Spectral Manipulation Research Articles

Flexible Meta-Tape with Wide Gamut, Low Lightness and Low Infrared Emissivity for Visible-Infrared Camouflage.

Full-spectral optical camouflage is of broad interest and in urgent demand because of everlasting safety pursuit in modern society. However, the widely existing dim scenarios call for not only broadband low thermal detectivity but also wide-gamut camouflaging colors with both low lightness and minimal chromatism. Here, a tape-like metamaterial (meta-tape) with broad spectral manipulation bandwidth from visible to mid-infrared is demonstrated. The ultrathin meta-tapes can exhibit different colors with wide gamut and low lightness from 20 to 40, enabling low color difference under various backgrounds down to 1.2 L*a*b*. The infrared emissivity is simultaneously suppressed down to 3.8% across 3 - 14µm. The outstanding optical performances are well preserved under various mechanical and thermal stability tests. The pronounced multispectral camouflage, combined with flexible and robust tape-like nature, makes the meta-tape a promising solution for VIS-IR compatible camouflage in diverse scenarios.

Spectral phase-based valence state conversion manipulation in BaFCl: Sm³+ nanocrystals for multilevel information recording and display

Spectral phase-based valence state conversion manipulation in BaFCl: Sm³+ nanocrystals for multilevel information recording and display

Specialized greenness sustainability tools for evaluation of the spectrophotometric methodologies greenness: spectral signal manipulation for resolving the interfering telmisartan and metoprolol succinate spectra in their bulk and pharmaceutical formulation.

Hypertension is a leading cause of cardiovascular mortality, often accompanied by complications such as arrhythmia and stroke. This silent killer requires a multifaceted pharmacological approach for effective management. This article presents new, environmentally friendly spectrophotometric methods for simultaneous quantification of telmisartan (TER) and metoprolol succinate (MTR) in laboratory prepared mixtures and pharmaceutical formulations. The suggested methodologies include the following: area under the curve method (AUC) utilizing area at specific wavelength ranges 228 -233 nm (λ1 – λ2) and 240 – 245 nm (λ3 – λ4) for each analyte and Fourier self-deconvolution method (FD) depending on built-in function to address spectral interferences. In addition, the induced dual wavelength method (IDWL) employing equality factors to obtain absorbance differences at designated wavelengths, ratio difference method (RD) utilizing divisor-based ratio spectra where the utilized divisors were TER 40 μg/mL and MTR 90 μg/mL, and ratio derivative method (RDV) generating spectra through first derivative application that was measured at 266 nm and 246 nm for TER and MTR, respectively. These methods offer green alternatives for the accurate and precise determination of TER and MTR with exceptional linearity of 3 – 45, and 15 – 200 μg/mL for TER and MTR, respectively. Furthermore, the methods showed a coefficient of determination exceeding 0.9995 and good detection and quantification levels. A comprehensive greenness assessment, employing five distinct evaluation tools, confirmed the reduced environmental impact of the proposed methods in terms of waste generation, chemical consumption, and instrument safety. Successful analysis of pharmaceutical formulations and laboratory prepared mixtures containing different TER and MTR ratios confirmed the validity of the proposed methods. Standard addition studies further supported these findings, and the statistical results were comparable to those obtained using a reference method.

Environmental permittivity-asymmetric BIC metasurfaces with electrical reconfigurability

Achieving precise spectral and temporal light manipulation at the nanoscale remains a critical challenge in nanophotonics. While photonic bound states in the continuum (BICs) have emerged as a powerful means of controlling light, their reliance on geometrical symmetry breaking for obtaining tailored resonances makes them highly susceptible to fabrication imperfections, and their generally fixed asymmetry factor fundamentally limits applications in reconfigurable metasurfaces. Here, we introduce the concept of environmental symmetry breaking by embedding identical resonators into a surrounding medium with carefully placed regions of contrasting refractive indexes, activating permittivity-driven quasi-BIC resonances (ε-qBICs) without altering the underlying resonator geometry and unlocking an additional degree of freedom for light manipulation through active tuning of the surrounding dielectric environment. We demonstrate this concept by integrating polyaniline (PANI), an electro-optically active polymer, to achieve electrically reconfigurable ε-qBICs. This integration not only demonstrates rapid switching speeds and exceptional durability but also boosts the system’s optical response to environmental perturbations. Our strategy significantly expands the capabilities of resonant light manipulation through permittivity modulation, opening avenues for on-chip optical devices, advanced sensing, and beyond.

