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The effect of planar photonic crystal on CZTS/CdS solar cell is systematically investigated. The reflective properties of PhC ARC which consists of the periodic stack of ZnO and HfO2 with two numbers of periods having quarter wavelength thickness are analyzed. Similarly, the DBR having periodic stacks of HfO2 and ZnO dielectric layers with four numbers of periods having half wavelength thickness in CZTS/CdS solar cells are explored. Moreover, the results of the photovoltaic properties of CZTS/CdS solar cells are also analyzed. The outcome of the findings obtained from the computation using the transfer matrix method are very well agreeable with the recent literature. The planar (ZnO /HfO2)2 PhC ARC and (ZnO/HfO2)4 DBR has been expected to provide significant improvement in the performance of CZTS/CdS solar cells.

Although the optical properties of nanocrystalline cesium tungsten bronze have been widely studied, there is a lack of research on the effect of particle size on its optical properties. In order to further investigate size and shape effect on the NIR shielding performance, cesium tungsten bronze nanoparticles with different sizes and morphologies were prepared by two methods. The size of irregular shaped samples prepared by solvothermal method is tens of nanometers, while the size of hexagonal prism shaped samples prepared by solid state reaction method is hundreds of nanometers. The element spectrums shows that there are more oxygen vacancies in large particles than in small particles. The NIR shielding performance of large particles far lower than that of small particles, indicating that the influence of shape and size on optical properties is more obvious than that of oxygen vacancy. Theoretical calculation on hexagonal prism shaped particles exhibits that the NIR extinction of large aspect ratio is better at longer wavelength and small aspect ratio is better at shorter wavelength.

A fluorescent carbon quantum dots(N-S CQDs) doped with nitrogen, and sulfur with tunable wavelength was successfully prepared by one-step hydrothermal reaction for sensitive detection of Pb2+. The doping of N and S narrows the band gap of the CQDs and makes the wavelength red shift, so that the carbon quantum dots displayed maximum emission peak at 540 nm under 460 nm excitation. The addition of Pb2+ quenched the fluorescence due to the specific combination of Pb2+ with the carboxyl and sulfhydryl on the surface of the CQDs formed a coordination structure. Under optimal conditions, the carbon quantum dots revealed outstanding anti-interference capability and a favorable linear relation was obtained in the scope of 0.2-12 μM and 40-200 μM with the limit of detection of 0.097 μM and 5.624 μM for Pb2+. Besides, the CQDs had been successfully used for monitoring Pb2+ in river water with well accuracy and recovery.

A five-wavelength-switchable thulium-doped fiber laser with a fiber Bragg grating (FBG)-based five-channel transmitting Fabry-Pérot (F-P) filter and a multi-coupler based triple-ring cavity (CTRC) filter, is experimentally proposed. For the first time, a multi-channel F-P filter and specially-designed coupler-based compound cavity filter were combined to realize multi-wavelength-switchable operation, with single-longitudinal-mode (SLM) lasing for each wavelength channel in a 2 µm band fiber laser. The theoretical analysis of the CTRC filter and the principle for achieving SLM operation by corporately using the F-P filter and CTRC filter were presented in detail. The experimental results demonstrated the good performance of the proposed filters. Five lasing wavelengths (1941.13 nm, 1941.22 nm, 1941.30 nm, 1941.39 nm, and 1941.47 nm) were obtained with good switchability, and each operated in a stable SLM state. The OSNR of each lasing wavelength was higher than 50 dB, and the linewidths of all obtained wavelengths were less than 8 kHz.

Two layers of Saharan dust observed over Leipzig, Germany, in February and March 2021 were used to provide the first-ever lidar measurements of the dust lidar ratio (extinction-to-backscatter ratio) and linear depolarization ratio at all three classical lidar wavelengths (355, 532 and 1064 nm). The pure-dust conditions during the first event exhibit lidar ratios of 47 ± 8, 50 ± 5 and 69 ± 14 sr and particle linear depolarization ratios of 0.242 ± 0.024, 0.299 ± 0.018 and 0.206 ± 0.010 at wavelengths of 355, 532 and 1064 nm, respectively. The second, slightly polluted-dust case shows a similar spectral behavior of the lidar and depolarization ratio with values of the lidar ratio of 49 ± 4, 46 ± 5 and 57 ± 9 sr and the depolarization ratio of 0.174 ± 0.041, 0.298 ± 0.016 and 0.242 ± 0.007 at 355, 532 and 1064 nm, respectively. The results were compared with Aerosol Robotic Network (AERONET) version 3 (v3) inversion solutions and the Generalized Retrieval of Aerosol and Surface Properties (GRASP) at six and seven wavelengths. Both retrieval schemes make use of a spheroid shape model for mineral dust. The spectral slope of the lidar ratio from 532 to 1064 nm could be well reproduced by the AERONET and GRASP retrieval schemes. Higher lidar ratios in the UV were retrieved by AERONET and GRASP. The enhancement was probably caused by the influence of fine-mode pollution particles in the boundary layer which are included in the columnar photometer measurements. Significant differences between the measured and retrieved wavelength dependence of the particle linear depolarization ratio were found. The potential sources for these uncertainties are discussed.

Current effort able to dye-sensitized solar cell (DSC) is effectively considered by TiO2 mixture Ceramic (Ce) / Vanadium (V) (CeVTiO2). The powder films of a CeVTiO2 studied in spectroscopies agree to take to Mie theory, respectively. The new samples analyzed a morphology study XRD values, TEM, and SEM. Electrical, optical properties of doping nanoparticles were considered in GC–MS chemical compounds by the view of Mie theory. The atomic force microscopy (AFM) is measured by the fill factor absorption of the samples. An experimental energy wavelength is 520 nm. Photocurrent absorption to a sample with efficiency is 44.2%, 24.1% and 8.6% and overall performance is 8% with new samples showed in benefit of the potential materials by a solar cell.

