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Indoor hydroponic farming is an advanced cultivation technique with diverse sustainability benefits, such as facilitating local produce, minimizing transportation costs and emissions, and enabling year-round crop cultivation. To optimize crop growth for enhanced yield, improved crop quality, and reduced environmental footprint, precise monitoring and replenishment of essential nutrients within hydroponic systems is crucial. Current methods employed in most commercial farms for online nutrient supply monitoring is limited to pH and conductivity measurements. These techniques can only offer an indication of the overall change in the complex nutrient mixture and lack the capability to precisely identify the specific nutrient or quantify the nutrient content. Most of the existing techniques for measuring individual nutrient levels are expensive and invasive, necessitating sample preparation, frequent recalibration, and skilled personnel for operation. In this context, we propose and demonstrate a real-time, on-site monitoring system for the precise analysis of hydroponic nutrient supply based on laser-induced breakdown spectroscopy (LIBS). We also discuss the system design considerations, parametric optimizations, limit of detection (LOD), and limit of quantitation (LOQ) of key nutrient components such as potassium (K), sodium (Na), calcium (Ca), and magnesium (Mg), using the proposed approach. The detection range of the developed LIBS-based monitoring system can encompass the typical concentration range observed in hydroponic nutrient solutions used at agricultural farms. This technique offers rapid online monitoring of individual nutrient components, providing precise, real-time analysis and the potential to enable comprehensive automation capabilities for current and future hydroponic farms. [ABSTRACT FROM AUTHOR]

The nanoscale mode volumes of surface plasmon polaritons have enabled plasmonic lasers and condensates with ultrafast operation1–4. Most plasmonic lasers are based on noble metals, rendering the optical mode structure inert to external fields. Here we demonstrate active magnetic-field control over lasing in a periodic array of Co/Pt multilayer nanodots immersed in an IR-140 dye solution. We exploit the magnetic nature of the nanoparticles combined with mode tailoring to control the lasing action. Under circularly polarized excitation, angle-resolved photoluminescence measurements reveal a transition between the lasing action and non-lasing emission as the nanodot magnetization is reversed. Our results introduce magnetization as a means of externally controlling plasmonic nanolasers, complementary to modulation by excitation5, gain medium6,7 or substrate8. Further, the results show how the effects of magnetization on light that are inherently weak can be observed in the lasing regime, inspiring studies of topological photonics9–11. Researchers demonstrate the tuning of a plasmonic laser by magneto-optical effects. The results offer a new pathway for externally adjusting nanolasers. [ABSTRACT FROM AUTHOR]

We herein report a rapid and effective method for the synthesis of graphene oxide quantum dots (GOQDs) with excellent linear and nonlinear optical properties. The GOQDs were prepared by chemical cutting of graphite oxide and characterized using Fourier transform infrared spectroscopy, X-ray diffraction, UV-Vis absorption spectroscopy, Raman spectroscopy and transmission electron microscopy. The Commission International de l'Éclairage 1931 chromaticity coordinates for GOQDs (x = 0.21, y = 0.23) demonstrated that highly pure blue-light emission was achieved upon 330 nm excitation wavelength. Optical nonlinearity measurements conducted at 532 nm using 5 ns laser pulses indicated saturable absorption behavior, which tends to the onset of reverse saturable absorption as the input light fluence was increased. [ABSTRACT FROM AUTHOR]

