arXiv subjects

Arseniy Kuznetsov

Publications and source records attributed to Arseniy Kuznetsov.

10 recordsLinked to original sources

arXiv2026

Characterization of the MUSE NFM PSF as a function of atmospheric conditions: TipTop calibration

The Multi Unit Spectroscopic Explorer (MUSE) achieves exceptional spatial resolution in narrow-field mode (NFM) thanks to the GALACSI adaptive optics (AO) system. However, limitations in point spread function (PSF) characterization still hinder the full exploitation of its capabilities. In particular, the current exposure time calculator (ETC) lacks an accurate PSF model, preventing users from reliably predicting the signal-to-noise ratio of NFM observations during proposal preparation. To address this limitation, we analyzed a large set of archival standard-star observations to quantify how NFM PSF properties vary with observing conditions, including airmass, seeing, coherence time, wind speed, and wavelength. We then used this reference dataset to calibrate TipTop, a fast AO PSF simulation tool that will be integrated into the next release of the MUSE NFM ETC. Our results demonstrate that calibration against real on-sky data is essential for accurate PSF modeling. In particular, we find that reproducing realistic PSFs requires both an additional static aberration term and an airmass-dependent tip-tilt jitter component. The calibration performs well at wavelengths longer than 7000 A, while additional corrections are still required at shorter wavelengths, likely due to unmodeled chromatic aberrations. Once implemented in the ETC, this tool will provide condition-dependent NFM PSF predictions and more reliable signal-to-noise estimates.

astro-ph.IM↗

arXiv2026

Data-calibrated point spread function prediction: General description of the method and demonstration on MUSE-NFM

Precise knowledge of the point spread function (PSF) underpins many data analysis steps in astronomy, from photometry and astrometry to source de-blending and deconvolution. In adaptive optics (AO) observations, however, the PSF is highly variable with wavelength, field position, and observing conditions, making it difficult to model. Traditional PSF reconstruction (PSF-R) requires full AO telemetry and complex infrastructures, limiting its routine use, especially for tomographic systems. We present a practical framework for fast, accurate, and data-calibrated PSF modeling that captures the spatial and spectral variability of AO-corrected PSFs without relying on complete AO telemetry. Our approach builds on a Fourier-based PSF model inspired by astro-TIPTOP. As inputs, our model uses only a compact set of physically meaningful parameters retrievable from the ESO archive. A lightweight neural network corrects these inputs to achieve the best match with real data. It is trained end to end with the PSF model, allowing it to learn any miscalibrations directly from on-sky data. The framework achieves high accuracy on on-sky data. On a test set of MUSE-NFM standard stars, it yields median errors of 13.5% in the Strehl ratio and 10.9% in the core full width at half maximum (FWHM). In crowded MUSE-NFM observations of $\omega$ Centauri, the method predicts dozens of off-axis, wavelength-dependent PSFs with a Strehl error of <5% and a FWHM error of 4.6%, enabling source separation without per-star PSF extraction. Our compact, physics-informed, and data-calibrated model delivers accurate, polychromatic, and field-varying PSFs without relying on full AO telemetry. While demonstrated on MUSE-NFM, the method is still transferable to other AO-assisted instruments.

astro-ph.IM↗

arXiv2024

Wavelength Control of Perovskite Metasurface Lasing via Electrical Microheaters

Perovskites have recently brought significant advances to active nanophotonics, offering a unique combination of gain and phase-change properties for tunable light-emitting devices. However, current wavelength-tunable devices often rely on tuning mechanisms or device architectures that lead to slow modulation or bulky setups. In this study, we overcome limitations on speed and size by demonstrating a compact tunable microlaser embedding electrical microheaters beneath a perovskite metasurface. This architecture allows to efficiently deliver heat and rapidly modulate the phase transition. Our device leverages the optical gain and crystallographic phase tuning of the perovskite, and a high-quality factor cavity design based on bound states in the continuum. With it, we demonstrate reversible laser wavelength switching between 763 nm and 783 nm within 13 ms at 2.3 V. This work unlocks the potential of perovskite metasurfaces for electrically tunable light sources and introduces a flexible platform which can be easily extended to the dynamic control of polarization or directionality for optical communication, sensing and spectroscopy.