The fluorescent probe fluorescein hydrazide was designed for mercury sensing by fluorescence assay. The probe was color less and non-fluorescent in the absence of Hg2+ ions and highly fluorescent and green colored in the presence of Hg2+ ions. The probe is highly specific to Hg2+ ions under pH 12 buffer conditions. No other ions interfered during fuolrimetric analysis of the Hg2+ ions. The fluorescence assay was done at excitation wavelength of 502 nm and emission wavelength at 520 nm. The emission wavelength measured at 520 nm is proportional to the concentration of Hg2+ ions in the assay solution. The developed fluorescence assay protocol based on fluorescein hydrazide as fluorescent probe was used for mercury speciation in lead acid battery samples successfully.

The typical aza-BODIPYs in the dye family are known for bright fluorescence, excellent stability, and tunable absorption wavelengths. Hence, these dyes are attracting the increasing attention. Aza-BODIPYs having the maxima absorption in the near-infrared (NIR) region (650–900 nm) are very favorable for bioimaging in vivo due to the less photo-damage, deeper tissue penetration, and less interference from background auto-fluorescence by biomolecules in the living systems. Many strategies have been employed to modify the structures of the aza-BODIPY core to provide the NIR absorbing dyes. Among these, the most effective method is the fusion of the aromatic rings in aza-BODIPY system. This review allsidedly summarizes the recent development of ring-fused aza-BODIPY dyes (λabs> 700 nm) focusing on the design, synthesis, and potential applications in the NIR region since 2002.

Metal oxide-based plasmonics is an emergent field for which indium tin oxide (ITO) is a promising material. Improving the performance of ITO-based surface plasmon resonance (SPR) sensors requires a deeper knowledge of their optical and electrical properties. The effects of microstructural parameters and defects on mobility, which strongly influences SPR in the near-IR regime was explored. The proposed model incorporates different scattering mechanisms and non-parabolic conduction bands to obtain realistic values of mobility. The results show that larger grain sizes and higher carrier concentrations in ITO thin films improve SPR performance at near-IR wavelengths as low as 1300 nm

In this work, we propose a simple yet highly sensitive multi-channel hexagonal photonic crystal fiber (PCF) based surface plasmon resonance (SPR) refractive index (RI) sensor for detecting multiple analytes. The target analytes and the plasmonic materials, such as, gold (Au), Au with Tantalum Pentoxide (Ta2O5) and Au with Titanium Dioxide (TiO2) are employed around the exterior of the sensor for the feasibility of the operation. Twelve circular air-holes in two layers constitute the fiber structure which makes the fabrication process easy and realizable. Numerical investigations are carried out employing a full-vector finite element method (FEM) to obtain the sensing performance of the PCF-SPR structure. After optimizing the structural parameters, the sensor achieves maximum wavelength sensitivity (WS) of 38100 and 21600 nm/RIU, for channels-1 and -2, respectively. For channel-3, the sensor achieves a maximum WS of 45800 nm/RIU. To the best of our knowledge, the proposed sensor achieves better performance in terms of wavelength sensitivity, wavelength resolution, amplitude sensitivity, amplitude resolution, figure of merit, etc., compared to the existing literature. In the case of cancerous cell detection, the proposed sensor achieves maximum WS and amplitude sensitivity of 12000 nm/RIU and -2440.30 RIU-1, respectively, for HeLa cells. We envisage that the proposed sensor has a high potential to detect unknown RI for different chemical and biomedical applications due to its superior performance, simple design, and multi-analyte detection ability.

Publisher Copyright: IEEE Silicon solar cells are known to suffer from poor emitter performance that is seen as reduced external quantum efficiency at wavelengths below 500 nm. This is due to common tradeoff between electrical and optical performance. Here we demonstrate that no such tradeoff is needed when optimized boron implantation parameters are combined with non-reflective nanostructures and atomic layer deposited Al2O3 surface passivation. As a result, in our solar cells the external quantum efficiency actually increases with decreasing wavelength and reaches even above 100% at short wavelengths. This result indicates that carrier multiplication caused by absorption of high energy photons could be utilized for energy production in solar cells.

A simple synchronous fluorescent chemosensor 3-hydroxy-2-(4-methoxyphenyl)-4H-chromen-4-one (3-HC) has been synthesized for the selective analysis of Al3+. On the addition of Al3+, 3-HC displayed a redshift with a change in wavelength of emission maximum from 436 to 465 nm along with enhancement in fluorescence intensity, which formed the basis for its sensitive detection. Under optimized conditions, 3-HC was applied for the determination of Al3+ in the concentration range of 1 × 10-7-1 × 10-6 M. The limit of detection (LOD) and limit of quantification (LOQ) values were found out to be 1.69 × 10-8 and 5.07 × 10-8 M respectively. Further, the developed method was applied for the analysis of Al3+ in real water samples (tap water, bottled water, and tube well water) which showed good recovery values in the range of 95-99.7% with RSD less than 4%.

To investigate the effect of photon-induced carrier transition mechanism on switch stability, the time jitters of 2-mm-gap gallium arsenide photoconductive semiconductor switches (GaAs PCSSs) are compared when triggered by lasers of two different wavelengths, i.e., 1064 and 532 nm. The time jitter model is proposed to clarify the synergy of the multiple adjustable macroparameters of trigger conditions. The carrier valley occupation rates with respect to bias electric field are simulated, where the influence of the microprocedures, i.e., carrier generation, carrier intervalley transition, and carrier transportation, is considered. Our experimental results illustrate that the time jitter of the GaAs PCSS exhibits a nonmonotonous behavior and obtains a local minimum at ~3 kV/cm for 1064 nm; however, it shows a monotonous decrease to a constant value at about 3 kV/cm for 532 nm. Our analysis indicates that the discrepancy in GaAs PCSS time jitter is attributed to the difference in the relative fluctuation of the carrier velocity affected by the carrier valley occupation rate. This article is of great significance in optimizing the stability of GaAs PCSS and pulse power system by adjusting the macroparameters in the time jitter model.

