共查询到20条相似文献,搜索用时 31 毫秒
1.
Modification of the fused silica glass network associated with waveguide fabrication using femtosecond laser pulses 总被引:1,自引:0,他引:1
J.W. Chan T.R. Huser S.H. Risbud D.M. Krol 《Applied Physics A: Materials Science & Processing》2003,76(3):367-372
Atomic-scale structural changes have been observed in the glass network of fused silica after modification by tightly focused
800-nm, 130-fs laser pulses at fluences between 5 and 200 J cm-2. Raman spectroscopy of the modified glass shows an increase in the 490 and 605-cm-1 peaks, indicating an increase in the number of 4- and 3-membered ring structures in the silica network. These results provide
evidence that densification of the glass occurs after exposure to fs pulses. Fluorescence spectroscopy of the modified glass
shows a broad fluorescence band at 630 nm, indicating the formation of non-bridging oxygen hole centers (NBOHC) by fs pulses.
Waveguides that support the fundamental mode at 633 nm have been fabricated inside fused silica by scanning the glass along
the fs laser beam axis. The index changes are estimated to be approximately 0.07×10-3.
Received: 17 December 2001 / Accepted: 9 July 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. Fax: +1-925/423-2463, E-mail: dmkrol@ucdavis.edu 相似文献
2.
N. Yasumaru K. Miyazaki J. Kiuchi 《Applied Physics A: Materials Science & Processing》2003,76(6):983-985
We report observation of nanostructures formed on thin TiN and DLC films that were irradiated by 800- and 267-nm, femtosecond
(fs) Ti:sapphire laser pulses at an energy fluence slightly above the ablation threshold. On the ablated thin-film surfaces,
the linearly polarized fs pulses produce arrays of fine periodic structures that are almost oriented to the direction perpendicular
to the laser polarization, while the circularly polarized light forms fine-dot structures. The size of these surface structures
is 1/10–1/5 of the laser wavelength and decreases with a decrease in the laser wavelength.
Received: 3 September 2002 / Accepted: 4 September 2002 / Published online: 17 December 2002
RID="*"
ID="*"Corresponding author. Fax: +81-778/62-3306, E-mail: yasuma@fukui-nct.ac.jp 相似文献
3.
Diode-pumped Cr:LiCAF fs regenerative amplifier system seeded by an Er-doped mode-locked fiber laser
A fs regenerative amplifier based on Cr:LiCAF is demonstrated for the first time. With direct diode pumping, 8 μJ of pulse
energy are obtained directly from the amplifier. When seeded by an Er-doped fiber laser, the amplified seed pulses are compressed
down to 252 fs, limited by residual net third-order dispersion of the compression gratings and intracavity elements. Pulse
broadening due to second- and third-order dispersion is theoretically investigated and compared to experimental results. Dispersion
generated by the geometrical cavity arrangement is measured experimentally.
Received: 19 November 2001 /
Revised version: 28 January 2002 / Published online: 14 March 2002 相似文献
4.
Boron isotopic enrichment is observed in the laser ablation of B4C target using nanosecond (ns) wide 532 nm laser beam of a Nd-YAG laser. B10/B11 ratio of 0.9 against the natural abundance of 0.25 is obtained at a laser power density of 8×108 W/cm2 (fluence of 6.4 J/cm2). The enrichment as a function of laser power density is demonstrated using a quadrupole mass spectrometer. Apart from higher
enrichment factor, only singly charged ions are found in the laser plume from the B4C target, in contrast to the multiply charged ions from the BN target reported in a recent report using femtosecond (fs) laser
pulses. This study indicates the possibility of using less expensive, widely used ns lasers, which can also yield a higher
throughput per pulse than a fs laser for isotope enrichment.
Received: 28 September 2001 / Accepted: 4 February 2002 / Published online: 3 June 2002
RID="*"
ID="*"Corresponding author. Fax: +91-4114/480-065, E-mail: mj@igcar.ernet.in 相似文献
5.
M. Yorozu J. Yang Y. Okada T. Yanagida F. Sakai K. Takasago S. Ito A. Endo 《Applied physics. B, Lasers and optics》2002,74(4-5):327-331
A short-pulse X-ray-generation experiment was performed by Compton scattering through interaction between a 3-ps electron
beam and 100-fs laser photons in a 90° scattering configuration. The observed X-ray intensity was typically 3×104 photons/pulse and roughly matched the theoretically expected intensity. The X-ray energy and pulse duration were estimated
theoretically to be 2.3 keV and 280 fs from the observed electron- and laser-beam parameters. The fluctuation of the X-ray
output was measured as 25% (rms) during a 30-min operation. The fluctuation was expressed as a function of the fluctuation
of the timing between the electron and laser beams. The measured fluctuation of the X-rays was approximately consistent with
that caused by the fluctuation of the timing between the beams.
