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1.
Laser emission, consisting of three primary colors, is generated by frequency conversions of the second-harmonic emission of a picosecond (120 ps) Nd:YAG laser by means of stimulated Raman scattering and subsequent four-wave Raman mixing in molecular deuterium. In the double-pass configuration, the fundamental beam (532 nm, 14.16 mJ, 100%) is converted to blue (459 nm, 1.71 mJ, 12.1%), green (532 nm, 7.04 mJ, 49.7%), and red (632 nm, 4.90 mJ, 34.6%), resulting in a total conversion efficiency of 96.4%. 相似文献
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We report the experimental generation of a family of flattened Gaussian beams with bell-shaped, flattened, and annular intensity profiles in an electro-optically Q-switched Nd:YAG laser with a variable reflectivity mirror of a Gaussian reflectivity profile as an output coupler. The laser beams of different profiles were generated by modifying the resonator magnification. The propagation characteristics of the experimentally generated flat Gaussian beams were found to be in agreement with theory. To the best of our knowledge this is the first time such a family of flattened Gaussian beams is experimentally generated intracavity using a single variable reflectivity mirror. 相似文献
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Hyeonggeun Yoo 《Thin solid films》2010,518(10):2775-2778
Metal thin-film patterning is of technological significance because modern electronic devices commonly require an electrode or metallization pattern. There are many cases where this pattern consists of two different metallic layers in order to improve the mechanical and electrical contact. We here show that double-layered metal thin films evaporated on glass can be directly patterned by a spatially-modulated pulsed Nd-YAG laser beam incident from the backside of the substrate. This method utilizes a pulsed laser-induced thermo-elastic force exerting on the film which plays a role to detach it from the substrate. Since the film is polycrystalline with nano-sized grains, a spatially-modulated thermo-elastic force may enable selective removal of the material by shearing along the weakly-bonded grain boundary regions. Many different combinations of Al, Ag, and Au layers have been investigated and their pattern fidelity and morphology are discussed, along with the simulation results for double-layered nanocystalline films. 相似文献
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Nanosecond pulsed Bessel--Gauss beam generated directly from a Nd:YAG axicon-based resonator 总被引:3,自引:0,他引:3
We present what we believe to be a novel, simple, and compact axicon-based resonator Nd:YAG laser in which a nanosecond pulsed Bessel-Gauss beam is generated directly for the first time. Using the theory of the Bessel-Gauss beam, theoretical analysis and numerical simulation are consistent with the experimental results. 相似文献
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Chao-yu Li 《Journal of Modern Optics》2013,60(14):1323-1330
AbstractThe incident pump beam waist-dependent pulse energy generation in Nd:YAG/Cr4+:YAG composite crystal passively Q-switched microchip laser has been investigated experimentally and theoretically by moving the Nd:YAG/Cr4+:YAG composite crystal along the pump beam direction. Highest pulse energy of 0.4 mJ has been generated when the Nd:YAG/Cr4+:YAG composite crystal is moved about 6 mm away from the focused pump beam waist. Laser pulses with pulse width of 1.7 ns and peak power of over 235 kW have been achieved. The theoretically calculated effective laser beam area at different positions of Nd:YAG/Cr4+:YAG composite crystal along the pump beam direction is in good agreement with the experimental results. The highest peak power can be generated by adjusting the pump beam waist incident on the Nd:YAG/Cr4+:YAG composite crystal to optimize the effective laser beam area in passively Q-switched microchip laser. 相似文献
7.
Jiangrui G Hai W Maoquan H Changde X Kunchi P Zhenggang Y Changqin M Xuning W 《Applied optics》1995,34(9):1519-1522
Generation of an up to 1.5-W single-frequency and a 650-mW frequency-stabilized second harmonic at 1.06 μm has been demonstrated in a cw ring Nd:YAG laser with a pair of properly oriented KTP crystals in which the walk off between the intracavity modes has been eliminated. The frequency stability is better than 5 MHz for the second-harmonic output level of 650 mW. The fluctuation of power is less than 4%. PACS: 42.60. By. 42.65 Ky. 相似文献
8.
