Nonlinear Optical Research Articles

Generation of patterns and higher harmonics in 1D quantum droplets in tilted and driven quasi-periodic confinements

The generation of patterns by breaking the spatial symmetry in external confinement is a captivating area of physics. The emergence of patterns is a fundamental inquiry spanning various disciplines such as nonlinear optics, condensed matter physics, and fluid dynamics. The article investigates the generation of a variety of patterns in a one-dimensional binary mixture of Bose–Einstein condensate forming quantum droplets. By solving the extended Gross–Pitaevskii equation in the presence of tilted and driven engineered bi-chromatic optical lattices (BOL), the out-of-equilibrium dynamics of droplets under strong dc and ac fields are illustrated. Under the influence of a dc field, a stripe-like pattern emerges in the temporal domain, while the scenario with ac fields demonstrates temporal periodic and bi-periodic oscillations of density waves. The width and period of formed patterns are directly correlated with the strength of ac and dc fields. Moreover, temporal modulation of the BOL potential depth yields various harmonics in the oscillations of the condensate density pattern. Through Fast Fourier Transform (FFT) analysis, it is confirmed that these harmonics encompass multiple and combinational frequencies, suggesting potential applications in generating desired frequency combs within quantum droplets. We have also carried out a thorough numerical stability check of the obtained solutions and found them sufficiently stable.

Driven-dissipative phases and dynamics in non-Markovian nonlinear photonics

Interactions between photons (nonlinearities) enable a powerful form of control over the state of light. This control has enabled technologies such as light sources at new wavelengths, ultra-short optical pulses, frequency-comb metrology systems, even quantum light sources. Common to a wide variety of nonlinear optical technologies is an equilibrium between an energy source, such as an external laser, and dissipation, such as radiation loss or absorption. In the vast majority of these systems, the coupling between the system and the outside world (which leads to loss) is well described as “Markovian,” meaning that the outside world has no memory of its past state. In this work, we introduce a class of driven-dissipative systems in which a nonlinear cavity experiences non-Markovian coupling to the outside world. In the classical regime, we show that these non-Markovian cavities can have extremely low thresholds for nonlinear effects, as well as self-pulsing instabilities at THz rates, and rich phase diagrams with alternating regions of stability and instability. In the quantum regime, we show how these systems, when implemented on state-of-the-art platforms, can enable generation of strongly squeezed cavity states with intensity fluctuations that can be more than 15 dB below the classical limit, in contrast to the Markovian driven-dissipative cavity, in which the limit is 3 dB. In the regime of few-photon nonlinearity, such non-Markovian cavities can enable a deterministic protocol to generate Fock states of high order, which are long-desired, but still elusive at optical frequencies. We expect that exploiting non-Markovian couplings in nonlinear optics should in the future lead to even richer possibilities than those discussed here for both classical and quantum light manipulations.

Spiro-Buckybowls: Synthesis and Selective Transformations Toward Chiral and Nonlinear Optical Polycycles.

Integration of spirocycles with buckybowls is a promising strategy to construct three-dimensional (3D) curved π-systems and to endow distinctive physicochemical features arising from buckybowls. Herein, a series of carbon-bridged spiro-type heterosumanenes (spiro-HSEs) were synthesized by combining 9,9'-spirobifluorene and dichalcogenasumanenes (DCSs). It is found that spiro-conjugation plays an important role in the geometric and electronic structures of spiro-HSEs. The bowl depth of DCSs moiety becomes larger in the spiro-HSEs. Owing to the Jahn-Teller (J-T) effect, two DCSs segments of spiro-HSEs have different bowl depths accompanied with the unequal distribution of charge in radical cation state. Taking advantage of the typical reactions of DCSs, selective transformations of spiro-HSEs have been adopted in accordance to the nature of chalcogen atoms (S, Se, Te) to bestow the value-added functionalities. The emissive property is enhanced by converting the thiophene rings of S-doped spiro-HSE into thiophene S,S-dioxides. A chiroptical polycycle could be produced by ring-opening of the edge benzene of Se-doped spiro-HSE. The covalent adduct of Te-doped spiro-HSE with Br2 forms non-centrosymmetric halogen-bonded networks, resulting in the high performance second-order nonlinear optics (NLO).

