共查询到20条相似文献,搜索用时 15 毫秒
1.
D. Nodop J. Rothhardt S. H?drich J. Limpert A. Tünnermann 《Applied physics. B, Lasers and optics》2009,94(3):399-401
We present a Q-switched microchip laser emitting 1064-nm pulses as short as 100 ps synchronized to a cavity dumped femtosecond
laser emitting 800-nm pulses as short as 80 fs. The synchronization is achieved by presaturating the saturable absorber of
the microchip laser with femtosecond pulses even though both lasers emit at widely separated wavelengths. The mean timing
jitter is 40 ps and thus considerably shorter than the pulse duration of the microchip laser. 相似文献
2.
Hong-Dao Yang Xiao-Hong Li Guo-Qiang Li Cai Wen Rong Qiu Wen-Hao Huang Jun-Bo Wang 《Applied Physics A: Materials Science & Processing》2011,104(2):749-753
A single-crystal silicon(111) wafer surface fixed on an x–y translation stage is scanned with a focused femtosecond laser beam at a wavelength of 800 nm under different atmospheres
(air, vacuum, and nitrogen). Different colors from different angles on the surface of the silicon then appear. From the result
of the experiments, periodic ripple surface structures emerge on the surface of colorized silicon, and the phenomenon is more
obvious in vacuum and nitrogen than in air. The periods of the surface structures on silicon are not the same in the different
atmospheres. Under vacuum, the period is the longest and is closer to the wavelength of the laser irradiation. Different from
metals, the range of energy density is smaller when the colorized silicon appears with femtosecond laser pulses. Through SEM,
TEM, and AFM, we observe in detail the microstructures of colorized silicon that forms in air, vacuum, and nitrogen and analyze
the possible physical mechanism. Finally, research into the optical reflection of the colorized silicon indicates that the
reflectivity is not higher than 30% in the 250–800 nm range. 相似文献
3.
Lingling Ran Zhongyi Guo Shiliang Qu 《Applied Physics A: Materials Science & Processing》2010,100(2):517-521
Self-organized periodic surface structures on ZnO have been observed after multiple linearly polarized femtosecond laser pulse
irradiation. The observed self-organized structures are attributed to the second harmonics in the sample surface excited by
the incident laser. The grating orientation could be adjusted by the laser polarization direction. We also find that fluences
play an important role in the formation of self-organized nanostructures. 相似文献
4.
P. Kumar 《Applied Physics A: Materials Science & Processing》2010,99(1):245-250
Controlled single step fabrication of silicon conical surface modulations on [311] silicon surface is reported utilizing KrF excimer laser [λ=248 nm] at laser fluence below ablation threshold laser fluence. When laser fluence was increased gradually from 0 to 0.2 J/cm2 for fixed 200 numbers of shots; first nanopores are observed to form at 0.1 J/cm2, then very shallow nanocones evolve as a function of laser fluence. At 0.2 J/cm2, nanoparticles are observed to form. Up to 0.15 J/cm2 the very shallow nanocone volume is smaller but increases at a fast rate with laser fluence thereafter. It is observed that the net material volume before and after the laser irradiation remains the same, a sign of the melting and resolidification without any ablation. 相似文献
5.
A. Jurgilaitis R. Nüske H. Enquist H. Navirian P. Sondhauss J. Larsson 《Applied Physics A: Materials Science & Processing》2010,100(1):105-112
In this paper, we present the investigation and characterization of the laser-induced surface structure on an asymmetrically
cut InSb crystal. We describe diffraction from the ripple surface and present a theoretical model that can be used to simulate
X-ray energy scans. The asymmetrically cut InSb sample was irradiated with short-pulse radiation centred at 800 nm, with fluences
ranging from 10 to 80 mJ/cm2. The irradiated sample surface profile was investigated using optical and atomic force microscopy. We have investigated how
laser-induced ripples influence the possibility of studying repetitive melting of solids using X-ray diffraction. The main
effects arise from variations in local asymmetry angles, which reduce the attenuation length and increase the X-ray diffraction
efficiency. 相似文献
6.
