arXiv subjects

Subhendu Kahaly

Publications and source records attributed to Subhendu Kahaly.

22 records · Page 2Linked to original sources

arXiv2019

Imaging the source of high-harmonics generated in atomic gas media

We report the application of the time gated ion microscopy technique in accessing online the position of the source of harmonics generated in atomic gas media. This is achieved by mapping the spatial extreme-ultraviolet (XUV)-intensity distribution of the harmonic source onto a spatial ion distribution, produced in a separate focal volume of the generated XUV beam through single photon ionization of atoms. It is found that the position of the harmonic source depends on the relative position of the harmonic generation gas medium and the focus of the driving infrared (IR) beam. In particular, by translating the gas medium with respect to the IR beam focus different virtual source positions are obtained online. Access to such online source positioning allows better control and provides increased possibilities in experiments where selection of electron trajectory is important. The present study gives also access to quantitative information which is connected to the divergence, the coherence properties and the photon flux of the harmonics. Finally, it constitutes a precise direct method for providing complementary experimental info to different attosecond metrology techniques.

physics.atom-ph↗

arXiv2019

Advances in high-order harmonic generation sources for time-resolved investigations

We review the main research directions ongoing in the development of high-harmonic generation-based extreme ultraviolet sources for the synthesization and application of trains and isolated attosecond pulses to time-resolved spectroscopy. A few experimental and theoretical works will be discussed in connection to well-established attosecond techniques. In this context, we present the unique possibilities offered for time-resolved investigations on the attosecond timescale by the new Extreme Light Infrastructure Attosecond Light Pulse Source, which is currently under construction.

physics.optics↗

arXiv2007

Sub-lambda gratings, surface plasmons, hotter electrons and brighter x-ray sources- enhanced absorption of intense, ultrashort laser light by tiny surface modulations

We observe near 100 % absorption of light in intense ultrashort laser plasma interaction in a metal coated (Au on glass) sub-lambda grating structure under suitable conditions and the subsequent 'hot' electron generation from the grating plasma. In the low intensity regime we determine the conditions in which a monochromatic infrared light (lambda = 800nm corresponding to the central wavelength of the ultrashort laser that we used in subsequent experiments) efficiently excites surface plasmon in the grating. Then we study how the surface plasmon resonance condition changes when we excite them using low intensity ultrashort pulses. We look at the reflectivity of light varying the incident light intensity over a wide range (2x10e12Wcm-2-2x10e15Wcm-2). The reflectivity of grating with the resonance condition satisfied is the lowest over the whole range of intensity. We compare the data with those obtained from highly polished (lambda/10) Au mirror target under identical conditions. At high intensities we look at the hard x-ray emission from both the targets with and without the resonance condition. The hard X-ray spectrum shows a bimaxwellian i.e two temperature hot electron distribution with a hotter component present under the resonance condition while in all other cases it shows the presence of only one low temperature component.

physics.plasm-ph↗

arXiv2007

Mapping giant magnetic fields around dense solid plasmas by high resolution magneto-optical microscopy

We investigate distribution of magnetic fields around dense solid plasmas generated by intense p-polarized laser (~10^{16} W.cm^{-2}, 100 fs) irradiation of magnetic tapes, using high sensitivity magneto optical microscopy. We present evidence for giant axial magnetic fields and map out for the first time the spatial distribution of these fields. By using the axial magnetic field distribution as a diagnostic tool we uncover evidence for angular momentum associated with the plasma. We believe this study holds significance for investigating the process under which a magnetic material magnetizes or demagnetizes under the influence of ultrashort intense laser pulses.

cond-mat.other↗