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Optics (physics.optics)

Fri, 26 May 2023

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1.Large field-of-view and multi-color imaging with GaP quadratic metalenses

Authors:Anton V. Baranikov, Egor Khaidarov, Emmanuel Lassalle, Damien Eschimese, Joel Yeo, N. Duane Loh, Ramon Paniagua-Dominguez, Arseniy I. Kuznetsov

Abstract: Metalenses, in order to compete with conventional bulk optics in commercial imaging systems, often require large field of view (FOV) and broadband operation simultaneously. However, strong chromatic and coma aberrations present in common metalens designs have so far limited their widespread use. Stacking of metalenses as one of the possible solutions increases the overall complexity of the optical system and hinders the main benefit of reduced thickness and light weight. To tackle both issues, here we propose a single-layer imaging system utilizing a recently developed class of metalenses providing large field of view. Using it, we demonstrate full-color imaging with a FOV of 100 degrees. This approach, empowered by computational imaging techniques, produce high quality images, both in terms of color reproduction and sharpness. Suitable for real-time unpolarized light operation with the standard color filters present in prevalent camera systems, our results might enable a pathway for consumer electronics applications of this emerging technology.

2.Photon diffusion in space and time in a second-order nonlinear disordered medium

Authors:Rabisankar Samanta, Romain Pierrat, Rémi Carminati, Sushil Mujumdar

Abstract: We report experimental and theoretical investigations on photon diffusion in a second-order nonlinear disordered medium under conditions of strong nonlinearity. Experimentally, photons at the fundamental wavelength ($\lambda=1064$ nm) are launched into the structure in the form of a cylindrical pellet, and the second-harmonic ($\lambda=532$ nm) photons are temporally analyzed in transmission. For comparison, separate experiments are carried out with incident green light at $\lambda=532$ nm. We observe that the second harmonic light peaks earlier compared to the incident green photons. Next, the sideways spatial scattering of the fundamental as well as second-harmonic photons is recorded. The spatial diffusion profiles of second-harmonic photons are seen to peak deeper inside the medium in comparison to both the fundamental and incident green photons. In order to give more physical insights into the experimental results, a theoretical model is derived from first principles. It is based on the coupling of transport equations. Solved numerically using a Monte Carlo algorithm and experimentally estimated transport parameters at both wavelengths, it gives excellent quantitative agreement with the experiments for both fundamental and second-harmonic light.

3.Motion of charged particles in bright squeezed vacuum

Authors:Matan Even Tzur, Oren Cohen

Abstract: The motion of laser-driven electrons quivers with an average energy termed pondermotive energy. We explore electron dynamics driven by bright squeezed vacuum (BSV), finding that BSV induces width oscillations, akin to electron quivering in laser light, with an equivalent ponderomotive energy. In the case of bound electrons, width oscillations may lead to tunnel ionization with noisy sub-cycle structure. Our results are foundational for strong-field and free-electron quantum optics, as they shed light on tunnel ionization, high harmonic generation, and nonlinear Compton scattering in BSV.

4.Multi-wavelength Q-plate Arithmetic in an All-Liquid-Crystal Modular Setup

Authors:Jacek Piłka, Michał Kwaśny, Magdalena Czerniewicz, Mirosław Karpierz, Urszula Laudyn

Abstract: Vortex beams are a type of structured light characterized by phase rotation around the propagation axis, resulting in orbital angular momentum. Their properties make them useful in various applications such as high-resolution microscopy, optical tweezing, and telecommunications. This has led to a comprehensive development of methods for their generation, ranging from using single-purpose glass elements to utilizing computer-generated holograms using spatial light modulators. One of the most commonly used elements for vortex transformation is a vortex half-wave retarder called a q-plate, which can transform a Gaussian beam into a scalar vortex or vector beam depending on the input polarization. Although the commercially available ones are limited in the range of possible output topological charges, they can be stacked to perform arithmetic operations to expand them. However, changing the output or working wavelength requires rearranging the elements. We present an improvement to this method that solves these problems by introducing Q-modules, easy-to-fabricate, electrically tunable liquid crystal devices that combine the features of q-plates and half-wave plates and can be used as building blocks in modular assemblies. Electrical tuning makes it possible to change the working wavelength as well as the topological output charge or polarization order without the need to interact mechanically with the setup.

5.On-target delivery of intense ultrafast laser pulses through hollow-core anti-resonant fibers

Authors:Athanasios Lekosiotis, Federico Belli, Christian Brahms, Mohammed Sabbah, Hesham Sakr, Ian A. Davidson, Francesco Poletti, John C. Travers

Abstract: We report the flexible on-target delivery of 800 nm wavelength, 5 GW peak power, 40 fs duration laser pulses through an evacuated and tightly coiled 10 m long hollow-core nested anti-resonant fiber by positively chirping the input pulses to compensate for the anomalous dispersion of the fiber. High output pulse quality and a guided peak intensity of 3 PW/cm2 were achieved by suppressing plasma effects in the residual gas by pre-pumping the fiber after evacuation. This appears to cause a long-term removal of molecules from the fiber core. Identifying the fluence at the fiber core-wall interface as the damage origin, we scaled the coupled energy to 1.8 mJ using a short piece of larger-core fiber to obtain 20 GW at the fiber output. This scheme can pave the way towards the integration of anti-resonant fibers in mJ-level nonlinear optical experiments and laser-source development.