Received: 19 November 2001 / Revised version: 23 January 2002 / Published online: 14 March 2002 相似文献
6.
T. Miura H. Nagaoka K. Takasago K. Kobayashi A. Endo K. Torizuka M. Washio F. Kannari 《Applied physics. B, Lasers and optics》2002,75(1):19-23
Two mode-locked Ti:sapphire lasers of different wavelengths were precisely synchronized by a simple feedback system employing
sum-frequency generation (cross correlation). When the timing error exceeded the pulse duration, the periodic bunch of the
sum-frequency pulse was used for rough timing adjustment. Using cross correlation with a stretched pulse, we struck a balance
between wide locking range and sensitive timing detection. When the two lasers were well-synchronized, we obtained a continuous
cross-correlation pulse train for 3 min. The holding time of the laser synchronization was extended to over one hour by adding
a motorized stage to the PZT-mounted cavity mirror. We estimated the rms timing jitter between the two lasers by a scanning
cross-correlation measurement. We confirmed that the rms timing jitter of the two lasers during 1.8 s was 28 fs.
Received: 30 January 2002 / Revised version: 14 June 2002 / Published online: 8 August 2002 相似文献
7.
A multiscale multiphoton microscopy (MPM) and optical coherence tomography (OCT) system has been developed using a sub-10 fs Ti:sapphire laser. The system performs cross-sectional OCT imaging over millimeter field-of-view and en-face high-resolution MPM imaging with submicrometer resolution from the same sample location. With fish cornea, we have demonstrated cross-sectional imaging of cornea tissue layers using OCT, and the zoom-in imaging of cells and collagen fibers in each layer using MPM. The multiscale MPM/OCT system shows the potential of a rapid coarse scan to search for abnormal regions and the subsequent fine zoom-in imaging for diagnosis. 相似文献
8.
A 50 cm silver coated hollow fiber with inner diameter of 250 μm and filled with argon has been used to compress optical pulses
from a Ti:sapphire laser at 800 nm. Input pulses with energy of 250 μJ and duration of 110 fs were used and compressed pulses
with energy of 220 μJ and duration of 20 fs were generated by using a prism compressor. Numerical and experimental results
are compared. There is good agreement between the measured beam diameters of the hollow-fiber output pulse and the calculated
values obtained from propagation of the HE11 mode into free space. For comparison, a similar uncoated fused-silica hollow fiber was also used to obtain 20 fs compressed
pulses with an energy of 190 μJ.
Received: 7 September 2002 / Published online: 26 March 2003
RID="*"
ID="*"Corresponding author. Fax: +1-780/492-1811, E-mail: mohebbi@ee.ualberta.ca 相似文献
9.
A. Marcinkevičius V. Mizeikis S. Juodkazis S. Matsuo H. Misawa 《Applied Physics A: Materials Science & Processing》2003,76(2):257-260
We studied the peculiarities of femtosecond laser microfabrication in silica glass with a refractive index that did not exactly
match the value for which the focusing optics is designed. Spherical aberrations resulting from a small refractive index mismatch
were found to increase the size and distort the shape of photodamaged regions, thus reducing the spatial resolution of the
microfabrication. However, these undesirable effects can be minimized, providing that the focusing depth inside the glass
is not too large, and the laser intensity is kept close to the light-induced damage threshold.
Received: 3 December 2001 / Accepted: 11 April 2002 / Published online: 10 September 2002
RID="*"
ID="*"Corresponding author. Fax: +81-88/656-7598, E-mail: misawa@eco.tokushima-u.ac.jp 相似文献
10.
J. Biegert 《Applied physics. B, Lasers and optics》2002,75(1):25-29
A source of bichromatic coherent radiation is described with independent tunability in wavelength, energy and pulse duration.
The system is able to deliver pulses in the visible to infrared region with possible extension into the ultraviolet. Pulse
durations can be tailored to be from 15 ps to 310 fs with collimated beam fluences of several mJ/cm2.
Received: 28 January 2002 / Revised version: 24 April 2002 / Published online: 12 July 2002 相似文献
11.
We developed a high-power oscillator–regenerative amplifier femtosecond laser system. Based on chromium-doped forsterite.
The system is operating near 1.25 μm at a 5–10 kHz repetition rate. Chirped-pulse amplification produced 0.86 W (0.75 W) of
average power, or 465 mW (400 mW) after compression at 5 kHz (10 kHz). Nearly bandwidth-limited pulses of duration 135 fs
(shortest) and 150 fs (typical) are available with an energy of 93 μJ and 40 μJ at 5 and 10 kHz, respectively.
