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1.
Structural changes in fused silica after exposure to focused femtosecond laser pulses 总被引:7,自引:0,他引:7
Using in situ Raman scattering in a confocal microscopy setup, we have observed changes in the network structure of fused silica after modifying regions inside the glass with tightly focused 800-nm 130-fs laser pulses at fluences of 5-200 J cm(-2). The Raman spectra show a large increase in the peaks at 490 and 605cm(-1), owing to 4- and 3-membered ring structures in the silica network, indicating that densification occurs after exposure to the femtosecond laser pulses. The results are consistent with the formation of a localized plasma by the laser pulse and a subsequent microexplosion inside the glass. 相似文献
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High power supercontinuum generation by dual-color femtosecond laser pulses in fused silica 下载免费PDF全文
High power supercontinuum (SC) is generated by focusing 800 nm and 400 nm femtosecond laser pulses in fused silica with a microlens array. It is found that the spectrum of the SC is getting broader compared with the case of a single laser pulse, and the spectral energy density between the two fundamental laser wavelengths is getting significantly higher by optimizing the phase matching angle of the BBO. It exceeds μJ/nm over 490 nm range which is from 380 nm to 870 nm, overcoming the disadvantage of relative lower power in the ranges far from the fundamental wavelength. 相似文献
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Yukun Han Xinwei Lan Tao Wei Hai-Lung Tsai Hai Xiao 《Applied Physics A: Materials Science & Processing》2009,97(3):721-724
We report the fabrication of surface enhanced Raman spectroscopy (SERS) fused silica glass substrates using fast femtosecond-laser
(fs-laser) scan, followed by silver chemical plating. A cross-section enhancement factor (EF) of 2.5×106, evaluated by Rhodamine 6G (10−7 M solution), was obtained. The Raman mapping indicated a good uniformity over the fs-laser scanned area. The dimension and
pattern of the SERS activated region can be conveniently controlled by laser 2D scanning, potentially enabling integration
of SERS into a high-order optical–chemical analysis system on a glass chip. 相似文献
5.
Water-assisted drilling of microfluidic chambers inside silica glass with femtosecond laser pulses 总被引:1,自引:0,他引:1
R. An Y. Li Y. Dou D. Liu H. Yang Q. Gong 《Applied Physics A: Materials Science & Processing》2006,83(1):27-29
Microfluidic chambers embedded in silica glass are drilled by water-assisted ablation with a femtosecond laser. The continuous scanning ablation increases the processing speed up to 50 μm/s. Not only may microchambers or microtrenches be obtained at high speed and in one step, but also combined structures consisting of cascaded microchambers and microtrenches may be fabricated. The inner-wall morphology of the microchambers is analyzed by a scanning electron microscope. PACS 87.80.Mj; 52.38.Mf; 82.50.Pt; 42.62.-b; 42.70.Ce 相似文献
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K.C. Vishnubhatla S. Venugopal Rao R. Sai Santosh Kumar Maurizio Ferrari D. Narayana Rao 《Optics Communications》2009,282(23):4537-4542
Herein we present results on the femtosecond laser direct writing and optical characterization studies of two dimensional gratings in fused silica, GE 124, and Foturan™ glasses. Varieties of structures were achieved with varying input energy and spatial orientation of the samples. Various characterization techniques including fluorescence spectroscopy, micro-Raman spectroscopy, and laser confocal microscopy were employed to analyze the structural and physical modifications at the focal volume resulting in change of refractive index. Diffraction efficiencies of 9–12% were observed from the grating structures. A broad-band emission was observed in the laser-modified region of the Foturan glass. The obtained results are analyzed in the light of recent work in similar glasses and exploring the applications of such structures in the fields of photonics. 相似文献
7.
Optical waveguide arrays induced in fused silica by void-like defects using femtosecond laser pulses
C. Méndez J.R. Vázquez de Aldana G.A. Torchia L. Roso 《Applied physics. B, Lasers and optics》2007,86(2):343-346
We report a new approach to the microfabrication of permanent optical waveguide arrays inside fused silica induced by focusing
infrared femtosecond laser pulses with microjoule energy. These arrays consist of waveguides limited by void-like damage zones
with very loose coupling among adjacent guides, thus allowing the excitation of a single one. The proposed method shows the
possibility of using created void-like structures for both the fabrication of integrated optical devices as well as for the
control of previously induced refractive index change regions.
PACS 42.65.Re; 42.82.Et; 42.79.-e 相似文献
8.
Optical seizing and merging of voids in silica glass with infrared femtosecond laser pulses 总被引:3,自引:0,他引:3
We demonstrate that one can seize and translate voids formed by IR femtosecond laser pulses inside silica glass and can also cause two voids to merge into one. We also present clear evidence of a void and its surrounding region by showing scanning electron microscope images of cleaved voids, which we produced by cleaving through the glass along a plane that included a thin laser-ablated line on the surface of the glass and the voids formed inside. 相似文献
9.
The competition between optical breakdown (OB) and laser-pulse filamentation (FL) in bulk fused silica is investigated by using a 1-kHz femtosecond infrared laser. We measure input powers corresponding to the threshold of OB and FL in terms of external focusing conditions. The results demonstrate that OB precedes FL for tight focusing, whereas for sufficiently long focal lengths FL takes places at a lower power than OB does. 相似文献
10.
Christian Voigtländer Daniel Richter Jens Thomas Andreas Tünnermann Stefan Nolte 《Applied Physics A: Materials Science & Processing》2011,102(1):35-38
We present volume Bragg gratings (VBGs) with a period of 1.075 μm inscribed in fused silica using a femtosecond laser and
a phase mask. The femtosecond-inscribed VBGs can be used as reflecting elements with reflectivities of about 80% for a 1-mm-long
grating. Due to the non-sinusoidal refractive-index shape, higher order Bragg resonances up to the 7th reflection order could
be measured. Therefore, the Bragg gratings also reflect light in the visible-wavelength range. 相似文献
11.