Influence of wavelengths and beam profiles of a pulsed Nd3+:YAG laser on the formation of a polycrystalline-silicon (poly-Si) on a-Si thin film is investigated. Two sets of samples of amorphous-Silicon (a-Si) thin films deposited on glass (a-Si/glass) and crystalline Si (a-Si/c-Si) substrates were treated with different laser-fluence values. After the laser treatment, the films were analyzed by a scanning electron microscope, the Raman spectroscopy technique and the resistance-measurement technique. In the case of the third harmonics (355 nm) of the Nd3+:YAG laser, poly-Si films were obtained with laser-fluence values ranging from 260 mJ/cm2 to 560 mJ/cm2, where as in the case of the second harmonics (532 nm), the process window for the formation of poly-Si films, in terms of the laser fluence, was ranging from 300 mJ/cm2 to 480 mJ/cm2. On the other hand, in the case of samples treated with the fundamental wavelength (1064 nm), a narrow process window with higher laser-fluence values around 1100 mJ/cm2 was observed. Further, the substrate was also affected because of the higher laser-fluence value. It has also been observed that the crystallization characteristics of poly-Si films improved with the flat-top intensity distribution as compared to the Gaussian intensity distribution of the Nd3+:YAG laser beam. A theoretical simulation based on thermal modeling was performed to understand the mechanism of crystallization. 相似文献
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G S Sithambaranathan J J Stamnes 《Journal of the Optical Society of America. A, Optics, image science, and vision》2001,18(7):1670-1677
We derive integral representations that are suitable for studying the transmission of an electromagnetic Gaussian beam through a plane interface that lies between an isotropic medium and a biaxially anisotropic crystal for the case in which the interface normal is along one of the principal axes of the crystal. To that end, we use recently developed exact solutions for the transmitted fields to derive explicit expressions for the corresponding dyadic Green's functions as well as integral representations that are suitable for asymptotic analysis and efficient numerical evaluation. 相似文献
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Stamnes JJ Dhayalan V 《Journal of the Optical Society of America. A, Optics, image science, and vision》2012,29(4):486-497
For a linearly polarized three-dimensional Gaussian beam in air that is normally incident upon a plane interface with a uniaxial crystal with optic axis in an arbitrary direction, we present integral representations for the transmitted field suitable for asymptotic analysis and efficient numerical evaluation and derive analytical expressions for transmitted nontruncated Gaussian beams for the cases in which the incident beam is polarized parallel to the plane containing the optic axis and the interface normal and transverse to it. The general solution for an arbitrary polarization state of an incident Gaussian beam follows by superposition of these two solutions. 相似文献
13.
Seshadri SR 《Journal of the Optical Society of America. A, Optics, image science, and vision》2003,20(9):1818-1826
Electromagnetic beams in a uniaxial crystal are treated with emphasis on the extraordinary mode. A virtual source that generates a basic elliptical Gaussian wave propagating obliquely to the optic axis is identified. An exact expression is obtained for this basic elliptical Gaussian wave that simplifies to the corresponding basic elliptical Gaussian beam in the appropriate limit. In the direction of amplitude propagation, the paraxial result becomes identical to the exact result and the sum of all the nonparaxial contributions vanish. The characteristics of the basic elliptical Gaussian beam are illustrated with a numerical example. From the spectral representation of the basic Gaussian wave, the first three orders of nonparaxial corrections for the basic elliptical Gaussian beam are determined. The nonparaxial results reduce correctly to those of the fundamental Gaussian beam in an isotropic medium. 相似文献
14.