Spiro‐Buckybowls: Synthesis and Selective Transformations Toward Chiral and Nonlinear Optical Polycycles

AbstractIntegration of spirocycles with buckybowls is a promising strategy to construct three‐dimensional (3D) curved π‐systems and to endow distinctive physicochemical features arising from buckybowls. Herein, a series of carbon‐bridged spiro‐type heterosumanenes (spiro‐HSEs) were synthesized by combining 9,9′‐spirobifluorene and dichalcogenasumanenes (DCSs). It is found that spiro‐conjugation plays an important role in the geometric and electronic structures of spiro‐HSEs. The bowl depth of DCSs moiety becomes larger in the spiro‐HSEs. Owing to the Jahn‐Teller (J‐T) effect, two DCSs segments of spiro‐HSEs have different bowl depths accompanied with the unequal distribution of charge in radical cation state. Taking advantage of the typical reactions of DCSs, selective transformations of spiro‐HSEs have been adopted in accordance to the nature of chalcogen atoms (S, Se, Te) to bestow the value‐added functionalities. The emissive property is enhanced by converting the thiophene rings of S‐doped spiro‐HSE into thiophene S,S‐dioxides. A chiroptical polycycle could be produced by ring‐opening of the edge benzene of Se‐doped spiro‐HSE. The covalent adduct of Te‐doped spiro‐HSE with Br2 forms non‐centrosymmetric halogen‐bonded networks, resulting in the high performance second‐order nonlinear optics (NLO).

The influence of spin-orbit coupling on the electronic structure and optical properties of α-BiB3O6 crystals: a first-principles investigation

The α-BiB3O6 (BIBO) crystal is highly regarded in the field of nonlinear optical (NLO) due to its excellent ultraviolet (UV) NLO properties, including a short ultraviolet cutoff edge (270 nm), appropriate birefringence (Δn = 0.175@546 nm), and strong second harmonic generation (deff = 3.20 pm V−1). In this study, the first-principles computational software PWmat was employed to conduct theoretical calculations on BIBO crystals, including the non-negligible spin-orbit coupling (SOC) effects induced by the presence of the heavy element bismuth (Bi). The results show that after the inclusion of the SOC, the calculated birefringence (0.173@546 nm) and effective second harmonic generation (SHG) coefficient (deff = 3.16 pm V−1) are in good agreement with experimental data. Furthermore, comparative analysis has demonstrated that the changes in the band structure induced by the SOC effect are significant factors influencing the optical properties of the material.

The poisson property of extreme events in optics

Statistics of extreme events in optics, defined as above-threshold counts of an optical signal, is shown to converge, in the large-sample-size limit, to a generalized Poisson distribution whose mean is found via the exponent of the respective extreme-value distribution. Specifically, extreme-event readouts from polynomial and exponential optical nonlinearities are shown to converge in their statistics to Poisson distributions whose means are, respectively, exponential and slower-than-exponential functions of the extreme-event-counter threshold. Extreme-event counts of a phase readout, on the other hand, converge to a Poisson process whose mean is a light-tailed function of the threshold. The Poisson-limit property of extreme events in optics suggests a powerful resource for a unified treatment of a vast variety of extreme-event phenomena, ranging from optical rogue waves to laser-induced damage.

Solitonic Analysis of the Newly Introduced Three-Dimensional Nonlinear Dynamical Equations in Fluid Mediums

The emergence of higher-dimensional evolution equations in dissimilar scientific arenas has been on the rise recently with a vast concentration in optical fiber communications, shallow water waves, plasma physics, and fluid dynamics. Therefore, the present study deploys certain improved analytical methods to perform a solitonic analysis of the newly introduced three-dimensional nonlinear dynamical equations (all within the current year, 2024), which comprise the new (3 + 1) Kairat-II nonlinear equation, the latest (3 + 1) Kairat-X nonlinear equation, the new (3 + 1) Boussinesq type nonlinear equation, and the new (3 + 1) generalized nonlinear Korteweg–de Vries equation. Certainly, a solitonic analysis, or rather, the admittance of diverse solitonic solutions by these new models of interest, will greatly augment the findings at hand, which mainly deliberate on the satisfaction of the Painleve integrability property and the existence of solitonic structures using the classical Hirota method. Lastly, this study is relevant to contemporary research in many nonlinear scientific fields, like hyper-elasticity, material science, optical fibers, optics, and propagation of waves in nonlinear media, thereby unearthing several concealed features.