6.Multipolar Pseudochirality Induced Optical Torque

Authors:Karim Achouri, Mintae Chung, Andrei Kiselev, Olivier J. F. Martin

Abstract: It has been observed that achiral nano-particles, such as flat helices, may be subjected to an optical torque even when illuminated by normally incident linearly polarized light. However, the origin of this fascinating phenomenon has so far remained mostly unexplained. We therefore propose an exhaustive discussion that provides a clear and rigorous explanation for the existence of such a torque. Using multipolar theory, and taking into account nonlocal interactions, we find that this torque stems from multipolar pseudochiral responses that generate both spin and orbital angular momenta. We also show that the nature of these peculiar responses makes them particularly dependent on the asymmetry of the particles. By elucidating the origin of this type of torque, this work may prove instrumental for the design of high-performance nano-rotors.

7.Calibration method for complex permittivity measurements using s-SNOM combining multiple tapping harmonics

Authors:Dario Siebenkotten, Bernd Kaestner, Arne Hoehl, Shuhei Amakawa

Abstract: Scattering-type scanning near-field optical microscopy (s-SNOM) enables sub-diffraction spectroscopy, featuring high sensitivity to small spatial permittivity variations of the sample surface. However, due to the near-field probe-sample interaction, the quantitative extraction of the complex permittivity leads to a computationally demanding inverse problem, requiring further approximation of the system to an invertible model. Black-box calibration methods, similar to those applied to microwave vector network analysers, allow the extraction of the permittivity without detailed electromagnetic modelling of the probe-sample interaction. These methods, however, are typically designed for stationary setups. In contrast, the distance between the sample and the probe tip of the s-SNOM is slowly modulated, which is required for the lock-in detection used to extract the near-field interaction buried in the far-field background. Here we propose an improved calibration method that explicitly takes probe tapping into account. We validate our method for an s-SNOM operating in a mid-infrared spectral range by applying it to measurements of silicon microstructures of different but well characterised doping.

8.Electrodynamics of an oscillating particle without cheating PART I : In vacuo. PART II : Near a dispersive bulk

Authors:Mauricio Garcia-Vergara, Guillaume Demésy, André Nicolet, Frédéric Zolla

Abstract: In this paper, the electromagnetic radiation from an oscillating particle placed in the vicinity of an object of size comparable to the wavelength is studied. Although this problem may seem academic at first sight, the details of the calculations are presented throughout without any detail left under the carpet. A polyharmonic decomposition of the radiation sources allows the diffraction problem to be fully characterised while satisfying energy conservation. Finally, the source expressions obtained are suitable for use in a numerical code. A 3D illustration using finite elements is provided.

9.Spectrally-encoded non-scanning imaging through a fiber

Authors:Ningzhi Xie, Quentin A. A. Tanguy, Johannes E. Fröch, Karl F. Böhringer, Arka Majumdar

Abstract: With the advent of neuroimaging and microsurgery, there is a rising need for capturing images through an optical fiber. We present an approach of imaging through a single fiber without mechanical scanning by implementing spatial-spectral encoding. The spectral encoding is achieved through a microfabricated spectral filter array, where light from different spatial pixels is coded with a highly orthogonal spectrum. The image is then computationally recovered via pseudo inverse of the encoding process. We demonstrate imaging of a $4 \times 4$ binary object at the proximity of the spectral filter array using $560-625nm$ wavelength band. The recovered image maintains an error rate of $<11\%$ when measured using a spectrometer with a spectral resolution of $1.5nm$. The image remains unchanged with fiber bending or moving. Thus our approach shows a more robust way to image through a single optical fiber, with potential applications in compact endoscopes and angioscopes.

10.Inspecting the use of SLMs for the control of photonic quantum states

Authors:Sebastián Bordakevich, Dudbil Pabón, Lorena Rebón, Silvia Ledesma

Abstract: Spatial light modulators (SLMs) are widely used to coherently control quantum states of light. When carrying out these experiments, some assumptions are made. For instance, it is supposed that the position-momentum correlations between twin photon pairs are not affected by the use of a liquid crystal display (LCD) as a SLM. Furthermore, it is assumed that the characterization of such devices performed with an intense laser source, is still valid in the single photon regime. In this work, we show that such assumptions are acceptable, within the experimental uncertainties, for a liquid crystal on silicon (LCoS) display. This is especially important when considering the use of this kind of displays for the coherent control of quantum states based on twin photon sources.

11.Generation and control of non-local quantum equivalent extreme ultraviolet photons

Authors:Geoffrey R. Harrison, Tobias Saule, R. Esteban Goetz, George N. Gibson, Anh-Thu Le, Carlos A. Trallero-Herrero

Abstract: We present a high precision, self-referencing, common path XUV interferometer setup to produce pairs of spatially separated and independently controllable XUV pulses that are locked in phase and time. The spatial separation is created by introducing two equal but opposite wavefront tilts or using superpositions of orbital angular momentum. In our approach, we can independently control the relative phase/delay of the two optical beams with a resolution of 52 zs (zs = zeptoseconds). In order to explore the level of entanglement between the non-local photons, we compare three different beam modes: Bessel-like, and Gaussian with or without added orbital angular momentum. By reconstructing interference patterns one or two photons at a time we conclude that the beams are not entangled, yet each photon in the attosecond pulse train contains information about the entire spectrum. Our technique generates non-local, quantum equivalent XUV photons with a temporal jitter of 3 zs, just below the Compton unit of time of 8 zs. We argue that this new level of temporal precision will open the door for new dynamical QED tests. We also discuss the potential impact on other areas, such as imaging, measurements of non-locality, and molecular quantum tomography.