YAG Green Laser Research Articles

Fabrication and improved response of ZnO-CdO composite films under different laser irradiation dose

Promising Zinc Oxide (ZnO) and Cadmium Oxide (CdO) alloy (ZnO-CdO) films were fabricated on glass substrates by screen printing route for optoelectronic applications. The Nd:YAG green diode laser of wavelength 532 nm and laser fluence of 1.8 J/cm2 was used to irradiate the fabricated films at room temperature. The characterization of these films were systematically studied by means of X-ray diffraction (XRD), UV–vis, photoluminescence (PL), Raman spectroscopy and two probe method for conductivity measurement. The XRD pattern shows that all the films were well crystallized with maximum diffraction of (101) plane and mixed phases of ZnO and CdO were detected. The structure, space group and other crystal related parameters were confirmed from Rietveld refinement of XRD data. The basic optical parameters (band gap, refractive index and extinction coefficient) have been estimated using absorbance spectra. The PL spectrum of ZnO-CdO composite films exhibits red shift and blue- green emissions shift upon laser irradiation were confirmed from CIE 1931 diagram. The Raman spectroscopy indicates that the quality of the ZnO-CdO films was increased while their structure defects were increased. DC conductivity measurement confirms semiconductor behaviour. All the parameters such as particle size, optical constants, colour emission and activation energy have been significantly improved upon laser irradiations dose of 1.8 J/cm2 for different durations of time. This study could be appropriate for optoelectronic applications.

2PA induced optical limiting behaviour of metal (Ni, Cu, Zn) niobate decorated reduced graphene oxide

Nanopulsed Nd:YAG green laser induced nonlinear absorption and optical limiting properties of metal niobate decorated reduced graphene oxide were studied by single beam Z-scan experiment. Initially reduced graphene oxide was decorated with metal niobates MNb2O6 (with M = Ni/Cu/Zn) using one-step hydrothermal method. Formation of stable orthorhombic (nickel, copper and zinc) niobate by annealing at different temperatures (950 °C, 850 °C and 900 °C) and metal niobate/rGO composites was confirmed through XRD and Raman studies. SEM with EDS exposed the incorporation of inorganic species and agglomerated spherical metal niobate morphologies upon graphene layers. The absorption band edge of pure metal niobate was observed around 320 nm (ZnNb2O6) and it was blue shifted to 300 nm in metal niobate:rGO composite (ZnNb2O6:rGO). Open aperture Z-scan pattern ascertained the presence of reverse saturable absorption (RSA) ascribed due to genuine two-photon (2 PA) absorption process. Metal niobate decorated rGO possess high 2 PA coefficient (1.42 × 10−10 m/W) and onset optical limiting threshold (1.05 × 1013 W/m2) than pure metal niobates and rGO. Among the samples, ZnNb2O6: rGO showed stronger nonlinear absorption and optical limiting performance than its counterparts and other known OL materials like GO, Au: GO, C60 etc., excited under similar excitation conditions. The obtained result consolidates that enhanced OL action of metal niobate decorated rGO find potential application in laser safety devices and energy stabilizer in most widely used 532 nm, 9ns laser domain.

Energy absorbing and energy spreading optical limiting action of 2-amino 5-nitropyridinium derivatives

By Nd:YAG green laser driven Z-scan experiment, nonlinear optical properties of 2-amino 5-nitropyridinium derivatives (2A5NPCl and 2A5NPBr) are studied. Both the samples exhibit genuine 2 PA induced electro-optic based optical limiting action process under pulsed (5 ns, 100 μJ) mode. And they display self-defocusing promoted thermo-optic based optical limiting action under continuous wave (50 mW) mode. NLO coefficients and thermodynamic properties of 2A5NPBr is higher than 2A5NPCl. Results show 2A5NPBr molecular liquids are superior for energy absorbing and energy spreading optical limiting applications to prevent the laser damages from nano pulsed and CW green laser excitation.

Genuine two photon absorption and excited state absorption in Fe nanowires decorated β-BaB2O4 nanoplatelets

