共查询到20条相似文献,搜索用时 15 毫秒
1.
Masato Ohmukai Nobutomo Uehara Tetsuya Yamasaki Yasuo Tsutsumi 《Czechoslovak Journal of Physics》2004,54(7):781-784
We have investigated the effects of chemical etching on Raman spectra of porous silicon. The as-anodized porous silicon consisted
mainly of crystalline silicon, as indicated by the Raman spectra. The background in the spectrum was strong, indicating that
the porous silicon surface was rough due to the presence of pores. When chemical etching was performed five times, the Raman
spectrum revealed the presence of spherically shaped nanocrystalline silicon whose diameter was around 3.5 nm. Further chemical
etching, however, extinguished the nanocrystallites, in addition to smoothing the surface morphology. 相似文献
2.
3.
We performed time-resolved spectroscopy of ZnO quantum dots (QD), and observed exciton energy transfer and dissipation between
QD via an optical near-field interaction. Two different sizes of ZnO QD with resonant energy levels were mixed to test the
energy transfer and dissipation using time-resolved photoluminescence spectroscopy. The estimated energy transfer time was
144 ps. Furthermore, we demonstrated that the ratio of energy transfer between the resonant energy states could be controlled. 相似文献
4.
V. L. Kasyutich 《Applied physics. B, Lasers and optics》2009,96(1):141-148
Propagation of an elliptical Gaussian beam in a multiple-pass optical cell formed by two twisted cylindrical mirrors has been
described by means of complex curvature tensors. Using the ABCD tensor approach various light patterns were computed for the use in tunable laser absorption spectroscopy with a multiple-pass
optical cell. Light patterns with high beam-spot density can be also defined for a cavity formed by two twisted cylindrical
high-reflectivity mirrors. In order to achieve higher cavity output intensity, a high-reflectivity cylindrical mirror cavity
with at least one mirror that has a central transparent spot for laser beam injection has been described for applications
in non-resonant cavity enhanced absorption spectroscopy.
The author was with TDL Sensors Ltd., when the experimental part of this work was performed. 相似文献
5.
G. J. Spühler K. J. Weingarten R. Grange L. Krainer M. Haiml V. Liverini M. Golling S. Schön U. Keller 《Applied physics. B, Lasers and optics》2005,81(1):27-32
We present two novel semiconductor saturable absorber mirror (SESAM) designs which can exhibit more than ten times lower saturation
fluence than classical SESAM devices. Design considerations and characterization data are presented. These devices are particularly
suited for passively mode-locked lasers with ultra-high repetition rates. 相似文献
6.
A master oscillator power amplifier (MOPA) system in which the output from an end-pumped Nd:YAG oscillator cavity dumped at
500 kHz is scaled up by a four-stage Nd:YVO4 amplifier is reported. Decrease in extraction efficiency of the amplifier chain with crystals different from that in the
oscillator was analyzed. With the 5.4 W seed output, 118 W of power was extracted from the amplifier chain at the pump power
of 345 W, with an extraction efficiency of 34.2% and an overall optical–optical efficiency of 30.9% for the MOPA system. The
beam quality factors were measured as M
x
2=1.45 and M
y
2=1.59 in two orthogonal directions, respectively. 相似文献
7.
H. R. Chen J. H. Lin K. T. Song K. H. Lin W. F. Hsieh 《Applied physics. B, Lasers and optics》2009,96(1):19-23
We demonstrated a diode-pumped passively mode-locked c-cut Nd:LuVO4 picosecond laser with a semiconductor saturable-absorber mirror (SESAM) at a wavelength of 1067.8 nm. Due to the wide bandwidth
of 0.48 nm, stable mode-locking has been generated with a duration as short as 3.7 ps, which is shorter than for the a-cut
Nd:LuVO4 laser. A maximum output power of 1.67 W was achieved to give a highest peak power of 3.47 KW at 18 W absorbed pump power. 相似文献
8.
M. Hoffmann Y. Barbarin D. J. H. C. Maas M. Golling I. L. Krestnikov S. S. Mikhrin A. R. Kovsh T. Südmeyer U. Keller 《Applied physics. B, Lasers and optics》2008,93(4):733-736
We report the first successful modelocking of a vertical external cavity surface emitting laser (VECSEL) with a quantum dot
(QD) gain region. The VECSEL has a total of 35 QD-layers with an emission wavelength of about 1060 nm. In SESAM modelocked
operation, we obtain an average output power of 27.4 mW with 18-ps pulses at a repetition rate of 2.57 GHz. This QD-VECSEL
is used as-grown on a 450 μm thick substrate, which limits the average output power. 相似文献
9.
