共查询到20条相似文献,搜索用时 31 毫秒
1.
K. Okazaki S. Torii T. Makimura H. Niino K. Murakami D. Nakamura A. Takahashi T. Okada 《Applied Physics A: Materials Science & Processing》2011,104(2):593-599
We investigated a simple and productive micromachining method of silica glass by ablation using a TEA CO2 laser (10.6 μm) with a spatial resolution down to sub-wavelength scale. The silica glass was irradiated by the TEA CO2 laser light through a copper grid mask with square apertures of 20×20 μm2 attached to the silica glass surface. After the irradiation, circular holes with a diameter of several μm were formed on
the silica glass surface at the centers of the apertures due to the Fresnel diffraction effect. The minimum diameter of the
holes was 3.4 μm. The characteristics of the micromachining are discussed based on the electric field distributions of the
CO2 laser light under the mask using a three-dimensional full-wave electromagnetic field simulation. 相似文献
2.
This paper presents a specially designed optical parametric oscillator (OPO) which achieved high-efficiency mid-infrared laser
of 2.83 μm. The cascaded nonlinear interactions of OPO and optical parametric amplifier (OPA) were simultaneously realized
in a single MgO:PPLN crystal. The signal oscillation of 1.70 μm was used to pump a secondary parametric process that resulted
in amplification of the idler laser of 2.83 μm. When the MgO:PPLN crystal with a grating period of 31.2 μm was pumped by a
1.064 μm laser and operated at 148°C, the quasi-phase-matching of both OPO and OPA could be simultaneously achieved. Average
output power of 7.68 W at 2.83 μm was obtained for 25 W of pump at 7 kHz. The power conversion efficiency of 2.83 μm laser
was 30.7%, which was evidently higher than common OPOs. 相似文献
3.
Mohammod Aminuzzaman Akira Watanabe Tokuji Miyashita 《Journal of nanoparticle research》2010,12(3):931-938
This article describes fabrication of Ag micropatterns on a flexible polyimide (PI) film by laser direct writing using an
Ag nanoparticle-dispersed film as a precursor. Ag micropatterns are characterized by optical microscopy, atomic force microscopy
(AFM), field emission scanning electron microscopy (FE-SEM), surface profilometry, and resistivity measurements. The line
width of Ag micropatterns can be effectively controlled by altering the experimental parameters of laser direct writing especially
laser intensity, objective lens, and laser beam scanning speed etc. Using an objective lens of 100× and laser intensity of
170.50 kW/cm2, Ag micropatterns with a line width of about 6 μm have been achieved. The Ag micropatterns show strong adhesion to polyimide
surface as evaluated by Scotch-tape test. The resistivity of the Ag micropatterns is determined to be 4.1 × 10−6 Ω cm using two-point probe method. This value is comparable with the resistivity of bulk Ag (1.6 × 10−6 Ω cm). 相似文献
4.
Fei He Haiyi Sun Min Huang Jian Xu Yang Liao Zenghui Zhou Ya Cheng Zhizhan Xu Koji Sugioka Katsumi Midorikawa 《Applied Physics A: Materials Science & Processing》2009,97(4):853-857
We report on rapid fabrication of optical volume gratings in Foturan glass using a modulated femtosecond laser focused with
cylindrical lenses. An optical volume grating with an area of 2 mm ×3 mm and ∼2 mm thickness can be achieved within 10 min
by use of this method. Optical micrography confirms the volume nature of the gratings and shows that they consist of 10 μm-thickness
planes with a period of 15 μm. The diffraction efficiency is examined to be ∼56%. The limitations and future implementations
of the fabricated volume gratings are discussed. 相似文献
5.