The article presented concerns the application of fluorescein as a fluorescent material for anti-counterfeiting technology which will allow the labeling and identification of legitimate articles in the textile field. Fluorescein has been applied to polyester fabrics by microwave irradiation technique in the presence of a UV absorber. Thus, its presence in the textile substrate is detectable following an excitation at a specific wavelength belonging to the Ultra-violet zone, which makes this material very effective for tracking and detecting counterfeit articles. Fluorescent samples are characterized morphologically by scanning electron microscopy (SEM) and quantitatively by optical spectroscopy such as reflectance and transmission measurements. The treated samples show under UV light a yellowish green emission with a slight yellow coloration of the polyester fiber. The UV absorber applied to the fluorescent solution improves the light resistance of the treated samples by 25%. Their addition to the bath can also ensure the production of a protective fabric against UV.

The search for nonlinear optical (NLO) crystals with excellent comprehensive properties is a formidable challenge. In this work, two guanidine antimony fluorides, C(NH2)3Sb2F7 and C(NH2)3SbF4, were obtained by conjunction of [C(NH2)3] groups with π-conjugated configuration and stereochemically active Sb3+ cations. Due to the different coordination modes of Sb-F bonds and H-F hydrogen bonds, the crystal structure of C(NH2)3Sb2F7 is centrosymmetric (CS), while C(NH2)3SbF4 is noncentrosymmetric (NCS). Optical measurements show that the UV cutoff wavelengths of the title compounds were both less than 240 nm. Thermal studies indicate that these crystals are stable up to 250 °C. In addition, the second harmonic generation (SHG) response of C(NH2)3SbF4 is 2 times that of KH2PO4 (KDP) with the phase-matchable capacity. Theoretical calculations reveal that the large SHG effects of C(NH2)3SbF4 were attributed to the synergy between the planar [C(NH2)3] units and the distorted [SbF4] groups. These results demonstrate that the guanidine antimony fluorides will have potential value as UV NLO materials.

Spectroscopic stimulated Raman scattering (SRS) imaging has become a useful tool finding a broad range of applications. Yet, wider adoption is hindered by the bulky and environmentally sensitive solid-state optical parametric oscillator (OPO) in a current SRS microscope. Moreover, chemically informative multiwindow SRS imaging across C-H, C-D, and fingerprint Raman regions is challenging due to the slow wavelength tuning speed of the solid-state OPO. In this work, we present a multiwindow SRS imaging system based on a compact and robust fiber laser with rapid and wide tuning capability. To address the relative intensity noise intrinsic to a fiber laser, we implemented autobalanced detection, which enhances the signal-to-noise ratio of stimulated Raman loss imaging by 23 times. We demonstrate high-quality SRS metabolic imaging of fungi, cancer cells, and Caenorhabditis elegans across the C-H, C-D, and fingerprint Raman windows. Our results showcase the potential of the compact multiwindow SRS system for a broad range of applications.

Cold and ultracold collisions are dominated by quantum effects, such as resonances, tunneling, and nonadiabatic transitions between different electronic states. Due to the extremely long de Broglie wavelength in such processes, quantum reactive scattering is most conveniently characterized using the time-independent close-coupling (TICC) methods. However, the TICC approach is difficult for systems with a large number of channels because of its steep numerical scaling laws. Here, a recently proposed quantum wave packet (WP) approach for solving adiabatic reactive scattering problems at low collision energies is extended to include nonadiabatic transitions. To impose the outgoing boundary conditions, the total scattering wavefunction is split into three parts, the interaction, the asymptotic, and the long-range regions. Each region is associated with a different set of basis functions, which could be optimized separately. In this way, an extremely long grid can be used to accommodate the characteristic long de Broglie wavelengths in the scattering coordinate. The better numerical scaling laws of the WP approach have the potential for handling larger nonadiabatic reactive systems at low temperatures in the future.

Intense interests in mid-infrared (MIR) nonlinear optical (NLO) crystals have erupted in recent years due to the development of optoelectronic applications ranging from remote monitoring to molecular spectroscopy. Here, two polar crystals Ca3(TeO3)2(MO4) (M = Mo, W) were grown from TeO2-MO3 flux by high-temperature solution methods. Ca3(TeO3)2(MoO4) and Ca3(TeO3)2(WO4) are isostructural, which feature novel structures consisting of asymmetric MO4 tetrahedra and TeO3 trigonal pyramids. Optical characterizations show that both crystals display ultrawide transparency ranges (279 nm to 5.78 μm and 290 nm to 5.62 μm), especially high optical transmittance over 80% in the important atmospheric transparent window of 3-5 μm, and superhigh laser damage thresholds (1.63 GW/cm2 and 1.50 GW/cm2), 54.3 and 50 times larger than that of state-of-the-art MIR NLO AgGaS2, respectively. Notably, they exhibit the widest band gaps and the loftiest laser-induced threshold damages among the reported tellurates so far. Moreover, Ca3(TeO3)2(MO4) exhibit type I phase matching at two working wavelengths owing to their large birefringence and strong second-harmonic generation responses from the distorted anions, as further elucidated by the first-principles calculations. The above characteristics indicate that Ca3(TeO3)2(MO4) crystals are high-performance MIR NLO materials, especially applying in high-power MIR laser operations.