Nemoto S 《Applied optics》1986,25(21):3859-3863
A simple method is presented for determining the waist position and the waist size of a Gaussian beam from measured spot sizes. The method does not require any least-squares process, and substitution of measured spot sizes directly into the formulas gives the waist parameters. Only few data are required to determine the parameters accurately as long as measured spot sizes contain small errors. 相似文献
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Lina Zhang 《Journal of Modern Optics》2013,60(14):1224-1232
Paraxial propagation of a linearly polarised twisted Gaussian Schell-model (TGSM) beam in a uniaxial crystal is investigated. With the help of a tensor method, an analytical formula for the cross-spectral density (CSD) of a TGSM beam propagating in a uniaxial crystal orthogonal to the optical axis is derived. The evolution properties of the intensity distribution, the coherence widths and the twist factor of a TGSM beam in a uniaxial crystal are illustrated numerically. It is shown that the TGSM beam becomes an anisotropic TGSM beam in a uniaxial crystal and its evolution properties are closely related with its initial coherence, twist factor and the parameters of the crystal. The uniaxial crystal provides an effective way for modulating the properties of a TGSM beam, which will be useful in some applications, such as free-space optical communications and nonlinear optics, where a partially coherent beam with controlled beam profile and twist factor is required. 相似文献
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Acoustooptic 2-D profile shaping of a Gaussian laser beam has been achieved by two plane ultrasonic waves progressing in orthogonal directions. The spot size W of the Gaussian laser beam must be considerable less than the wavelength lambda of the ultrasonic wave at the acoustooptic interaction region. The ultrasonic cell is dealt with as a Raman-Nath 2-D phase grating but serves as a 2-D beam deflector in time for the interaction scheme of interest. The wave front of the Gaussian laser beam must be almost plane in the interaction region. The profile shaping condition is 0.15 < or = (W/lambda) < or = 0.30 only when the Raman-Nath parameter dependent on the ultrasonic power has values between v = 1.0 and 2.0. 相似文献
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J J Stamnes V Dhayalan 《Journal of the Optical Society of America. A, Optics, image science, and vision》2001,18(7):1662-1669
We study the transmission of a two-dimensional (2-D) TM Gaussian beam through a plane interface between an isotropic medium (e.g., air) and a uniaxially anisotropic crystal. The optic axis of the crystal is taken to be in the plane of incidence but is arbitrarily oriented relative to the interface normal. We show that, in the paraxial approximation, a nontruncated transmitted 2-D TM Gaussian beam inside a uniaxial crystal can be expressed in a form similar to that of a scalar Gaussian beam that propagates in a homogeneous medium. We also show that the transmitted beam corresponding to an incident 2-D TM Gaussian beam with its main propagation direction along the interface normal is tilted inside the crystal by the same angle as is the transmitted axial ray that corresponds to a normally incident ray. 相似文献
18.
Delivery of 10-MW Nd:YAG laser pulses by large-core optical fibers: dependence of the laser-intensity profile on beam propagation 总被引:2,自引:0,他引:2
A large-core multimode optical fiber of a few meters length is studied as a 10-MW beam delivery system for a 15-ns pulsed Nd:YAG laser. A laser-to-fiber vacuum coupler is used to inhibit air breakdown and reduce the probability of dielectric breakdown on the fiber front surface. Laser-induced damage inside the fiber core is observed behind the fiber front surface. An explanation based on a high power density is illustrated by a ray trace. Damaged spots and measurements of fiber output energies are reported for two laser beam distributions: a flat-hat type and a near-Gaussian type. Experiments have been performed to deliver a 100-pulse mean energy between 100 and 230 mJ without catastrophic damage. 相似文献
19.
We show that the temporal broadening of a pulsed, tightly focused TEM(00) beam propagating in a scattering medium can be accurately modeled as a convolution between the initial pulse profile and an effective impulse response that is given by the propagation behavior of an infinitely thin pulse in the said medium. The impulse response is obtained with a Monte Carlo (MC) analysis of the propagating photons in the impulse. Our algorithm is 2 orders of magnitude less complex than the full MC solution of the pulse propagation problem. The accuracies, however, are comparable even for scattering path lengths that are 20 times the mean free path. 相似文献
20.
L.C. Nistor V.S. Teodorescu M. Dinescu N. Frangis C. Liutas 《Materials Research Bulletin》2004,39(13):2089-2101
Hydroxyapatite (HA) thin films has been successfully deposited by Nd:YAG laser ablation at λ = 532 nm. The morphology and microstructure of the deposited layers was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). Polycrystalline HA films were directly obtained with the substrate at 300 °C and without introducing water vapors in the deposition chamber. Electron paramagnetic resonance (EPR) measurements show that the oxygen stoichiometry in the HA films is also maintained. Depositions performed at λ = 335 nm laser wavelength and 300 °C substrate temperature resulted in polycrystalline layers of mixed composition of HA and tricalciumphosphate (TCP). 相似文献