Laser Level Research Articles

Growth, spectroscopic, and 2.7-μm Q-switched laser properties of Cr,Er:YAP crystal by xenon-lamp pumping

We demonstrate a high-peak-power and narrow pulse mid-infrared (MIR) laser with xenon-lamp pumping and La3Ga5SiO14 (LGS) Q-switching on the Cr,Er:YAP crystal grown by Czochralski method. X-ray powder diffraction and x-ray rocking curves suggest the crystal has high crystalline quality. Segregation coefficients of the Cr3 + and Er3 + in the as-grown Cr,Er:YAP crystal are 4.96 and 1.07, respectively. The absorption and fluorescence spectra indicate that the Cr,Er:YAP crystal is a promising material for MIR laser by xenon-lamp pumping. The fluorescence lifetimes of the upper (I11/24) and lower (I13/24) laser levels are 0.86 and 3.57 ms, respectively. A maximum energy of 632 mJ is acquired at 5 Hz by xenon lamp pumping. By the LGS electro-optic Q-switching technology, single pulse energy of 148.6 mJ is achieved at 5 Hz with a pulse width of 35.4 ns and peak power of 4.2 MW. The results show that the LGS Q-switched Cr,Er:YAP crystal pumped by xenon lamp possesses potential application as a short-pulse and high-energy laser device.

Improving symmetry of nipple–areola complex (NAC) position in reduction mammoplasty using laser level projection

Symmetrical height of the nipple-areola complex (NAC) is a key factor in the perception of breast symmetry. For preoperative markings, we mainly rely on conventional anthropometric measurements of distances in correlation to anatomical landmarks. In this study, we evaluated whether the use of a class 2 laser projection water level would lead to better symmetry of nipple height in reduction mammoplasty procedures when used for preoperative planning. We analysed 100 patients undergoing reduction mammoplasty with a supero-medial pedicle and wise-pattern skin resection. We compared the bilateral differences in nipple height of the last 50 reduction mammoplasty procedures before using the laser projection water level (group A; no laser) with the first 50 reduction mammoplasties after implementation of this device (group B; laser). The follow-up period was 12 months. A total of 48 patients were included in group A and 44 patients in group B. Patient demographics, mean resection weight and complications did not differ statistically significantly. Nipple height differences were significantly lower in group B (laser), measuring 0.22±0.20cm (0-0.9; n=44), than those in group A (no laser; p < 0.001), measuring 0.61±0.28cm (0.2-1.2; n=49). Using laser level projection helped improve nipple height symmetry in reduction mammoplasty. We consider a difference of more than 1 cm in nipple height to be unacceptable in aesthetic reduction mammoplasty. This simple tool facilitates preoperative markings, and we find it to be safe, quick to install and very helpful in daily practice.

Carbon footprints of rice-wheat cultivation across farm size categories: Evidence from Punjab in India

Carbon footprint (CF) can be a powerful tool to guide sustainable food production systems. The present study quantified the CF and analyzed the variability in CF across farm categories along with share of different contributing inputs for rice and wheat production in the Punjab state. The carbon footprint of rice was found to be much higher (6.34tons CO2eqha-1 and 0.91tons CO2eqton-1) than wheat (1.41 tons CO2eqha-1 and 0.28 tonsCO2eqton-1). Methane emissions contributed about 60 per cent to the emissions followed by free electricity for irrigation (17.9%), N2O (10.8%), plant protection chemicals (7.5%), diesel (6.1%) and fertilizers (3%) for rice while for wheat the major share of emissions were from N2O(41.3%) followed by diesel fuel (28.1%), fertilizers (11.8%), electricity (10.6%) and chemicals (5.1%). Across farm categories, the share of fertilizers (in terms of on-farm (11.2%) and off emissions (3.1)) remained the maximum for marginal farmers while large farmers contributed the most to the GHG emissions (18.5%) by using free electricity. The share of on-farm emissions was higher for rice (95.5%) than for wheat (80.1%) because of cultivation of rice under flooded conditions leading to methane emissions. The major contributors to the higher off-farm wheat emissions were fertilizers especially P2O5, followed by the use of diesel fuel and chemicals. The study stresses the need for sustainable management of agro-inputs which will not only offset the associated GHG emissions but also will improve the soil health. In addition, awareness of climate-smart agricultural practices and access to technologies like DSR, laser leveling, and Happy seeder are key factors in determining the utilization of farm and land management practices that may simultaneously decrease these emissions and increase the adaptive capacity of farmers, and thus improve food security.