S.?Sujecki L.?Sójka E.?Bere?-Pawlik Z.?Tang D.?Furniss A.?B.?Seddon T.?M.?Benson 《Optical and Quantum Electronics》2010,42(2):69-79
A simple Dy3+-doped chalcogenide glass fibre laser design for mid-infrared light generation is studied using a one dimensional rate equation
model. The fibre laser design employs the concept of cascade lasing. The results obtained demonstrate that efficient cascade
lasing may be achieved in practice without the need for fibre grating fabrication, as a sufficient level of feedback for laser
action is provided by Fresnel light reflection at chalcogenide glass fibre–air interfaces. Further enhancement of the laser
efficiency can be achieved by terminating one of the fibre ends with a mirror. A numerical analysis of the effect of the Dy3+ doping concentration and fibre loss on the laser operation shows that with 5 W of pump power, at 1.71 μm wavelength, output
powers above 100 mW at ∼ 4.5 μm wavelength can be achieved with Dy3+ ion concentrations as low as 3 × 1019 cm−3, when fibre loss is of the order 1dB/m. 相似文献
6.
Otto?H?nninen Irene?Brüske-Hohlfeld Miranda?Loh Tobias?Stoeger Wolfgang?Kreyling Otmar?Schmid Annette?Peters 《Journal of nanoparticle research》2010,12(1):91-99
Several studies have reported laser printers as significant sources of nanosized particles (<0.1 μm). Laser printers are used
occupationally in office environments and by consumers in their homes. The current work combines existing epidemiological
and toxicological evidence on particle-related health effects, measuring doses as mass, particle number and surface area,
to estimate and compare the potential risks in occupational and consumer exposure scenarios related to the use of laser printers.
The daily uptake of laser printer particles was estimated based on measured particle size distributions and lung deposition
modelling. The obtained daily uptakes (particle mass 0.15–0.44 μg d−1; particle number 1.1–3.1 × 109 d−1) were estimated to correspond to 4–13 (mass) or 12–34 (number) deaths per million persons exposed on the basis of epidemiological
risk estimates for ambient particles. These risks are higher than the generally used definition of acceptable risk of 1 × 10−6, but substantially lower than the estimated risks due to ambient particles. Toxicological studies on ambient particles revealed
consistent values for lowest observed effect levels (LOELs) which were converted into equivalent daily uptakes using allometric
scaling. These LOEL uptakes were by a factor of about 330–1,000 (mass) and 1,000–2,500 (particle surface area) higher than
estimated uptakes from printers. This toxicological assessment would indicate no significant health risks due to printer particles.
Finally, our study suggests that particle number (not mass) and mass (not surface area) are the most conservative risk metrics
for the epidemiological and toxicological risks presented here, respectively. 相似文献
7.
T. Asshauer G. Delacrétaz E.D. Jansen A.J. Welch M. Frenz 《Applied physics. B, Lasers and optics》1997,65(4-5):647-657
5 Pa served as tissue phantoms to evaluate such effects. Holmium laser pulses (wavelength: 2.12 μm, duration: 180 μs FWHM),
were delivered through 400 and 600 μm diameter optical fibers inserted into cubes of clear gel. Bubble effects were investigated
using simultaneous flash micro-videography and pressure recording for radiant exposures of 20–382 J/cm2.
Bubble formation and bubble collapse induced pressure transients were observed regardless of phantom stiffness. Bubbles of
up to 4.2 mm in length were observed in gels with a Young’s modulus of 2.9×105 Pa at a pulse energy of 650 mJ. An increase of Young’s modulus (reduction in water content) led to a monotonic reduction
of bubble size. In the softest gels, bubble dimensions exceeded those observed in water. Pressure amplitudes at 3 mm decreased
from 100±14 bars to 17±6 bars with increasing Young’s modulus over the studied range. Theoretical analysis suggested a major
influence on bubble dynamics of the mass and energy transfer through the bubble boundary.
Received: 26 August 1996/Revised version: 10 February 1997 相似文献
8.
