共查询到20条相似文献,搜索用时 15 毫秒
1.
N. C. Wong 《Applied physics. B, Lasers and optics》1995,61(2):143-149
A method for building an optical-to-microwave frequency chain and for measuring optical frequencies relative to the cesium primary frequency standard is described. Based on optical frequency division via parametric oscillators, the concept is to generate two known ratios (1/2 and 4/9) of an optical calibration frequencyf
1 whose frequency difference is measured relative to the cesium clock. The (1/2) ratio is obtained by either a 2:1 frequency division off
1 or second-harmonic generation of (l/2)f
1. The (4/9) ratio off
1 can be generated with a 3:1 frequency divider driven by a second laser atf
2 that is chosen to be near (2/3)f
1, which in turn is obtained with af
1-pumped 3:1 frequency divider. A set of auxiliary Optical Parametric Oscillators (OPOs) with outputs centered at (1/2)f
1 is used to facilitate the difference-frequency measurement between the two ratios. A practical configuration utilizing a YAG and a Ti: Al2O3 laser and its application to a number of precision measurements of interest are presented. 相似文献
2.
H.-St. Albrecht P. Heist J. Kleinschmidt D. van Lap T. Schröder 《Applied physics. B, Lasers and optics》1992,55(4):362-364
We demonstrate the optical Kerr shutter technique as a simple and powerful tool for the measurement of femtosecond pulses in the ultraviolet as well as in the visible spectral region. The method provides the third-order intensity correlation function which gives information about pulse asymmetry and pulse structures. 相似文献
3.
M. Laroche L. Kervevan H. Gilles S. Girard J. K. Sahu 《Applied physics. B, Lasers and optics》2005,80(4-5):603-607
Accurate and highly sensitive speed measurements have been successfully demonstrated by the optical feedback velocimetry technique using the self-mixing modulation effect in a double-clad Er–Yb-doped fiber laser. The sensitivity to back-scattered light has been investigated regarding the Doppler frequency shift or the target distance, and it has been shown that the velocimeter is still sensitive to a target located at 20 m and for speeds as high as 13 m s–1. 相似文献
4.
International comparisons of I2 stabilized ion lasers operated at 514.5 nm have shown a laser frequency reproducibility of 2·10−10
v to 5·10−12
v. These results encouraged the international acceptance of the wavelength value λvac=514.673467 for thea
3 hyperfine component of the127I2 line 43-0P(13). 相似文献
5.
In sub-10 nm low flying height (FH) region, system calibration is a significant challenge to achieve precise FH measurement. Unloading calibration mechanism is utilized for every FH measurement using three-wavelength interferometry. Our experiment has shown that the cutoff frequency of photodetectors and the bandwidth of optical filters induce calibration falloff during the calibration process. As a result, the FH measured is underestimated, i.e., the FH measured is lower than its true value. In this paper, mathematical models are proposed to eliminate the side effects due to the bandwidth of optical filters and the cutoff frequency of photodetectors. Results indicate that the proposed compensation schemes are effective in terms of improving the calibration accuracy. 相似文献
6.
G. M. Tino M. Barsanti M. de Angelis L. Gianfrani M. Inguscio 《Applied physics. B, Lasers and optics》1992,55(4):397-400
A visible diode laser emitting at 690 nm at room temperature has been frequency-stabilized using a simple scheme based on optical feedback from a diffraction grating. The possibilities offered by these lasers for high-resolution spectroscopy are demonstrated by recording the sub-Doppler signal of the 689 nm intercombination line of strontium and resolving the hyperfine structure of the close P63 R70 (8, 4) transitions of iodine. 相似文献
7.
C. V. Sellathamby H. J. J. Seguin D. R. Akitt 《Applied physics. B, Lasers and optics》1993,57(4):267-276
As advancements in laser technology result in higher-power devices, increased thermal loads experienced by resonator optical components generate instabilities in the output beam. Consequently, methods for maintaining and optimizing output-beam parameters are necessary for efficient long-term operation. This study examines a vision-based feedback control system which monitors a sampled cross-sectional image of the laser's output, and regulates both cavity mirrors, as well as the excitation level, to stabilize beam uniformity, beam steer, and output-power level.The system optimizes the output-power distribution achievable from a given laser, while significantly reducing beam steering effects. Direction of beam propagation is restricted to within 60 rad of the desired setpoint, while the output power is stabilized to within 4%. Results clearly document a considerable improvement in laser performance through maximization of beam uniformity, minimization of beam steering, and stabilization of total output power. As such, an important degree of consistency and repeatability in output-beam parameters, essential to precision laser applications, is easily achieved. Valuable diagnostic capabilities pertaining to output beam intensity and energy profiles are also incorporated into the control system. These data may be monitored on-line or stored for subsequent analysis. 相似文献
8.
The mode-hop behavior and the power characteristics of a laser diode with wavelength-selective optical feedback are experimentally
investigated. The feedback is provided by external volume holographic gratings, also called ‘Bragg mirrors’, at normal incidence.
