Design and characterization of a flexible diode pumped solid state laser neodymium orthovanadate

The main goal of this research is to determine temperature variation of stimulated emission cross section of laser crystal through alternative method. Neodymium-doped yttrium vanadate (Nd:YVO4) laser crystal has been utilized as the gain medium. A 808 nm laser diode was employed as the pumping source. A laser system was designed and then a prototype was created. Performance of the laser system was quantified with 97 % reflective at 1064 nm output coupler. It was found that slope efficiency and threshold power of the system were 46.9 % and 0.109 W respectively. The focal power of the laser crystal was varied with absorbed pump power at a rate of 0.228 D/W. From output fluorescence spectrums recorded at various crystal temperatures, variation of linewidth, wavelength and intensity of 1064 nm emission were determined. The rate of change of linewidth, wavelength and intensity with temperature were 5.4 pm/oC, 3.7 pm/oC and 0.075 arb. unit/oC respectively. Through spectroscopic method, stimulated emission cross section variation with temperature was found to be -0.462 %/oC with respect to stimulated emission cross section at 20 oC. For stimulated emission cross section determination through performance method, larger pump beam radius and 70 % reflectivity at 1064 nm output coupler were used. To obtain linear graph, a graph of Pout/f1 against Pabs was drawn. At 30 oC, gradient of the graph, threshold power and cavity loss were found to be 46.6 %, 0.760 W and 6.6 % respectively. Through performance method, stimulated emission cross section variation with temperature was found to be -0.447 %/oC with respect to stimulated emission cross section at 20 oC. The change of stimulated emission cross section with temperature obtained through performance method is in good agreement with spectroscopic method

Assessing Habitat Quality of Forest-Corridors through NDVI Analysis in Dry Tropical Forests of South India: Implications for Conservation

Most wildlife habitats and migratory routes are extremely threatened due to increasing demands on forestland and forest resources by burgeoning human population. Corridor landscape in Biligiri Rangaswamy Temple Tiger Reserve (BRT) is one among them, subjected to various anthropogenic pressures. Human habitation, intensive farming, coffee plantations, ill-planned infrastructure developments and rapid spreading of invasive plant species Lantana camara, pose a serious threat to wildlife habitat and their migration. Aim of this work is to create detailed NDVI based land change maps and to use them to identify timeseries trends in greening and browning in forest corridors in the study area and to identify the drivers that are influencing the observed changes. Over the four decades in BRT, NDVI increased in the core area of the forest and reduced in the fringe areas. The change analysis between 1973 and 2014 shows significant changes; browning due to anthropogenic activities as well as natural processes and greening due to Lantana spread. This indicates that the change processes are complex, involving multiple driving factors, such as socio-economic changes, high population growth, historical forest management practices and policies. Our study suggests that the use of updated and accurate change detection maps will be useful in taking appropriate site specific action-oriented conservation decisions to restore and manage the degraded critical wildlife corridors in human-dominated landscape

Measurement Of Film Thickness And Temperature On Horizontal Metal Spray Coated Tube Falling Film Evaporator Using Interferometric Techique

’Water’ is the ’Essence of Life’. It is an irreplaceable precious resource that is core of life on earth, a vital commodity that is critical for human survival, socio-economic developments and for the preservation of a healthy ecosystem. Current trends indicate that two-thirds of the world’s population will be living in water-stressed countries by 2025(wat (2006)). In order to eradicate or to provide sufficient water requirement for mankind desalination plays a pivotal role. This paper presents studies on horizontal tube falling film evaporator for Multi effect desalination (MED) system with spray coated tubes. The most important component in any MED system is the falling film evaporator. The wide acceptance for this kind of evaporators is because of the fact that it is characterized by a very low-pressure drop. In MED systems, falling film evaporation takes place outside the tube geometry utilizing the latent heat of condensing vapour inside the tube. Convective evaporation, as well as low-temperature nucleate boiling, occur in the film as it flows over the tube depending on the operating conditions(Abraham and Mani (2015)). The liquid falls on the top of the tube and flows down along the curved tube surface. There is a phase change on both sides of the tube and the evaporation outside the tube helps vapour to be separated from the liquid as soon as it is formed. Two different tubes surfaces were studied, namely bare copper tube and copper tube coated with alloy of Al2O3 and TiO2. Scanning electron microscope, Energy-dispersive X-ray spectroscopy, 3D surface profilometer were utilized to study about the surface texture, composition and to find surface roughness values attributed with each tubes. An optical shadow method (non-intrusive) incorporating Otsus’s algorithm was used to evaluate the film thickness around the circumference of the cylinder, and a Mach-Zehnder Interferometer (MZI) was employed to visualize the isotherm formation (Maliackal et al. (2021)). All studies were performed for complete wetting of the tube. The measured film thickness was compared with commonly used empirical formulas. Further, the effectiveness of using those empirical formulas for small diameter tubes was analyzed. A novel interferometric technique was used to analyze the film interface temperature, and a comparative study was performed for the two different tube geometries. A standard error of mean (SEM) analysis was performed on every data set