Upconversion pumping of lasers via excited-state absorption: an analytical rate-equation formulation

Coupled power-gain equations were used to model lasers where optical pumping occurs as a result of a weak ground-state absorption followed by strong pump excited-state absorption (ESA). Inspired by the gain dynamics and energy-level structure of upconversion-pumped 2.3 µm T m 3 + lasers and 3.4 µm E r 3 + lasers, the model assumes that population in the lower laser level relaxes via a fast nonradiative decay to an intermediate storage level, which typically has a considerably slower decay rate than that of the upper laser level. After obtaining a description of the rate equation model, the continuous-wave regime was investigated by deriving analytical expressions for the power-dependent absorption, threshold pump power for lasing, output laser power, and laser slope efficiency. Results indicate that a slow decay rate of the lower level is necessary, so that sufficient population buildup can lead to enhanced nonlinear absorption via ESA. Furthermore, the asymptotic slope efficiency of the ESA pumped laser is similar to that of the ideal four-level laser, where the linear absorption is replaced by the effective nonlinear absorption.

Erbium-doped ZBLAN fiber laser pumped at 1.7 µm for emission at 2.8 µm.

In this paper, a novel, to the best of our knowledge, efficient pump scheme for an erbium-doped fluoride fiber laser with emission at 2.8 µm in the mid-infrared region is proposed and demonstrated. A singular pump source at 1.7 µm is used to excite Er3+ ions from ground state 4I15/2 to lower laser level 4I13/2, and then further boost the ions to 4I9/2, where a non-radiation transition occurs for the Er3+ ions to reach upper laser level 4I11/2. This scheme can efficiently recycle ions on the lower laser level 4I13/2 by excited-state absorption, therefore realizing population inversion and enhancing laser efficiency. In our demonstration, a 660-mW laser output at 2.8 µm is achieved from a 1.7-µm core-pumped erbium-doped fluoride fiber laser, where the slope efficiency versus launched pump power is 23.7%. The proposed innovative pump scheme shows great potential to realize high-power, high-efficiency erbium-doped fiber lasers at 2.8 µm.

Gain saturation effects in THz quantum cascade lasers

The effect of gain saturation in quantum-cascade structures with 2–4 quantum wells per period is herein analyzed on the basis of a system of balance equations. It is shown that the nonlinearity parameter decreases with an increase in the relaxation rate of laser levels, but the total current through the structure also increases. The use of the proposed multiphoton designs leads to a decrease in the non-linearity parameter without increasing the operating current. For example, in a two-photon scheme of laser transitions with the same transition probabilities and differential gains, two times slower saturation of the gain with an increase in the photon density is achieved, which leads to a high generation efficiency than in single-photon schemes.

Yield and Profitability Comparisons of Modern Agricultural Production Technologies Adoption: Evidence From Cotton-wheat Punjab (Pakistan)

Based on the survey data, the study has made yield and profitability comparisons in the contexts of modern agricultural production technologies adopted by the cotton growers of district Bahawalpur. The extent of modern agricultural production technologies adoption was gauged through constructing a modern farming index (MFI). Based on the points scored regarding MFI, the cotton growers were classified into five categories. By applying independent samples t-test, the comparisons of means were made between technologies adopters and non-adopters with respect to per acre yield, cost of production, gross income, and profit earned. On an average, in comparison with the non-adopters, the categories of good adopters and exceptional were obtaining respectively, 17% and 22% higher per acre yield and in the same order, 19% and 27% higher per acre profit. On an average, in comparison with the cotton growers without land laser levelling, those having land laser levelled were obtaining 11% higher per acre yield and 10.6% higher per acre profit. Likewise, in comparison with the cotton growers applying pesticides manually, those applying pesticides through boom sprayer were obtaining about 17% higher per acre yield and 18.2% higher per acre profit. The study concludes that technology adoption in agriculture is pivotal to productivity, production, and profitability outcomes at farm level, hence at national level.

Ecological Significance of Laser Leveling of Lands.

The economic efficiency of laser leveling of lands is that in Uzbekistan the cultivation of agricultural crops is based on irrigated agriculture, where 90-95% of the crop is grown. Caring and cultivation of crops is carried out by applying several agro-technical measures, the most important of which is land leveling. In agriculture, the main purpose of land leveling is to carry out irrigation and mechanized agro-technical measures while maintaining the slope of the field.

