This thesis presents the design and development of a smart irrigation monitoring system that utilizes infrared (IR) laser detection to assess soil moisture levels and provides automated alert notifications via a GSM communication module. The proposed system is built around an Arduino microcontroller, integrating a laser diode transmitter, a photodiode receiver, and a relay-controlled water pump, offering a non-contact, energy-efficient solution for precision agriculture. The IR laser beam is directed at the soil, and the reflected signal is captured by a photodiode. Variations in the intensity of the received signal, governed by Lambert-Beer’s Law, indicate the moisture condition of the soil. When dry soil is detected, the system activates the water pump and simultaneously sends a Short Message Service (SMS) alert to the user, thereby enabling remote monitoring and intervention. The system was tested under controlled conditions to validate detection accuracy, system responsiveness, and communication reliability. Results demonstrate that the system can detect soil moisture changes with over 95% accuracy, and its automated alert mechanism responds within 1.2 seconds of moisture change detection. The laser-based sensing approach provides non-invasive, low- maintenance operation with a detection range up to 20 meters, while the GSM module ensures real-time alerts in remote agricultural settings. The study concludes that the integration of infrared optical sensing and wireless communication can significantly improve water management practices, reduce labor demands, and support the development of sustainable smart farming systems. Future enhancements may include solar power integration, cloud-based data logging, machine learning algorithms for predictive irrigation, and deployment across multiple agricultural zones for large-scale monitoring.

A novel method for through-silicon via characterization based on diffraction fringe analysis.

Recent experimental and theoretical results have demonstrated the possibility of accelerating electrons in the MeV range by focusing tightly a few-cycle laser beam in ambient air [S. Vallières et al., High dose-rate MeV electron beam from a tightly-focused femtosecond IR laser in ambient air, Laser Photonics Rev. 18, 2300078 (2024)1863-888010.1002/lpor.202300078]. Using Particle-In-Cell (PIC) simulations, this configuration is revisited within a more accurate modeling approach to analyze and optimize the mechanism responsible for electron acceleration. In particular, an analytical model for a linearly polarized tightly focused ultrashort laser field is derived and coupled to a PIC code, allowing us to model the interaction of laser beams reflected by high-numerical aperture mirrors with laser-induced plasmas. A set of 3D PIC simulations is performed where the laser wavelength is varied from 800nm to 7.0µm while the normalized amplitude of the electric field is varied from a_{0}=3.6 to a_{0}=7.0. The preferential forward acceleration of electrons, as well as the analysis of the laser intensity evolution in the plasma and data on electron number density, confirm that the relativistic ponderomotive force is responsible for the acceleration. We also demonstrate that the electron kinetic energy reaches a maximum of ≈1.6 MeV when the central wavelength is of 2.5µm.

We innovatively propose broadband hyper-reflective bilayer polymer dispersed cholesteric liquid crystal (PDCLC) films with difficult diffusion between the upper and lower films. Single-layer PDCLC films with broadband reflective properties were prepared using light-induced molecular diffusion and a polymer network-anchored pitch. Then, bilayer PDCLC films with broadband hyper-reflective properties were prepared by filling liquid crystal mixtures of opposite rotations into a specially designed bilayer liquid crystal cassette, and further broadened the reflective broadband by constructing a bilayer liquid crystal system. In the upper liquid crystal polymerisation layer, a pitch gradient is formed inside the liquid crystal film by controlling the content of the polymerisable monomer RM257 and the polymerisation conditions to produce broadband reflections. Subsequently, the left-handed liquid crystal composite system was filled under the upper film, which made it difficult for the lower chiral compounds to diffuse into the upper layer due to the dense mesh structure of the upper layer. The S5011 content was controlled so that the reflection broadband of the lower liquid crystal film overlapped with that of the upper liquid crystal film, and the whole liquid crystal composite system achieved a broadband hyper-reflective effect with a maximum reflection broadband of 1104 nm. We have verified the film's application in infrared reflection and anti-counterfeiting with good results by making temperature simulation models and patterning the film.