Observation of coupling interaction between surface plasmons and Tamm plasmons.

The optical effect analogous to electromagnetically induced transparency (EIT) in atomic systems has attracted broad attention in the field of photonics due to its promising applications in optical storage and integrated devices. Herein, we firstly report the experimental observation of the EIT-like effect generated from the coupling between surface plasmons (SPs) and Tamm plasmons (TPs) in a hybrid multilayer system at the near-infrared band. This multilayer system is composed of a nanofabricated silver grating on a silver/Bragg mirror with a SiO2 spacer. The experimental results show that a narrow reflection peak can appear in the wide reflection spectral dip due to the coupling between the SPs in the silver grating and TPs in the silver/Bragg mirror, which agree well with the finite-difference time-domain (FDTD) simulations. It is also found that the dip position of the EIT-like spectrum presents a redshift with the increase of the silver grating width. These results will provide a new way, to the best of our knowledge, for the generation of the EIT-like effect and light spectral manipulation in multilayer structures.

Stacking spectral lines with multiplexed Bragg gratings in an acousto-optical tunable filter.

Volume Bragg gratings are a useful tool for spectral manipulation in a variety of settings. In a previous paper [Astron. & Astrophys. to be published, (2024)] we simulated an astronomical instrument that detects molecules on exoplanets by optically creating matched filters using multiplexed Bragg gratings, which optically stack spectral lines. Here, we confirm that we can freely modify and multiplex Bragg gratings, with an acousto-optical tunable filter (AOTF) and that we can stack spectral features in a lab setup using a commercially available AOTF. We find that we are able to multiplex an additional grating or modify an existing grating without altering other multiplexed gratings, so long as the bandpasses do not overlap. We can also successfully stack emission and absorption lines, producing comparable results when optically overlaying spectral lines and computationally summing images of separate lines.

High power spectrum-tailorable superfluorescent fiber source

High-power, spectrum-tailorable superfluorescent fiber sources (SFSs) have garnered considerable attention owing to their unique temporal-spectral characteristics and power scalability. However, previously reported SFSs exhibit limited spectral manipulation capabilities due to gain competition and nonlinear effects at high powers. In this paper, we demonstrate a kilowatt-level SFS with exceptional spectral regulation capabilities by employing seed spectrum pre-compensation and power scaling with three amplifier stages. Specifically, a maximal 1.1 kW is achieved under single wavelength operation with a 1058–1080 nm tuning range. Furthermore, the SFS exhibits a wide linewidth tuning range of 2.71–27.25 nm, and an adjustable wavelength number of 1–7. Under multi-wavelength operation, the SFS demonstrates adjustable wavelength, intensity and interval. This work presents a new approach for agile spectrum shaping, which expands the potential applications of SFSs in spectral combination, nonlinear frequency conversion, and even inertial confinement fusion.