P. Haro-González I. R. Martín S. González-Pérez L. L. Martin F. Lahoz D. Puerto J. Solís 《Applied Physics A: Materials Science & Processing》2010,98(4):879-884
Localized modification of the optical properties of erbium doped strontium barium niobate (SBN) glass has been performed using
femtosecond laser irradiation. The samples, with composition SrO–BaO–Nb2O5–B2O5 and doped with 5%mol of Er3+, were fabricated using a melt-quenching method. The samples were irradiated with different number of pulses per spot (1–50
pulses) at two different laser fluences (2.6 and 5.6 J/cm2) by using an fs laser amplifier operating at 800 nm and generating pulses with a duration of 120 fs.
Micro-luminescent microscopy, using an Ar+ laser as excitation source, has been used to analyze the modifications of the luminescent properties of the sample upon fs
laser exposure. The emissions of the Er3+: 4I11/2→4I15/2 and 4I13/2→4I15/2 transitions allow appreciating the structural modifications caused by femtosecond laser exposure. The lifetimes of the levels
involved in these transitions were measured inside and outside the laser irradiated region. These measurements have been compared
with those obtained in bulk glass ceramic sample, which is obtained from the glass precursor by a thermal treatment in order
to estimate the optimal conditions to produce nanocrystals in a localized region by ultrafast laser irradiation. 相似文献
7.
C. W. Cheng W. C. Shen C. Y. Lin Y. J. Lee J. S. Chen 《Applied Physics A: Materials Science & Processing》2010,101(2):243-248
A method is proposed for the fabrication of micro/nano crystalline indium tin oxide (c-ITO) structures using a Ti:Sapphire
laser with a repetition rate of 1 kHz and a wavelength of 800 nm. In the proposed approach, an amorphous ITO (a-ITO) thin
film is transformed into a c-ITO micro/nano structure over a predetermined area via laser beam irradiation, and the residual
a-ITO thin film is then removed using an etchant solution. The fabricated c-ITO structures are observed using scanning electron
microscopy (SEM) and cross-sectional transmission electron microscopy (TEM). The observation results show that the use of
a low repetition rate laser induces a high thermal cycling effect within the ITO film and therefore prompts the formation
of micro-cracks in the c-ITO structure. In addition, it is shown that as the laser power approaches the ablation threshold
of the a-ITO thin film, nanogratings and disordered nanostructures are formed along the center lines of the c-ITO patterns
formed using linearly polarized and circularly polarized laser beam irradiation, respectively. The nanogratings are found
to have a period of approximately 200 nm (i.e. one-quarter of the irradiation wavelength), while the nanostructures have an
average diameter of approximately 100–160 nm. 相似文献
8.
C. H. Lin L. Jiang Y. H. Chai H. Xiao S. J. Chen H. L. Tsai 《Applied Physics A: Materials Science & Processing》2009,97(4):751-757
This article reports the fabrication of high-fill-factor plano-convex cylindrical and spherical microlens arrays horizontally
and vertically embedded in a photosensitive Foturan glass chip by femtosecond (fs) laser micromachining. The microlens arrays
were fabricated by modifying the microstructure of Foturan glass using fs laser direct writing followed by thermal treatment,
wet etching, and additional annealing. The focusing ability and image quality of the microlens arrays were examined, showing
that the lens arrays not only can focus light well but also provide an imaging capability that holds great potential for lab-on-a-chip
applications. 相似文献
9.
L. Kuna C. Sommer E. Zinterl J. R. Krenn P. Pachler P. Hartmann S. Tasch G. Leising F. P. Wenzl 《Applied Physics A: Materials Science & Processing》2008,93(2):421-427
We report on the micro-fabrication of diffractive optical elements (DOEs) such as 1D, 2D and concentric grating structures
inside the volume of thin silicone films by femtosecond laser direct writing. In addition, we show that such structures can
also be integrated into silicone films that act as encapsulation layers of high power light-emitting diodes. The latter strategy
opens new possibilities to homogenize and to control the light emitted from such devices. 相似文献
10.
E. Takahashi S. Kato Y. Matsumoto I. Okuda 《Applied physics. B, Lasers and optics》2010,98(2-3):501-505
External-laser-induced preionization of excimer lasers was investigated. A discharge XeF laser was preionized by two different UV lasers [a KrF laser (λ=249 nm) and an ArF laser (λ=193 nm)], and the improvements in performance of the XeF laser were compared. The XeF laser beam profiles were measured by an intensified CCD (ICCD) camera with temporal resolution of 10 ns. Striated XeF laser profiles were obtained with 249 nm laser preionization, whereas there was no striation in the profiles for 193 nm laser preionization. These striations originated from discharge in the XeF laser induced by laser preionization. The influence of excited rare-gas atoms on the discharge instability was examined. 相似文献
11.
