Green Laser Beam Research Articles

Three-Dimensional Direct Laser Writing of PEGda Hydrogel Microstructures with Low Threshold Power using a Green Laser Beam

Three-Dimensional Direct Laser Writing of PEGda Hydrogel Microstructures with Low Threshold Power using a Green Laser Beam

Chaotic Macropulse Green Laser Beam Generated by Modulating a 520 nm Laser Diode with Optical Feedback

We describe a novel chaotic macropulse green laser designed employing the pulse modulation of a 520 nm laser diode with optical feedback. We analyze the characteristics of these chaotic macropulses, in view of effects of the feedback intensity, injection current, modulation voltage, duty cycle, and modulation frequency on the pulses, including their full width at half maximum (FWHM) values and peak side-lobe levels (PSLs). We determine an optimum feedback intensity of 11.7% based on the maximum peak optical power and the scope of the amplitude jitter of the chaotic macropulse. The optimum injection currents are approximately between 60 and 70 mA, and the modulation voltages between 2.0 and 3.0 V are limited by the radio-frequency (RF) power. We found that chaos also occurred at the bottom of the macropulse when the duty cycle was less than approximately 30%. The modulation frequencies were loaded from 4 to 20 MHz; this range was restricted by the performance of the RF input port on the laser diode mount. The range resolution of the chaotic macropulses is approximately 3 cm in seawater; it is achieved with lower power consumption than a continuous wave chaotic laser.

Motion tracking and analysis of spray water droplets studied by high-speed photography using an iPhone X

Smartphones are not only becoming an inseparable part of our daily lives, but also a low-cost, powerful optical imaging tool for more and more scientific research applications. In this work, we hypothesized that some smartphones could be used as a low-cost, high-speed, photographic alternative to expensive equipment, such as those typically found in scientific research labs, to accurately perform motion tracking and analysis of fast-moving objects. This demonstrative experiment was done at home at very low cost by using a low-power green laser (<0.1 W) purchased from Amazon, an iPhone X, and a water spray bottle. The sprayed water droplets were illuminated by a divergent green laser beam and recorded with a smartphone using the Slow-Motion Video function (240 frames per second), which allows us to record high-speed events. The Slow-Motion Video was converted to a series of consecutive images taken every 1/240 second (or 4.16 ms), enabling tracking and motion analysis of the sprayed water droplets. By analyzing these consecutive images, the speed and flight trajectory of water droplets in the air were obtained, thereby enabling us to estimate the area of the water droplets landing on the ground.

Measurement of the thermo-optic coefficient and Ring surface profile of sulfadiazine azo dye by using milli watts cw laser beams

We report on the observation of thermal lens as well as multiple diffraction ring patterns due to the irradiation of the azo dye “1.8-Dihydroxy-naphthalin-3, 6 disulfonic acid [2-(4-Azo)]-N-(5-methyl-3-isoxazolyl)-benzene sulfonamide” at same time by three continuous wave, green (λ=532 nm), red (λ=635 nm) and blue (λ=473 nm), laser beams. This effect we observed at power input less than 10 mW for the pump 532 nm green laser and as low as 50 μW of beams from other two wavelengths. The number of rings for all three beams is totally controlled by the level of pump input power. The optical limiting of the azo dye solution using the 532 nm green laser beam is also demonstrated. The change in the material refractive index, Δn, the nonlinear refractive index, n 2, and the thermo-optical coefficient dn/dT are calculated based on thermal lens and diffraction ring techniques. The three quantities are found to be in the range of 10−4, 10−7 cm 2/W and 10−5 K −1 respectively by both techniques.

Two-Dimensional Periodic Nanostructure Fabricated on Titanium by Femtosecond Green Laser.

Laser-induced periodic surface structures (LIPSS) is the sub-wavelength periodic nanostructure, which is generally generated by the femtosecond laser. There are two kinds of LIPSS, low spatial frequency LIPSS (LSFL) and high spatial LIPSS (HSFL), and the period size is close and less than half of the laser wavelength, respectively. Fabrication of two-dimensional (2D) LSFL and HSFL on a titanium surface with a linear-polarized femtosecond green laser beam (wavelength 515 nm) and cross-scanning strategies is demonstrated in this study. Four types of LIPSS structures are obtained by controlling the laser fluence, irradiated pulses, and cross-scanning strategies: 1D-LSFL perpendicular to laser polarization with a period of 300–360 nm, 1D-HSFL parallel to laser polarization with a period of 55–75 nm, 2D-LSFL dot-like structures with a period ~200 nm, and 2D-HSFL net-like structures with a period of 50–100 nm.

