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1.
This work demonstrates a semi-automatic optical frequency counter based on two mode-locked fiber laser combs. The mode number
of the comb line involved in the optical frequency measurement is determined by operating the two laser combs at three different
repetition rates, with two of them similar enough to have the same mode number of the beating comb lines. The determination
of the mode number is independent of the frequency fluctuation of the laser under measurement. The whole measurement process
was automated, except for the frequency stabilization of the laser combs and the optimization of the beat signal–to–noise
ratio. 相似文献
2.
A. Ancona D. Nodop J. Limpert S. Nolte A. Tünnermann 《Applied Physics A: Materials Science & Processing》2009,94(1):19-24
We have investigated the ultra-fast microdrilling of metals using a compact and cheap fiber amplified passively Q-switched
microchip laser. This laser system delivers 100-ps pulses with repetition rates higher than 100 kHz and pulse energies up
to 80 μJ. The ablation process has been studied on metals with quite different thermal properties (copper, carbon steel and
stainless steel). The dependence of the ablation depth per pulse on the pulse energy follows the same logarithmic scaling
laws governing laser ablation with sub-picosecond pulses. Structures ablated with 100-ps laser pulses are accompanied only
by a thin layer of melted material. Despite this, results with a high level of precision are obtained when using the laser
trepanning technique. This simple and affordable laser system could be a valid alternative to nanosecond laser sources for
micromachining applications. 相似文献
3.
The Lamb dip of CO rovibrational transition is detected by a room temperature extracavity RF optogalvanic cell and employed
to stabilize the frequency of a CO laser. The S/N ratio of optogalvanic signal is about 2000
at optical power < 1 W. The relative depth of Lamb dip is 2.3%. The S/N ratios of first and third harmonic demodulated saturation
signals are about 40
and 10
, respectively. The CO laser is stabilized using the first harmonic demodulated signal, and the frequency stability is better
than 300 kHz.
Concurrently, the influences of operational parameters, which include the coil current, partial pressures of gas mixture,
are investigated. A simple model for the influence of coil current is presented, and further improvements are addressed as
well. 相似文献
4.
D. Nodop S. Linke F. Jansen J. Limpert A. Tünnermann L. Rindorf 《Applied physics. B, Lasers and optics》2008,92(4):509-512
We report for the first time, to the best of our knowledge, on the fabrication and characterization of CO2-laser written long-period gratings in a large-mode area photonic crystal fiber with a core diameter of 25 μm. The gratings
have low insertion losses (<1 dB) and high attenuation (>10 dB) at the resonant wavelengths, making them particularly interesting
for high power applications. 相似文献
5.
J. Sato M. Kikukawa S. Yamaguchi M. Endo K. Tei K. Nanri T. Fujioka 《Applied physics. B, Lasers and optics》2009,96(4):741-744
A flexible and portable trace nitrogen dioxide sensor based on cavity ringdown spectroscopy using an optical fiber-coupled
high-finesse cavity was successfully demonstrated. Tailoring the spatial mode matching condition of the core of an optical
fiber and high-finesse external cavity allows for effective optical feedback into an antireflection-coated laser diode for
stable resonant enhancement of the external cavity. The external cavity, which works as a ringdown cavity, could be remotely
located from the light source and receiver section by only a single mode optical fiber. The sensitivity was found to be 1.0×10−7 cm−1 in a compact 1-cm3 ringdown cavity volume. 相似文献
6.
B. Cocquelin D. Holleville G. Lucas-Leclin I. Sagnes A. Garnache M. Myara P. Georges 《Applied physics. B, Lasers and optics》2009,95(2):315-321
We report on a diode-pumped vertical external-cavity surface-emitting laser emitting around 852 nm for Cesium atomic clocks
experiments. We have designed a 7-quantum-well semiconductor structure optimized for low laser threshold. An output power
of 330 mW was achieved for 1.1 W of incident pump power. Furthermore, a compact setup was built for low-power single-frequency
emission. We obtained an output power of 17 mW in a single longitudinal mode, exhibiting both broad (9 nm) and continuous
(14 GHz) tunability around the Cesium D2 line. The laser frequency has been stabilized on an atomic transition with residual frequency fluctuations ∼300 kHz. Through
a beatnote experiment the −3 dB laser linewidth has been measured to <500 kHz over 10 ms. 相似文献
7.
In the present paper, polyimide surfaces were processed with pulsed KrF laser radiation at fluences near the ablation threshold.