Received: 7 June 2002 / Published online: 15 November 2002
RID="*"
ID="*"Corresponding author. Fax: +49-30/63921289, E-mail: petrov@mbi-berlin.de 相似文献
12.
The micromachining of hydroxyapatite (HAp) is highly important for orthopedics and dentistry, since human bone and teeth consist
mainly of HAp. We demonstrate ultrashort Ti:sapphire laser ablation of HAp, using pulse-widths of 50 fs, 500 fs, and 2 ps
at a wavelength of 820 nm and at 1 kpps. The crucial medical issue is to preserve the chemical properties of the machined
(ablated) surface. If the chemical properties of HAp change, the human bone or tooth cannot re-grow after laser processing.
Using X-ray photoelectron spectroscopy, we observe chemical properties of HAp ablated in air. The HAp is ablated at laser
fluences of 3.2 J/cm2 (6.4×1013 W/cm2 at 50 fs), 3.3 J/cm2 (6.6×1012 W/cm2 at 500 fs), and 9.6 J/cm2 (4.8×1012 W/cm2 at 2 ps), respectively. As a result it is found that the ablated surface is unchanged after laser ablation over the pulse-width
range used in this experiment.
Received: 7 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +81-45/566-1533, E-mail: obara@obara.elec.keio.ac.jp 相似文献
13.
Transmission electron microscopy studies of femtosecond laser induced modifications in quartz 总被引:1,自引:0,他引:1
T. Gorelik M. Will S. Nolte A. Tuennermann U. Glatzel 《Applied Physics A: Materials Science & Processing》2003,76(3):309-311
Cross-sectional transmission electron microscopy investigations of femtosecond laser induced sub-micrometer structural modifications
inside crystalline quartz were carried out. Modifications from single laser shots and from lines built of overlapping shots
were imaged. Both single laser shot modifications and line structures show an amorphous core surrounded by a disturbed crystalline
structure. A strong strain field surrounding the central, irradiated, core is responsible for an increase of the refractive
index. Finite element method calculations of the strain field show maxima on both sides of the irradiated core, which are
in good agreement with optical measurements of the refractive-index change.
Received: 29 September 2001 / Accepted: 9 July 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. Fax: +49-3641/947792, E-mail: tatiana.gorelik@rz.uni-jena.de 相似文献
14.
T. Andres P. Haag S. Zelt J.-P. Meyn A. Borsutzky R. Beigang R. Wallenstein 《Applied physics. B, Lasers and optics》2003,76(3):241-244
A synchronously pumped femtosecond optical parametric oscillator based on congruent MgO-doped periodically poled lithium niobate
(c-MgO:PPLN) is reported. The system, operating at room temperature, was pumped by a mode-locked Ti:sapphire laser. The wavelengths
of the signal and idler waves were tuned from 870 nm to 1.54 μm and 1.58 to 5.67 μm, respectively, by changing the pump wavelength,
the grating period or the cavity length. Pumped by 1.1 W of 755 nm laser radiation, the OPO generated 310 mW of 1080 nm radiation.
This signal output corresponds to a total conversion efficiency of 50%. Without dispersion compensation the OPO generated
phase-modulated signal pulses of 200 fs duration. Besides the OPO of c-MgO:PPLN, an OPO of stoichiometric (s) MgO:PPLN was
investigated. Because of the reduced sensitivity to photorefractive damage, both crystals allowed efficient OPO operation
at room temperature.
Received: 19 August 2002 / Revised version: 11 December 2002 / Published online: 19 March 2003
RID="*"
ID="*"Corresponding author. Fax: +49-631/205-3906, E-mail: andres@physik.uni-kl.de 相似文献
15.
Ito S. Ishikawa H. Miura T. Takasago K. Endo A. Torizuka K. 《Applied physics. B, Lasers and optics》2003,76(5):497-503
We present a 7-TW Ti:sapphire laser system operating at 50 Hz for laser Compton femtosecond X-ray generation. This laser system
delivers 8.4 W of average output power at a repetition rate of 50 Hz with a pulse width of 24 fs. It demonstrates successful
management using a dynamically stable resonator in the regenerative amplifier and compensation for thermal lensing by a convex
mirror in a ring-type four-pass power amplifier. We also present the results of closed-loop corrections for distorted wavefronts
of amplified and compressed laser pulses, using an adaptive optical system consisting of a Shack–Hartmann-type wavefront sensor
and a deformable mirror. This closed-loop correction results in dramatic improvements, reducing wavefront distortions below
0.05 λ rms.