InAs Terahertz Metalens Emitter for Focused Terahertz Beam Generation

Metasurfaces have opened doors to combining multiple photonic functionalities in a single compact device. In particular, the ability to generate short terahertz (THz) pulses with precise wavefront engineering in a single THz metasurface redefined the role metasurfaces can play in THz systems. Here, an InAs metalens emitter which generates and focuses a THz pulse beam is demonstrated using a 130 nm thick InAs metasurface designed as a binary‐phase Fresnel zone plate. The THz beam is focused to a spot of ≈430 μm at 1 THz with a short focal length of 5 mm and large numerical aperture of 0.5. Nanoscale InAs Mie resonators comprising the metasurface enable THz generation with an amplitude as high as 20 times compared to plasmonic THz emitters and several times compared to a 1 mm thick ZnTe crystal. This InAs metasurface emitter provides a new paradigm for designing THz imaging, spectroscopy, and communication systems, where THz beam generation and shaping are performed with a single device without compromising the generation efficiency, while eliminating losses and avoiding limitations of phase matching of conventional nonlinear optics approaches.

Non-linear optical properties of hybrid materials of (OLi3) superalkali doped perylene diimide (PDI) derivative: comprehensively study via silico-technique

PDI-Imidazole and PDI-Imidazole combined with OLi3 (OLi3@PDI-Imidazole) were the two types of materials that we examined in this study to see how light behaved in each of the complex. To explore this, we employed the three different method such as rB3LYP/6–31G(d, p) DFT, CAM-B3LYP and WB97XD. The impact of PDI-Imidazole and OLi3@PDI-Imidazole geometries, maximum absorption ( λmax ), FMO, vertical ionization energies ( EVI ), Binding Energies ( Eb ), Hyperpolarizabilities, DOS, Dipole Moments (μ), ESP, EDDM, and Global Reactivity parameters have been examined. The type of contacts as well as the vibrational frequencies of PDI-Imidazole and OLi3@PDI-Imidazole were investigated using NCl, iso-surface, Raman spectroscopy, and IR research. The electron transport characteristics of the OLi3@PDI-Imidazole surface was significantly enhanced in comparison to the PDI-Imidazole surface by lowering the bandgap energies from 1.27 eV to 1.03 eV. In contrast to the pure PDI-Imidazole surface, which had lower values for linear polarizability ( α0 ) (547.08 au) and first hyperpolarizability ( β0 )(201.133au), OLi3@PDI-Imidazole surface displayed significant enhancements in linear polarizability ( α0 = 706.472 au) and first hyperpolarizability ( β0 = 21314.360 au). It was observed by TD-DFT calculations that all the compounds had appreciable improvements in their interaction energies, HOMO–LUMO and UV–vis absorption and vertical ionization potential. Future development of nonlinear optical (NLO) devices has been discovered to benefit from the addition of OLi3 to the PDI-Imidazole surface.

Synthesis, photophysical properties, and in-silico nonlinear optics of 3-hydroxy-N-phenyl-2-naphthamide and its acetate, acrylate, and benzoate derivative

In this study, we report the successful growth of single crystals of 3-hydroxynaphthalene-2-carboxanilides (NAS) with a monoclinic structure in the P21/c space group and space group number of 14 for the first time. We have developed a yield and time-effective modified synthetic procedure using a synthetic reactor by replacing the traditional microwave method. Additionally, acylated derivatives of NAS, including novel acryloyl derivative (NAS AC), are synthesized with a modified procedure, replacing pyridine with triethylamine.We investigate the structural, photophysical, and quantum chemical properties of N-(4-acetylphenyl)-2-oxo-2H-chromene-3-carboxamide (NAS) and its acylated derivatives (NAS AC, NAS ACT, NAS BZ). Photophysical studies reveal significant Stokes shifts observed in different solvents, including time-enhanced fluorescence in DMSO, attributed to solvent relaxation processes. Natural bond orbital (NBO) analysis, molecular electrostatic potential (MEP) maps, and frontier molecular orbital (FMO) provide insights into electronic interactions and asymmetric charge distribution. Low-lying LUMO values of these compounds (-2.31 eV to -1.95 eV) support candidature for the electron acceptor applications. Nonlinear optical properties were thoroughly investigated, with NAS displaying the highest static first-order hyperpolarizability (17.89 × 10−30 esu) and NAS BZ exhibiting the highest second-order hyperpolarizability (113.09 × 10−36 esu), indicating significant nonlinear optical responses. Thermal stability (TGA and DTA) highlights the significant range of temperatures for the NLO applications.