Power scaling of diode-pumped Er:Y2O3 ceramic laser at 2.7 μm

We report on the high-power and room temperature operation of an Er:Y2O3 ceramic laser at ∼2.7 μm based on home-developed high optical quality ceramic samples. Pumped directly into the upper laser level with a spectrally narrowed 976 nm laser diode beam shaped to have a 1D top-hat profile, the laser-generated 13.4 W of CW output power with a slope efficiency of 16.0% with respect to absorbed pump power. In a modified resonator design, a lasing slope efficiency of 23.7% has been demonstrated. To our knowledge, this represents the highest power at ∼2.7 μm spectral region from a room temperature sesquioxide laser.

Perturbation approach in Heisenberg equations for lasers

Nonlinear Heisenberg-Langevin equations are solved analytically by operator Fourier-expansion for the laser in the LED regime. Fluctuations of populations of lasing levels are taken into account as perturbations. Spectra of operator products are calculated as convolutions, preserving Bose commutations for the lasing field operators. It is found that fluctuations of population significantly affect spontaneous and stimulated emissions into the lasing mode, increase the radiation rate, the number of lasing photons and broad the spectrum of a bad cavity thresholdless and the superradiant lasers. The method can be applied to various resonant systems in quantum optics.

Dual effects on Ho3+ ∼4.0 μm emission by Nd3+ ions in (Y,Gd)AlO3 crystal.

For the first time, to the best of our knowledge, the use of Nd3+ codoping for enhancing the ∼4.0 μm emission from the Ho3+:5I5 → 5I6 transition was investigated in a Ho3+, Nd3+-codoped Gd0.1Y0.9AlO3 [(Y,Gd)AlO3] crystal [Ho/Nd:(Y,Gd)AlO3]. In this study, the ∼4.0 μm emission characteristics and energy transfer were investigated in detail, and it was found that the codoped Nd3+ ions in the Ho/Nd:(Y,Gd)AlO3 crystal significantly enhanced the Ho3+:∼4.0 μm emission, depopulated the lower laser level of Ho3+:5I6, and had little effect on the higher laser level of Ho3+:5I5. It was also found that the energy transfer efficiency from Nd3+:4F3/2 to Ho3+:5I5 was as high as 43.0%, indicating that Nd3+ ions can be used as an effective sensitizer for Ho3+ ions and that Ho/Nd:(Y,Gd)AlO3 crystal has the potential to be pumped by a commercialized InGaAs laser diode (LD). These results suggest that Ho/Nd:(Y,Gd)AlO3 crystals are likely to become attractive hosts for developing solid-state lasers at around 4.0 μm under a conventional 808 nm LD pump.

Improved Irrigation Practices for Higher Agricultural Productivity: A Review

Technological innovations will leads to meet the present and future challenges of agriculture sector. Water is one of important natural resource, since time immemorial, also acted as catalyst during Green Revolution and helped India achieve self-sufficient status in food grain production. Fresh water is only 2.6% of the total water resources of the world has to be utilized efficiently. Inspite of coverage under irrigation in India and phenomenal growth in production from irrigated area, water use efficiency remains very low as irrigation water is lost during conveyance and application. Prevalent irrigation methods used in agriculture are primarily based on gravity based flow. Surface Irrigation methods viz., Land configuration, Laser levelling and Cablegation can increase production and can save 33% of water. Likewise sprinkler and drip Irrigation practices can also increase both productivity and water saving by 70-90%. The modern methods of irrigation (sprinkler, drip and micro-sprinkler) are becoming increasingly popular with application efficiencies as high as 90 to 95% when compared to 50 to 60% in conventional irrigation methods. Whereas irrigation practices like Pre-irrigation, hydrogel led to significant increase the yield levels by 36% and water saving by 27%. At present, the area under micro-irrigation is only very less when compared to large rain fed area in India. So in order to increase the higher agricultural productivity, we have to shift towards the latest innovative methods as compared to traditional methods of irrigation.