Spectral Manipulations of Random Fiber Lasers: Principles, Characteristics, and Applications

AbstractRandom fiber lasers (RFLs), a new variety of random lasers, have become a vigorous research spot over the past decades. RFLs possess superiorities in efficiency, structural flexibility, directionality, cost, etc. Particularly, RFLs are discovered to be good platforms for the construction of various forms of high‐performance lasers. Herein, recent progress in the spectral manipulation of RFLs and the applications of spectral‐tailored RFLs are reviewed. Both theoretical and experimental investigations of the unique spectral properties of RFLs up to now are presented. The superior wavelength flexibility of RFLs which can achieve any desired lasing wavelength in the 1–2.1 µm band is highlighted. Via spectral manipulation, RFLs have shown the capability of high‐spectral‐purity, narrow‐bandwidth, and multi‐wavelength output. Furthermore, the RFLs featuring unique spectral properties can lead to various promising applications, which are concisely summarized, including optical fiber communication, optical fiber sensing, imaging, supercontinuum generation, nonlinear‐frequency conversion, mid‐infrared lasing pump sources, and laser‐driven inertial confinement fusion motivation. The challenges and prospects for RFLs are also discussed.

Structural-color meta-nanoprinting embedding multi-domain spatial light field information

Abstract Recently, multifunctional metasurface has showcased its powerful functionality to integrate nanoprinting and holography, and display ultracompact meta-images in near- and far-field simultaneously. Herein, we propose a tri-channel metasurface which can further extend the meta-imaging ranges, with three independent images located at the interface, Fresnel and Fourier domains, respectively. Specifically, a structural-color nanoprinting image is decoded right at the interface of the metasurface, enabled by varying the dimensions of nanostructures; a Fresnel holographic image and another Fourier holographic image are present at the Fresnel and Fourier (far-field) domains, respectively, enabled by geometric phase. The spectral and phase manipulation capabilities of nanostructures have been maximized, and the spatial multiplexing capabilities for diffraction in metasurfaces have also been fully exploited. By leveraging the design freedom enabled through the tuning of the geometric size and orientation of nanostructures, as well as optimizing the diffraction spatial light wave transformation, the encoding of multiple images on the single-celled metasurface is achieved. More interestingly, due to the spatial separation of images across different channels, crosstalk is virtually eliminated, effectively enhancing imaging quality. The proposed metasurface offers several advantages, including a compact design, easiness of fabrication, minimal crosstalk, and high storage density. Consequently, it holds promising applications in image display, data storage, information encryption, anti-counterfeiting, and various other fields.

Spectral and Temporal Manipulation of Ultralong Phosphorescence Based on Melt‐Quenched Glassy Metal–Organic Complexes for Multi‐Mode Photonic Functions

AbstractTransparent glasses are ideal and robust hosts for a range of emission centers, while the simultaneous manipulation of the temporal and spectral characteristics of emission remains a tremendous challenge for inorganic glasses. Here, the development and functionalization of melt‐quenched transparent coordinate polymer glasses with a tailorable ultralong room‐temperature phosphorescence are demonstrated. Dynamic modulation of the phosphorescence is achieved by utilization of the high molecular rigidity and manipulation of the spin‐orbital coupling effects within the glass systems. By introducing dye molecules into the glasses, Phosphorescence resonance energy transfer from the glass matrix to the dye molecules is exploited and controllable multicolor long‐lived luminescence is demonstrated. Further design of the component and concentration of the encapsulated dyes allows for wavelength‐tunable long‐lived delayed fluorescence via an efficient delayed sensitization process, featuring a tunable emission spectrum covering a wide range from 520 to 630 nm. Leveraging the multiple spectral tuning channels of the hybrid glass, multi‐mode optical information storage, and dynamic anti‐counterfeiting applications are further demonstrated. This work provides a new hybrid material platform and design methodology for realizing lifetime‐adjustable and wavelength‐tunable long‐lived luminescence, which can find wide applications in time‐rsesolved information display, high‐density information storage, and dynamic anti‐counterfeiting.

Measurement of ultrashort laser pulses with a time-dependent polarization state using the d-scan technique

The dispersion scan (d-scan) technique is extended to measurement of the time-dependent polarization state of ultrashort laser pulses. In the simplest implementation for linearly polarized ultrashort pulses, the d-scan technique records the second harmonic generation spectrum as a function of a known spectral phase manipulation. By applying this method to two orthogonally polarized projections of an arbitrary polarized electric field and by measuring the spectrum at an intermediate angle, we can reconstruct the evolution over time of the polarization state. We demonstrate the method by measuring a polarization gate generated from 6fs pulses with a combination of waveplates. The measurements are compared to simulations, showing an excellent agreement.

