Article
Optics
Dunjian Wang, Jie Luo, Zhouzhou Sun, Yun Lai
Summary: This work demonstrates a unique approach to realize geometry-invariant multi-channel coherent perfect absorbers by embedding ultrathin conductive films in zero-index media, revealing a mechanism to change material responses between zero-index media and coherent perfect absorbers.
Article
Physics, Applied
Come Olivier, Anis Maddi, Gaelle Poignand, Guillaume Penelet
Summary: This paper describes some exotic scattering properties of a one-dimensional network of thermoacoustic cells and characterizes them experimentally. The research results demonstrate that systems with exotic acoustic scattering properties can be designed by utilizing the interaction between temperature gradients and acoustic waves.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Nanoscience & Nanotechnology
Jeng Yi Lee, Pai-Yen Chen
Summary: With consideration of PT symmetry, Lorentz reciprocity theorem, and real Bloch phase, this work proposes a generalized parametric space to comprehensively illustrate the PT phase transition, Bloch phase, and necessary conditions of exotic wave scattering in finite periodic PT photonic structures. Parametrization is used to derive analytical formulas for the complex relative permittivities of the unit cells composed of subwavelength gain-loss heterostructures, providing a guideline for manipulating different PT scattering events. Several one-dimensional PT photonic systems are studied to achieve exotic wave scattering enabled by PT symmetry. This work offers a theoretical underpinning for studying extraordinary wave phenomena in PT-symmetric photonics and opens avenues for manipulation of light.
Article
Physics, Multidisciplinary
Zhi-Wei Jia, Li Li, Yi-Yan Guo, An-Bang Wang, Hong Han, Jin-Chuan Zhang, Pu Li, Shen-Qiang Zhai, Feng-Qi Liu
Summary: In this study, the dynamic states of mutual-coupled mid-infrared quantum cascade lasers were investigated numerically in the parameter space of injection strength and detuning frequency. Various types of period-one states and dynamic behaviors such as square-wave, quasi-period, pulse-burst, and chaotic oscillations were observed.
Article
Optics
A. Verbitskiy, A. Yulin, A. G. Balanov
Summary: We investigated the response of an optical system with Kerr nonlinearity to a periodic train of coherent pulses. The intensity of the excited field in the system was found to depend resonantly on the pulses' period. Numerical and analytical results demonstrated that the system's response is stronger when the pulse period is commensurate with the period of Bloch oscillations. Moreover, sufficiently large pulses can induce instabilities leading to chaotic Bloch oscillations of the wave-function envelope in both time and space. These instabilities are associated with period-doubling bifurcations, with a cascade of such bifurcations triggering the chaotic behavior.
Article
Physics, Multidisciplinary
Caixing Fu, Min Yang, Zhi Hong Hang
Summary: We present a methodology for achieving symmetrical broadband coherent perfect absorption in an air tube, demonstrating its reliability and feasibility through experiments. Analytical calculations reveal that the causality principle imposes a minimal volume requirement based on absorption capability, making it possible to approach but not achieve idealistic coherent symmetrical perfect absorption within a finite volume. As a demonstration, we design and realize a side-loaded near-perfect absorber that operates at a broad bandwidth of 300 to 5000 Hz without blocking the tube. The absorber size is also super-subwavelength, only 1% of the longest working wavelength. Experimental measurements in both frequency and time domains confirm its broadband and tunable near-perfect coherent absorption properties. Additionally, we manipulate sound waves in a ventilated tube using sound pulses.
PHYSICAL REVIEW RESEARCH
(2023)
Article
Mathematics, Interdisciplinary Applications
Hongyan Jia, Zhonggao Chen, Wenxin Shi, Guoyuan Qi
Summary: The paper introduces a new generalized Hamiltonian chaotic system with transient quasi-periodic flows and intermittent chaos, which exhibits conservative characteristics and various coexisting flows. The Hamiltonian energy of the system meets certain conditions and is only related to initial points.
INTERNATIONAL JOURNAL OF BIFURCATION AND CHAOS
(2022)
Article
Optics
J. Rivera-Dean, Th Lamprou, E. Pisanty, P. Stammer, A. F. Ordonez, A. S. Maxwell, M. F. Ciappina, M. Lewenstein, P. Tzallas
Summary: Recent research has shown that strong laser-matter interactions can be used to generate nonclassical states of light. By using high-harmonic generation and above-threshold ionization, researchers have demonstrated the potential of strong laser fields for generating controllable high-photon-number coherent-state superpositions, achieving the highest reported optical cat state with nine photons.