We demonstrate that a Bragg mirror forces a laser diode to operate only within a narrow wavelength range, and that the emission
wavelength of the laser diode is stabilized against variations of the injection current. Moreover, we present periodic undulations
of the power characteristics of the laser, depending on the driving current. They can be qualitatively explained with a simple
model which takes into account that the threshold gain in the laser system strongly depends on the wavelength. 相似文献
9.
The immission load of nitric oxide due to traffic is investigated in the cities of Lyon, Geneva, and Stuttgart using a mobile differential absorption LIDAR system (DIAL). Horizontal and vertical maps of the NO mixing ratio, as well as 24 hour records are presented. It is shown that street canyons favor high immission values, whereas broad main axes are efficiently ventilated (Lyon); inversion conditions rise the average immission load within a city mainly independent of traffic (Geneva and Stuttgart), whereas highly frequented intersections favor high immission values regardless of weather conditions (Geneva); the observed maximum immission loads also depend on the traffic density during rush hours (Stuttgart). 相似文献
10.
11.
A technique is presented for determining the frequency modulation transfer function of a laser. The method is based on a Mach–Zehnder interferometer, with a significant difference in the optical path lengths of the two arms. A frequency-modulated laser beam incident on the interferometer produces a phase-modulated photocurrent signal with an effective modulation index that is related to the amplitude of the optical frequency modulation. Techniques for determining both the amplitude and the phase of the optical frequency modulation from the photocurrent signal are described. 相似文献
12.
K. J. Moh W. M. Lee W. C. Cheong X.-C. Yuan 《Applied physics. B, Lasers and optics》2005,80(8):973-976
An optical line trap has the ability to simultaneously trap and align microparticles in line formation due to its intensity profile. In this paper, we demonstrate a straightforward means to generate multiple optical line traps by simply placing a phase-only rectangular ridge in the path of a laser beam. By carefully positioning the rectangular ridge, we were able to control the separation between the optical trapping lines, which were then used to create multiple line formations of trapped particles. The simplicity of the proposed technique lends itself to the realization of a highly efficient optical line trap converter for easy modification of existing optical microscopes. 相似文献
13.
This paper demonstrates a method to determine the bidirectional transmittance distribution function (BTDF) using an integrating sphere. Information about the sample’s angle-dependent scattering is obtained by making transmittance measurements with the sample at different distances from the integrating sphere. Knowledge about the illuminated area of the sample and the geometry of the sphere port in combination with the measured data combines to a system of equations that includes the angle-dependent transmittance.The resulting system of equations is an ill-posed problem which rarely gives a physical solution. A solvable system is obtained by using Tikhonov regularization on the ill-posed problem. The solution to this system can then be used to obtain the BTDF.Four bulk-scattering samples were characterised using two goniophotometers and the described method to verify the validity of the new method. The agreement shown is excellent for the more diffuse samples. The solution to the low-scattering samples contains unphysical oscillations, but still gives the correct shape of the solution. The origin of the oscillations and why they are more prominent in low-scattering samples are discussed. 相似文献
14.
M. Uebernickel C. Fiebig G. Blume K. Paschke B. Eppich R. Güther G. Erbert 《Applied physics. B, Lasers and optics》2008,93(4):823-827
Continuous wave power of more than 400 mW at 488 nm has been generated by frequency doubling of 2.45 W at 976 nm obtained
from a distributed Bragg reflector tapered diode laser. This results in a wavelength conversion efficiency of 16.5% and an
electrical-to-optical efficiency of more than 4.5%. We used a 50 mm long periodically poled MgO:LiNbO3 bulk crystal in single-pass configuration for the second harmonic generation. This is to the author’s knowledge the highest
output power and the highest wavelength conversion efficiency at 488 nm generated by a monolithic semiconductor laser device
in single pass configuration with a bulk crystal. A deviation from the quadratic dependency of the frequency doubling is explained
by the decrease of the beam quality of the fundamental wave. 相似文献
15.
S. Amoruso V. Berardi R. Bruzzese R. Capobianco R. Velotta M. Armenante 《Applied Physics A: Materials Science & Processing》1996,62(6):533-541
We report on Time-of-Flight Mass Spectrometry (TOFMS) analysis of plasmas produced in laser ablation of Al targets. We used both the second (532 nm) and third (355 nm) harmonic of a Nd: YAG laser system, carrying out the investigation in a regime of relatively high laser fluence (up to 70 J/cm2), where the production of ionized species in the plume is maximized. We present TOF mass spectra of ions in the laser-produced plasma, and a detailed analysis of the relative abundance of different charged species as a function of the laser fluence. The presence of single, doubly and triply ionized Al atoms has been observed and the fluence threshold for their production is reported. We also studied the total ion and electron yield at different laser fluences, its saturation above specific energy densities, and singly ionized cluster-ions produced in the laser plasma. 相似文献
16.