Enhanced high-harmonic generation in a polarization-insensitive all-dielectric metasurface exploiting dual-Fano resonance

Nonlinear optics demands efficacious techniques for nonlinear properties engineering. Metasurfaces, as a flat technology with easy fabrication in various arrangements and without the need for phase-matching conditions, are suitable platforms for nonlinear optics. This study proposes a silicon metasurface with special geometry that provides high conversion efficiency by exploiting Fano resonances and the excitation of magnetic and toroidal dipoles. The results indicate the high efficiencies of third harmonic generation of 5.17×10−3 W−2 and fifth harmonic generation of 7.92×10−9 W−4 under 1 GW/cm2 pump intensity in the near-infrared regime. More specifically, linear and nonlinear optical responses of the structure are completely polarization-independent.

Investigating electronic, linear and nonlinear optical characteristics of Cr-Substituted ZnS materials

The electronic, linear, and nonlinear optical (NLO) characteristics of the Cr-substituted ZnS (ZnCrS) materials are reported within density functional theory (DFT) by using the mBJ potential. The results showed a cubic symmetry with a lattice constant decreasing as the Cr concentration increased, but the bulk modulus showed the opposite tendency. ZnS is a direct wide bandgap semiconductor; however, incorporating 75 % Cr in the ZnCrS materials causes a change in electronic bandgap nature. This change occurs due to Cr-induced defects and structural modifications, leading to new electronic transitions yielding novel optical features. The electronic and optical bandgap energy decreases with Cr content, depicting CrS as a semi-metallic material with significant light absorbance in the near-infrared and visible wavelengths accompanying the enhancement of the NLO response. It is noticed that a decrease in Εopt significantly impacted the NLO response, resulting in a significant change in the value of third-order susceptibility (χ(3)) from 5.862 × 10−11 to 2.074 × 10−9 esu. The NLO refractive index (n2) also follows the same changing trend, varying from 5.113 × 10−11 to 1.735 × 10−8 esu. This Cr-induced nonlinearity depicts strong polarizability and these materials can be significantly employed in near-infrared activated nanophotonic, photovoltaic, and optoelectronic devices.

Nonlinear optical cyanurate crystals

The exploration of ultraviolet (UV) nonlinear optical (NLO) crystals is of great significance in various fields, such as optical communication, medical diagnosis, deep space exploration and optical digital signal processing. Accordingly, cyanurates attracted widespread attention due to their strong second-harmonic-generation (SHG) effects, large birefringence for phase-matching, short UV cutoffs, high solar blind transmittances and easy crystal preparations. This article reviews the optical properties of so far reported cyanurate NLO crystals, describes the preparation approaches of cyanurates, compares their structures to further analyze the source of their large SHG effect, and provides some insights for designing and synthesizing new UV cyanurates in the future.

Theoretical calculations of nonlinear optical responses for interpreting nonconjugated molecular systems to affect non-optimal properties

Understanding the intricacies of polymorphic origins in nonconjugated crystal systems is crucial for optimizing their properties. This study focuses on the crystal growth, characterization, and nonlinear optical (NLO) responses of a system analyzed using single crystal X-ray analysis, revealing a monoclinic geometry. Hirschfeld surface analysis emphasized the significance of intermolecular interactions in driving polymorph development, shedding light on the structural nuances influencing the material’s properties. Through the evaluation of density functional theory parameters, the research found that the NLO responses of the system were as efficient as those of widely recognized materials like urea and KDP. Moreover, the stability of the system was confirmed through (NBO) analysis, showcasing its potential for practical applications. By manipulating the polymorphic crystal forms, researchers can potentially unveil new crystalline materials with tailored properties suitable for applications in optical and optoelectronic devices. This work underscores the importance of exploring novel crystal engineering strategies to harness the full potential of materials in the realm of advanced technologies.