The morphology of the processed surfaces was studied by scanning electron microscopy and chemical analyses performed by electron
dispersive spectroscopy. The formation of conical structures was observed for radiation fluences lower than 0.5 J/cm2. The areal density of cones increases with the number of pulses and decreases with the radiation fluence. At low fluences
(<150 J/cm2), cones are formed due to shadowing by calcium phosphate impurities while for higher fluences the main mechanism of cones
formation is believed to be radiation hardening. 相似文献
8.
A. Waxman M. Givon G. Aviv D. Groswasser R. Folman 《Applied physics. B, Lasers and optics》2009,95(2):301-305
The influence of Zn-atom additive on ‘pure’ copper vapor laser output characteristics is studied. The laser pulse width, energy
and power are found to increase under the diffusion of zinc atoms from a zinc-containing reservoir into the discharge of the
copper-vapor laser at temperatures above 500°C. Additional absorption experiments and calculations are consistent with the
conclusion that not only optical resonant pumping by the 213.9-nm Zn I line, but also other processes, should be taken into
account to explain the effects of additive influence. 相似文献
9.
Chie Hosokawa Suguru N. Kudoh Ai Kiyohara Yoichiroh Hosokawa Kazunori Okano Hiroshi Masuhara Takahisa Taguchi 《Applied Physics A: Materials Science & Processing》2008,93(1):57-63
An all-wet femtosecond laser microprocessing technique was utilized for patterning and cutting functional network of living
neuronal cells on a multi-electrode dish (MED). The neuronal cells cultured on a source substrate were transferred onto an
electrode in a MED probe in solution by utilizing a femtosecond laser-induced impulsive force and a pattern of neuronal cells
were formed on the MED probe. The cellular activity of the detached neurons was supported that neurites could be regenerated
around the electrodes. As another processing method, the neurons stretching between electrodes were selectively cut by the
direct femtosecond laser irradiation and the spontaneous electrical activity of the neuronal network was evaluated. While
the spontaneous action potentials of neurons were synchronized before the cutting, the synchronization disappeared after the
cutting, indicating that the neuronal network is locally disconnected by the laser cutting. The present method is applicable
to artificial reconstruction of living neuronal network. 相似文献
10.
M. Galiová J. Kaiser K. Novotný J. Novotný T. Vaculovič M. Liška R. Malina K. Stejskal V. Adam R. Kizek 《Applied Physics A: Materials Science & Processing》2008,93(4):917-922
Single-pulse Laser-Induced Breakdown Spectroscopy (LIBS) and Laser-Ablation Inductively Coupled Plasma Mass-Spectrometry (LA-ICP-MS)
were applied for mapping the silver and copper distribution in Helianthus Annuus L. samples treated with contaminant in controlled conditions. For Ag and Cu detection the 328.07 nm Ag(I) and 324.75 nm Cu(I)
lines were used, respectively. The LIBS experimental conditions (mainly the laser energy and the observation window) were
optimized in order to avoid self-absorption effect in the measured spectra. In the LA-ICP-MS analysis the Ag 107 and Cu 63
isotopes were detected. The capability of these two analytical techniques for high-resolution mapping of selected trace chemical
elements was demonstrated. 相似文献
11.
H. Jelínková J. Pašta M. Němec J. Šulc P. Koranda 《Applied Physics A: Materials Science & Processing》2008,92(4):975-980
Comparison of the eye tissue transmission for laser radiations with the wavelengths 0.75, 1.08, 1.34, 1.44, 1.54, 1.66, 2.01,
2.69, and 2.94 μm was made with the aim to understand the possible tissue injury by the particular light. From the step by
step transmission measurements of the various human eye tissues (in vitro) it was recognized that the value of the transmitted
energy in particular segments is different for various wavelengths yielding substantial fluence differences on the retina
and anterior segments, mainly. 相似文献
12.
Trace gas sensor based on quartz tuning fork enhanced laser photoacoustic spectroscopy 总被引:1,自引:0,他引:1
K. Liu J. Li L. Wang T. Tan W. Zhang X. Gao W. Chen F. K. Tittel 《Applied physics. B, Lasers and optics》2009,94(3):527-533
A compact photoacoustic gas sensor based on a quartz tuning fork and fiber-coupled distributed feedback (DFB) diode laser
for detection of trace gas at atmospheric pressure has been developed. The sensor performance was evaluated by detection of
water vapor in ambient air at normal atmospheric pressure. A normalized noise equivalent absorption coefficient of 1.68×10−8 cm−1 W/Hz1/2 was achieved. Influence of different acoustic microresonators and sample pressure on the sensor performance, and the characterization
of the sensor response time were investigated. Approaches to improve the current sensor performance are discussed. 相似文献
13.