Concentration dependent nonlinear absorption and optical limiting action of Fe nanowires decorated β-BaB2O4 nanoplatelets was studied by Z-scan experiment using Q-switched nano pulsed Nd:YAG green laser. Open aperture Z-scan curves with valley like pattern indicates the existence of reverse saturable nonlinear absorption (RSA). Intensity dependent nonlinear absorption studies shows the Fe concentration dependent transition of genuine two photon absorption (2 PA) to excited state absorption (ESA). Interesting transition to ESA process in 0.05 M Fe decorated β-BaB2O4 arises due to the availability of near-resonant state (trapped defect state, 2.3 eV). Along with transition in nonlinear absorption, incorporation of Fe in β-BaB2O4 enhanced NLO behavior leading to strong optical limiting action than pristine β-BaB2O4. 0.05 M Fe nanowires decorated β-BaB2O4 nanoplatelets possess higher 2 PA coefficient (1.6 × 10−10 m/W) and lower onset limiting threshold (1.03 × 1012 W/m2) and thus ensure its superiority for OL applications. Earlier Fe decorated β-BaB2O4 were prepared by hydrothermal method with three decorating concentration (0.01 M, 0.03 M and 0.05 M). The incorporation and distribution of Fe3+ ions in β-BaB2O4 was confirmed by XRD, EDS and FTIR analysis. FESEM and HRTEM confirm the presence of densely packed nanowires of Fe ions upon BBO nanoplatelets through densification process arising from the strong attractive force of Fe3+ ions. Altogether Fe decorated β-BaB2O4 nanostructure with superior NLO coefficients finds potential application as laser safety devices for widely used 532 nm nanopulsed laser.

Second and third-order NLO response of 2-amino-5-nitropyridinium tetrafluoroborate

Based on host-guest chemistry, a semiorganic NLO material 2-amino-5-nitropyridinium tetrafluoroborate [2A5NPFB] was synthesized and grown as single crystals. SXRD of 2A5NPFB reveals its crystal structural details as orthorhombic crystal system, Fdd2 space group, a = 22.474 (1) Å, b = 30.127 (9) Ǻ, c = 4.9584 (1) Ǻ and α = β = γ = 90°. Protonation site, charge transfer interaction and molecular structure were studied by FTIR analysis. Thermal studies predicts the melting point of 2A5NPFB as 145 °C. 2A5NPFB possess strong absorption (λmax = 350 nm) in ultraviolet region and has a broad transparency window (420–1100 nm). Kurtz and Z-scan technique explores the second and third-order NLO response of 2A5NPFB single crystal. Compared to KDP crystal, 2A5NPFB single crystal possesses 35 times higher Second Harmonic Generation efficiency. 2A5NPFB crystal exhibit saturable absorption, self defocusing and optical limiting action under continuous wave Nd:YAG green laser.

Growth of KDP single crystal in second harmonic direction by modified Sankaranarayanan–Ramasamy method

KDP single crystal was successfully grown in second harmonic direction (SHD) in aqueous solution by modified Sankaranarayanan–Ramasamy method. Apart from usual characterization techniques employed to study the physical properties of the grown crystal such as X-ray diffraction, Fourier transform infrared, UV–Vis spectroscopy techniques and Vicker,s microhardness measurement, the grown crystal was subjected to a Nd:YAG laser (1064 nm) and green color laser light (532 nm) was observed. UV–Vis analysis of second harmonic and directions showed that the transmission of the later one was higher. Vicker’s microhardness studies of direction showed that it is harder than SHD.

Surface modification of Y2O3:Er,Yb upconversion nanoparticles prepared by laser ablation in water

Y2O3:Er,Yb upconversion nanoparticles were prepared by laser ablation in liquid and capped with poly(ethylene glycol) (PEG). A Nd:YAG green laser with nanosecond pulse duration was used. Capping was carried out by a two-step process. The first step is surface modification using a silane coupling agent, (3-aminopropyl)triethoxysilane (APTES), to aminate the surface of nanoparticles. The second step was the conjugation of PEG chains to the surface by amido binding reaction between the surface amino groups and activated esters connected to PEG. The prepared upconversion nanoparticles were highly crystalline polycrystals, the particle size of which was approximately 20 nm. Dopants in phosphor nanoparticles were not removed by laser irradiation. The spectra of PEG-capped nanoparticles were almost the same as those of uncapped nanoparticles. The capped nanoparticles would be useful for biomedical applications.

325 mJ and 46 ns 532 nm Q-switched Nd:YAG laser at 500 Hz

A laser diode side-pumped electro-optical Q-switched Nd:YAG green light laser with high repetition rates, short pulse width, and high peak power was demonstrated. We studied the performance of the oscillator at the repetition rates from 100 to 500 Hz. At 500 Hz, 61 mJ, 5 ns of 1064 nm infrared light pulses were obtained with an oscillator-amplifier system. The peak power of the pulse was 12 MW. By frequency doubling with a LiB(3)O(5)(LBO) crystal, 32.5 mJ, 4.6 ns of 532 nm green light was achieved, corresponding to a peak power of 7 MW. The frequency conversion efficiency was 53.3%.

