arXiv subjects

Lev Merensky

Publications and source records attributed to Lev Merensky.

4 recordsLinked to original sources

arXiv2026

Reducing the Carrier-Envelope-Phase-dependence of High-Harmonic-Generation by Vectorial-Time-Polarization-Gating

A well-known shortcoming of High Harmonic Generation (HHG) is the strong dependence of the broadband HHG spectra (HGS) on the carrier envelope phase (CEP) of the driver. Here we numerically show that compared to the current well-established scalar (linearly polarized) schemes for generating broadband HGS, namely a short driver [Amplitude gating (AG)], Polarization-Gating (PG) or Time-Gating (TG), the vectorial driver of the Vectorial-Time-Polarization-Gating (VTPG) scheme renders the cutoff HGS much less sensitive to the CEP of the driver. The polarization state (helicity) of the emitted radiation is likewise CEP-resilient. Unlike scalar schemes, where the number of recollisions heavily depends on the CEP, in VTPG the CEP keeps this number almost unchanged, and only controls the partitioning of the recollisions between two orthogonal directions. This reduces the CEP-dependence of the HGS and decreases the spectral modulations. The CEP-resilience of the VTPG scheme holds promise for a variety of applications in attosecond science benefiting from quasicontinuous, helical HHG sources liberated from the necessity to stabilize the CEP of the laser.

physics.optics↗

arXiv2025

Chiral broadband High Harmonic Generation Source by Vectorial Time-Polarization-Gating

Chiral (highly helical) extreme ultraviolet (XUV) sources are pivotal for investigating chiroptical phenomena on the ultrafast electronic timescale. Table-top, coherent High Harmonic Generation (HHG)-based sources are particularly well-suited for these studies. However, chiral materials, such as organic chiral molecules and solid-state magnetic materials, exhibit fine spectral features which necessitate broadband radiation for their complete interrogation. The generation of radiation that is both broadband and helical through HHG presents a seemingly paradoxical challenge: while chiral HHG emission requires at least two recollisions occurring along different directions in the polarization plane, the Floquet limit might already be reached with as few as three recollisions, resulting in a sparse spectrum characterized by pronounced discrete harmonic peaks. Here we propose a straightforward scheme that enables the interrogation of fine spectral features, in principle restricted only by the resolution of the XUV spectrometer, with chiral XUV light. Our method is based on using a vectorial two-color driver with close central-frequencies with slight symmetry breaking. It integrates the time-gating and polarization-gating techniques to generate a vectorial driver which induces well-controlled bursts of recollisions, occurring along different directions in the polarization plane. The method satisfies the dual requirements of an XUV source which is both broadband and helical. We perform polarization scan and demonstrate that the broadband XUV radiation exhibits rapid modulations in its spectral ellipticity, and fast alternation in its spectral helicities. The phase of modulations could be controlled by introducing a slight symmetry breaking. This allows us to control and modulate the XUV polarization state, which should enable the detection of chiroptical signals with enhanced sensitivity.

physics.optics↗

arXiv2024

Controlling the Bandwidth of High Harmonic Emission Peaks with the Spectral Polarization of the Driver

We demonstrate a High-Harmonic-Generation scheme which offers control over the bandwidth of the spectral peaks. The scheme uses a vectorial two-color driver with close central frequencies, generated by spectrally splitting a linearly-polarized input femtosecond-duration laser pulse and subsequent recombining the two halves after their polarizations are made cross-elliptical and counter-rotating. This results in the generation of new emission channels which coalesce into broad odd-integer HHG peaks, the bandwidth of each being proportional to the frequency difference between the two colors, to the harmonic order and inversely-proportional to the driver fields' ellipticities. Peak-broadening to the extent that a supercontinuum is formed is also demonstrated. This source will find use in HHG applications benefiting from high-flux broadband extreme ultra-violet radiation, such as attosecond transient absorption spectroscopy.

physics.optics↗

arXiv2022

High Harmonic Generation without Tunnel-Ionization

A new High Harmonic Generation (HHG) scheme, which doesn't rely on Tunnel-Ionization as the ionization mechanism but rather on Single-Photon Ionization, is theoretically proposed and numerically demonstrated. The scheme uses two driver fields: an extreme-ultraviolet driver which induces the ionization, and a circularly-polarized, co-rotating, two-color infrared driver carried at a fundamental frequency and its second harmonic which induces the recollision. Using Classical and time-dependent Schrödinger equation simulations of a model Argon atom, we show that in this scheme ionization is essentially decoupled from recollision. Releasing the process from being Tunneling-dependent reduces its degree of nonlinearity, which offers new capabilities in attosecond science, such as generation of High Harmonics from highly-charged ions, or from specific deep core electronic levels. It is shown that the emitted high harmonics involve the absorption of photons of one color of the infrared driver, and the emission of photons of the second color. This calls for future examination of the possible correlations between the emitted high harmonics.

physics.atom-ph↗