Article
Engineering, Electrical & Electronic
Jingya Ruan, Sze-Chun Chan
Summary: Optical injection into a semiconductor laser can generate chaos for fast random bit generation. Coherent detection using two dimensions of intensity and phase enhances the baseband signals, resulting in higher bit rates. This technique has been experimentally proven to meet randomness tests and has the potential for high-speed data transmission.
IEEE JOURNAL OF QUANTUM ELECTRONICS
(2023)
Article
Physics, Multidisciplinary
Aleksandra Gajic, Jelena Radovanovic, Nikola Vukovic, Vitomir Milanovic, Dmitri L. Boiko
Summary: This study investigates the influence of a magnetic field on multimode self-pulsations, revealing that an external magnetic field can slow down decoherence and diffusion rates in quantum cascade lasers, reducing the pump current required to achieve self-pulsations. As the magnetic field strength increases, the self-pulsation frequency and spectrum width remain practically unchanged.
Proceedings Paper
Instruments & Instrumentation
Alexander Pouliot, Gehrig Carlse, Thomas Vacheresse, Anantharaman Kumarakrishnan
Summary: This paper demonstrates a technique for accurately measuring the diffusion coefficients for alkali vapor in an inert buffer gas. The authors establish a spatially periodic density grating and observe the decaying coherent emission from the grating to obtain the most accurate determination of the Rb-N-2 diffusion coefficient.
OPTICAL AND QUANTUM SENSING AND PRECISION METROLOGY II
(2022)
Article
Optics
Stefano Longhi
Summary: In this study, a novel design for laser arrays is proposed, which achieves stable emission and strong suppression of supermode competition by tuning the complex frequencies of edge resonators. The design offers strong robustness and is applicable to systems with structural imperfections and dynamical instabilities.
Article
Physics, Multidisciplinary
Stefano Longhi
Summary: A unique feature of non-Hermitian systems is the skin effect, which refers to the edge localization of a considerable number of bulk-band eigenstates in a lattice with specific boundaries. Unlike Bloch waves in Hermitian systems, the skin modes in non-Hermitian systems are normalizable eigenstates originating from the intrinsic non-Hermitian point-gap topology of the Bloch band energy spectra. Additionally, these skin modes exhibit a fascinating property known as self-healing, where they can reconstruct their shape after being scattered by a space-time potential.
PHYSICAL REVIEW LETTERS
(2022)
Article
Multidisciplinary Sciences
Stefano Longhi
Summary: Non-Hermitian quasi-edge modes are exponentially localized states in systems with non-Hermitian skin effect. By tailoring on-site potentials at the edges of a finite lattice, selective and tunable excitation of topological quasi-edge states can be achieved.
PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2022)
Article
Chemistry, Analytical
Alessandro Tuniz, Alex Y. Song, Giuseppe Della Valle, C. Martijn de Sterke
Summary: This study proposes a simplified coupled mode theory approach for evaluating and optimizing the sensing properties of plasmonic waveguide refractive index sensors. By calculating propagation constants instead of mode overlap integrals, this method provides a rapid and convenient framework for designing dielectric-plasmonic sensor prototypes.
Article
Physics, Multidisciplinary
Stefano Longhi
Summary: Anderson localization predicts that wave spreading in disordered lattices can stop completely, providing a universal mechanism for dynamical localization. In the one-dimensional Hermitian Anderson model, there is a correspondence between dynamical and spectral localization. However, this correspondence may be broken in disordered dissipative lattices.
ANNALEN DER PHYSIK
(2023)
Article
Optics
Stefano Longhi
Summary: Anderson localization is a common phenomenon in wavy systems that have strong static and uncorrelated disorder. However, in one-dimensional lattices with off diagonal disorder, Anderson localization can persist for arbitrary time-dependent drivings that do not break a hidden conservation law originating from the chiral symmetry, leading to the dubbed localization without eigenstates.
Article
Materials Science, Multidisciplinary
Silvia Rotta Loria, Beatrice Roberta Bricchi, Andrea Schirato, Luca Mascaretti, Cristina Mancarella, Alberto Naldoni, Andrea Li Bassi, Giuseppe Della Valle, Margherita Zavelani-Rossi
Summary: Ultrafast plasmonics is gaining attention for exploring new plasmonic materials that overcome the limitations of noble metals. Titanium nitride (TiN) is particularly notable due to its refractory properties and extremely fast electron-lattice cooling time (<100 fs) compared to gold (approximately 1 ps). However, the exact explanation for the ultrafast and giant optical response of TiN-based materials under femtosecond laser excitation is still unknown.
