Morphology adjustable microlens array fabricated by single spatially modulated femtosecond pulse

Silica microlens arrays (MLAs) with multiple numerical-apertures (NAs) have high thermal and mechanical stability, and have potential application prospects in 3D display and rapid detection. However, it is still a challenge to rapidly fabricate silica MLAs with a larger range of NAs and how to obtain multiple NAs in the same aperture diameter. Here, a wet etching assisted spatially modulated femtosecond laser pulse fabricating technology is proposed. In this technology, Gaussian laser pulse is modulated in the axial direction to create a pulse with a large aspect ratio, which is used to modify the silica to obtain a longer modification distance than traditional technology. After that, a microlens with a larger NA can be obtained by etching, and the NA variable range can be up to 0.06–0.65, and even under the same aperture, the variable NA can range up to 0.45–0.65. In addition, a single focus is radially modulated into several focus with different axial lengths to achieve a single exposure fabricating of MLA with multiple NAs. In characterization of the image under a microscope, the multi-plane imaging characteristics of the MLA are revealed. The proposed technology offers great potential toward numerous applications, including microfluidic adaptive imaging and biomedical sensing.

High-power single-mode 894 nm VCSELs operating at high temperature (> 2 mW @ 365 K)

In this study, we realize the high-power output of a single-mode 894 nm vertical-cavity surface-emitting laser (VCSEL) at high temperature. The effects of the dimensional parameters of oxide aperture and surface relief on the transverse mode and threshold gain of VCSEL were analyzed. Through collaborative optimization of the oxide aperture and relief, the VCSEL with 8 µm oxide aperture diameter and 5 µm surface relief inner diameter can operate at high temperature of 365 K with single-mode output power of 2.02 mW and side-mode suppression of 29.2 dB.

Prediction of Focal Image for Solar Parabolic Dish Concentrator With Square Facets – An Analytical Model

Solar parabolic dish concentrator is one of the high-temperature applications of more than 400 °C for thermal and electrical power generation. In the solar parabolic dish concentrator, the arrangement of reflectors over the surface area is the significant factor for effective concentration of solar radiation. Also, focal image is one of the most influencing parameters in the design of receiver. Among the various reflectors, the square shaped reflectors (facets) are comparatively effective in converging the incoming radiations to attain better focal image. In this regard, an attempt has been made to predict the focal image diameter of a solar parabolic dish concentrator with a square facet of different influencing parameters using a novel mathematical model. The influencing parameters considered for the study are aperture diameter, rim angle, and facet length of the dish concentrator. Based on the proposed model, the focal image dimension and aperture area of a solar parabolic dish concentrator with square facets can be predicted accurately for efficient design of a solar parabolic dish collector system. Finally, the proposed model is validated with the experimentally obtained focal image diameter and it is observed that the predicted result is in good agreement with the experimental one. Thus, the proposed model can be effectively used for the design of parabolic dish system for sustainable development.

Study of Novel Punched-Bionic Impellers for High Efficiency and Homogeneity in PCM Mixing and Other Solid-Liquid Stirs

Improvement of stirring performance is one of the primary objectives in solid–liquid mixing processes, such as the preparation of phase change materials (PCMs) for energy saving in refrigeration and heat pump systems. In this paper, three novel impellers are proposed: pitched-blade punched turbine (PBPT), bionic cut blade turbine (BCBT) and bionic cut punched blade turbine (BCPBT). An experimental test was conducted to validate the stirring system model based on the Eulerian–Eulerian method with the kinetic theory of granular flow. Then the performance of the novel impellers was predicted, studied, and compared. The outcomes indicate that a novel impeller, specifically BCPBT, can effectively suspend particles and dramatically reduce power consumption. A better solid–liquid suspension quality was obtained with an aperture diameter of 8 mm and aperture ratio of 13%. Within the range of impeller speeds and liquid viscosity studied in this this paper, higher impeller speeds and more viscous liquids are more conducive to particle dispersion. One of the most important contributions of this work lies in the design of novel impellers, an extent of energy conservation to 17% and efficient mixing was achieved. These results have reference significance for improving the energy efficiency of temperature regulation systems.