Возможности использования низкоэнергетических параметров лазера при фемто-SMILE

Purpose. To study the influence of various laser energy parameters on the refractive result and the terms of visual rehabilitation of patients in the correction of myopia using SMILE. Material and methods. 120 patients (120 eyes) with moderate myopia, in some cases with myopic astigmatism, operated on using SMILE. Divided into 4 groups depending on the energy level applied during the operation (130–160 nJ). Patients underwent complete ophthalmic examinations preoperatively and over 3 months postoperatively. Results. A statistically significant increase in UCVA was obtained in the group with an energy of 130 nJ from 0,09±0,05 to 1,02±0,06 on the first day after surgery and up to 1,17±0,06 after 1 week. The use of low laser energies didn’t lead to an increase in HOAs. The black spots &amp; areas: 1 – 3,33% (4), 2 – 3,33% (4), 3 – 4,17% (5), 4 – 8,33% (10 eyes). The largest number of cases of OBL formation was noted in group 1 (160 nJ) – 40% (12), 2 – 26% (8), 3 – 17% (5), 4 – 7% (2 eyes). The actual residual stromal thickness (OCT) after SMILE was 78,32%±0,02, 78,76%±0,02, 78,81%±0,02, and 79,23%±0,02 in each of groups in accordance with the applied energy (no significant differences). Conclusion. The use of low laser energies in SMILE contributes to a rapid recovery of vision in the early postoperative period with less energy impact on the corneal tissue, which allows to obtain a better surface without OBL, rapid healing and restoration of corneal thickness after correction. Keywords: SMILE, myopia, lower laser energy levels of femtosecond laser, OBL, Black spots &amp; Areas.

Synthesis and Laser-Related Spectroscopy of Er:Y2O3 Optical Ceramics as a Gain Medium for In-Band-Pumped 1.6 µm Lasers

In this paper, Er:Y2O3 optical ceramics were fabricated and details of the synthesis were presented. The spectral–luminescent properties of Er3+:Y2O3 optical ceramics were investigated. The absorption and emission cross-section spectra were determined. The luminescence kinetics at near 1.6 µm was single exponential and the lifetime of erbium 4I13/2 energy level was determined. In the frame of the conventional Judd–Ofelt theory, the emission properties of the energy levels of erbium 4I13/2 and 4I11/2 involved in laser operation at near 1.6 µm were calculated. The gain coefficient curves for typical values of the relative population of the upper laser level 4I13/2 were presented. The composition and structure were studied using the SEM, XRD, FTIR spectroscopy, and X-ray computer tomography techniques.

Optimization of Laser Beam Welding Parameters for 90/10 Cupronickel Alloy Welds Using Taguchi Method

Abstract This study is to identify the most important control elements that will result in improve the tensile strength of Laser Beam Welded Cu-Ni 90/10 alloy joints. The different laser welding process parameters and levels were used for joining of Cu-Ni alloy. The process parameters like Laser Power (LP), Shielding Gas (argon) (SG), Focal Position (FP), &amp; Welding Speed (WS) were chosen in the experimental study. The welding was carried on 4mm thick plate as per Taguchi’s experimental design. The mechanical properties were evaluated and microstructural observations were carried out. It was discovered that highest tensile strength of 234 MPa &amp; hardness of 83 Hv were obtained which has 90 % and 87 % of the base material. The most influential optimal process parameters were determined using S/N analysis and the percentage contribution of each process parameter was estimated using ANOVA. It was found that laser power was influential parameter with a 64 % contribution in obtaining highest strength of laser welded joints. The experimental values and the results of the confirmation experiments were in good agreement.

Growth, thermal, and spectroscopic properties of Yb,Ho,Pr:LuYAG single crystal: a novel ∼2.9 μm laser material

A novel Yb,Ho,Pr:LuYAG laser crystal was successfully grown and investigated in detail, which belongs to the cubic system with a space group of Ia-3d. The X-ray rocking curve of the as-grown crystal implied high crystalline quality. The dislocation defects were revealed by the chemical method. Moreover, the density, thermal expansion coefficient and thermal conductivity were determined. The absorption coefficient at 935 nm and the emission cross-section at 2.911 μm were obtained to be about 15.18 cm−1 and 2.23 × 10−21 cm2, respectively. The lifetime of the lower laser level 5I7 was shown to decrease from 7.58 to 5.88 ms, while that of the upper laser level 5I6 basically remained unchanged, suggesting that the co-doped Pr3+ possessed an efficient deactivation effect and was beneficial in attaining population inversions of Ho3+. The corresponding findings illustrate that the Yb,Ho,Pr:LuYAG crystal can serve as a novel promising gain medium for realizing the 2.911 μm laser pumped by ~ 940 nm high-power InGaAs laser diode.