Wind Integrated Thermal Unit Commitment Solution Using Grey Wolf Optimizer

The augment of ecological shield and the progressive exhaustion of traditional fossil energy sources have increased the interests in integrating renewable energy sources into existing power system. Wind power is becoming worldwide a significant component of the power generation portfolio. Profuse literature have been reported for the thermal Unit Commitment (UC) solution. In this work, the UC problem has been formulated by integrating wind power generators along with thermal power system. The Wind Generator Integrated UC (WGIUC) problem is more complex in nature, that necessitates a promising optimization tool. Hence, the modern bio-inspired algorithm namely, Grey Wolf Optimization (GWO) algorithm has been chosen as the main optimization tool and real coded scheme has been incorporated to handle the operational constraints. The standard test systems are used to validate the potential of the GWO algorithm. Moreover, the ramp rate limits are also included in the mathematical WGIUC formulation. The simulation results prove that the intended algorithm has the capability of obtaining economical resolutions with good solution quality

Hydrogen production by infrared laser electrolysis on NaCl solution

A method referred as Hydrogen Production by Infrared assisted Electrolysis (HyPIR) is presented in this work. Two graphite electrodes are immersed in electrolytic cell containing 0.517 g of NaCl and 7 ml of ethanol C2H5OH solution which act as supplements for a partial oxidation reaction. Erbium YAG laser with wavelength of 2.94 mm and 57.6 mJ energy per pulse at a pulse rate of 4 Hz is illuminated directly on the electrolytic solution. The irradiating light facilitates the dissociation of water by stretching the inter-atomic hydrogen-oxygen bonds in the electrolytic solutions and directly increase the rate of hydrogen yields

Enhancement of second harmonic generation in DPSS laser

High-power diode-pumped compact visible lasers have attracted much attention. A diode-pumped solid-state laser (DPSSL) with high efficiency, high output power, a good spatial beam profile, and good stability is highly desired for use in a lot of applications such as material processing holography, range finding, target illumination and designation, satellite and lunar ranging, thermonuclear fusion, plasma experiments, and in general for scientific work requiring high power densities such as pumping other laser crystals. Laser diode with 808 nm wavelength is the key component in the development of diode pumped solid state laser (DPSSL). Much higher pumping intensity can be achieved using laser diodes instead of flashlamps as pump sources for solid-state lasers because of laser diode high spatial and spectral brightness. The main advantages of diode lasers over flashlamps as pump sources are overall laser efficiency and extended pump-source lifetime. The increase in efficiency is due to improved use of the optical pump radiation. Solid state laser like Nd:YVO4 has optical absorption only in relatively narrow wavelength bands; thus only small portion of the broadband flashlamp energy passes can be absorbed and the rest just passing through the material without being absorbed. On the other hand, diode laser output is narrowband; thus most of it is absorbed and utilized