D. J. Whitehead P. L. Crouse M. J. J. Schmidt L. Li M. W. Turner A. J. E. Smith 《Applied Physics A: Materials Science & Processing》2008,90(1):123-127
The energy relaxation of electrons in InN epilayers is investigated by excitation- and electric field-dependent photoluminescence
(PL). From the high-energy tail of PL, we determine the electron temperature of the hot carriers. It was found that the electron
temperature variation can be explained by a model in which the longitudinal optical (LO)-phonon emission is the dominant energy
relaxation process. The LO-phonon lifetime is fitted to be 0.89 ps, which is higher than the theoretical phonon lifetime.
This deviation is attributed to the presence of the non-equilibrium hot-phonon effects.
PACS 78.55.Cr; 78.66.Fd; 61.66.Fn; 78.20.Jq; 63.20.kd 相似文献
14.
Yu-Chia Chang Larry A. Coldren 《Applied Physics A: Materials Science & Processing》2009,95(4):1033-1037
High-efficiency, high-speed, tapered-oxide-apertured vertical-cavity surface-emitting lasers (VCSELs) emitting at 980 nm have
been demonstrated. By carefully engineering the tapered oxide aperture, the mode volume can be greatly reduced without adding
much optical scattering loss for the device sizes of interest. Consequently, these devices can achieve higher bandwidth at
lower current and power dissipation. In addition, the parasitics are reduced by implementing deep oxidation layers and an
improved p-doping scheme in the top mirror. Our devices show modulation bandwidth exceeding 20 GHz, a record for 980 nm VCSELs. Moreover,
35 Gb/s operation has been achieved at only 10 mW power dissipation. This corresponds to a data-rate/power-dissipation ratio
of 3.5 Gbps/mW. Most importantly, our device structure is compatible with existing manufacturing processes and can be easily
manufactured in large volume making them attractive for optical interconnects. 相似文献
15.
The first use of CO2 laser photoacoustic measurements for detecting the methanol contents in alcohol-like solutions is presented. With an intracavity
cell configuration, the minimum detectable concentration was ∼200 ppm for methanol and the linear range of the calibration
curve for methanol was from 200 to 70000 ppm. For demonstrating the reliability of analysis in alcoholic beverages, a series
of different concentrations of two-component samples was prepared and measured by the same procedures. The results showed
the feasibility on determining methanol and ethanol contents accurately within a specific tolerance, limited mainly by background
signal and laser stability. This potential method with no pre-treatment of samples takes only ∼10 min to finish one single
measurement. It suggests that the PA detection is suitable for routine diagnosis of adulterated wines in commercial products. 相似文献
16.
High-performance SOA-based multiwavelength fiber lasers incorporating a novel double-pass waveguide-based MZI 总被引:1,自引:0,他引:1
In this paper, using a direct double-pass and a novel isolator-assisted double-pass waveguide-based Mach-Zehnder interferometer
(MZI), high-performance SOA-based multiwavelength fiber lasers (MFL) are proposed and demonstrated experimentally. The filtering
characteristics of the proposed isolator-assisted double-pass MZI are analyzed and examined theoretically in comparison with
those of the single-pass and direct double-pass MZI. Using a direct double-pass waveguide-based MZI with the single-pass free
spectral range (FSR) of 43 GHz, up to 115- and 104-channel simultaneous oscillations spaced at 21.5 GHz in the L-band and
C-band are obtained, respectively, with a power non-uniformity of less than 3 dB and an extinction ratio of ∼30 dB. To the
best of our knowledge, it is the highest lasing-channel count that has been achieved from an SOA-based MFL. To enhance the
extinction ratio while maintaining the FSR, the proposed isolator-assisted double-pass MZI is then utilized in the laser cavity,
and a stable 55-wavelength simultaneous oscillation spaced at 43 GHz is accordingly achieved in C-band with an extinction
ratio of higher than 50 dB. Compared with the lasing linewidth of 0.058 nm with the conventional single-pass MZI, narrower
linewidths of 0.038 and 0.028 nm are obtained with the isolator-assisted and direct double-pass MZI configurations, respectively.
The lasers are stable with a maximum power fluctuation per channel of less than 0.8 dB during an hour’s test. 相似文献
17.