M. B. Agranat S. I. Ashitkov S. I. Anisimov A. V. Ovchinnikov A. B. Shvartsburg D. S. Sitnikov V. E. Fortov 《Applied Physics A: Materials Science & Processing》2009,94(4):879-887
The experimental study of absorption in silicon in infrared and visible spectral ranges, where the photon energy is less or
more than the bandgap width, is performed by means of the ultrafast interferometry technique. The exactly solvable model in
the electromagnetic of heterogeneous lossy plasma layer was developed. The density of carriers, their frequency of collisions,
absorbing depth of the probing waves, real and imaginary parts of dielectric function of nonuniform layer and their spatial
gradients are determined from the reflectance data by means of this model subject to the pump fluence. The heterogeneity-induced
effects are visualized due to comparison of obtained plasma parameters with those calculated in the framework of homogeneous
plasma model It is shown that in the intensity range near thresholds of melting and ablation the absorption, occurring in
both cases mainly within a thin (∼10 nm) absorbing layer (similarly to metals), is due to free carrier intraband absorption. 相似文献
12.
Ming-Chun Tien Aaron T. Ohta Kyoungsik Yu Steven L. Neale Ming C. Wu 《Applied Physics A: Materials Science & Processing》2009,95(4):967-972
Heterogeneous integration of InGaAsP microdisk lasers on a silicon platform is demonstrated experimentally using an optofluidic
assembly technique. The 200-nm-thick, 5- and 10-μm-diameter microdisk lasers are fabricated on InP and then released from
the substrates. They are reassembled on a silicon platform using lateral-field optoelectronic tweezers (LOET). The assembled
laser with 5-μm diameter exhibits a threshold pump power of 340 μW at room temperature under pulse condition. The heterogeneously-integrated
InGaAsP-on-Si microdisk laser could provide the much needed optical source for CMOS-based silicon photonics. The small footprint
and low power consumption make them attractive for optical interconnect applications. The optofluidic assembly technique enables
efficient use of the III–V epitaxial materials in silicon photonic integrated circuits. 相似文献
13.
Huiying Lao Haisheng Zhu Xianfeng Chen 《Applied Physics A: Materials Science & Processing》2010,101(2):313-317
Fabricating domain reversal directly induced by femtosecond laser is a novel and promising method to induce micron-period
or even submicron-period inverted domain structure for it averts the domain spreading and mergence which is hard to avoid
by traditional electric-field poling method. In this paper, the domain reversal process in lithium niobate crystal by irradiation
of femtosecond pulses whose spatial and temporal distributions are taken into consideration is numerically simulated in the
framework of Fahy’s model. The simulation results manifest the domain inversion window theory and predict the threshold reversal
fluence. The experiment to form domain reversal via direct illumination with femtosecond laser in Y-cut lithium niobate samples was conducted at room temperature. The multi-ring-like structures on the processed samples tally
with the inversion window theory and the calculated threshold reversal fluence is well within the scope obtained by simulation,
which serves as a corroborative evidence to prove the domain reversals can be formed by direct irradiation with femtosecond
laser in lithium niobate. 相似文献
14.
Csaba László Sajti Svea Petersen Ana Menéndez-Manjón Stephan Barcikowski 《Applied Physics A: Materials Science & Processing》2010,101(2):259-264
In-situ functionalization of gold nanoparticles with fluorophore-tagged oligonucleotides is studied by comparing femtosecond
laser ablation in stationary liquid and in biomolecule flow. Femtosecond laser pulses induce significant degradation to sensitive
biomolecules when ablating gold in a stationary solution of oligonucleotides. Contrary, in-situ conjugation of nanoparticles
in biomolecule flow considerably reduces the degree of degradation studied by gel electrophoresis and UV–Vis spectrometry.
Ablating gold with 100 μJ femtosecond laser pulses DNA sequence does not degrade, while the degree of fluorophore tag degradation
was 84% in stationary solution compared to 5% for 1 mL/min liquid flow. It is concluded that femtosecond laser-induced degradation
of biomolecules is triggered by absorption of nanoparticle conjugates suspended in the colloid and not by ablation of the
target. Quenching of nanoparticle size appears from 0.5 μM biomolecule concentration for 0.3 μg/s nanoparticle productivity
indicating the successful surface functionalization. Finally, increasing the liquid flow rate from stationary to 450 mL/min
enhances nanoparticle productivity from 0.2 μg/s to 1.5 μg/s, as increasing liquid flow allows removal of light absorbing
nanoparticles from the ablation zone, avoiding attenuation of subsequent laser photons. 相似文献
15.