Computational intelligence spectrophotometric scenarios for screening and quantification of single-dose triple therapy banned by the World Anti-Doping Agency in some sports

Efficient, accurate, and cost-effective spectrophotometric scenarios via innovative methods have been established, validated, and confirmed for the synchronous determination andanalyzingof the single-dose triple anti-hypertensive therapy of Atenolol (ATN), Amiloride hydrochloride (AMI) and Hydrochlorothiazide (HCT). This therapy is explicitly prohibited in various sports by the World Anti-Doping Agency (WADA) due to unfair advantage for dishonest athletes during athletic competition, it has performance-enhancing effect as well as it can lessen the detection of some doping drugs. Novel intelligence spectrophotometric solutions based on coupling of data analysis and spectral manipulation including three methods, namely, ratio conversion (RC), derivative ratio transformation (DDT) and advanced derivative ratio transformation (ADDT). Linearity ranges were 25.0–255.0 µg/mL, 2.0–23.0 µg/mL and 2.0–24.0 µg/mL for ATN, AMI and HCT, respectively. All suggested approaches were validated and confirmed in compliance with ICH guidelines, and the results were satisfactory and within approved bounds. The findings obtained using the suggested procedures and those obtained using the officially and reported methods were statistically compared, and there was no discernible difference. Evaluation of the greenness of the indicated methods was performed and compared with the reported HPLC method via utilizing the Analytical greenness metric tool [AGREE] whereas it confirmed that the applied methods are environmentally beneficial. The accomplished results together with the easiness, accessibility, low-cost and affordability of the indicated methods supported their suitability for routine quality control investigation of authentic materials, pharmaceutical preparations in addition their efficacy in cited drugs’ screening and quantification in spiked human urine.

Statically Multiple Colors and Dynamically Infrared Emissivity Modulation Compatible Electrochromic Devices via Simple Fabry–Perot Photonic Structures

AbstractThe development of electrochromic devices (ECDs) that can dynamically modulate infrared (IR) emissivity while maintaining a wide color gamut distribution for visible (VIS)‐IR compatible spectral manipulation has been a long‐standing challenge. Current ECDs are limited by simultaneous changes in IR emissivity and VIS colors when subjected to external potential, restricting their potential applications. This work presents, for the first time, VIS–IR compatible ECDs capable of displaying VIS multicolor and dynamically modulating IR emissivity via a Ge/HfO2 Fabry–Perot cavity structure. The all‐solid‐state VIS‐IR compatible ECD with the structure of ITO/NiO/Ta2O5/Li/WO3/ITO/Ge/HfO2 achieves not only emissivity modulation of 0.20 at potentials of −2.5 V and +2.5 V in the wavelength range of 2.5–25 µm, but also, due to the presence of Fabry–Perot cavity, the novelty compatible device structure achieves static multicolor modulation, thus decoupling VIS and IR emissivity modulation. Additionally, a flexible VIS‐IR compatible ECD based on polyaniline is also constructed. This novel approach offers a promising possibility for multispectral compatible manipulation, VIS multicolor, and IR signal processing applications.