High power downconversion deep-red emission from Ho3+-doped fiber lasers

Abstract It has been a big challenge in decades for Ho3+-doped fiber laser to produce high emission power in deep-red due to its intrinsic long carrier lifetime in 5I7 energy level. Here, we advance the development of this visible fiber lasers by a novel pumping method that leverages the advantages of blue laser diode downconversion mechanisms to fully pumping, while shortening the lifetime of the lower energy level of the deep-red laser through excited state absorption. For the first time, we demonstrate a downconversion fiber laser using a single wavelength of 532 nm solid-state laser pump source to excite the Ho3+-doped ZBLAN fiber, which achieves a record high maximum output power of 1.64 W at 752.10 nm, as well as free-running of deep-red lasers with watt-level output. This technology represents a milestone in high power deep-red fiber lasers. Importantly, it is readily to be extended to other wavelengths that evidenced its huge application potentials in fiber laser industry.

Metal-halide perovskite-based edge emitting lasers

Edge-emitting metal halide perovskites-based 1st order distributed feedback lasers are realized and studied for the first time. The properties and performances of these devices are compared in details to those of the well-studied 2nd order DFB perovskite lasers. As expected, 1st order lasers exhibit superior properties in terms of edge emission, rendering them highly attractive for applications such as photonic integrated circuits. In addition, it is found that, unexpectedly, the threshold levels of the 1st order lasers are higher than those of the 2nd order devices. We show that this phenomenon stems from the efficiency of the optical excitation which depends on the incidence angle and the gratings period.

Novel resource conservation technologies for increasing the production and productivity of rice-wheat cropping system in Indo-Gangetic plains of India

The rice-wheat cropping system (RWCS) is the predominant cropping system, covering about 13.5 million hectares area in South Asia, out of which 10.3 million hectares is in the Indo-Gangetic Plains (IGP) of India. Rice and wheat crops are the main staple food for the people of the country and considered as the backbone for food grain security. Contributing 70 per cent to total cereal production in India due to its wider adoption, it has depleted soil organic carbon status, ground water, decreased soil fertility and has overall reduced factor productivity. Efforts to sustain higher productivity with focused approach on reversing the trend in natural resource degradation by adopting resource conservation technologies (RCTs) like direct seeded rice (DSR), system of rice intensification (SRI), aerobic rice, brown manuring, crop residue incorporation, furrow irrigated raised bed system (FIRBS), zero tillage (ZT) and leaf colour chart (LCC) that not only improved the production and productivity but also maintained the soil health. The RCTs helped in soil and water conservation, weed control and nutrient supplementation with brown manuring, reduction in seepage, deep drainage losses and water saving (10-30%) with AWD, reduced global warming potential of rice-wheat system by 41 per cent as compared to conventional system under DSR-ZT wheat. Apart from this, new emerging technologies like system of wheat intensification (SWI), LCC application for nitrogen management, bed transplanting in rice followed by laser levelling in wheat with zero tillage wheat with incorporation of rice residues over conventional transplanting also showed promising results. Thus, adoption of RCTs led to sustainable improvement in RWCS by improving soil health, nutrient and water use efficiency with higher sustained yields along with reduction in cost of cultivation and also helped to minimize environmental pollution.

Temporal-filtering dissipative soliton in an optical parametric oscillator

Abstract Dissipative solitons have been realized in mode-locked fiber lasers in the theoretical framework of the Ginzburg–Landau equation and have significantly improved the pulse energy and peak power levels of such lasers. It is interesting to explore whether dissipative solitons exist in optical parametric oscillators in the framework of three-wave coupling equations in order to substantially increase the performance of optical parametric oscillators. Here, we demonstrate a temporal-filtering dissipative soliton in a synchronously pumped optical parametric oscillator. The temporal-gain filtering of the pump pulse combined with strong cascading nonlinearity and dispersion in the optical parametric oscillator enables the generation of a broad spectrum with a nearly linear chirp; consequently, a significantly compressed pulse and high peak power can be realized after dechirping outside the cavity. Furthermore, we realized, for the first time, dissipative solitons in an optical system with a negative nonlinear phase shift and anomalous dispersion, extending the parameter region of dissipative solitons. The findings may open a new research block for dissipative solitons and provide new opportunities for mid-infrared ultrafast science.