ADVANCED OPTICAL MATERIALS
(2023)
Article
Multidisciplinary Sciences
Shulin Wang, Chengzhi Qin, Lange Zhao, Han Ye, Stefano Longhi, Peixiang Lu, Bing Wang
Summary: This paper introduces a new class of reconfigurable linear optics circuits harnessing Floquet LZT, which has versatile applications in temporal beam control, signal processing, quantum simulations, and information processing.
Article
Physics, Multidisciplinary
Ermanno Pinotti, Stefano Longhi
Summary: A quantum particle constrained between two high potential barriers can exhibit quasi-bound states. The decay of the wave function in such states can be accelerated by additional lateral barriers, contrary to intuition. This acceleration is due to resonant tunneling effects and results in deviations from exponential decay.
Article
Optics
Stefano Longhi
Summary: This article discusses the differences in particle behavior in unbounded potentials between classical mechanics and wave mechanics, and introduces a new class of unbounded potentials where wave delocalization is observed. Experimental verification of this phenomenon is done through light dynamics in synthetic photonic lattices.
Article
Nanoscience & Nanotechnology
Morteza Afshar, Andrea Schirato, Luca Mascaretti, S. M. Hossein Hejazi, Mahdi Shahrezaei, Giuseppe Della Valle, Paolo Fornasiero, Stepan Kment, Alessandro Alabastri, Alberto Naldoni
Summary: We report the development of high aspect ratio, nanoporous titanium oxynitride nanotubes with quasi-unitary broadband absorption. The efficient light-heat conversion is explained in terms of localized field distribution and heat dissipation within the nanopores. A numerical model is developed to describe the space-dependent electric permittivity distribution, which can explain the large broadband absorption observed. The potential application of these nanotubes as solar absorbers is explored through photothermal experiments.
Article
Nanoscience & Nanotechnology
Luca Carletti, Cormac Mcdonnell, Unai Arregui Leon, Davide Rocco, Marco Finazzi, Andrea Toma, Tal Ellenbogen, Giuseppe Della Valle, Michele Celebrano, Costantino De Angelis
Summary: We investigated the nonlinear THz generation from lithium niobate films and crystals of different thicknesses. The results show a significant enhancement in the nonlinear response compared to optical frequencies. This enhancement is attributed to specific optical phonon modes and is most pronounced in films thinner than 2 μm. These findings are important for the development of broadband THz emitters and detectors as well as the control of optical-to-THz conversion in nanophotonic structures.
Article
Materials Science, Multidisciplinary
Andrea Schirato, Mychel G. Silva, Danielle C. Teles-Ferreira, Cristian Manzoni, Ana Maria de Paula, Giulio Cerullo, Giuseppe Della Valle, Marcel Di Vece
Summary: The photoexcitation of plasmonic nanostructures with ultrashort laser pulses allows for understanding the ultrafast nonlinear optical response and fundamental processes triggered by light absorption. The effects of photoexcitation on plasmonic nanostructures are studied using broadband transient absorption spectroscopy and semiclassical nonlinear simulations. The results provide a comprehensive understanding of the thermo-modulational nonlinearities of plasmonic nanostructures exhibiting resonances close to the interband transition threshold.
ADVANCED PHOTONICS RESEARCH
(2023)
Article
Materials Science, Multidisciplinary
Stefano Longhi
Summary: We investigate the energy spectral phase transitions in one-dimensional superlattices with M sites and an imaginary gauge field. It is found that in models with nearly flat bands, a smooth phase transition from real to complex energies can be observed as the imaginary gauge field increases, becoming sharper with increasing M. This phase transition can be observed even in superlattices without disorder. These predicted phenomena can be realized in non-Hermitian photonic quantum walks using existing experimental apparatus.
Article
Materials Science, Multidisciplinary
Stefano Longhi, Liang Feng
Summary: In many classical and quantum systems with a non-Hermitian Hamiltonian, a spectral phase transition can occur when a non-Hermitian parameter exceeds a critical value, leading to a transition from a completely real-energy spectrum to a complex spectrum. The phenomenon is particularly evident in systems with parity-time (PT) symmetry, where the energy spectrum is real in the unbroken PT phase and becomes complex in the broken PT phase. However, when the system is cyclically and slowly cycled, the phase transition can become imperfect due to the complex Berry phase associated with the adiabatic evolution of the system.