J. Delhay P. Desgroux E. Therssen H. Bladh P.-E. Bengtsson H. H?nen J. D. Black I. Vallet 《Applied physics. B, Lasers and optics》2009,95(4):825-838
Control and reduction of soot particle emissions from aeronautic turbines requires a monitoring system suitable for quantification
of these emissions. Currently, such emissions are estimated using the technique of smoke number. This is an extractive method,
which is not sensitive enough for the low emission levels of modern gas turbines. Within a recent European project, AEROTEST,
part of the project aimed at investigating an alternative soot monitoring technique, laser-induced incandescence (LII) as
an in-situ optical diagnostic for quantification of soot emissions. For aero-engine applications, especially those involving
large-scale turbines, it is necessary to perform the measurements at long distance from the turbine. The LII technique is
favourable in this respect as it provides for non-intrusive measurements and, by detecting the isotropic LII signal along
the same axis as the incoming laser beam (so called backward LII), both the laser and the detector can be built inside one
system located several meters from the turbine. The concept was initiated in the previous European projects, AEROJET I and
II. This paper describes the modified version of the system and the procedure developed to achieve reliable and quantitative
soot volume fraction measurements in the exhausts of aero-engines. Application of the backward LII technique is demonstrated
in the exhaust of a military turbojet engine for different engine speeds. 相似文献
18.
S. Wang H. J. Eichler X. Wang F. Kallmeyer J. Ge T. Riesbeck J. Chen 《Applied physics. B, Lasers and optics》2009,95(4):721-730
Diode lasers with peak powers in the kW range and pulse durations of micro- to milli-seconds have been available since several
years. Pumping solid state lasers with such sources yield high output pulse energies in spiking or Q-switched operation. The
output energy is limited by the thermal lens effects, which are measured and calculated. The time dependent heat conduction
equation in the laser crystal is solved numerically to predict the overall temperature rise and thermal lensing. The thermally
induced optical path difference is approximated by a quadratic distribution to obtain the focal length f of the thermal lens. The thermal lens coefficient K=1/(f⋅P
av), which depends only weakly on the heat transfer coefficient H of the laser crystal to the heat sink, decreases exponentially with increasing pump frequency until the steady state is reached.
Experiments were done with a Nd:YAG crystal at different pump frequencies up to 100 Hz. The thermal lens coefficients obtained
by the power maxima of asymmetric flat-flat resonators agree with our calculations. 相似文献
19.
D. Mathew P. J. M. Peters H. M. J. Bastiaens K.-J. Boller 《Applied physics. B, Lasers and optics》2009,95(1):155-159
The effect of addition of xenon on the long term homogeneity of discharges in F2and ArF excimer laser gas mixtures was investigated in a small-volume discharge chamber. The gas mixture in the discharge
chamber was preionized by X-rays. A special electrical excitation circuit containing a pulse forming line provided a long,
square-shaped current pumping pulse of a predetermined duration to the discharge electrodes. The initiation and the development
of the discharge was monitored via its fluorescence signal with an intensified CCD camera. We found that adding Xe up to partial
pressures of 0.53 mbar extended the homogeneous phase of the discharge from 80 ns to approximately 200 ns in He/F2as well as in He/Ar/F2and Ne/Ar/F2excimer laser gas mixtures. Monitoring of the ArF and XeF spontaneous emission signals showed that the formation of ArF excimers
remained unaffected by the addition of xenon (up to 1.3 mbar) to the laser gas mixture. 相似文献
20.
C. S. Delfino C. S. C. Pfeifer R. R. Braga M. N. Youssef M. L. Turbino 《Applied physics. B, Lasers and optics》2009,96(1):79-84
The objective of this study was to verify the influence of photoactivation with the argon ion laser on shrinkage stress (SS),
followed by evaluation of Vickers microhardness (VM), percentage of maximum hardness (PMH), flexural strength (FS), and flexural
modulus (FM) of a composite resin. The study groups were: L1-laser at 200 mW for 10 seconds; L2-laser at 200 mW for 20 seconds;
L3-laser at 250 mW for 10 seconds; L4-laser at 250 mW for 20 seconds; H-halogen light at 275 mW for 20 seconds. Data were
analyzed by ANOVA/Tukey’s test (α=5%). The values of SS (MPa) were statistically lower for the group L3 (1.3)c, followed by groups L1 (2.7)b, L4 (3.4)a, b,
L2 (3.7)a, and H (4.5)a. There was no difference in the values of VM when the same time of photoactivation was used, with
respective values being L1=70.1a, L2=78.1b, L3=69.9a, L4=78.1b and H=79.9b. All groups showed a PMH of at least 80%. Only
the group L1 showed differences in FS (MPa) and FM (GPa), the respective values of 86.2 and 5.4 being lower. Therefore, the
use of argon ion laser had influenced the composite resin polymerization. The L3 group presented adequate mechanical properties
and minimum SS, reducing the clinical working time for photoactivation of restorations with the tested resin by 50%. 相似文献