physics.optics↗

arXiv2024

All-Optical Generation and Detection of Coherent Acoustic Vibrations in Single Gallium Phosphide Nanoantennas Probed Near the Anapole Excitation

Nanostructured high-index dielectrics have shown great promise as low-loss photonic platforms for wavefront control and enhancing optical nonlinearities. However, their potential as optomechanical resonators has remained unexplored. In this work, we investigate the generation and detection of coherent acoustic phonons in individual crystalline gallium phosphide nanodisks on silica in a pump-probe configuration. By pumping the dielectric above its bandgap energy and probing over its transparent region, we observe the radial breathing mode of the disk with an oscillation frequency around 10 GHz. We analyze the performance of nanoantennas of various sizes in the 300-600 nm diameter range at fixed 125 nm height and find that the detection efficiency is maximum near the fundamental anapole state, in agreement with numerical simulations. By comparing with reference gold nanodisk and nanorod plasmonic resonators, we find that the dielectric nanoantennas display a modulation amplitude up to ~5 times larger. We further demonstrate the launching of acoustic waves through the underlaying substrate and the mechanical coupling between two nanostructures placed 3 {\mu}m apart, laying the basis for photonic-phononic signal processing using dielectric nanoantennas.

physics.optics↗

arXiv2024

Striving towards robust phase diversity on-sky: Implementing LIFT for VLT/MUSE-NFM

The recent IRLOS upgrade for VLT/MUSE narrow field mode (NFM) introduced a full-pupil mode to enhance sensitivity and sky coverage. This involved replacing the 2x2 Shack-Hartmann sensor with a single lens for full-aperture photon collection, which also enabled the engagement of the linearized focal-plane technique (LIFT) wavefront sensor instead. However, initial on-sky LIFT experiments have highlighted a complex point spread function (PSF) structure due to strong and polychromatic non-common path aberrations (NCPAs), complicating the accurate retrieval of tip-tilt and focus using LIFT. This study aims to conduct the first on-sky validation of LIFT on VLT/UT4, outline challenges encountered during the tests, and propose solutions for increasing the robustness of LIFT in on-sky operations. We developed a two-stage approach to focal-plane wavefront sensing, where tip-tilt and focus retrieval done with LIFT is preceded by the NCPA calibration step. The resulting NCPA estimate is subsequently used by LIFT. To perform the calibration, we proposed a method capable of retrieving the information about NCPAs directly from on-sky focal-plane PSFs. We verified the efficacy of this approach in simulated and on-sky tests. Our results demonstrate that adopting the two-stage approach has led to a significant improvement in the accuracy of the defocus estimation performed by LIFT, even under challenging low-flux conditions. The efficacy of LIFT as a slow and truth focus sensor in practical scenarios has been demonstrated. However, integrating NCPA calibration with LIFT is essential to verifying its practical application in the real system. Additionally, the proposed calibration step can serve as an independent and minimally invasive approach to evaluate NCPA on-sky.

astro-ph.IM↗

arXiv2023

TIPTOP: cone effect for single laser adaptive optics systems

TIPTOP is a python library that is able to quickly compute Point Spread Functions (PSF) of any kind of Adaptive Optics systems. This library has multiple objectives: support the exposure time calculators of future VLT and ELT instruments, support adaptive optics systems design activities, be part of PSF reconstruction pipelines and support the selection of the best asterism of natural guide stars for observation preparation. Here we report one of the last improvements of TIPTOP: the introduction of the error given by a single conjugated laser, commonly known as the cone effect. The Cone effect was not introduced before because it is challenging due to the non-stationarity of the phase. Laser guide stars are at a finite distance with respect to the telescope and probe beam accepted by the wavefront sensor has the shape of a cone. Given a single spatial frequency in an atmospheric layer, the cone effect arises from the apparent magnification or stretching of this frequency when it reaches the wavefront sensor. The magnification effect leads to an incorrect estimation of the spatial frequency. Therefore, we estimate the residual power by calculating the difference between two sinusoids with different periods: the nominal one and the magnified one. Replicating this for each spatial frequency we obtain the power spectrum associated with the cone effect. We compare this estimation with the one given by end-to-end simulation and we present how we plan to validate this with on-sky data.