Is it possible to form an image using light produced by stimulated emission? Here we study light scatter off an assembly of excited chromophores. Due to the Optical Theorem, stimulated emission is necessarily accompanied by excited state Rayleigh scattering. Both processes can be used to form images, though they have different dependencies on scattering direction, wavelength and chromophore configuration. Our results suggest several new approaches to optical imaging using fluorophore excited states., 11 pages, 4 figures

A dual-parameter fiber-optic sensor based on magnetic ionic liquids (MILs) functionalized side-hole fibers (SHFs) has been proposed and experimentally demonstrated for simultaneous measurement of temperature and magnetic field intensity. Multiple transmission dips are present in the transmission spectrum due to resonance coupling between the fundamental core mode and high-order modes in the MIL inclusion. The wavelength shifts of these resonance dips are highly sensitive to the environmental temperature and applied magnetic field intensity, providing an ideal sensing platform for simultaneous measurement of the above two physical parameters. Experimental results indicate that our proposed sensor exhibits temperature and magnetic field sensitivities up to −3.466 nm/°C and −0.0303 nm/Oe for the measurement ranges of 25 °C to 100 °C and 20 Oe to 200 Oe, respectively. The MILs-infiltrated SHFs sensor paves new way toward developing photonic devices for temperature/magnetic field dual-parameter sensing and high-precision wavelength-tuning based on functional materials.

A unique data set derived from remote sensing, airborne, and ground-based in situ measurements is presented. This measurement report highlights the known complexity of comparing multiple aerosol optical parameters examined with different approaches considering different states of humidification and atmospheric aerosol concentrations. Mie-theory-based modeled aerosol optical properties are compared with the respective results of airborne and ground-based in situ measurements and remote sensing (lidar and photometer) performed at the rural central European observatory at Melpitz, Germany. Calculated extinction-to-backscatter ratios (lidar ratios) were in the range of previously reported values. However, the lidar ratio is a function of the aerosol type and the relative humidity. The particle lidar ratio (LR) dependence on relative humidity was quantified and followed the trend found in previous studies. We present a fit function for the lidar wavelengths of 355, 532, and 1064 nm with an underlying equation of fLR(RH, γ(λ))=fLR(RH=0,λ)×(1-RH)-γ(λ), with the derived estimates of γ(355 nm) = 0.29 (±0.01), γ(532 nm) = 0.48 (±0.01), and γ(1064 nm) = 0.31 (±0.01) for central European aerosol. This parameterization might be used in the data analysis of elastic-backscatter lidar observations or lidar-ratio-based aerosol typing efforts. Our study shows that the used aerosol model could reproduce the in situ measurements of the aerosol particle light extinction coefficients (measured at dry conditions) within 13 %. Although the model reproduced the in situ measured aerosol particle light absorption coefficients within a reasonable range, we identified many sources for significant uncertainties in the simulations, such as the unknown aerosol mixing state, brown carbon (organic material) fraction, and the unknown aerosol mixing state wavelength-dependent refractive index. The modeled ambient-state aerosol particle light extinction and backscatter coefficients were smaller than the measured ones. However, depending on the prevailing aerosol conditions, an overlap of the uncertainty ranges of both approaches was achieved.

A procedure is developed for the growth of thick, conformal CdS shells that preserve the optical properties of 5 nm HgSe cores. The n-doping of the HgSe/CdS core/shell particles is quantitatively tuned through a simple postsynthetic Cd treatment, while the doping is monitored via the intraband optical absorption at 5 μm wavelength. Photoluminescence lifetime and quantum yield measurements show that the CdS shell greatly increases the intraband emission intensity. This indicates that decoupling the excitation from the environment reduces the nonradiative recombination. We find that weakly n-type HgSe/CdS are the brightest solution-phase mid-infrared chromophores reported to date at room temperature, achieving intraband photoluminescence quantum yields of 2%. Such photoluminescence corresponds to intraband lifetimes in excess of 10 ns, raising important questions about the fundamental limits to achievable slow intraband relaxation in quantum dots.

Up to date, solid-state carbon dots (CDs) with bright red fluorescence have scarcely achieved due to aggregation-caused quenching (ACQ) effect and extremely low quantum yield in deep-red to near infrared region. Here, we report a novel fluorine-defects induced solid-state red fluorescence (λem = 676 nm, the absolute fluorescence quantum yields is 4.17%) in fluorine, nitrogen and sulfur co-doped CDs (F,N,S-CDs), which is the first report of such a long wavelength emission of solid-state CDs. As a control, CDs without fluorine-doping (N,S-CDs) show no fluorescence in solid-state, and the fluorescence quantum yield/emission wavelength of N,S-CDs in solution-state are also lower/shorter than that of F,N,S-CDs, which is mainly due to the F-induced defect traps on the surface/edge of F,N,S-CDs. Moreover, the solid-state F,N,S-CDs exhibit an interesting temperature-sensitive behavior in the range of 80–420 K, with the maximum fluorescence intensity at 120 K, unveiling its potential as the temperature-dependent fluorescent sensor and the solid-state light-emitting device adapted to multiple temperatures.

We record stimulated Raman scattering spectra in chemically-pure glycerol with the formation of two Stokes satellites with equidistant Raman frequencies ν = 2889 cm−1. To excite the scattered radiation, we employ short pulses of the second optical harmonic of a YAG:Nd3+ laser with a wavelength of 532 nm. Using the fundamental harmonic of the YAG:Nd3+ laser λ = 1064 nm, we convert the infrared Stokes component of stimulated Raman scattering into the visible range of the spectrum with the help of a nonlinear crystal of barium titanate. The large Raman shift of the Stokes components of stimulated Raman scattering makes it possible to use glycerol to convert laser radiation into different spectral ranges.

An azobenzene (azo)-integrated asymmetric dual-S-taper fiber interferometer based on concatenated single-mode fiber S-tapers is proposed and fabricated. As the fiber interferometer is immersed into the ethyl orange (EO) solution, due to the photo-isomerization effect of azo materials, azo molecules would experience conformal change when 473 nm laser illumination is applied, resulting in the variation of ambient surrounding refractive index. Transmission spectra of the proposed dual-S-taper structure exhibit stable and regular wavelength shift under different illumination light intensities or EO weight percentages of EO solutions. An optimal EO weight percentage of 0.1 wt% was experimentally acquired with wavelength sensitivity reaching −27.6 pm/mW for a laser power range of 0 mW to 195 mW. Furthermore, repeated laser power increasing and decreasing experiments and the control experiment under the distilled water environment proves our proposed fiber interferometer with highly reversible and stable light-sensitive wavelength responses, making it a good candidate for light intensity sensing and light-controlled wavelength-tuning applications in future all-optical networking systems.