Role of focal laser ablation in the treatment of type 1 idiopathic juxtafoveolar retinal telangiectasis

Introduction Idiopathic juxtafoveolar retinal telangiectasis (IJRT) is a retinal vascular anomaly characterized by irregular dilation and incompetence of retinal vessels. Although the etiology of the condition is unknown, its various presentations have been characterized into three groups. Treatment is based mainly on disease classification and includes laser photocoagulation and observation besides other modalities. Aim The aim of the work was to study the role of focal laser treatment for type 1 IJRT. Patients and methods A retrospective noncomparative study was carried out at the Ophthalmology Department, Menoufia University, Egypt, during the period from January 2007 to December 2011, wherein four patients (three male and one female) diagnosed with type 1 (exudative) IJRT on the basis of fluorescein angiography and after ruling out other causes were included in the study. Four eyes with macular edema and exudation were subjected to focal laser treatment (double-frequency YAG) with green laser (wavelength 532 nm). The follow-up period after laser treatment extended from 6 to 24 months. Results Four patients diagnosed with type 1 IJRT were included in the study (three male and one female). Their age ranged from 40 to 42 years, with a mean age of 40.75 years. Focal double-frequency YAG green laser (wavelength 532 nm) treatment resulted in the reduction of both macular edema and exudation with improvement in visual acuity from one to two lines on follow-up. Conclusion Focal laser treatment of type 1 IJRT lesions proved to be effective. The treatment is a safe method for managing leakage and stabilizing vision.

Portable 532 nm Iodine-Stabilized DPSS Laser for Length Standard

A diode-pumped solid-state (DPSS) laser, such as a Nd:YAG green laser, has become smaller in size , lower in cost and higher in performance. Therefore, the DPSS lasers are widely used in many industries. For a laser interferometers and secondly length standards, stable light sources are in demand. We have developed 532 nm iodine-stabilized DPSS lasers used for the applications. The lasers have following features ; compact design (D 280×W 170×H 120 mm), high power (3 mW) , high stability ( < 1×10-10 : allann deviation k=1 at τ=1 sec), and easy operation.

大流量ウォータージェットの流動構造とボイド率分布

In this study, the laser tomography method was applied to measure the void fraction distribution of the water jet in radial direction and axial direction. The continuous laser beam emitted by Nd:YAG green laser (wavelength=532nm, beam diameter=0.25mm) is introduced into the water jet in normal to the flow direction. The laser beam is emitted toward the photo detector, which is located at the opposite side. The photo detector can detect the transmissivity of the laser beam passing across the cross section of the jet. By detecting the laser at the photo detector, we can get the transmissivity distribution of the jet in radial direction. By using this measured transmissivity distribution data, we can reconstruct the void fraction distribution inside of the jet by using the tomography method. For the image reconstruction, we applied ML-EM method (Maximum Likelihood — Expectation Maximization) and assumed that the water jet droplet follows some specific distribution. By using these techniques, the void fraction distribution of the extreme high speed water jet can be successfully measured.

Randomised trial of sequential pretreatment for Nd:YAG laser iridotomy in dark irides

AimsTo compare iridotomy outcomes in dark irides by 1064 nm pulsed Nd:YAG laser with and without 532 nm continuous-wave Nd:YAG (frequency-doubled) green laser pretreatment.Methods30 patients with occludable anterior chamber angles...

Titanium-doped sputter-deposited AlN infrared whispering gallery mode microlaser on optical fibers

Optical fibers of 12 μm diameter were coated with a sputter-deposited layer (4 μm thick) of titanium (1 at. %)-doped amorphous aluminum nitride. When optically pumped by an Nd:YAG green laser at 532 nm, laser action was observed in whispering gallery modes around the fiber (in a ring shape) at 780.5 nm with a quality factor Q > 1500. Other modes were also observed between 775 and 800 nm. The primary and secondary modes give a mode separation of 4.6 nm. No waveguide modes were observed in the cavity.

High repetition rate intracavity frequency doubled LD side-pumped ceramic Nd:YAG green laser based on BBO electro-optical Q-switch

a high repetition rate and high power 532 nm green laser generated by intracavity frequency doubling of a 808 nm laser diode side-pumped ceramic Nd:YAG laser based on BBO electro-optical Q-switch has been demonstrated. in the simple V-folded cavity, the maximum green laser average power 32.6 W was obtained with a pulse width of 58.5 ns at a repetition rate of 10 kHz by using a LBO crystal for frequency doubling, corresponding to a conversion efficiency of 10.9% from diode pumping power to green laser power. An instability of 1.9% was measured over a period of 30 minutes and the beam quality factors were measured to be M x 2 = 3.55, M y 2 = 3.89 at the maximum output power.

Laser diode end-pumped Yb:YAG/LBO green laser

With a type-I critical phase-matching LBO crystal, an intracavity frequency doubled solid-stated Yb:YAG green laser is reported. Using a plano-concave resonator, with pump power of 1.37 W, 24.5 mW TEM00 continuous wave laser at 525 nm was obtained. The optical conversion efficiency is 1.8%. By adjusting the placed angle of LBO, several lasers wavelength from 525.0 to 537.8 nm could be extracted. The maximum output power at 537.8 nm is 3.1 mW.