Utilizing LiB3O5, β-BaB2O4 crystals, and an Nd:YVO4 laser with an average power of 70 W and a repetition rate of 100 kHz, we systematically demonstrated and operated high-repetition-rate, high-power, all-solid-state, UV, and deep-UV picosecond laser sources via high-efficiency third-, fourth-, and fifth-harmonic generation (THG, FHG, and FiHG). The maximum output powers of the radiation at 355, 266, and 213 nm reached 31.2, 10.6, and 4.86 W, respectively, and the highest conversion efficiencies from the 1064 nm infrared laser beam to its third, fourth, and fifth harmonics were up to 44.6, 15.3, and 7.16%, respectively. The intensity autocorrelation traces of the generated 355, 266, and 213 nm radiation were measured based on a two-photon absorption (TPA), and the extracted pulse durations were 7.7, 6.1, and 5.9 ps, respectively. This work validates the performance of the β-BaB2O4 crystal in obtaining deep-UV radiation, laying the foundation for compact high-power deep-UV devices. Especially the power of 213 nm radiation may be the highest power, to our knowledge, for the picosecond deep-UV radiation near the wave band of ∼200 nm.

In peanut cultivation, the fact that the fruits develop underground presents significant challenges for mechanized harvesting, leading to high loss rates, with values that can exceed 30% of the total production. Since the harvest is conducted indirectly in two stages, losses are higher during the digging/inverter stage than the collection stage. During the digging process, losses account for about 60% to 70% of total losses, and this operation directly influences the losses during the collection stage. Experimental studies in production fields indicate a strong correlation between losses and the height of the windrow formed after the digging/inversion process, with a positive correlation coefficient of 98.4%. In response to this high correlation, this article presents a system for estimating the windrow profile during mechanized peanut harvesting, allowing for the measurement of crucial characteristics such as the height, width and shape of the windrow, among others. The device uses an infrared laser beam projected onto the ground. The laser projection is captured by a camera strategically positioned above the analyzed area, and through advanced image processing techniques using triangulation, it is possible to measure the windrow profile at sampled points during a real experiment under direct sunlight. The technical literature does not mention any system with these specific characteristics utilizing the techniques described in this article. A comparison between the results obtained with the proposed system and those obtained with a manual profilometer showed a root mean square error of only 28 mm. The proposed system demonstrates significantly greater precision and operates without direct contact with the soil, making it suitable for dynamic implementation in a control mesh for a digging/inversion device in mechanized peanut harvesting and, with minimal adaptations, in other crops, such as beans and potatoes.

The landscape of ultrafast structured light pulses has significantly advanced thanks to the ability of high-order harmonic generation (HHG) to translate the spatial properties of infrared laser beams to the extreme-ultraviolet (EUV) spectral range. In particular, the up-conversion of orbital angular momentum (OAM) has enabled the generation of high-order harmonics whose OAM scales linearly with the harmonic order and the topological charge of the driving field. Having a well-defined OAM, each harmonic is emitted as an EUV femtosecond vortex pulse. However, the order-dependent OAM across the harmonic comb precludes the synthesis of attosecond vortex pulses. Here we demonstrate a method for generating attosecond vortex pulse trains, i.e., a succession of attosecond pulses with a helical wavefront, resulting from the coherent superposition of a comb of EUV high-order harmonics with the same OAM. By driving HHG with a polarization tilt-angle fork grating, two spatially separated circularly polarized high-order harmonic beams with order-independent OAM are created. Our work opens the route towards attosecond-resolved light-matter interactions with two extra degrees of freedom, spin and OAM, which are particularly interesting for probing chiral systems and magnetic materials.