M.?Silies H.?Witte S.?Linden J.?Kutzner I.?Uschmann E.?F?rster H.?Zacharias 《Applied Physics A: Materials Science & Processing》2009,96(1):59-67
The interaction of ultrashort laser pulses with solid state targets is studied concerning the production of short X-ray pulses
with photon energies up to about 10 keV. The influence of various parameters such as pulse energy, repetition rate of the
laser system, focusing conditions, the application of prepulses, and the chirp of the laser pulses on the efficiency of this
highly nonlinear process is examined. In order to increase the X-ray flux, the laser pulse energy is increased by a 2nd multipass
amplifier from 750 μJ to 5 mJ. By applying up to 4 mJ of the pulse energy a X-ray flux of 4×1010 Fe K
α
photons/s or 2.75×1010 Cu K
α
photons/s are generated. The energy conversion efficiency is therefore calculated to η
Fe≈1.4×10−5 and η
Cu≈1.0×10−5. The X-ray source size is determined to 15×25 μm2. By focusing the produced X-rays using a toroidally bent crystal a quasi-monochromatic X-ray point source with a diameter
of 56 μm×70μm is produced containing ≈104 Fe K
α1 photons/s which permits the investigation of lattice dynamics on a picosecond or even sub-picosecond time scale. The lattice
movement of a GaAs(111) crystal is shown as a typical application. 相似文献
9.
The Analysis of Scattering Effect for the Transmission of 1.06?μm Laser In Lower Altitude Atmosphere
Shi-Quan Zhang 《International Journal of Infrared and Millimeter Waves》2007,28(6):491-497
On the basis of Mie’s scattering theory, the light scattering properties of atmospheric molecules and aerosol particles are
analyzed and a forward-scattering model for atmospheric transmission in city outskirts is built. Through theoretical analysis
and the numerical calculations to the irradiance distribution of the 1.06 μm pulse laser while transmitting in lower altitude
atmosphere, we can draw some conclusions which provide usable information for the research and manufacture of off-axis scattering
warning systems. 相似文献
10.
P. Frank F. Lang M. Mosbacher J. Boneberg P. Leiderer 《Applied Physics A: Materials Science & Processing》2008,93(1):1-4
Steam Laser Cleaning with a pulsed infrared laser source is investigated. The infrared light is tuned to the absorption maximum
of water (λ=2.94 μm, 10 ns), whereas the substrates used are transparent (glass, silicon). Thus a thin liquid water layer condensed on
top of the contaminated substrate is rapidly heated. The pressure generated during the subsequent phase explosion generates
a cleaning force which exceeds the adhesion of the particles. We examine the cleaning threshold in single shot experiments
for particles sized from 1 μm down to 300 nm. 相似文献
11.
Yihong Liu David D. Nolte Laura J. Pyrak-Nolte 《Applied Physics A: Materials Science & Processing》2010,100(1):181-191
Microporous structures are central to many fields of science and engineering, but many of these systems are complex with little
or no symmetry and are difficult to fabricate. We applied two-photon polymerization (2PP) and femtosecond laser direct-writing
techniques to fabricate broad-area large-format 3D microporous structures (450 μm × 450 μm × 40 μm) in the epoxy-based photoresist
SU-8. The appropriate exposure was determined by controlling average pulse energies and stage speeds to generate the exposure
curves. Mechanical distortion exhibited in suspended walls fabricated by 2PP laser writing was studied by controlling wall
lengths and widths. A simple thermal-expansion model is presented to explain the distortion caused by axial loadings of the
walls. 相似文献
12.
Y. H. Liu X. J. Lv Z. D. Xie X. P. Hu Y. Yuan J. Lu L. N. Zhao G. Zhao S. N. Zhu 《Applied physics. B, Lasers and optics》2012,106(2):267-270
We demonstrate a high efficiency mid-infrared laser source based on optical parametric oscillator (OPO) assisted by an intracavity
optical parametric amplification (OPA). The OPA-assisted-OPO scheme was realized in one piece of commensurable dual-periodic
superlattice in which the signal light generated from the OPO process serves as the pump light for the OPA process. A maximum
output power of 508 mW at 3.92 μm was achieved under a pump power of 2.85 W at 1.064 μm. The pump-to-idler conversion efficiency
is 17.8% and the slope efficiency is 23.8%, and the enhancements of them are 58.9% and 67.6%, respectively, comparing with
the standard OPO scheme. 相似文献
13.