Design, Construction, and Evaluation of the Performance of Dual-Axis Sun Trucker Parabolic Solar Cooker and Comparison of Cooker

Energy demand is increasing due to population increment and industrialization. To meet this energy demand, technologies that use renewable energy such as solar energy are being developed. A parabolic solar cooker is one of the main solar cookers, which can cook food and boil water at a high temperature within a short period. This study aimed to design, construct, and evaluate the performance of the constructed parabolic solar cookers. Moreover, this study aimed to compare the constructed cooker with firewood, charcoal, kerosene, and electricity in terms of cooking time and energy cost. The cooker was constructed using different materials such as old satellite dishes, tyres, steel, and aluminum foil. The aperture diameter, aperture area, receiver diameter, receiver area, depth of the parabola, focal length, rim angle, circumference of the circle, surface area, length of the circumference, and concentration of the cooker were 1.8 m, 2.54 m2, 0.16 m, 0.02 m2, 0.3 m, 0.67 m, 67.38°, 5.76 m, 2.81 m2, 5.76 m, and 123.46, respectively. The cooker can track the sun from north to south and from east to west. The performance of the cooker was evaluated by calculating the efficiency and power. The output energy, input energy, and average upcoming solar radiation of the constructed parabolic solar cooker were 0.182 kW/m2, 1.691 kW/m2, and 0.665 kW/m2, respectively. The efficiency and power of the cooker were 10.75% and 0.3 kW/hr, respectively. The constructed parabolic solar cooker relatively showed better performance in cooking different foods. A family, which has five members, was considered to compare the constructed cooker with other fuels in terms of energy cost of cooking. Since the parabolic solar cooker does not have any energy cost, it can save the energy cost of cooking foods. Therefore, parabolic solar cookers have a great advantage for developing countries including Ethiopia.

Optical Characteristics of Vitamin D3 Soft Gel

In this work, the linear properties of Vitamin D3-5000IU soft gel were investigated by measuring its absorption and fluorescence spectra. It was observed that there was a shift towards longer wavelength within limits (75 nm), with quantitative efficiency equal to (33.58%). The values of absorbance were used to calculate the extinction coefficient, optical refractive index, optical conductivity and optical dielectric constant values. The non-linear properties of Vitamin D3-5000IU soft gel was also studied using the Z-Scan technique by using Neodymium-doped Yttrium Garnet (Nd: YAG) continuous laser (CW) emitting in (532 nm) wavelength, by utilize open aperture to measure nonlinear absorption coefficient and close aperture (diameter 1.5mm) to measure nonlinear refractive index. The sample behaves as two-photon absorption, and the nonlinear refractive index was positive.

A Novel High Concentration Fresnel Lens as a Solar Concentrator

This paper describes the design methodology for a novel Fresnel lens. The original Fresnel lens is obtained from a plano-convex lens, whose spherical surface is split into a number of divisions (called facets), collapsed onto the flat base. Thus, all the facets of the original Fresnel lens have the same radius as that of the plano-convex lens. The proposed design aims to achieve better ray concentration and reduced spherical aberration than the original Fresnel lens by constructing spherical facets with unequal radii. The centers and radii of facets are constrained so that the ray refracted from the bottom vertex of each facet on one side of the optical axis and the ray refracted from the outer vertex of the corresponding facet on the other side of the optical axis must intersect at the focal plane. The proposed lens design has resulted in a 275% gain in the concentration ratio and a 72.5% reduction in the spherical aberration compared to the original lens of the same aperture diameter and number of facets. The performance of both novel and original Fresnel lenses when used as solar concentrators with a conical coil receiver is evaluated. The novel Fresnel lens led to increased heat gain and resulted in a compact solar collector design.

Numerical comparison between DPSK 33, DPSK 66 and duo binary in WOC system

OWC systems have turned into a state-of-the-art technology because of their superior performance uniqueness and its innumerable characteristic as compared to its RF. One of the OWC application is inter-satellite wireless optical communication (Is-WOC), this framework can be improved by using different ways such as advanced modulation formats and aperture diameter. We demonstrate an analysis based on the aperture diameter effect in transmission of single channel with 40 Gb/s Is-WOC system using three different modulation methods, differential phase-shift keying (DPSK) with a duty ratio to 66% and 33% and duobinary. Choosing these three modulations from various modulation format is done depending on the advantage they provide where the DPSK gives to fiber nonlinearity a powerful robustness and less susceptible to SPM and XPM and for system requirements of dispersion compensation in duobinary, it provides higher chromatic dispersion tolerance mitigate. The result shows the effect of different transmitter aperture diameter (from 2 to 20 cm) for a constant distance 200 km accomplished by quality factor and minimum BER. We conclude there is a great loss in the small aperture diameter, even in the presence of best modulation format, therefore as the aperture diameter increase the Q-factor increase, but some increased rise is linear and the other is changing from linear to non-linear in a fixed Q-factor point equal to 5.63.