We prepare and analyze Rydberg states with orbital quantum numbers ℓ≤6 using three-optical-photon electromagnetically induced transparency (EIT) and radio frequency (rf) dressing, and employ the high-ℓ states in electric-field sensing. Rubidium-85 atoms in a room-temperature vapor cell are first promoted into the 25F5/2 state via Rydberg-EIT with three infrared laser beams. Two rf dressing fields then (near-)resonantly couple the 25F, 25H(ℓ=5), and 25I(ℓ=6) Rydberg states. The dependence of the rf-dressed Rydberg-state level structure on rf powers, rf and laser frequencies is characterized using EIT. Furthermore, we discuss the principles of dc-electric-field sensing using high-ℓ Rydberg states and experimentally demonstrate the method using test electric fields of ≲50 V/m induced via photo-illumination of the vapor-cell wall. We measure the highly nonlinear dependence of the dc-electric-field strength on the power of the photo-illumination laser. Numerical calculations, which reproduce our experimental observations well, elucidate the underlying physics. Our paper is relevant to high-precision spectroscopy of high-ℓ Rydberg states, Rydberg-atom-based electric-field sensing, and plasma electric-field diagnostics. Published by the American Physical Society 2024

Microstructure, hardness, and tribological properties of CoCrFeNiX (X = Mo, Ti, W) high entropy alloy coating by red-blue composite laser cladding on copper alloy

Transferring energy without transferring mass is a powerful paradigm to address the challenges faced when the access to, or the deployment of, the infrastructure for energy conversion is locally impossible or impractical. Laser beaming holds the promise of effectively implementing this paradigm. With this perspective, this work evaluates the optical-to-electrical power conversion that is created when a collimated laser beam illuminates a silicon photovoltaic solar cell that is located kilometers away from the laser. The laser is a CW high-energy Yb-doped fiber laser emitting at a center wavelength of 1075 nm with ∼1 m2 of effective beam area. For 20 kW illumination of a solar panel having 0.6 m2 of area, optical simulations and thermal simulations indicate an electrical output power of 3000 W at a panel temperature of 550 K. Our investigations show that thermo-radiative cells are rather inefficient. In contrast, an optimized approach to harvest laser energy is achieved by using a hybrid module consisting of a photovoltaic cell and a thermoelectric generator. Finally, practical considerations related to infrared power beaming are discussed and its potential applications are outlined.

On passing through a thin crystalline silicon wafer, the profile of an infrared laser beam is changed from a quasi-Gaussian to a flat-top one, improving the LIBS technique's analytical performance. That is the proposed (WELIBS) Wavefront-enhanced laser-induced breakdown spectroscopy approach.

Infrared (IR) lasers are being tested as an alternative to radiofrequency (RF) and ultrasonic (US) surgical devices for hemostatic sealing of vascular tissues. In previous studies, a side-firing optical fiber with elliptical IR beam output was reciprocated, producing a linear IR laser beam pattern for uniform sealing of blood vessels. Technical challenges include limited field-of-view of vessel position within the metallic device jaws, and matching fiber scan length to variable vessel sizes. A transparent jaw may improve visibility and enable custom treatment. Quartz and sapphire square optical chambers (2.7 × 2.7 × 25 [mm3 ] outer dimensions) were tested, capable of fitting into a 5-mm-OD laparoscopic device. A 1470 nm laser was used for optical transmission studies. Razor blade scans and an IR beam profiler acquired fiber (550-µm-core/0.22NA) output beam profiles. Thermocouples recorded peak temperatures and cooling times on internal and external chamber surfaces. Optical fibers with angle polished distal tips delivered 94% of light at a 90° angle. Porcine renal arteries with diameters of 3.4 ± 0.7 mm (n = 13) for quartz and 3.2 ± 0.7 mm (n = 14) for sapphire chambers (p > 0.05), were sealed using 30 W for 5 s. Reflection losses at material/air interfaces were 3.3% and 7.4% for quartz and sapphire. Peak temperatures on the external chamber surface averaged 74 ± 8°C and 73 ± 10°C (p > 0.05). Times to cool down to 37°C measured 13 ± 4 s and 27 ± 7 s (p < 0.05). Vessel burst pressures (BP) averaged 883 ± 393 mmHg and 412 ± 330 mmHg (p < 0.05). For quartz, 13/13 (100%) vessels were sealed (BP > 360 mmHg), versus 9/14 (64%) for sapphire. Computer simulations for the quartz chamber yielded peak temperatures (78°C) and cooling times (16 s) similar to experiments. Quartz is an inexpensive material for use in a laparoscopic device jaw, providing more consistent vessel seals and faster cooling times than sapphire and current RF and US devices.