EFFECTS OF LASER IRRADIATION ON NORMAL AND ANEMIC HUMAN BLOOD

The effects of laser irradiation on the whole human blood were studied. The blood samples were taken from healthy donors with normal blood and donors with anemic blood. The blood samples were exposed to laser radiation. Two lasers of the same types, continuous wave (CW) diode pumped solid-state lasers (DPSSL’ s) were used to irradiate the blood samples. One of these laser has a wavelength 532 nm (green laser beam), while the other laser has a wavelength 671 nm (red laser beam). The output power of the two lasers can be varied over the range 0 - 100 mW. In the present study, the output power was fixed at 20 mW for both lasers. The blood samples were exposed to different irradiation times, 5, 15, and 30 min. Significant changes in the optical parameters of the irradiated blood samples were observed in comparison with that of the un-irradiated blood samples (the control samples). These optical parameters were determined from the measured absorbance spectra of the un-irradiated and irradiated samples. The absorbance spectra were measured using a UV-Visible double-beam spectrophotometer operating over the wavelength range 190 - 1100 nm.
 The results of the present study revealed that the laser irradiation can produce considerable effects on the human blood samples, suggesting the suitability of the laser beam irradiation for the biological and medical applications.

Caracterization of the Green Pointer Laser Beam Value as an Obstacle Sensor on Various Background Colors

Obstacle detection sensor is an important development tool of autonomous vehicles in recognizing its environment. Green laser pointer is an example of a sensor in the form of visibe light beam to detect the obstacles that are in the track of the tractor. This research aimed to Determine the variation of green laser beam as an obstacle sensors in different backgrounds and different intensity of light. This system used a CMOS camera and cctv lense 0-60 mm of focal length as the prime sensor and a green laser pointer at 532±10 nm with a maximum of 98 0 mW output power. Asicap software used to capture the image of the green laser pointer and then the image processed by using ArcMap 10.5 to determine the coordinat of the green laser and its RGB pixels. The camera is capable to detect the green laser pointer beam with intensities up to 50000 lux° with Temperature 51.6 ° C and 40.3% of humadity from 2 meters until 7 meters from Potition captured. From the tests carried out it appears that the normalization value of green laser light, especially for the maximum and minimum values of the components of green on various types of objects look the same. Especially for the minimum green value. This states that the various types of green laser beam sighting objects have the same minimum value, so the coding program will be the same.

Photocurrent spectra for above and below bandgap energies from photovoltaic PbS infrared detectors with graphene transparent electrodes

We discussed photocurrent spectra of photovoltaic PbS infrared detectors using multi-layer graphene as transparent electrode, where p-PbS films were deposited on TiO2/FTO substrates by chemical bath deposition. In the photocurrent spectra, we observed both above-bandgap and sub-bandgap photocurrent without any external bias. We discussed impurity band model and grain boundary model in order to explain the sub-bandgap photocurrent near 15 μm. Since FTO is transparent in the visible range, we were able to illuminate green laser beam from the FTO back-side, and photo-response up to 50 μm was found to be enhanced. This long wavelength photo-response was attributed to the excitation of the photo-electrons accumulated at the TiO2/PbS interface. Our photovoltaic PbS devices can detect not only short-infrared but also terahertz radiation at room temperature, which is highly applicable to various fields.

Three-Dimensional Direct Laser Writing of PEGda Hydrogel Microstructures with Low Threshold Power using a Green Laser Beam

Three-Dimensional Direct Laser Writing of PEGda Hydrogel Microstructures with Low Threshold Power using a Green Laser Beam

Simultaneous Spectral and Spatial Modulation for Color Printing and Holography Using All-Dielectric Metasurfaces.

Metasurfaces possess the outstanding ability to tailor phase, amplitude, and even spectral responses of light with an unprecedented ultrahigh resolution and thus have attracted significant interest. Here, we propose and experimentally demonstrate a novel meta-device that integrates color printing and computer-generated holograms within a single-layer dielectric metasurface by modulating spectral and spatial responses at subwavelength scale, simultaneously. In our design, such metasurface appears as a microscopic color image under white light illumination, while encrypting two different holographic images that can be projected at the far-field when illuminated with red and green laser beams. We choose amorphous silicon dimers and nanofins as building components and use a modified parallel Gerchberg-Saxton algorithm to obtain multiple subholograms with arbitrary spatial shapes for image-indexed arrangements while avoiding the loss of phase information. Such a method can further extend the design freedom of metasurfaces. By exploiting spectral and spatial control at the level of individual pixels, multiple sets of independent information can be introduced into a single-layer device; the additional complexity and enlarged information capacity are promising for novel applications such as information security and anticounterfeiting.