Multilevel phase-type diffractive lenses were fabricated by translating a filament of a femtosecond laser pulse into three-dimensional space inside synthesized silica. The profile of the lenses was designed by use of a multi-level approximation to a kinoform lens. Two-level diffractive lenses with multiple layers along the optical axis provided a maximum efficiency of 37.6% at a wavelength of 632.8 nm. A four-level diffractive lens provided a maximum efficiency of 56.9%. The lenses fabricated with filamentation were free from birefringence. 相似文献
12.
We investigate the ablation process in SiO2 by the superposition of 180 fs laser pulse (center=800 nm) with a 15 ns laser pulse (center=532 nm). Compared to femtosecond laser pulses alone, we measured an increase of 270±30% in volume of the ejected material with only a total increase of 40% of lasers fluences. This increase of ablation is the result of thermal and incubation effects generated by the femtosecond laser pulse. PACS 78.20.Nv; 61.80.Ba 相似文献
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Korte F. Serbin J. Koch J. Egbert A. Fallnich C. Ostendorf A. Chichkov B.N. 《Applied Physics A: Materials Science & Processing》2003,77(2):229-235
Detailed investigations of the possibilities for using femtosecond lasers for the nanostructuring of metal layers and transparent
materials are reported. The aim is to develop a simple laser-based technology for fabricating two- and three-dimensional nanostructures
with structure sizes on the order of several hundred nanometers. This is required for many applications in photonics, for
the fabrication of photonic crystals and microoptical devices, for data storage, displays, etc. Measurements of thermionic
electron emission from metal targets, which provide valuable information on the dynamics of femtosecond laser ablation, are
discussed. Sub-wavelength microstructuring of metals is performed and the minimum structure size that can be fabricated in
transparent materials is identified. Two-photon polymerization of hybrid polymers is demonstrated as a promising femtosecond
laser-based nanofabrication technology.
Received: 20 November 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +49-511/2788-100, E-mail: ch@lzh.de 相似文献
15.
In situ observation of photoinduced refractive-index changes in filaments formed in glasses by femtosecond laser pulses 总被引:5,自引:0,他引:5
We investigated the relationship between the formation of filaments and local refractive-index changes induced by femtosecond laser pulses in silica glass. In situ observation revealed that the location of a filament coincided with that of the refractive-index change. Observation also showed that the region of refractive-index change was elongated toward the upstream direction of the laser pulses with increasing exposure time. The region of refractive-index change was several hundred micrometers long, and its diameter was smaller than 2 mum. The refractive-index change was confirmed by two of three different methods to be as large as 0.8 x 10(-2). 相似文献
16.
A. V. Kuznetsov A. S. Kuzakov E. F. Martynovich 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(1):64-67
The formation of fluorescent channels with color centers in LiF crystals under the action of the multiple filamentation of femtosecond laser pulses is studied experimentally and theoretically for pulse powers around four orders of magnitude higher than the critical self-focusing value. 相似文献
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Three-dimensional hole drilling of silica glass from the rear surface with femtosecond laser pulses 总被引:4,自引:0,他引:4
By moving silica glass in a preprogrammed structure, we directly produced three-dimensional holes with femtosecond laser pulses in single step. When distilled water was introduced into a hole drilled from the rear surface of the glass, the effects of blocking and redeposition of ablated material were greatly reduced and the aspect ratio of the depth of the hole was increased. Straight holes of 4-mu;m diameter were more than 200 microm deep. Three-dimensional channels can be micromachined inside transparent materials by use of this method, as we have demonstrated by drilling a square-wave-shaped hole inside silica glass. 相似文献
19.
Cellular response to near-infrared femtosecond laser pulses in two-photon microscopes 总被引:2,自引:0,他引:2
The influence of femtosecond near-infrared (NIR) microirradiation on cell vitality and cellular reproduction has been studied. Chinese hamster ovary cells exposed to a highly focused 150-fs scanning beam at 730, 760, and 800 nm (80 MHz, 80-mus pixel dwell time) of =1 mW remained unaffected by the femtosecond microbeam. However, increased mean power led to impaired cell division. At >/=6 -mW mean power, cells were unable to form clones. They died or became giant cells. Complete cell destruction, including cell fragmentation, occurred at mean powers >10 mW. Cell death was accompanied by intense luminescence in the mitochondrial region. When we consider the diffraction-limited spot size in the submicrometer region, intensities and photon flux densities of 0.8-kW pulses (10-mW mean power) are of the order of terawatts per square centimeter (10(12)W/cm (2)) and 10(32) photons cm(-2) s(-1) , respectively. Extremely high fields may induce destructive intracellular plasma formation. The power limitations should be considered during NIR femtosecond microscopy of vital cells and in the design of compact NIR femtosecond solid-state lasers for two-photon microscopes. 相似文献
20.
We report a novel method to increase the UV photosensitivity of GeO(2): SiO(2) optical fibers based on exposure to CO(2) laser irradiation before grating writing. Fibers treated with a CO(2) laser can produce gratings with refractive-index modulation two times greater and a Bragg wavelength that can be 2 nm longer than those of untreated fibers. Experiments on GeO(2): SiO(2) preform samples treated with a CO(2) laser in a way similar to the fibers showed a marked increase of the 242-nm absorption band, which is associated with an increase of germanium oxygen-deficient centers and is believed to be responsible for the higher photorefractive response. 相似文献