On‐Demand Generation and Control of Giant Terahertz Nonlinearity with Metasurfaces

AbstractSimultaneous control of the optical linearity and nonlinearity of the materials plays key roles in next‐generation electronics and optics as it offers the potential of manipulating the fundamental properties while generating new frequencies of light. Such control is exceedingly challenging at the technologically important terahertz (THz) frequencies due to the severe scarcity of high‐performance nonlinear materials. Here, a unique method is introduced for achieving THz second‐order nonlinearity through Lorentz force‐driven anharmonic oscillations of free electrons in metasurfaces. It does not depend on natural nonlinear materials and provides ultrahigh design freedom. Using this approach, efficient THz second harmonic generation (SHG) is experimentally demonstrated with remarkably large values of the effective nonlinear susceptibility at room temperature. By engineering the geometry of the metasurfaces, the generation and suppression of the second harmonics can be controlled and customize their polarization states at will. This efficient, configurable, room‐temperature, and ultra‐compact platform for THz SHG provides new perspectives for developing high‐performance THz sources, frequency multipliers, and other nonlinear devices.

Suppression of Kerr-induced satellites in multi-pulse CPA

Amplification of bursts of ultrashort pulses is very challenging when the intraburst repetition frequency reaches the THz range, corresponding to (sub)-ps intervals between consecutive pulses. Periodic interference significantly modifies conditions for chirped pulse amplification (CPA), leading to temporal and spectral distortions during CPA due to optical Kerr nonlinearity. Multi-pulse chirped amplification to mJ energies may lead to a pronounced degradation of burst fidelity and the appearance of periodic temporal satellites after de-chirping the amplified waveform. We study, experimentally and numerically, the limitations of THz burst-mode CPA caused by self- and cross-phase modulation. A number of practical recipes to suppress nonlinear distortions and improve energy scaling by optimizing burst parameters and applying modulation techniques are presented.

Optical nonlinearity performance of a new isatin-thiazolidin-4-one hybrid molecule: synthesis, experimental, and DFT studies

Optical nonlinearity performance of a new isatin-thiazolidin-4-one hybrid molecule: synthesis, experimental, and DFT studies

Experimental analysis of Airy beam self-localization in nematic liquid crystals.

This study employs experimental demonstration of finite energy Airy beam (AB) propagation in nematic liquid crystals (NLCs), highlighting the reorientational optical nonlinearity that induces the generation of off-shoot solitons (OSS). The outcomes of our investigation indicate that the direction of the OSS is greatly influenced by optical power and the beam's walk-off, providing novel perspectives on light manipulation in NLCs. These findings significantly advance understanding Airy beam behavior in nonlinear materials and propose potential applications in photonic tools.

Growth, characterization and cognition of 2-cyanopyridinium perchlorate single crystals for nonlinear optical applications.

The fascinating electronic applications attracted researchers to explore the field of nonlinear optical (NLO) materials. The slow evaporation of solvent technique (SEST) was employed to grow the 2-cyanopyridinium perchlorate (2-CPPC) NLO single crystals. The cell parameters of the grown 2-CPPC crystal are confirmed by the single crystal X-ray diffraction (SCXRD) study. The powder X-ray diffraction studies confirm the crystallinity of 2-CPPC crystals, and the peaks were indexed. The computation for the geometry optimization, HOMO-LUMO energy gap, global reactivity parameters, natural bond orbital (NBO) analysis, polarizability, and hyperpolarizability of the 2-CPPC molecule was done using B3LYP (6-311G basis set) functional of DFT method. The experimental FTIR and UV-Vis results of the 2-CPPC compound were compared with the simulated results. The second harmonic generation (SHG) study for the 2-CPPC crystal was employed using Kurtz-Perry powder technique. Single beam Z-scan technique using He-Ne laser is used to study the third-order NLO properties.

RE(HSeO3)(SeO3)(H2O)·(H2O) (RE = Y, Gd): Two Rare-Earth Selenite Nonlinear Optical Crystals with Wide Band Gaps.

The band gap is one of the significant parameters for nonlinear optical (NLO) materials, which is the key factor in their application band in laser technology. This study reports the synthesis of two rare-earth selenite NLO crystals, namely, RE(HSeO3)(SeO3)(H2O)·(H2O) (RE = Y, Gd), utilizing the hydrothermal technique. The two compounds are isostructural, and both belong to the orthorhombic chiral space group of P212121 and possess three-dimensional structures consisting of two-dimensional rare-earth selenite layers connected by hydrogen bonds (O-H··O). These two compounds exhibit a moderate second harmonic generation intensity of 0.5/0.8 × KDP and wide energy band gaps reaching 4.8 eV. Comprehensive density functional theory analyses based on first-principles were carried out to unravel the relationship between the structural and corresponding properties. This work provides an approach for band gap enlargement in rare-earth selenite systems and is beneficial to the design of future NLO materials.