Multifunctional Dielectric Metasurfaces Consisting of Color Holograms Encoded into Color Printed Images

AbstractA hologram records the wavefront of light from an object, but it is usually not an image itself, and looks unintelligible under diffuse ambient light. Here a new paradigm to encode a color hologram onto a color printed image is experimentally demonstrated. The printed image can be directly viewed under white light illumination, while a low‐crosstalk color holographic image can be seen when the device is illuminated with red (R), green (G), and blue (B) laser beams. The device is a dielectric metasurface that consists of titanium dioxide (TiO2) cones on a glass substrate. The dimensions of the TiO2 cones are chosen to allow them to support visible‐wavelength resonances, thereby producing the desired reflection spectra and thus the color printed image. The detour phase method is furthermore used to encode the hologram into the metasurface. The approach is conceptually different from previously demonstrated color printed images or holograms and presents opportunities for optical document security and data storage applications.

Optical analysis, optical limiting and electrical properties of novel PbI2/PVA polymeric nanocomposite films for electronic optoelectronic applications

This paper studied the influence of changing the lead iodide (PbI2), concentration in the PVA matrix through the structural, optical and electric measurements. Nanocomposite films have been defined by X-ray diffraction and FT-IR spectrometer which reveal the interaction between PVA and PbI2. The interplanar distance, particle size, and the average inter-crystalline separation were calculated. The optical properties of PbI2/PVA composites have been examined. PVA optical band gap was reduced from 5 to 3.49 in indirect transition and from 5.48 to 4.88 indirect transition to cause an increase in optical conductivity. Dielectric constant, and dielectric loss, and electrical conductivity, σ is increased with increasing PbI2 concentrations. So, the electrical conductivity σ can be controlled by the PbI2 doping percentage. PbI2/PVA showed laser power attenuation for both He-Ne and solid-state green laser beams. The results indicate that the nanocomposites are highly recommended in optoelectronic, radiation detection and many other applications.

Fabrication and remote laser ignition of Al/CuO energetic nanocomposites incorporated with functional dyes for enhanced light absorption

In this study, we investigated the effects of dyes on the laser ignition characteristics of Al nanoparticles (NPs) and CuO NPs-based energetic nanocomposites. Various functional dyes (e.g., N-719, rose bengal (RB), methylene blue (MB)) were employed as a light absorbing medium for Al/CuO energetic nanocomposites. According to UV–vis spectrometer analysis results, N-719, RB, and MB dyes had relatively strong light absorption in the blue, green, and red wavelength ranges, respectively. The results of red, green, and blue (RGB) laser ignition tests for various dye-coated Al/CuO composites demonstrated that the laser ignition threshold power density for the composites gradually decreased with increasing dye concentration. To test the possibility of selective optical ignition, the various dye-coated Al/CuO composites were irradiated using RGB laser beams operating with a fixed and relatively low power density. The results showed that the N-719-, RB-, and MB-coated Al/CuO composites were only successfully ignited under the condition of blue, green, and red laser beam irradiation, respectively. This suggests that energetic nanocomposites coated with special dyes could be employed as potential igniters and heat energy sources, the reactions of which are initiated by selective and remote light-energy irradiation, in various thermal engineering applications.

Optical linearity and bandgap analysis of RhB-doped PMMA/FTO polymeric composites films: A new designed optical system for laser power attenuation

Thin films of PMMA doped with Rhodamine B-dye have deposited successfully on a fluorine-doped tin oxide (FTO) glass substrate as a new optical system by using a spin coating method. This new system is promising to be used in various technological applications as solar energy cells, electronic apparatuses, devices of optical filter properties and optoelectronic tools. X-ray diffraction (XRD) illustrates a uniform and semicrystalline structure in nature for the obtained thin films. A spectrophotometric investigation was applied on the prepared thin films at the range of (300–2500 nm) for the wavelength. Both linear refractive index and absorption index values were measured to be reduced as the wavelength was raised. Tauc’s plot indicated that direct and indirect transitions were displayed by the thin film. Both direct and indirect bandgaps were calculated and analyzed. Continuous waves of the green laser beam (operating at 532), and He-Ne laser beam (operating at 632.8 nm) were used to study the optical properties of the prepared thin films with different dye concentrations. The results illustrated that the polymeric composites films are highly attenuated for the laser beam of 532 nm. The designed RhB-doped PMMA/FTO composites can be extensively appropriate to the optoelectronic applications.

Overview of SEAHAWK: A Bathymetric LiDAR Airborne Mapping System for Localization in Korea

Kim, H.; Tuell, G.; Park, J.Y.; Brown, E., and We, G., 2019. Overview of SEAHAWK: A bathymetric LiDAR airborne mapping system for localization in Korea. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 376-380. Coconut Creek (Florida), ISSN 0749-0208.This paper described the system test including from ground test to the first flight of Seahawk system in Korea. Seahawk system has been developed since 2014 at the first time in Korea by Ministry of Oceans and Fisheries. Seahawk has been recently integrated and system shakedown testing (on the ground). Airborne engineering flight test was in the first of June and flight test in Korea was in first of July. Seahawk system features a light weight, compact opto-mechanical design and achieves co-registered green and IR laser beams using a novel HOE (Holographic Optical Element) circular scanner. The Real Time Computation Engine (RTCE) displays 3D point clouds on the monitor in real time during operation to check missing data. In this paper, we introduce Seahawk system and report on the progress of its development.