β-cyclodextrin-hydroxyquinoline functionalized graphene oxide (GO-CD-HQ) was facilely fabricated to monitor and quantitatively analyze cations in aqueous media. The optical probe was notably selective enhanced toward Pb2+ ions over the other tested ions like Cu2+, Hg2+, Ca2+, Na+, K+, Zn2+, Fe2+, Fe3+, Ag+, Mg2+, and Cd2+ at 468 nm as an emission wavelength. The probe was shown the best performance in pH value, 5, and optimum time 1 min. Absorption spectra have clearly confirmed the static type fluorescence enhancement mechanism of GO-CD-HQ. Under the optimal conditions, the detection limit of it and linear concentration range for Pb2+ ions were obtained as 3.72 × 10–5 M and (5–60) × 10–5 M, respectively. Additionally, the developed assay exhibited logic gate behavior with Pb2+ ions and vitamin C as a masking agent for cited ions.

We live with solar radiation from birth to death and have since the emergence of life on earth. Why then does skin cancer diagnosis remain so disturbingly high in Australia? Part of the problem is the majority of the population are of Northern European ancestry. Moving closer to the equator on mass we have carried with us a polymorphic melanocortin receptor gene on our melanocytes responsible for an incomplete tanning response. We attempt to protect ourselves with clothing and creams or remain indoors but this does not seem to be stemming the tide. Occupation, recreation or both drive us outside and into the sun. We need to be more successful at negotiating the potentially harmful effects by relooking at solar radiation and instead of focusing on the most harmful wavelengths look at the overall effect of the whole spectrum. We also need to re-examine our behaviour and exposure patterns. Prolonged periods indoors under artificial light punctuated with short bursts of intense irradiation is maladaptive. Creams aim to block the ultraviolet component, ignoring 90% of solar photons, the protective effect is incomplete, yet their use encourages more prolonged exposure. Protective behaviours are necessary for the most sensitive skin types but they are still at risk. For the rest of the population evolutionarily developed natural protective mechanisms can be employed. Regular moderate sun exposure, below the burn threshold, ideally aimed at early morning or late afternoon. Augmented with clothing, hats and creams with an appreciation of the incomplete protective effect of these measures.

In this paper, we report the performance evaluation of praseodymium doped fiber amplifier (PDFA) operating in 1.25–1.35 μm band of wavelengths based on theoretical simulation. The performance of the PDFA is evaluated by considering an optimized length of Pr $$^{3+}$$ doped fiber, concentration of Pr $$^{3+}$$ ions and pump power. Moreover, the impact of input signal wavelength on gain, amplified spontaneous emission (ASE) noise and noise figure (NF) of the amplifier is also investigated. A small signal peak gain of around 22.7 dB is achieved at 1.3 μm for Pr $$^{3+}$$ doped fiber having short length of 15.7 m at an optimized pump power of 300 mW. A minimum NF of 4 dB is observed at 1.284 μm.

The signal-to-noise ratio of infrared photodetectors can be improved by using resonant cavities, whereas the enhancement effect usually occurs in a narrow wavelength range. Here, we propose a dual-mode plasmonic resonant cavity which can enhance the performance of infrared photodetectors in a wide range of wavelengths from 3.5 $$\mu$$ m to 5.5 $$\mu$$ m. The optical cavity consists of an Au grating, an ultrathin (310 nm) detective layer of mercury cadmium telluride, and an Au film, which can exhibit nearly perfect absorption at resonant wavelengths with using optimal parameters. For wavelengths from 3.5 $$\mu$$ m to 5.5 $$\mu$$ m, the wavelength-averaged absorption in the detective layer can also be 62%, about 12 times of that without the resonant cavity. Such a high enhancement of absorption can occur for incident light in a broad range of angle ( $$\theta

A simple, Precise, Accurate method was developed for the estimation of Cenobamate by RP-HPLC technique. Chromatographic conditions used are stationary phase symmetry C18 (150 mm* 4.6 mm 5 µm), mobile phase Acetonitrile: 0.01NKH2PO4in the ratio of 55:45 and flow rate was maintained at 1.0ml/min, detection wave length was 272.0 nm; column temperature was set to 30oC. Retention time was found to be 2.908 min. System suitability parameters were studied by injecting the standard six times and results were well under the acceptance criteria. Linearity study was carried out between 25% to150 % levels, R2 value was found to be as 0.999.Precision was found to be 0.5 for repeatability and 0.8 for intermediate precision. LOD and LOQ are 0.01µg/ml and 0.03µg/ml respectively. By using above method assay of marketed formulation was carried out 100.32% was present. Degradation studies of Cenobamate were done, in all conditions purity threshold was more than purity angle and within the acceptable range.

This paper reports the photoluminescence and nonlinear optical (NLO) properties of Ce2O3–TiO2 nanocomposites synthesized via sol–gel process with different concentrations of cerium. The physical characterization studies by means of XRD indicated for the successful incorporation of Ce into the lattice of TiO2, while the UV-visible spectra for an absorption edge shift of TiO2 to the higher wavelength side following the Ce addition, and FESEM analysis for the morphology and particles sizes of the synthesized materials. On testing of the photoluminescence properties recorded through time-resolved fluorescence (TCSPC) technique, a decrease in the intensity of TiO2 with that of increased Ce concentration was observed and is due to an escalation in the number of oxygen vacancies. Further, the observation NLO properties for Ce2O3–TiO2 was done by a Z-scan technique of 5ns continuous wave (cw) laser at 532 nm, where the involvement of active mechanisms in the nonlinear refraction and nonlinear absorption are due to the saturable absorption (SA) and nonlinear thermal effects.