T. Calmano J. Siebenmorgen O. Hellmig K. Petermann G. Huber 《Applied physics. B, Lasers and optics》2010,100(1):131-135
Tracks of modified material were written with femtosecond-laser pulses in neodymium-doped YAG crystals. Due to a stress-induced
change of the refractive index, waveguiding beside the tracks and between two adjacent tracks with a distance of approximately
25 μm was observed. Loss measurements resulted in guiding losses of about 1.6 dB/cm for the double track waveguide. Spectroscopic
investigations of the 4
F
3/2→4
F
11/2 transmission lines of the neodymium ions, which are close to the modified region, revealed a small stress-induced red shift
of the lines. Laser oscillation of single-track waveguides and double-track waveguides was demonstrated with Ti:Sapphire laser
pumping at a wavelength of 808 nm. Best laser performance with about 1.3 W output power at 2.25 W launched pump power was
achieved using a double-track waveguide with a separation of 27 μm at an outcoupling transmission of 95%. 相似文献
16.
Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser.We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations.The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser. 相似文献
17.
Femtosecond laser-induced dissociation and Coulomb explosion of polyatomic molecule C_2H_6 were systematically investigated using a time-of-flight mass spectrometer and a chirped pulse amplifier laser. With the laser intensity varying from 2.4×10^{15}W/cm^{2} to 1.2×10^{16}W/cm^2, strong molecular ions C_2H_n^+ (n=0-6) and atomic ions C^{m+} (m=1-3) signals were observed. The double-peak structure of atomic ions indicated the occurrence of Coulomb explosion. Compared with the nearly isotropic distribution of C^{+}, highly charged ions C^{m+} (m=2-3) exhibited a sharply anisotropic angular distribution, which was attributed to the geometric alignment. 相似文献
18.
Sung Hoon Kim Ik-Bu Sohn Sungho Jeong 《Applied Physics A: Materials Science & Processing》2011,103(4):1053-1057
The self-organized formation of ripples in the direction parallel to the groove during the femtosecond laser machining of
microgrooves on aluminum nitride ceramic at laser fluences much higher than the single-pulse ablation threshold is reported.
These parallel ripples are notably different from the commonly observed polarization-perpendicular ripples and are produced
in grooves having an appropriate width and depth, irrespective of laser polarization. From subsequent experiments with narrow
and wide groove widths, it could be considered that the groove walls play an important role in the formation of these parallel
ripples, possibly by confining the laser-induced plasma. 相似文献
19.
We demonstrate a fundamentally mode-locked Yb-fiber laser with 3?GHz repetition rate and ~206 fs pulse duration. The laser incorporates two enabling technologies: a 1?cm heavily Yb-doped phosphate glass fiber as the gain medium and a high-dispersion (-1300 fs2) output coupler to manage cavity dispersion. The oscillator self-starts and generates up to 53?mW average power. 相似文献
20.
V. ?vr?ek T. Sasaki R. Katoh Y. Shimizu N. Koshizaki 《Applied physics. B, Lasers and optics》2009,94(1):133-139
Blue luminescent colloidal silicon nanocrystals (Si-ncs) were synthesized at room temperature by nanosecond pulsed laser ablation
of a single-crystal silicon target in de-ionized water. Irregular Si-nc fragments obtained by laser ablation are stabilized
into regularly shaped, spherical, and well-separated aggregates during the aging process in water. Aging in de-ionized water
for several weeks improved the photoluminescence (PL) intensity. At least two weeks of aging are necessary for observation
of broad blue room temperature PL with a maximum centered at 420 nm. Detailed structural analysis revealed that agglomerates
after aging for several months contain Si-ncs with irregular shape smaller than the quantum confinement limit (<5 nm). These
blue luminescent Si-ncs dispersed in de-ionized water exhibited a PL decay time of 6 ns, which is much faster than that of
Si-ncs prepared in traditional ways (usually on the order of microseconds). The oxidized Si-ncs with quantum confinement effects
are responsible for a PL band around 400 nm visible to the naked eye at room temperature. 相似文献