Nowadays, battery-electric drives and energy storage are elected to be the future technologies. In the manufacturing of parts for electric applications, laser beam welding is an appropriate and favorable welding method. The characteristics of high welding speed, local heat input, and the contact-free process allow efficient and automatable processes. For electrodes, mainly copper and aluminum are used. Many foils with thicknesses of an area of 10 μm have to be connected to create battery cells. Different than expected, aluminum is a more challenging material to produce than others. Pore formation is also extended in aluminum due to the presence of air between the foils. The connecting cross section is thereby reduced. Furthermore, there is detachment in the fusion area and a high weld seam undercut. In addition to insufficient clamping, a lack of material reduces strength and, thus, usability. In the research presented here, the use of aluminum filler wire (AA 1050A) and shielding gas are investigated for the application of welding 40 aluminum foils (AA 1050A) with a thickness of 15 μm to an aluminum sheet with a thickness of 2 mm using infrared laser beam wavelength. The aims of the process development are welds with high connection widths and high quality as well as reproducibility to provide excellent mechanical properties and the highest electrical conductivity.

There is an increasing need for developing a strategy to analyze the penetration of pesticides in cultures during postharvest control with minimal or no sample preparation. This study explores the combined use of laser ablation electrospray ionization mass spectrometry imaging (LAESI imaging) and tissue spray ionization mass spectrometry (TSI-MS) to investigate the penetration of thiabendazole (TBZ) in fruits, simulating a postharvest procedure. Slices of guava and apple were prepared, and an infrared laser beam was used, resulting in the ablation of TBZ directly ionized by electrospray and analyzed by mass spectrometry. The experiments were conducted for 5 days of fruit storage after TBZ administration to simulate a postharvest treatment. During postharvest treatment, TBZ is applied directly to the fruit peel after harvesting. Consequently, TBZ residues may remain on the peel if the consumer does not wash the fruit properly before its consumption. To evaluate the effectiveness of household washing procedures, TSI-MS was employed as a rapid and straightforward technique to monitor the remaining amount of TBZ in guava and apple peels following fruit washing. This study highlights the advantages of LAESI imaging for evaluating TBZ penetration in fruits. Moreover, the powerful capabilities of TSI-MS are demonstrated in monitoring and estimating TBZ residues after pesticide application, enabling the comprehensive unveiling of pesticide contaminants in fruits.

The Laser Interferometer Space Antenna (LISA) will be the first space-based gravitational wave observatory. LISA uses continuous-wave, infrared laser beams propagating among three widely separated spacecrafts to measure their distances with picometer accuracy via time-delay interferometry. These measurements put very high demands on the laser wavefront and are thus very sensitive to any deposits on laser optics that could be induced by laser-induced molecular contamination (LIMC). In this work, we describe the results of an extensive experimental test campaign assessing LIMC related risks for LISA. We find that the LIMC concern for LISA, even considering the high demands on the laser wavefront, may be greatly reduced compared to that observed at shorter wavelengths or with pulsed laser radiation. This result is very promising for LISA as well as for other space missions using continuous-wave, infrared laser radiation, e.g.,in free space laser communication or quantum key distribution.

Here, we describe our pulsed helium droplet apparatus for spectroscopy of molecular ions. Our approach involves the doping of the droplets of about 10nm in diameter with precursor molecules, such as ethylene, followed by electron impact ionization. Droplets containing ions are irradiated by the pulsed infrared laser beam. Vibrational excitation of the embedded cations leads to the evaporation of the helium atoms in the droplets and the release of the free ions, which are detected by the quadrupole mass spectrometer. In this work, we upgraded the experimental setup by introducing an octupole RF collision cell downstream from the electron impact ionizer. The implementation of the RF ion guide increases the transmission efficiency of the ions. Filling the collision cell with additional He gas leads to a decrease in the droplet size, enhancing sensitivity to the laser excitation. We show that the spectroscopic signal depends linearly on the laser pulse energy, and the number of ions generated per laser pulse is about 100 times greater than in our previous experiments. These improvements facilitate faster and more reproducible measurements of the spectra, yielding a handy laboratory technique for the spectroscopic study of diverse molecular ions and ionic clusters at low temperature (0.4K) in He droplets.