In this work, mode-locked thulium-doped fiber lasers operating in the 2 µm wavelength region were demonstrated using tantalum aluminum carbide (Ta2AlC)-based saturable absorbers (SAs) utilizing the evanescent wave interaction. The Ta2AlC MAX Phase was prepared by dissolving the Ta2AlC powder in isopropyl alcohol and then deposited onto three different evanescent field-based devices, which were the tapered fiber, side-polished fiber, and arc-shaped fiber. Flame-brushing and wheel-polishing techniques were used to fabricate the tapered and arc-shaped fibers, respectively, while the side-polished fiber was purchased commercially. All three SA devices generated stable mode-locked pulses at center wavelengths of 1937, 1931, and 1929 nm for the tapered, side-polished, and arc-shaped fibers. The frequency of the mode-locked pulses was 10.73 MHz for the tapered fiber, 9.58 MHz for the side-polished fiber, and 10.16 MHz for the arc-shaped fiber. The measured pulse widths were 1.678, 1.734, and 1.817 ps for each of the three SA devices. The long-term stability of the mode-locked lasers was tested for each configuration over a 2-h duration. The lasers also showed little to no fluctuations in the center wavelengths and the peak optical intensities, demonstrating a reliable, ultrafast laser system.

Accurate Rayleigh scattering and absorption cross sections of atmospheric gases are essential for understanding the propagation of electromagnetic radiation in planetary atmospheres. Accurate extinction cross sections are also essential for calibrating high-finesse optical cavities and differential optical absorption spectroscopy and for accurate remote sensing. In this study, we measured the scattering and absorption cross sections of carbon dioxide, nitrous oxide, sulfur hexafluoride, oxygen, and methane in the continuous wavelength range of 307–725 nm using broadband cavity-enhanced spectroscopy (BBCES). The experimentally derived Rayleigh scattering cross sections for CO2, N2O, SF6, O2, and CH4 agree with refractive index-based calculations, with a difference of (0.4 ± 1.2) %, (−0.6 ± 1.1) %, (0.9 ± 1.4) %, (2.8 ± 1.2) %, and (0.9 ± 2.2) %, respectively. The O2–O2 collision-induced absorption and absorption by methane are obtained with high precision at the 0.8 nm resolution of our BBCES instrument in the 307–725 nm wavelength range. New dispersion relations for N2O, SF6, and CH4 were derived using data in the UV–vis wavelength range. This study provides dispersion relations for refractive indices, n-based Rayleigh scattering cross sections, and absorption cross sections based on more continuous and more extended wavelength ranges than available in the current literature.

This work outlines a new instructional laboratory experiment focused on the photoelectric effect and the determination of Planck's constant. The described laboratory system employs contemporary experimental techniques, including real-time data acquisition based on the use of Arduino boards. The basis of this experiment is to measure the associated turn-on voltages of a small neon bulb as it is illuminated with several different optical wavelengths. Six different LED and laser illumination sources were used with wavelengths ranging from UV (383 nm) to red (659 nm). A plot of the bulb's turn-on voltage as a function of the inverse of the excitation wavelength showed a linear relationship with a high correlation coefficient. Planck's constant was determined from this plot, yielding a value of h=7.4±1.1×10−34 J·s. Additionally, the system allows for experimental verification of the independence between excitation light intensity and the energy needed to ionize the gas inside the bulb.

This paper presents the first results of a new way of using MODIS (Moderate Resolution Imaging Spectroradiometer) sensor data to visualize phytopigment inconstancy in the near-surface layer of water basins. Other sensors of this class alike, the MODIS spectral resolution is too low to reproduce the minimums of reflectance Rrs caused by phytopigments in water. However, MODIS is remarkable for the presence of a channel at 469 nm combined with channels at 412, 443, 488, 531, 547, and 555 nm. This makes it possible to distinguish the spectral limits of preferential light absorption by chlorophyll a (412–469 nm) and by accessory pigments (469–555 nm). These capabilities were realized thanks to spectral pixel indexation (SPI) of MODIS images of the sea surface. The SPI boils down to the fact that a user determines the presence of pigment minima in spectra of every image pixel, finds the sum of the wavelengths of these minima as a WRM code and assigns it to the image pixel as one of its attributes. WRM code = 100 is assigned to pixels free of the minima. Such indexation makes it possible to examine the inconstancy of phytopigments on the background of aquatic environment variability. Application of SPI approach to MODIS images of the Gulf of Mexico and the Baltic Sea made it possible to reveal new patterns of phytopigment dynamics during HABs events.

Reliability and controllability of selective removal of multiple paint layers from the surface of aircraft skin depend on effective online monitoring technology. An analysis was performed on the multi-pulse laser-induced breakdown spectroscopy (LIBS) on the surface of the aluminum alloy substrate, primer, and topcoat. Based on that, an exploration was conducted on the changes of the characteristic peaks corresponding to the characteristic elements that are contained in the topcoat, primer, and substrate with different layers of a laser action, in combination with analysis of microscopic morphology, composition, and depth of laser multi-pulse pits. The results show that the appearance and increase of the characteristic peak intensity of the Ca I at the wavelength of 422.7 nm can be regarded as the basis for the complete removal of the topcoat; the decrease or disappearance of the characteristic peak intensity can be regarded as the basis for the complete removal of the primer. Al I spectrum at the wavelength of 394.5 nm and 396.2 nm can be adopted to characterize the degree of damage to the aluminum alloy substrate. The feasibility and accuracy of the LIBS technology for the laser selective paint removal process and effect monitoring of aircraft skin were verified. Demonstrating that under the premise of not damaging the substrate, laser-based layered controlled paint removal (LLCPR) from aircraft skin can be achieved by monitoring the spectrum and composition change law of specified wavelength position corresponding tothe characteristic elements that are contained in the specific paint layer.