astro-ph.IM↗

arXiv2023

Dual-resonance nanostructures for colour down-conversion of colloidal quantum emitters

Linear colour conversion is a process where an emitter absorbs a photon and then emits another photon with either higher or lower energy, corresponding to up- or down conversion, respectively. In this regard, the presence of a volumetric cavity plays a crucial role in enhancing absorption and photoluminescence (PL), as it allows for large volumes of interaction between the exciting photons and the emissive materials, maximising the colour conversion efficiency. Here, we present a dual resonance nanostructure made of a titanium dioxide (TiO2) subwavelength grating to enhance the colour down-conversion efficiency of green light at ~530 nm emitted by gradient alloyed CdxZn1-xSeyS1-y colloidal quantum dots (QDs) when excited with a blue light at ~460 nm. A large mode volume can be created within the QD layer by the hybridisation of the grating resonances and waveguide modes. This allows increasing mode overlap between the resonances and the QDs, resulting in large absorption and tailored emission enhancements. Particularly, we achieved polarized light emission with maximum photoluminescence enhancement of ~140 times at a specific angular direction, and a total enhancement of ~34 times within 0.55 numerical aperture (NA) of the collecting objective. The enhancement encompasses absorption enhancement, Purcell enhancement and directionality enhancement (i.e., outcoupling). We achieved total absorption of 35% for green QDs with a remarkably thin colour conversion layer of ~ 400 nm (inclusive of the TiO2 layer). This work provides a guideline for designing large-volume cavities for practical application in absorption/fluorescence enhancement, such as down colour conversion in microLED displays, detectors or photovoltaics.

physics.optics↗

arXiv2023

Near-Unity Emitting, Widely Tailorable and Stable Exciton Concentrators Built from Doubly Gradient 2D Semiconductor Nanoplatelets

The strength of electrostatic interactions (EI) between electrons and holes within semiconductor nanocrystals profoundly impact the performance of their optoelectronic systems, and different optoelectronic devices demand distinct EI strength of the active medium. However, achieving a broad range, fine-tuning of the EI strength for specific optoelectronic applications is a daunting challenge, especially in quasi 2-dimensional core-shell semiconductor nanoplatelets (NPLs), as the epitaxial growth of the inorganic shell along the direction of the thickness that solely contributes to the quantum confined effect significantly undermines the strength of the EI. Herein we propose and demonstrate a novel doubly-gradient (DG) core-shell architecture of semiconductor NPLs for on-demand tailoring of the EI strength by controlling the localized exciton concentration via in-plane architectural modulation, demonstrated by a wide tuning of radiative recombination rate and exciton binding energy. Moreover, these exciton-concentration-engineered DG NPLs also exhibit a near-unity quantum yield, remarkable thermal and photo stability, as well as considerably suppressed self-absorption. As proof-of-concept demonstrations, highly efficient color converters and high-performance light-emitting diodes (external quantum efficiency: 16.9%, maximum luminance: 43,000 cd/m2) have been achieved based on the DG NPLs. This work thus opens up new avenues for developing high-performance colloidal optoelectronic device applications.

physics.optics↗

arXiv2023

The ESO's Extremely Large Telescope Working Groups

Since 2005 ESO has been working with its community and industry to develop an extremely large optical/infrared telescope. ESO's Extremely Large Telescope, or ELT for short, is a revolutionary ground-based telescope that will have a 39-metre main mirror and will be the largest visible and infrared light telescope in the world. To address specific topics that are needed for the science operations and calibrations of the telescope, thirteen specific working groups were created to coordinate the effort between ESO, the instrument consortia, and the wider community. We describe here the goals of these working groups as well as their achievements so far.

astro-ph.IM↗

arXiv2017

Nanosatellite aerobrake maneuvering device

In this paper, we present the project of the heliogyro solar sail unit for deployment of CubeSat constellation and satellite deorbiting. The ballistic calculations show that constellation deployment period can vary from 0.18 years for 450km initial orbit and 2 CubeSats up to 1.4 years for 650km initial orbit and 8 CubeSats. We also describe the structural and electrical design of the unit and consider aspects of its integration into a standard CubeSat frame.

astro-ph.IM↗