K. R. Allakhverdiev M. Ö. Yetis T. K. Baykara S. M. T. Özbek E. Yu. Salaev 《Laser Physics》2011,21(3):598-600
Two methods of preparation of the devices for visualization of pulsed and continuous near-IR (near infrared) are described
and the results of conversion of pulsed and continuous IR (800–1360 nm) laser radiation into the visible range of spectra
(400–680 nm) by using a transparent substrate covered with the particles (including nanoparticles) of effective nonlinear
materials of GaSe
x
S1 − x
(0.2 ≤ x ≤ 0.8) are presented. Converted light can be detected in transmission or reflection geometry as a visible spot corresponding
to the real size of the incident laser beam. Developed device structures can be used for checking if the laser is working
or not, for optical adjustment, for visualization of distribution of laser radiation over the cross of the beam and for investigation
of the content of the laser radiation. Low energy (power density) limit for visualization of the IR laser pulses with 2–3
ps duration for these device structures are: between 4.6–2.1 μJ (3 × 10−4−1 × 10−4 W/cm2) at 1200 nm; between 8.4–2.6 μJ (4.7 × 10−4−1.5 × 10−4 W/cm2) at 1300 nm; between 14.4–8.1 μJ (8.2 × 10−4–4.6 × 10−4 W/cm2) at 1360 nm. Threshold damage density is more than 10 MW/cm2 at λ = 1060 nm, pulse duration τ = 35 ps. The results are compared with commercially existing laser light visualizators. 相似文献
14.
Stabilization method of an infrared two-wavelength laser 总被引:1,自引:0,他引:1
H. Matsumoto 《Applied physics. B, Lasers and optics》1981,24(1):65-66
A simple method for stabilizing a He-Xe laser, which simultaneously operates at two wavelengths of 3.51 μm and 3.37 μm, is
described. This stabilization method depends on the comparison of the light intensities of the two wavelengths, and has a
possibility of realizing a stability of better than 1×10−8 with unmodulated output. 相似文献
15.
Ullah H. Davoudi B. Mariampillai A. Hussain G. Ikram M. Vitkin I. A. 《Laser Physics》2012,22(4):797-804
The increase of glucose levels in blood changes the viscosity of flowing fluids and shape of the erythrocytes. Both of these
can affect the details of light scattering as can be quantified via decorrelation times measured by optical coherence tomography
(OCT). The relative contributions of these competing effects have been studied by examining the motion dynamics of deformable
asymmetrical (red blood cells, RBCs with ∼7 μm diameter and ∼2 μm thickness) and non deformable symmetrical (polystyrene microspheres,
PSM with 1.4 μm diameter) flowing scattering particles. The fluid flow under the action of gravity was modulated by changing
the glucose concentrations. Quantitative analysis of the OCT’s M-mode autocorrelation functions enabled the derivations of
the translational diffusion coefficients. These systematic studies are aimed at eventual tissue imaging scenarios with speckle-variance
OCT to obtain local glucose concentrations maps. 相似文献
16.
We present observations of sub-micron- to micron-sized particles generated by high fluence (≈2 J/cm2) 248-nm laser ablation of pressed polytetrafluorethylene (PTFE) targets in air at atmospheric pressure. The original target
material was hydrostatically compressed ≈7 μm PTFE powder, sintered at 275 °C. Collected ejecta due to laser irradiation consists
of four basic particle morphologies ranging from small particles 50–200 nm in diameter to larger particles ≈10 μm in diameter.