Lithium niobate integrated photonics has recently received significant attention because it exploits the attractive properties of lithium niobate on an integrated platform which provides strong optical confinement as well as high photonic integration density. Although many optical functionalities of lithium niobate have been demonstrated on a chip in the telecom band, the visible and near-visible regimes are less explored. This is mainly because devices with a relatively smaller feature size are required which increases fabrication difficulty. Here, we explored the acousto-optic effect of lithium niobate on a chip at near-visible wavelengths (765–781 nm) and demonstrated acousto-optic modulation with the modulation frequency up to 2.44 GHz. We adopted an etchless process for the device fabrication and applied the principle of bound states in the continuum to optimize the device performance. By demonstrating functionality at near-visible wavelengths, our devices will enable many on-chip applications ranging from frequency metrology to quantum information processing.

Understanding fluid flows and mass transport in nanospaces is becoming important with recent advances in nanofluidic analytical devices utilizing nanopores and nanochannels. In the present study, we developed a super-resolution and fast particle tracking method utilizing defocusing images with spherical aberration and demonstrated the measurement of nanochannel flow. Since the spherical aberration generates the defocusing nanoparticle image with diffraction rings, the position of fluorescent nanoparticles was determined from the radius of the diffraction ring. Effects of components of an optical system on the diffraction ring of the defocusing image were investigated and optimized to achieve the spatial resolution exceeding the optical diffraction limit. We found that there is an optimal magnitude of spherical aberration to enhance the spatial resolution. Furthermore, we confirmed that nanoparticles with diameters in the order of 101 nm, which is much smaller than the light wavelength, do not affect the defocusing images and the spatial resolution because such nanoparticles can be regarded as point light sources. At optimized conditions, we achieved a spatial resolution of 19 nm and a temporal resolution of 160 μs, which are sufficient for the nanochannel flow measurements. We succeeded in the measurement of pressure-driven flow in a nanochannel with a depth of 370 nm using 67 nm fluorescent nanoparticles. The measured nanoparticle velocities exhibited a parabolic flow profile with a slip velocity even at the hydrophilic glass surface but with an average velocity similar to the Hagen-Poiseuille law. The method will accelerate researches in the nanofluidics and other related fields.

It remains a challenge to develop UV nonlinear optical (NLO) crystals that can achieve a desirable trade-off on UV absorption edge, second harmonic generation (SHG), and birefringence. Here we report a thiosulfate UV NLO crystal of a 2D van der Waals layered structure, [C(NH2)3]2SO3S. Remarkably, this thiosulfate realizes the desired trade-off, with a short absorption edge of 254 nm, a strong SHG response of approximately 2.8 times that of the benchmark KH2PO4, and a sufficient birefringence of 0.073 at the wavelength of 546 nm. In addition, it exhibits strong in-plane anisotropy of the SHG intensity. According to the first-principles calculations, the non-π-conjugated [SO3S]2- anion is the dominant SHG functional gene, while the π-conjugated [C(NH2)3]+ cation serves as the functional gene of birefringence. This is different from common UV NLO materials whose functionals of SHG and birefringence are the same. These findings indicate that combining different function genes may be an effective strategy to develop outstanding NLO materials with the desirable property trade-off.

Terahertz (THz) sources have attracted special attention for various applications. Compared to the standard silica-based optical fibers, silicon waveguides have more advantages such as higher refractive index and lower absorption loss over the THz region. In this paper, for the first time, a rib silicon waveguide based on the photonic crystal (PC) idea is designed and by using the scalar modulation instability (SMI) phenomenon, tunable wavelength conversion for THz wave generation is simulated. By changing the structural parameters such as the air-hole diameter of the PC and infiltration of optical fluids into the air holes, linear and nonlinear characteristics of the waveguide are controlled and hence the generated THz radiation is considered as a tunable source. Simulation presents that the maximum converted wavelength, 326.17 μm, is obtained when the air-hole diameter is set at d = 0.86 μm and the pump wavelength is in the normal dispersion regime. Also, we have infiltrated optical fluids into PC air holes in order to change the dispersion properties of the waveguide while keeping the geometrical parameters unchanged. This led to converted wavelengths of 70.5, 76.8 and 107.5 μm, all located in the THz region. The loss of this waveguide is less than 0.8 $$ \raisebox{1ex}{$ dB$}\!\left/ \!\raisebox{-1ex}{$ cm$}\right. $$ , which is less than that of previously reported in similar silicon waveguides.

The present work focuses the study of effect of solvent on third-order nonlinear optical (NLO) properties of reactive blue 19 dye dissolved in various polar solvents, namely ethanol, DMF and DMSO, respectively. Fourier Transform Infrared Spectroscopy (FT-IR) was used to find the functional groups present in reactive blue 19 dye. Third-order NLO features of reactive blue 19 dye was examined by a low power continuous wave laser of 650 nm wavelength. Reactive blue 19 dye exhibit negative nonlinear index of refraction of the power of 10−7 cm2/W and the nonlinear coefficient of absorption of the order of 10−3 cm/W. Both positive and negative nonlinear absorption coefficient of reactive blue 19 dye in different polar solvents is due to the characteristic behavior of saturable and reverse saturable absorption. Third-order NLO susceptibility of reactive blue 19 dye in polar solvents was determined to be the power of 10−6 esu. The experimental results reveal that the dye sample reactive blue 19 is a potential material for nonlinear optical applications.