Programming Wireless Security Through Learning‐Aided Spatiotemporal Digital Coding Metamaterial Antenna

The advancement of future large‐scale wireless networks necessitates the development of cost‐effective and scalable security solutions. Specifically, physical layer (PHY) security has been put forth as a cost‐effective alternative to cryptographic mechanisms that can circumvent the need for explicit key exchange between communication devices. Herein, a space–time‐modulated digitally‐coded metamaterial (MTM) leaky wave antenna (LWA) is proposed that can enable PHY security by achieving the functionalities of directional modulation (DM) using a machine learning‐aided branch‐and‐bound (B&B) optimized coding sequence. Theoretically, it is first shown that the proposed space–time MTM antenna can achieve DM through both the spatial and spectral manipulation of the orthogonal frequency division multiplexing signal. Simulation results are then provided as proof‐of‐principle, demonstrating the applicability of the approach for achieving DM in various communication settings. Furthermore, a prototype of the proposed architecture controlled by a field‐programmable gate array is realized, which achieves DM via an optimized coding sequence carried out by the learning‐aided B&B algorithm corresponding to the states of the MTM LWA's unit cells. Experimental results confirm the theory behind the space–time‐modulated MTM LWA in achieving DM, which is observed via both the spectral harmonic patterns and bit error rate measurements.

Nanotechnology-Enabled Polymer-Based Nanocomposite Hybrids for Advanced Optical Applications: A Review

Polymer nanocomposites (PNCs) are functional hybrids lying at the interface of organic and inorganic realm, whose high versatility offers numerous possibilities to develop tailor-made materials with advanced material behaviors. Accordingly, a considerate combination of optically effective additive and particle-stabilizing polymer often opens up unique design possibilities, thereby offering momentous lead in creating advanced functional materials for targeted techno-commercial applications. Accordingly, optically effective nanofillers characterized by particle size and dielectric constant of the surrounding medium-dependent surface plasmon resonance effects may induce entirely new optical functionalities (UV and visible light absorption, optical dichroism, spectral manipulation, photonic emission and so forth) in the polymeric host. Herein, we discuss the major causative factors, which enable nanostructured materials to exhibit unique properties, general introduction to nanotechnology-enabled polymer-based nanocomposites and present a comprehensive review on functional properties and related applications of PNCs, with special emphasis on optical functionalities (photonic absorption encompassing UV shielding, color switching and refractive index engineering and photonic emission covering photoluminescence and spectral manipulations). This review also sheds light on the effect of nature of filler, filler morphology, filler size and filler composition and dispersion homogeneity on optical behaviors of polymer nanocomposites.

Exciton-induced Fano resonance in metallic nanocavity with tungsten disulfide atomic layer.

Photon-exciton coupling behaviors in optical nanocavities attract broad attention due to their crucial applications in light manipulation and emission. Herein, we experimentally observed a Fano-like resonance with asymmetrical spectral response in an ultrathin metal-dielectric-metal (MDM) cavity integrated with an atomic-layer tungsten disulfide (WS2). The resonance wavelength of an MDM nanocavity can be flexibly controlled by adjusting dielectric layer thickness. The results measured by the home-made microscopic spectrometer agree well with the numerical simulations. A temporal coupled-mode theoretical model was established to analyze the formation mechanism of Fano resonance in the ultrathin cavity. The theoretical analysis reveals that the Fano resonance is attributed to a weak coupling between the resonance photons in the nanocavity and excitons in the WS2 atomic layer. The results will pave a new way for exciton-induced generation of Fano resonance and light spectral manipulation at the nanoscale.

Interplay of bound states in the continuum empowers spectral-lineshape manipulation in all-dielectric metasurfaces

The bound states in the continuum (BICs) in optical metasurfaces have latterly received prominent attention for their ultrahigh quality factors and the promise that they hold for realizing lowthreshold nanolasers, high-harmonic generation, and slow-light devices. In this scenario, the flexible tuning of the BIC is at the heart of multifunctional and tunable metadevices underpinning the central role in the modulation of optical spectral responses. Most BIC-inspired works are limited to single types of BICs modes only affected by the structural perturbation without tunable functionality, while different types of BIC modes have received little attention in manipulating the spectral line shapes in optical metasurface. Here, we show that the simultaneous generation and tailored interplay of two types of BIC modes can empower the realization of tailorable spectral lineshape manipulation in all-dielectric metasurfaces. In particular, the magnetic symmetry-protected BICs and accidental BIC result from the preserved reflection symmetry and geometrical parameter perturbation, respectively. The varied asymmetric parameters and the polarization angle of the incident light are responsible for the generation and interplay of the symmetry-protected and accidental quasi-BIC modes. Additionally, the interplaying quasi-BICs enable the implementation of the dual-wavelength passive optical switches throughout the related telecom bands, and can exhibit the tunable spectral features of different types of Fano resonances and EIT analog-based slow-light effect. These results could offer exploration potential for the development of multifunction and high-performance metadevices.