Many particles formed in air carry electric charge. Using charged electrodes we are able to collect charged particles to determine
relative numbers of ± charge. We observe roughly equal numbers of positively and negatively charged particles except for the
largest particles which were predominantly negative. For a range of particle sizes we are able to measure the sign and magnitude
of this charge with a Millikan-oil-drop technique and determine surface charge densities. The implications of these observations
with respect to pulsed laser deposition of PTFE thin films and coatings are discussed.
Received: 15 January 1999 / Accepted: 18 January 1999 / Published online: 7 April 1999 相似文献
17.
Scattering matrices of an aqueous suspension of quartz were measured at a wavelength of 0.63 μm in the scattering angle range
of 10°–150°. The angular dependences of matrix elements were measured with a laser polarimeter the optical scheme of which
contained two electro-optical modulators. The results of measurements were compared with the data of calculation for scatterers
having the shape of prolate ellipsoids. It was shown that, under conditions of wide distribution of particles by size and
at a dimensional parameter value of 2.1, the uncertainty of the shape of the distribution leads to an increase in the error
of the retrieval of the parameters of the suspension particle distribution. 相似文献
18.
Wen-Yang Chang Te-Hua Fang Yu-Cheng Lin 《Applied Physics A: Materials Science & Processing》2008,92(3):693-701
Physical characteristics of polyimide films, including optical, micro/nano mechanical, and thermophysical characteristics
were investigated using a photometric, a nanoindentation, and a thermomechanical analyzer for applications in flexible sensors.
Experimental results show that UV light cannot transmit into the polyimide films. The transmittances, with a maximum of about
86%, at VIS and near IR lights decrease with increasing PI film thicknesses. The mechanical characteristics were determined
using tensile, bending moment, and nanoindentation testing. The stress–strain curve approximated bilinear characteristics,
the load–unload bending moment exhibited hysteresis, and nanoindentation generated elastic energy dissipation in the loading–unloading
region. Nanoindentation showed an almost uniform hardness and a reduced Young’s modulus of about 0.181±0.03 and 3.21±0.06 GPa,
respectively, when the penetrating depth was more than about 2 μm. Thermophysical characteristics were greatly influenced
on 8.3 and 25 μm specimens due to the higher relaxation of thin PI films. The thermal expansion remained steady when the thickness
was over 50 μm. The results show that PI films have potential in flexible sensing and higher temperature fabrication. 相似文献
19.
An optical clock based on an Er3+ fiber femtosecond laser and a two-mode He–Ne/CH4 optical frequency standard (λ=3.39 μm) is realized. Difference-frequency generation is used to down convert the 1.5-μm frequency comb of the Er3+ femtosecond laser to the 3.4-μm range. The generated infrared comb overlaps with the He–Ne/CH4 laser wavelength and does not depend on the carrier–envelope offset frequency of the 1.5-μm comb. In this way a direct phase-coherent
connection between the optical frequency of the He–Ne/CH4 standard and the radio frequency pulse repetition rate of the fiber laser is established. The stability of the optical clock
is measured against a commercial hydrogen maser. The measured relative instability is 1×10−12 at 1 s and for averaging times less than 50 s it is determined by the microwave standard, while for longer times a drift
of the He–Ne/CH4 optical standard is dominant. 相似文献
20.
H. Heidrich R. Kaiser P. Albrecht S. Fidorra M. Hamacher W. Rehbein 《Applied physics. B, Lasers and optics》2001,73(5-6):581-583
Optical crosstalk from a 1.3 μm laser to a 1.55 μm photodiode on a single InP substrate, and its suppression within 1.3 μm/1.5 μm
Y-junction transceiver OEICs, has been analyzed experimentally. The results indicate that the optical crosstalk suppression
is limited by the accumulated light in the OEIC substrate coming mainly from the spontaneous emission of the integrated laser
and from stray light at the laser–waveguide butt joint interface. For OEICs, integrating lasers and photodetectors, the achievable
optical intra-chip crosstalk at present will be in the range of 30–40 dB at the required small die dimensions.
Received: 16 May 2001 / / Published online: 23 October 2001 相似文献