Oxide crystals have been widely used in the nonlinear optical (NLO) field in the ultraviolet-visible and near-infrared region. Most of the traditional oxide crystals are restricted in the mid-infrared region due to their narrow transmission window. Hence, attempting to extend infrared cutoff wavelength of oxide has attracted much attention. In our work, we reported two new tellurate Li 2 TiTeO 6 (LTT) and Li 2 SnTeO 6 - (LST) with broad transparent region 0.38-6.72 and 0.38-6.86 μm, respectively, which could be excellent candidates for the mid-infrared NLO application. Both LTT and LST are crystallized in the orthorhombic space group P nn 2. The LTT crystal exhibits intense powder second-order generation efficiency (26×KDP) under the fundamental wavelength of 1064 nm. The first-principles calculations and dipole moments were used to illustrate the results of the powder second-harmonic generations based on the crystal structures. Our results provide a novel oxide NLO crystal with a strong SHG and wide transparency range. It also paves a way to design new oxide mid-IR NLO crystals.

The paper presents the data obtained by the authors in 2012-2021 during field trips to freshwater reservoirs of Altai Krai. According to hydro-optical measurements, values of light attenuation index in the range of 400-800 nm calculated using the natural logarithm varied greatly within 2.3-19.7 m-1 and 2.9-35.0 m-1 in the surface layer of lakes Lapa and Krasilovskoye during the study period. The relative spectral contribution of water suspension and contributions of yellow matter, chlorophyll, and pure water constituents at wavelengths of 430, 550, and 670 nm were estimated to assess the optical effect of water suspension on the total light attenuation index. The calculation results demonstrated that water suspension had the maximum effect on light attenuation in waters of eutrophic lake Lapa during the autumn-winter period. The maximum effect at all three wavelengths was observed in autumn of 2015, and the contribution of water suspension to light attenuation reached 88.5%, whereas its minimum (1.8-2.4 %) was recorded in 2017. The maximum contribution of water suspension on light attenuation in waters of eutrophic-hypereutrophic lake Krasilovskoye slightly exceeded the value of 70% during the winter of 2014. The next maximums were revealed during the spring of 2014 and had values of 71.3 % at λ =430 nm and 71.1 % at λ =550 nm. Optical microscopy was used to estimate the size and concentration of water suspense particles. The average weighted value of radius for water suspense particles in the surface layer of lakes Lapa and Krasilovskoye was found to be 1.2 and 1.4 microns, respectively. The average particulate count for water suspense during the observation period varied in the range of 0.2·106 cm-3-14.7·106 cm-3 with values of 3.3·106 cm-3 for lake Lapa and 3.0·106 cm-3 for lake Krasilovskoye., Материалы, использованные и представленные в данной работе, получены авторами в период 2012-2021 гг. в ходе полевых выездов на пресноводные водоемы Алтайского края. За исследуемый период, по данным гидрооптических измерений, значения показателя ослабления света в диапазоне 400-800 нм, рассчитанных при натуральном основании логарифма в поверхностном слое озер Лапа и Красиловское, варьировали в широких пределах 2,3-19,7 м-1 и 2,9-35,0 м-1 соответственно. Для оценки оптического влияния водной взвеси на суммарный показатель ослабления света рассчитан ее относительный спектральный вклад, а также вклад желтого вещества, хлорофилла и чистой воды на следующих длинах волн: 430, 550 и 670 нм. В результате расчетов получено, что в воде эвтрофного озера Лапа взвесь оказывает максимальное влияние на показатель ослабления света в осенне-зимний период. Осенью максимальный вклад взвеси наблюдался в 2015 г. (на всех трех длинах волн), достигая 88,5 %, минимальные вклады взвеси приходились на 2017 г.: 1,8-2,4 %. Для эвтрофно-гипер-эвтрофного озера Красиловское максимальные вклады взвеси в показатель ослабления света несколько более 70 % зафиксированы в 2014 г. зимой и весной — 71,3 % при λ=430 нм и 71,1 % при λ=550 нм соответственно. Для определения размерного состава и счетной концентрации частиц водной взвеси использован метод оптической микроскопии. В результате получено, что средневзвешенный радиус частиц в поверхностном слое оз. Лапа за исследуемый период составил 1,2 мкм, в оз. Красиловское — 1,4 мкм. Среднее значение счетной концентрации частиц взвеси в озерах за период наблюдений изменялось в пределах от 0,2·106 см-3 до 14,7·106 см-3 и составило порядка 3,3·106 см-3 для оз. Лапа и 3,0·106 см-3 для оз. Красиловское.

We report, to our best knowledge, the first observation of two-photon and three-photon fluorescence of Triton X-100 (TX-100) in water and cyclohexane. The observed multiphoton fluorescence (MF) falls in the ultraviolet region 280-340nm as its one photon fluorescence does. Effects of excitation wavelengths and solution concentrations on the fluorescence spectra are investigated. We found the optimal excitation wavelength and solution concentration to obtain the strongest MF. For relatively weaker three-photon fluorescence, there exists fluctuation in its spectrum due to its small SNR. The peak wavelength is around 300nm and only varies slightly with the solution concentration, solvent type, and excitation wavelength, which is quite different from those of other luminophors. This work has extended the wave band of MF to the purple and ultraviolet regions of 280-340nm and study of TX-100 to nonlinear optics field. The results may be potentially applied in ultraviolet MF detection and in manufacturing ultraviolet multiphoton laser in the future. Although for the latter case, there is still a long way to go to enhance its fluorescence efficiency and cross section of stimulated emission beforehand.

Free-standing thin films of polyaniline (PANI) with polyvinyl chloride (PVC) were synthesized and studied for variations in the structural, optical, and thermal properties with changing polyaniline concentration in the composites. Fourier transform infrared spectra show interactions between polymeric entities. XRD shows an increase in peak intensities with polyaniline with an exception at 50% polyaniline content. SEM micrographs verify the morphological changes of the composites. The reduction in chain length of composites with increased concentration of PANI is supported by the shift in absorption edge of UV-VIS spectra towards longer wavelengths. A reduction in direct and indirect band gaps and Urbach’s energy with increasing PANI concentration was observed. A monotonic increase in the intensity of photoluminescence with PANI concentration was observed with an exception for 40% polyaniline content. The glass transition temperature (Tg) for PANI/PVC composites showed a slow reduction with increased PANI concentration.