Canine Motion Control Using Bright Spotlight Devices Mounted on a Suit

Engineering to produce stimuli that trigger an organism’s habits allows us to control it noninvasively. Because canines already have the habit to follow a light spot, light is a good stimulus for controlling their motion. We employed green laser beams to successfully control canine motion indoors. We developed a suit equipped with laser beam devices that face front, left, and right. The canine wore the suit and followed a light spot on the ground. Its trajectory was controlled remotely by switching the lights on the suit. However, this laser beam spot was too weak and small to be visible in grassy fields outdoors. Here, we propose a spotlight device that irradiates a bright and large spot (70 mm in diameter) for outdoor environments. The proposed spotlight device consists of a high brightness LED and a convex lens. To evaluate its performance, we conducted indoor and outdoor experiments using three canines. In the indoor experiments, the success rates of controlling the canine’s motions were 100%, 83.3%, and 93.3% for each of the three canines, respectively. In outdoor experiments, these rates were 100%, 57.1%, and 62.5%, respectively. Hence, the proposed spotlight devices are effective for controlling a canine even in outdoor environments.

High-Power Chaotic Green Laser Beam Generated by Perturbing a 520 nm Laser Diode with Optical Feedback

We designed a compact and efficient high-power laser that generates chaotic green light by perturbing a 520 nm laser diode with optical feedback. This achieved a continuous output power of 30 mW with a bandwidth of more than 1 GHz and an electrical-to-green conversion efficiency of 6.25%. All possible chaotic states were demonstrated for different diode-driving currents and feedback intensities. The FWHM and the peak side-lobe level (PSL) are affected by the injection current and feedback intensity. The FWHM increases with increasing feedback intensity, and the PSL increases with both injection current and feedback intensity. The compact chaotic laser could be used in underwater detection to suppress backscattering because of its intrinsic intensity modulation at high frequency. We finally found the optimum range of chaotic states for underwater detection, for which the ratio of input current to threshold current is 1.5 : 2.1.

Plasmon-mediated discrete diffraction behaviour of an array of responsive waveguides.

We investigate the discrete diffraction phenomenon in a Polymer-Liquid Crystal-Polymer Slices (POLICRYPS) overlaying a random distribution of gold nanoparticles (AuNPs, plasmonic elements). We study the propagation of a CW green laser beam through the waveguide structure as a function of beam polarization, laser intensity and sample temperature. It turns out that the plasmonic field created at the interface between AuNPs and POLICRYPS waveguides enables and stabilizes the optical field propagation within the responsive nematic liquid crystal channels. The active role of the liquid crystal is pointed out by a polarization, temperature and beam divergence experimental analysis and evidenced by a peculiar trumpet-shaped discrete diffraction pattern. Theoretical simulations confirm that the observed optical behavior is governed by the interaction of the nematic liquid crystal with optical and plasmonic fields.

Photoinduced Oxidation of a Surface of CaV0.5Mo0.5O3 − δ

CaV0.5Mo0.5O3 − δ with the structure of perovskite is synthesized in an atmosphere of humid hydrogen. It is found that when the material under study is moved into air, a nonequilibrium state forms due to the enhanced concentration of oxygen over the surface of the highly reduced oxide. It is shown that photoinitiated oxidation is observed on the surface of the material under the action of a low-power laser beam (50 mW), where it selectively occurs under a green laser beam (λ = 532 nm). This phenomenon is observed for such materials for the first time.

Single floating cell irradiation technique with an X-ray microbeam

A single floating cell irradiation technique with X-ray microbeam has been developed for the microscopic research of radiation effects on floating cells in a liquid medium. This technique is a combination of X-ray microbeam and laser technologies. A preliminary experiment on the survival of budding cells of the yeast Saccharomyces cerevisiae (RAD52) was performed with the X-ray microbeam system. Micro-pits were fabricated on the bottom of a culture dish in a liquid medium, using green laser beams. The yeast cells were put into the micro-pits one by one by using focused infrared laser beams. A 50-kV X-ray microbeam 12 μm (FWHM) in diameter was propagated into the targeted yeast cell. The maximum dose rate on the targeted cell was estimated to be 0.09 Gy/s from the results of beam profile measurements and photon-electron transport calculations. The X-ray irradiation effect on the cell lethality was clearly observed for the cell exposed to X-rays of 100 Gy.