Plant organelles are associated with each other through tethering proteins at membrane contact sites (MCS). Methods such as total internal reflection fluorescence (TIRF) optical tweezers allow us to probe organelle interactions in live plant cells. Optical tweezers (focused infrared laser beams) can trap organelles that have a different refractive index to their surrounding medium (cytosol), whilst TIRF allows us to simultaneously image behaviors of organelles in the thin region of cortical cytoplasm. However, few MCS tethering proteins have so far been identified and tested in a quantitative manner. Automated routines (such as setting trapping laser power and controlling the stage speed and distance) mean we can quantify organelle interactions in a repeatable and reproducible manner. Here we outline a series of protocols which describe laser calibrations required to collect robust data sets, generation of fluorescent plant material (Nicotiana tabacum, tobacco), how to set up an automated organelle trapping routine, and how to quantify organelle interactions (particularly organelle interactions with the endoplasmic reticulum). TIRF-optical tweezers enable quantitative testing of putative tethering proteins to reveal their role in plant organelle associations at MCS. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Microscope system set-up and stability Basic Protocol 2: Generation of transiently expressed fluorescent tobacco tissue by Agrobacterium-mediated infiltration Basic Protocol 3: Setting up an automated organelle trapping routine Basic Protocol 4: Quantifying organelle interactions.

Spherical copper oxide nanoparticles (CuO/Cu2O NPs) were synthesized by pulsed laser ablation in liquids (PLAL). The copper target was totally submerged in deionized (DI) water and irradiated by an infrared laser beam at 1064 nm for 30 min. The NPs were then characterized by dynamic light scattering (DLS) and atomic emission spectroscopy (AES) to determine their size distribution and concentration, respectively. The phases of copper oxide were identified by Raman spectroscopy. Then, the antibacterial activity of CuO/Cu2O NPs against foodborne pathogens, such as Salmonella enterica subsp. enterica serotype Typhimurium DT7, Escherichia coli O157:H7, Shigella sonnei ATCC 9290, Yersinia enterocolitica ATCC 27729, Vibrio parahaemolyticus ATCC 49398, Bacillus cereus ATCC 11778, and Listeria monocytogenes EGD, was tested. At a 3 ppm concentration, the CuO/Cu2O NPs exhibited an outstanding antimicrobial effect by killing most bacteria after 5 h incubation at 25 °C. Field emission scanning electron microscope (FESEM) confirmed that the CuO/Cu2O NPs destructed the bacterial cell wall.

Nonlinear silicon photonics has a high compatibility with CMOS technology and therefore is particularly attractive for various purposes and applications. Second harmonic generation (SHG) in silicon nanowires (NWs) is widely studied for its high sensitivity to structural changes, low-cost fabrication, and efficient tunability of photonic properties. In this study, we report a fabrication and SHG study of Si nanowire/siloxane flexible membranes. The proposed highly transparent flexible membranes revealed a strong nonlinear response, which was enhanced via activation by an infrared laser beam. The vertical arrays of several nanometer-thin Si NWs effectively generate the SH signal after being exposed to femtosecond infrared laser irradiation in the spectral range of 800-1020 nm. The stable enhancement of SHG induced by laser exposure can be attributed to the functional modifications of the Si NW surface, which can be used for the development of efficient nonlinear platforms based on silicon. This study delivers a valuable contribution to the advancement of optical devices based on silicon and presents novel design and fabrication methods for infrared converters.

Laser induced generation of hydrogen by using NdAlO3 nanocrystals as photocatalysts in alcohols