkar, Amol R.; Bandyopadhyay, Jayendra N.We studied the high-harmonic generation by the interaction of sub-cycle laser pulses with the He atom. The sub-cycle pulses are modeled using the complex source vector beam model, which is an exact solution to Maxwell's equations and accurately models the sub-cycle field profiles. We observed that the harmonic cutoff could be extended with the variation of the sub-cycle pulse duration, mainly because of the inherent blueshift associated with shorter pulses. The scaling laws for the harmonic yield and harmonic cutoff energy with pulse duration and fundamental driver wavelengths are also deduced. Furthermore, a detailed wavelet analysis of harmonic generation by sub-cycle pulses is carried out. The appropriate filtering and superposition of the harmonics gave rise to a single attosecond pulse of duration ∼100 as.