Wood engraving by Q-switched diode-pumped frequency-doubled Nd:YAG green laser

Laser deep engraving is one of the most promising technologies to be used in wood carver operations. In this method, a laser beam is used to ablate a solid wood bulk, following predetermined patterns. The sculpture is obtained by repeating this process on each successive thin layer. Obviously, in order to achieve larger material removal rates, the process needs a controllable variation of the depth to carve a 3D (three dimensional) profiles. The degree of precision of the shape, the removal rate and the surface quality during the engraving process strictly depend on the materials properties, the laser source characteristics and the process parameters. The aim of this work is to investigate the influence of the process parameters on the material removal rates by engraving panels made of different types of wood using a Q-switched diode-pumped Nd:YAG green laser working with a wavelength λ=532 nm. The examined parameters were: the mean power that depends on the pulse frequency, the beam speed and the number of laser scansions, also called repetitions. The working parameters and the engraved depth were related and an energy-based model was proposed in order to predict the latter. Experimental results showed that the Q-switched diode-pumped frequency-doubled Nd:YAG green laser can be successfully used to machine different types of wood, obtaining decorative drawing and 3D engraved geometries without burning. However, an accurate selection of the wood types and the process parameters is necessary in order to obtain deep engraving without carbonization and a homogeneous carving.

Design of diode-pumped dual-frequency Nd:YAG green laser with large frequency difference for absolute-distance interferometry

A novel scheme of diode-pumped dual-frequency Nd:YAG green laser with large frequency difference is proposed in this paper. When a polarized beam splitter (PBS) is placed in resonant cavity of a diode-pumped intracavity KTP-frequency-doubled Nd:YAG green laser, a new birefringent filter consisting of PBS and KTP is formed (i.e., PBS-KTP) to select single longitudinal mode. A diode-pumped two-cavity dual-frequency green laser with a common medium of Nd:YAG has been designed, each resonant cavity of which is enforced to operate in single longitudinal mode by means of the birefringent filter of PBS-KTP. The frequency difference of the dual-frequency Nd:YAG laser at 532-nm can be tuned in a range of 0∼360GHz, and its stability can be achieved approximately 10−6 by use of the Pound-Drever-Hall technique. Such a dual-frequency laser will be employed as an ideal light source of an absolute-distance interferometric system. The design principle is introduced briefly, the scheme and its feasibility of the dual-frequency laser are described and analyzed, respectively, and some preliminary results obtained experimentally are given.

LD side-pumped intracavity frequency-doubled high power Nd: YAG green laser based on acousto-optic Q-switch

A highly efficient and high power green laser generated by intracavity frequency doubling of a diode-sidepumped Q-switched Nd: YAG laser has been demonstrated. In the simple L-shaped cavity geometry, the maximum green output power of 28.5 W was obtained with a pulse width of 95 ns at a pulse repetition rate of 10 kHz by using a LBO crystal for frequency doubling, corresponding to a conversion efficiency of 11% from diode pump power to pulse green power. At a pulse repetition rate of 1. kHz, 6.9 mJ of pulse energy, 25 ns of pulse duration and 276 kW of peak power were obtained.

Diode end-pumped self-Q-switched and mode-locked Nd,Cr:YAG /KTP green laser

We first experimentally demonstrate a laser-diode end-pumped self-Q-switched and mode-locked Nd,Cr:YAG green laser with a KTP crystal as the intra-cavity frequency doubler. The device produces an average output power of 680 mW at 532 nm. The corresponding pulse width of the Q-switched envelope of the green laser is 170 ± 20 ns. The mode-locked pulses have a repetition rate of approximately 183 MHz and the average pulse duration is estimated to be around sub-nanosecond. It is found that the intra-cavity frequency doubling greatly improves the modulation depth and stability of the mode-locked pulses within the Q-switched envelope.

1TW, 10 Hz and 0.1TW, 1 kHz All-Solid-State Femtosecond Lasers

We have designed and developed two types of all-solid-state femtosecond Ti: sapphire laser systems by using diode-pumped Nd: YAG green laser systems as pump sources. One is a high-peak-power femtosecond laser system with a peak power of 1.1 TW, a pulse duration of 74 fs, and a beam quality factor M2≤1.4 at a repetition rate of 10 Hz, the other is a high-repetition-rate femtosecond laser system with an average power of 10.1 W, a peak power of 0.1 TW, a pulse duration of 100 fs, and a beam quality factor M2≥1.5 at a high repetition rate of 1 kHz. We also discuss the development of the diode-pumped Nd: YAG green laser systems for pumping these Ti: sapphire laser systems.