Lead-free perovskite materials with superior physical properties are currently explored for ferroelectric and optoelectronic applications. Ferroelectric materials that have large spontaneous polarization concomitantly possess large nonlinear optical response which is highly suitable for novel photonic applications. Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) is one such novel lead-free ferroelectric material with large piezoelectric response arising from existence of morphotropic phase boundary. Conventional sol-gel technique was adopted for synthesizing nanostructured BCZT (nano-BCZT) powder using citrate precursor route. X-ray powder diffraction confirmed the phase purity and high-resolution transmission electron microscopy (HRTEM) proved that the as-synthesized BCZT was indeed nanostructured. Supportively, Raman vibrational analysis was employed to validate the site occupancies of dopants and structural correlations when compared to undoped and pristine barium titanate. Nanostructured barium titanate is extensively studied as biomarkers in second harmonic generation (SHG) microscopy for bio-medical applications. In our current work, we have explored both second- and third-order nonlinear optical response of nano-BCZT. These were found to exhibit stronger SHG signal than potassium di-hydrogen phosphate (KDP) which is a well-known SHG standard. Subsequently, we also have investigated their third-order nonlinear optical properties using open aperture Z-scan technique at 532-nm excitation wavelength in the nanosecond regime. Nano-BCZT was found to exhibit strong two-photon absorption behavior. Such materials with multiphoton absorption behavior are favorable for nonlinear photonics devices such as optical limiters and contrast agents in nonlinear optical microscopy. [ABSTRACT FROM AUTHOR]

Random lasers are resonator-less light sources where feedback stems from recurrent scattering at the expense of spatial profile and directionality. Suitably-doped nematic liquid crystals can random lase when optically pumped near resonance(s); moreover, through molecular reorientation within the transparency region, they support self-guided optical spatial solitons, i.e., light-induced waveguides. Here, we synergistically combine solitons and collinear pumping in weakly scattering dye-doped nematic liquid crystals, whereby random lasing and self-confinement concur to beaming the emission, with several improved features: all-optical switching driven by a low-power input, laser directionality and smooth output profile with high-conversion efficiency, externally controlled angular steering. Such effects make soliton-assisted random lasers an outstanding route towards application-oriented random lasers. Owing to their lack of a conventional cavity, random lasers typically do not emit a defined beam in a specific direction. Here, the authors combine spatial solitons and collinear pumping to achieve light-confined random lasing with a smooth output profile and a controllable direction of emission. [ABSTRACT FROM AUTHOR]

A series of silver nanoparticle-embedded multicomponent Eu3+-doped tellurite glasses are prepared using the technique of melt quenching and the effects of the addition of Ag nanoparticles on its spectroscopic properties of the as-synthesized glasses were systematically examined in detail. The basic compositional, thermal, and structural properties and the mechanism of energy transfer between luminescent centers were investigated. EDS detected all the elements expected in the glass composition including Ag nanoparticles. X-ray diffraction reveals the amorphous glassy nature and TEM analysis evidenced the formation of a homogeneous allocation of Ag nanoparticles having the average particle size of 10 nm in the matrix. This result supported by the band at 495 nm corresponds to surface plasmon resonance in the UV–Vis–NIR absorption spectrum of Eu3+/Ag-co-doped glass. Judd–Ofelt parameters, emission probabilities, radiative lifetime, branching ratio of luminescence, and the stimulated cross-section for prominent 5D0 → 7F2 transition were calculated by evaluating the emission spectra. Photoluminescence analysis provides an experimental observation of three-fold enhancement in the fluorescence of the Eu3+ ions in tellurite glasses for 0.3 mol% of the Ag co-doping, and a subsequent quenching in luminescence intensity is observed for further addition of Ag dopant. The enhancement in luminescence is accredited to the localized electric field produced by the silver metal. These glasses under investigation exhibit interesting spectroscopic properties that propose them to be utilized for lasers, photonic applications, and color displays. [ABSTRACT FROM AUTHOR]

KBiFe2O5 polycrystalline powder was synthesized via citrate assisted sol–gel route. Its structural, microstructural, linear, nonlinear optical and photocatalytic properties were investigated. X-ray diffraction analysis revealed its structure to be monoclinic phase at room temperature. Nonlinear optical absorption of this material was investigated using open aperture z-scan technique. A three-photon type absorption mechanism fitted well with the experimental data, and the corresponding nonlinear absorption coefficient was calculated to be 4 × 10−23 m3/W2. The band gap of this material as determined by diffuse reflectance spectroscopy was found to be 1.75 eV. This makes it suitable for visible light driven photocatalytic applications. The photocatalytic property of KBiFe2O5 was investigated by degradation of methylene blue under visible light irradiation at different pH. The degradation rate constant was found to be 0.031 min−1 at a pH of 11. [ABSTRACT FROM AUTHOR]