Received: 31 October 2002 / Revised version: 3 March 2003 / Published online: 5 May 2003
RID="*"
ID="*"Corresponding author. Fax: +81-298/61-3349, E-mail: ito@festa.or.jp 相似文献
16.
Ultrashort-laser-pulse-driven rewritable phase-change optical recording in Sb-based films 总被引:1,自引:0,他引:1
This paper reviews the work we have carried out over the last years on the development of ultrashort-laser-pulse-driven, rewritable,
phase-change optical memories. The materials we have tailored for this application are non-stoichiometric, Sb-rich amorphous
thin films, which can be crystallized upon irradiation with ultrashort laser pulses, showing a large optical contrast upon
transformation. This result makes them very promising for the development of rewritable phase-change optical memories under
ultrashort pulses, since the reversibility of the process has also been demonstrated. Adequate control of the heat-flow conditions
has allowed us to achieve a full transformation time faster than 400 ps for crystallization/amorphization using 30-ps pulses.
The crystallization threshold fluence has been found to decrease upon irradiation with pulses shorter than 800 fs, thus suggesting
the relevance of high-electronic-excitation-induced processes in the amorphous-to-crystalline phase transition. This has been
confirmed by the observation of an ultrafast, non-thermal phase transition occurring 200–300 fs after the arrival of the laser
pulse at the surface, for fluences above the crystallization threshold. The presence of this transient phase conditions the
final state induced therefore enabling the applicability of this material as a rewritable recording medium using femtosecond
pulses.
Received: 11 October 2001 / Accepted: 9 July 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. Fax: +34-91/564-5557, E-mail: J.Solis@io.cfmac.csic.es 相似文献
17.
Shingo Kanehira Kiyotaka Miura Kazuyuki Hirao Naoya Shibata Yuichi Ikuhara 《Applied Physics A: Materials Science & Processing》2008,92(4):913-916
We show a unique technique to form dense dislocations locally inside a MgO single crystal with a rock-salt type structure
using femtosecond (fs) laser irradiation. Cross-shaped patterns of micrometer size, originating from densely introduced dislocations,
are formed spontaneously around the focal point. We controlled the three-dimensional propagation of the dislocations by adjusting
the pulse energy of the fs laser and NA of objective lens. The technique may open up a new field of dislocation technology
for optical applications. 相似文献
18.
W. Husinsky S. Mitterer G. Grabner I. Baumgartner 《Applied physics. B, Lasers and optics》1989,49(5):463-467
Photoablation studies of biological material (human cornea) with UV and visible laser light show that effective, apparently non-conventional thermal photoablation can be achieved by introducing energy absorbing dopants in the tissue. Previously unknown high ablation rates of 80 Gmm/pulse have been observed. The results allow one to clearly postulate different ablation mechanisms for increasing laser fluence. The results are compared with the photoablation rates observed with 193 nm UV laser light on undoped human cornea. Explosive desorption has been found the dominant process involved. 相似文献
19.
Düsterer S. Schwoerer H. Ziegler W. Salzmann D. Sauerbrey R. 《Applied physics. B, Lasers and optics》2003,76(1):17-21
The influence of prepulses on the conversion efficiency (CE) of laser radiation into 13 nm extreme ultraviolet (EUV) radiation,
resulting from lithium-like oxygen ions from O20 μm water droplets, was investigated. The laser pulse durations in the experiment
ranged from 200 fs to 120 ps. Applying prepulses preceding the main pulse at various delays of up to 11 ns, it was shown that
the CE increases differently for each measured pulse duration. The strongest dependence on the introduction of a prepulse
was observed for 2 ps laser pulses with a 20 mJ laser pulse energy. The EUV CE was improved by a factor of 15 by the introduction
of a prepulse. Calculations on the atomic physics of oxygen ions and simulations of the laser–plasma interaction revealed
the influence of the prepulse on the EUV yield.
Received: 25 October 2002 / Published online: 22 January 2003
RID="*"
ID="*"Corresponding author. Fax: +49-3641/947-202, E-mail: duesterer@ioq.uni-jena.de 相似文献
20.
Subpicosecond pulses at a fixed wavelength produced with a low-Q cavity dye laser pumped by a single, nanosecond laser (Q-switched Nd:YAG) are converted into tunable high-power sub-100 femtosecond pulses by generation, spectral selection, amplification and compression of a supercontinuum. The tunable, chirped, high-energy pulses obtained are compressed with a prism pair. Energies up to 50 J in sub-100 fs pulses were obtained in the 540 to 650 nm range using 40 mJ of the Nd: YAG-laser pumping pulses at 532 nm. The whole sub-100 fs system including the low-Q dye laser uses only one Nd:YAG laser as a pump source. 相似文献