J. Cifre J. Bertomeu J. Puigdollers M. C. Polo J. Andreu A. Lloret 《Applied Physics A: Materials Science & Processing》1994,59(6):645-651
Silicon films were deposited at moderate substrate temperatures (280–500° C) from pure silane and a silane-hydrogen mixture (10% SiH4, 90% H2) in a hotwire CVD reactor. The morphology, structure and composition of the samples were studied with scanning electron microscopy, transmission electron microscopy, transmission electron diffraction, X-ray diffraction, Raman spectroscopy and secondary ion mass spectrometry. The sample deposited at 500° C with pure silane has an amorphous structure, whereas the samples obtained from silane diluted in hydrogen have a polycrystalline structure, even that grown at the lowest temperature (280° C). Polycrystalline samples have a columnar structure with 0.3–1 m crystallite sizes with preferential orientation in [220] direction. Deposition rates depend on the filament-substrate distance and range from 9.5 to 37 Å/s for the polycrystalline samples. The high quality of the polycrystalline samples obtained makes the hot-wire technique very promising. Moreover, it is expected to be easily scaled up for applications to large-area optoelectronic devices and to photovoltaic solar cells. 相似文献
10.
K. Tanaka G. W. Burr T. Grosjean T. Maletzky U. C. Fischer 《Applied physics. B, Lasers and optics》2008,93(1):257-266
Metal-coated dielectric tetrahedral tips (T-tip) have long been considered to be interesting structures for the confinement
of light to nanoscopic dimensions, and in particular as probes for scanning near-field optical microscopy. Numerical investigations
using the Finite-Difference Time-Domain (FDTD) method are used to explore the operation of a T-tip in extraction mode. A dipole
source in close proximity to the apex excites the tip, revealing the field evolution in the tip, the resulting edge and face
modes on the metal-coated surfaces, and the coupling from these modes into highly directional radiation into the dielectric
interior of the tip. These results are the starting point for illumination-mode numerical investigations by a Volume Integral
equation method, which compute the field distribution that develops in a T-tip when a Gaussian beam is incident into the tip,
and which show that a highly confined electric field is produced at the apex of the tip. The process of light confinement
can be considered as a superfocussing effect, because the intensity of the tightly confined light spot is significantly higher
than that of the focussed yet much wider incident beam. The mechanism of superfocussing can be considered as a dimensional
reduction of surface plasmon modes, where an edge plasmon is the most important link between the waveguide-modes inside the
tip and the confined near field at the apex. 相似文献
11.
S. C. Huang H. L. Chang K. W. Su A. Li S. C. Liu Y. F. Chen K. F. Huang 《Applied physics. B, Lasers and optics》2009,94(3):483-487
An AlGaInAs quantum-well structure grown on a Fe-doped InP transparent substrate is developed to be a gain medium in a high-peak-power
nanosecond laser at 1570 nm. Using an actively Q-witched 1064 nm laser to pump the gain chip, an average output power of 135 mW
is generated at a pulse repetition rate of 30 kHz and an average pump power of 1.25 W. At a pulse repetition rate of 20 kHz,
the peak output power is up to 290 W at a peak pump power of 2.3 kW. 相似文献
12.
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
13.
Christophe Hecquet Franck Delmotte Marie-Fran?oise Ravet-Krill Sébastien de Rossi Arnaud Jérome Fran?oise Bridou Fran?oise Varnière Evgueni Meltchakov Frédéric Auchère Angelo Giglia Nicola Mahne Stefano Nanaronne 《Applied Physics A: Materials Science & Processing》2009,95(2):401-408
In this paper, we present a study on two-channel multilayer mirrors which can operate at two wavelengths in Extreme Ultraviolet
(EUV) spectral range. We propose a new method to design two-channel EUV multilayer mirrors with enhanced spectral selectivity.
The mirror structure is a stack of two periodic multilayers separated by a buffer layer. We have defined the main parameters
which allow adjustment of the distance between different order Bragg’s peak and of wavelength positions of reflectivity minima.