You-Lin Xiang 《Physics letters. A》2009,373(15):1325-1328
A two-mode saturation laser model with cross-correlation between the real and imaginary parts of the quantum noise is considered. The laser intensity Langevin equation and corresponding Fokker-Planck equation are derived by the phase-locking method. The effects of the cross-correlation strength λ between the real and imaginary parts of quantum noise and the cavity decay constant K on the steady-state intensity distribution Q(I1,I2), the mean light intensity 〈I〉, the normalization autocorrelation λ11(0) and cross correlation λ12(0) are studied by numerical calculation. The results show that as λ increases the Qs(I1,I2) show two extrema, and λ almost does not affect the 〈I〉, λ11(0) and λ12(0) when the laser system is operated far above threshold. Nevertheless, when the laser system is operated at and below threshold, λ makes the curves of Qs(I1,I2) have the higher peak and drop faster. Furthermore, it enhances the deviation of λ11(0) and λ12(0) and lessens the mean light intensity 〈I〉 when the laser system is operated at and below threshold. 相似文献
17.
L. Feenstra O.B. Hoekstra P.J.M. Peters W.J. Witteman 《Applied physics. B, Lasers and optics》2000,70(2):231-235
An X-ray preionised ArF and KrF excimer laser has been studied with three different spiker-sustainer excitation circuits.
We observed large differences in the laser performance, when the preionisation delay timing was varied on a nanosecond timescale.
The behaviour of both lasers was found to be equivalent. The observations can be understood by considering the effect of the
discharge excitation technique on the preionisation process. An excitation mode with a prepulse well above the steady-state
voltage VSS with a subsequent reversed overshoot voltage for initiating the discharge, in combination with a well-timed preionisation
pulse is found to give the best results. Optimum output energies of 50 mJ with ArF and 175 mJ with KrF were obtained from
an active volume of 60×1.5×1.2 cm in the so-called swing mode, with the preionisation applied 60 ns before the discharge breakdown.
Received: 23 February 1999 / Revised version: 4 June 1999 / Published online: 16 September 1999 相似文献
18.
Frequency stabilization of a diode laser on the Cs D2 resonance line by the Zeeman effect in a vapor cell 总被引:3,自引:0,他引:3
N. Beverini E. Maccioni P. Marsili A. Ruffini F. Sorrentino 《Applied physics. B, Lasers and optics》2001,73(2):133-138
Hyperfine optical pumping of a Cs-vapor cell through a diode laser in frequency standards requires a high purity of the laser
emission spectrum, and a high stability of the emission frequency. We present here a frequency-locking scheme that is able
to produce a discrimination signal without any modulation, by using the dichroism induced by a magnetic field on the atomic
vapor. The larger line-width of the reference signal (Doppler-broadened) is compensated by its larger amplitude, when compared
with the saturated absorption signal. As a final result, the slope is similar, and the large line-width warrants a large locking
range, making robust the lock against external perturbations. This error signal is used to lock the frequency of an external
cavity diode laser, with a grating reflector in Littman configuration. A fast correction band is obtained by changing the
cavity length through an intra-cavity electro-optic modulator. The possible sources of instabilities of the locking point
are discussed and estimated through a simulation computer program.
Received: 28 November 2000 / Revised version: 21 May 2001 / Published online: 18 July 2001 相似文献
19.
Aaron F. Matthews 《Optics Communications》2009,282(9):1789-1271
I studied experimentally beam self-collimation and splitting in two-dimensional microwave photonic crystals. Using a microwave photonic crystal fabricated from alumina rods, I present an experimental proof of principle for an earlier theoretical proposal [A.F. Matthews, S.K. Morrison, Yu.S. Kivshar, Opt. Commun. 279 (2007) 313] of a photonic crystal beam splitter based on the self-collimation effect. 相似文献
20.
A. Dreizler S. Lindenmaier U. Maas J. Hult M. Aldén C.F. Kaminski 《Applied physics. B, Lasers and optics》2000,70(2):287-294
This study reports the application of a novel, high speed laser-detector system for the time-resolved study of flame propagation
in a well-controlled spark ignition system. The ignition system allowed full and reproducible control over the energy deposited
during breakdown and the ensuing arc discharge of the spark plasma. Ignition was performed in a closed vessel which was filled
with stoichiometric mixtures of methane and air. Four sequential snapshots of two-dimensional OH distributions were recorded
during single ignition events by the use of planar laser-induced fluorescence (PLIF). From these OH distributions flame front
velocities have been extracted with an accuracy of better than 2%. One-dimensional numerical simulations of the ignition event
including detailed chemistry and transport processes have been performed. Experimental results and results from the simulations
have been compared to each other with respect to flame front velocities as well as spatial concentration profiles of OH radicals.
In general a good agreement was obtained. In this way the ignition system was carefully characterised.
Received: 6 April 1999 / Published online: 27 October 1999 相似文献