Zeolite-Encaged Luminescent Silver Nanoclusters.

Silver nanoclusters (Ag NCs) are nanoscale aggregates that possess molecular-like discrete energy levels, resulting in electronic configuration-dependent tunable luminescence spanning the entire visible range. Benefiting from the efficient ion exchange capacity, nanometer dimensional cages, and high thermal and chemical stabilities, zeolites have been employed as desirable inorganic matrices to disperse and stabilize Ag NCs. This paper reviewed the recent research progresses on the luminescence properties, spectral manipulation, as well as the theoretical modelling of electronic structure and optical transition of Ag NCs confined inside various zeolites with different topology structures. Furthermore, potential applications of the zeolite-encaged luminescent Ag NCs in lighting, gas monitoring and sensing were presented. This review concludes with a brief comment on the possible future directions in the study of zeolite-encaged luminescent Ag NCs.

Spectrophotometric platform windows' exploitation for the green determination of Alcaftadine in presence of its oxidative degradation product

This study presents the determination of Alcaftadine (ALF) in its oxidative degradation product presence by applying comprehensive study comparative of four different green stability indicating spectrophotometric approaches through successful exploitation of different spectrophotometric platform windows. Window I; based on absorption spectrum zero order data manipulation using the newly developed extended absorbance difference (EAD). Window II; based on derivative spectra by second order derivative (D2) data manipulation. Window III; based on ratio spectra applying constant multiplication (CM) and absorptivity centering via factorized ratio difference spectrum (ACT-FSRΔP) methods data manipulation. Finally, window IV; based on derivative of ratio spectrum by virtue of first derivative of ratio spectral (DD1) method data manipulation. Calibration curves construction were over linearity range; 1.0–14.0 µg/mL for ALF. The proposed methods accuracy, precision, and linearity range were determined and validated as per ICH guidelines. Moreover, they were able to analyze ALF in raw form, dosage form and in existence of its oxidative degradation product. Statistical comparisons were done between the proposed methods and the reported one showing no significant difference concerning accuracy and precision. Furthermore, greenness profile assessment was accomplished by means of four metric tools; namely: analytical greenness (AGREE), green analytical procedure index (GAPI), analytical eco-scale, and national environmental method index (NEMI).

Mode-modulation-induced high power dual-wavelength generation in a random distributed feedback Raman fiber laser.

An all-fiberized random distributed feedback Raman fiber laser (RRFL) with mode-modulation-induced wavelength manipulation and dual-wavelength generation has been demonstrated, where an electrically controlled intra-cavity acoustically-induced fiber grating (AIFG) is employed to adjust the input modal content at the signal wavelength. The wavelength agility of both the Raman effect and the Rayleigh backscattering in RRFL benefits on broadband laser output in case of broadband pumping. The feedback modal content at different wavelengths can be adjusted by AIFG, and then the output spectral manipulation can be ultimately manifested through the mode competition in RRFL. Under the efficient mode modulation, the output spectrum can be continuously tuned from 1124.3 nm to 1133.8 nm with single wavelength, while ulteriorly the dual-wavelength spectrum can be formed at 1124.1 nm and 1134.7 nm with a signal-noise-ratio of 45 dB. Throughout, the power is beyond 47 W with good stability and repeatability. To the best of our knowledge, this is the first dual-wavelength fiber laser based on mode modulation and the highest output power ever reported for an all-fiberized continuous wave dual-wavelength fiber laser.