Two mirrors have been designed and deposited for solar EUV telescope applications by using this method. The first mirror reflects
Fe IX–X line (17.1 nm) and Fe XVI (33.5 nm) lines with attenuation of the He II line (30.4 nm). The second mirror reflects
Fe IX–X and He II lines with attenuation of Fe XV (28.4 nm) and Fe XVI lines. Measurements with synchrotron radiation source
confirm that, in both cases, for these mirrors, we are able to adjust reflectivity maxima (Bragg peak position) and minima.
Such multilayers offer new possibilities for compact design of multi-wavelength EUV telescopes and/or for high spectral selectivity. 相似文献
14.
The photoluminescence correlation from a single CdSe nanocrystal under pulsed excitation is studied, and a single photon is
realized at wavelength 655 nm at room temperature. The single colloidal CdSe quantum dot is prepared on a SiO2/silicon surface by a drop-and-drag technique. The long-term stability of the single-photon source is investigated; it is
found that the antibunching effect weakens with excitation time, and the reason for the weakening is attributed to photobleaching.
The lifetimes of photoluminescence from a single quantum dot are analyzed at different excitation times. By analyzing the
probability distribution of on and off times of photoluminescence, the Auger assisted tunneling and Auger assisted photobleaching models are applied to explain
the antibunching phenomenon. 相似文献
15.
P. Scholz S. Schwieger B. Ashall D. Zerulla E. Runge 《Applied physics. B, Lasers and optics》2008,93(1):111-115
The influence of the nanowire shape on the excitation of surface plasmon polaritons at metallic nanowire arrays is studied
numerically. For a system of silver nanowires housed on a polymer substrate, nanowires with rectangular and elliptical cross
sections are compared. It was found that in the case of rectangular nanowires the excitation efficiency is higher for surface
plasmons at the polymer–metal interface than for surface plasmons at the air–metal interface. Conversely, in the case of elliptical
nanowires the air–metal plasmon modes are stronger. Further, it is noted that the nanowire shape directly influences the position
of the surface plasmon resonance. 相似文献
16.
Intensity-independent self-trapping of optical beams in photorefractive crystals was found recently. But we show that due to the existence of dark conductivity in some photorefractive materials or coherent and non-coherent background irradiance, the self-trapping of weak optical beams in photorefractive materials, such as SBN, becomes intensity dependent. The threshold condition of the applied external de electric field for self-trapping is determined as function of the material parameters as well as the initial transverse sizes and relative intensities of the beams. 相似文献
17.
A. A. Sirotkin L. Di Labio A. I. Zagumennyi Yu. D. Zavartsev S. A. Kutovoi V. I. Vlasov W. Lüthy T. Feurer A. A. Onushchenko I. A. Shcherbakov 《Applied physics. B, Lasers and optics》2009,94(3):375-379
The use of glasses doped with PbS nanocrystals as intracavity saturable absorbers for passive Q-switching and mode locking
of c-cut Nd:Gd0.7Y0.3VO4, Nd:YVO4, and Nd:GdVO4 lasers is investigated. Q-switching yields pulses as short as 35 ns with an average output power of 435 mW at a repetition
rate of 6–12 kHz at a pump power of 5–6 W. Mode locking through a combination of PbS nanocrystals and a Kerr lens results
in 1.4 ps long pulses with an average output power of 255 mW at a repetition rate of 100 MHz. 相似文献
18.
19.
We use a grating spectrometer with a time resolution of 17.4 μs and a spectral resolution of 5 GHz to analyze a superluminescent
source operating near 1350 nm. Polychromatic beating noise is shown to dominate single-shot measurements of the source spectrum;
the observed noise level is within 19% of the theoretical beating noise level. By adopting a delayed pulse referencing scheme
used previously with wavelength-swept sources, the beating noise is virtually eliminated, allowing spectral measurements limited
only by shot noise and camera read noise. 相似文献
20.
S. Rivier U. Griebner V. Petrov H. Zhang J. Li J. Wang J. Liu 《Applied physics. B, Lasers and optics》2008,93(4):753-757
Passive mode locking of the self-frequency doubling Yb:YAB crystal with a saturable absorber mirror is studied at the fundamental
wavelength. This laser has a very low threshold, and pulses as short as 85 and 87 fs are obtained for Ti:sapphire and diode
laser pumping, respectively. 相似文献