pengaruh serbuk gergaji kayu jati terhadap kekuatan mekanis komposit partikel

Limbah serbuk gergaji hasil proses penggergajian kayu log maupun papan, sangatlah melimpah dan belum termanfaatkan secara maksimal, penelitian ini bertujuan untuk mengetahui pengaruh perbandingan fraksi volume serbuk gergaji kayu jati terhadap kekuatan mekanis komposit partikel. Resin yang digunakan dalam penelitian ini adalah Poliester tak jenuh BQTN 157 dan serbuk gergaji yang digunakan adalah limbah penggergajian kayu jati, perbandingan fraksi volume yang digunakan adalah 90%:10%, 80%:20%, 70%:30%, 60%:40%, ukuran serbuk gergaji kayu jati adalah ± 0,84mm – 1mm. Proses pengeringan serbuk gergaji dengan suhu 90 ºC selama 1 jam. Campuran resin katalis dan serbuk gergaji kayu jati sesuai dengan perhitungan fraksi volume yang telah ditentukan. Proses pencetakan menggunakan metode hand lay-up dan diberikan tekanan sebesar 1 MPa lama waktu penekanan 15 menit, proses pengeringan komposit selama 24 jam, komposit dilakukan proses post curring dengan suhu 62ºC waktu penahanan 4 jam. Dimensi spesimen uji tarik mengikuti standar ASTM D 638 dan spesimen uji bending mengikuti standar ASTM D 790. Hasil penelitian kekuatan tarik dan kekuatan bending tertinggi didapatkan pada perbandingan fraksi volume 90% : 10% yaitu 17,14 MPa dan 27,62 MPa, semakin bertambahnya serbuk kayu mengakibatkan kekuatan tarik dan bending menurun, untuk perbandingan fraksi volume 60% : 40 % masih masuk kedalam standar SNI 03-215-2006 dan SNI 03-2015-1996 untuk pengujian bending dan pengujian tarik. Semakin bertambah serbuk gergaji mengakibatkan nilai densitas semakin menurun

Stimulated emission cross section at various temperatures based on laser performance

The determination of stimulated emission cross sections at various temperatures is reported. Neodymium doped yttrium orthovanadate crystal (Nd:YVO4) was employed as a gain medium. The temperature of the crystal holder varied between 20 and 60 °C. The cross section was determined based on laser performance. The slope efficiency of the diode end-pumped Nd:YVO4 laser system decreased from 40.2% to 31.7%, while the threshold power increased from 0.744 to 1.028 W. The far-field beam diameter increased linearly with the absorbed pump power at a constant temperature. There was no correlation between the rate of change of the beam diameter with temperature due to mechanical stress fluctuation. The stimulated emission cross section was found to decrease at a rate of -0.45% °C-1 which concurs with previous works. The stimulated emission cross section of various solid-state gain mediums can be determined through this method

Transition from saturable absorption to reverse saturable absorption of carmoisine dye under low-powered continuous wave laser excitation

Unique nonlinear optics (NLO) properties i.e. intensity-dependent nonlinear absorption and refraction of carmoisine (food dye) is studied using a single beam z-scan technique. A switchover behavior from a saturable absorption (SA) to reverse saturable absorption (RSA) is observed by increasing concentration of carmoisine dye. The flip in the absorption response is attributed to the aggregated dye molecules under intense laser beam, which induces the formation of carmoisine dimers. In the UV–Vis absorption analysis, the appearance of two bands at higher concentration confirms the formation of carmoisine dimers. Fourier transform infrared spectroscopy (FTIR) suggests the intermolecular charge transfer (ICT) within the naphtyl-azo bonds. Huge magnitude of χ(3) is calculated in the order of 10−5 esu due to ICT process within the dye molecules. Optical limiting (OL) behavior is observed with low OL action threshold ∼0.01 kW/cm2 under continuous wave laser beam. The experimental findings shows that carmoisine dye has potential as an optical material for photonics applications such as an optical limiter under low-powered continuous wave laser

A review on surface tension measurements by optical method for medical application

Surface tension is a surface characteristic that is related to the forces of molecules residing at the interface. The presence of surface active substance in biological or body fluids which adsorb at interface influences the norm surface tension value. Such the changes indicate valuable signs in the medical field, particularly in pathological states. The conventional surface tension measurements suffered several flaws including lack of dynamic control and required a direct contact with the samples. The optical method seems to be attractive and useful in the surface phenomena owing to non-contact capabilities, non-destructive procedures and required a finite sample volume. In this paper, various optical techniques for surface tension measurement are reviewed and the potential applications regarding the surface tension through the meniscus formation are well discussed. This paper finds the simplicity and credibility of the optical method offers a good opportunity in fields such as medical and diagnostic analysis for monitoring applications