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1.
This paper reports on the alignment requirements of a scalable multidisc laser with respect to the internal reflection losses of the resonator. Considering the polarization state of the mode, these losses are generated due to a polarization mismatch at the disc surfaces. Measurements of the polarization of the output beam from a laser containing tilted discs were compared with computer simulations. The losses were calculated for resonators containing discs deviating slightly from the ideal orientation in a random manner, in order to predict the alignment requirements for a multidisc system. Results for variable numbers of discs and angular deviations are presented. 相似文献
2.
The motion equation for ? between the molecular axis and laser polarization direction in a high-frequency off-resonance femtosecond laser field is deduced while simultaneously examining the effects of a permanent dipole moment and field-induced polarizability and hyperpolarizability to molecular rotation. Femtosecond-laser-induced dynamic alignment of CO, N2, and Br2 molecules are investigated by numerically solving the obtained rotation equation for the angle ?. The effects of the molecular permanent dipole moment and the field-induced polarizability and hyperpolarizability on the degree of alignment are presented at different intensities. Our computational results show that the dynamic alignment of molecules is primarily determined by field-induced polarizability and the second hyperpolarizability for the laser intensity range from 5 × 1014 to 5 × 1016 W/cm2. The contributions of higher order correction terms to molecular alignment can usually be neglected. The polarizability-field interaction makes the angular distributions of a molecule have a maximum along the polarization axis and a minimum perpendicular to it. The role of the second hyperpolarizability keeps the molecular counts maximum along the laser polarization direction but minimum at an angle of 45° between the molecular axis and the polarization direction. There is also a second maximum of molecular counts perpendicular to the polarization axis. For CO, N2, and Br2 molecules, the dependences of laser-induced dynamic alignment on laser intensity exhibit completely different characteristics. 相似文献
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Renard V Renard M Guérin S Pashayan YT Lavorel B Faucher O Jauslin HR 《Physical review letters》2003,90(15):153601
We report a direct nonintrusive observation of alignment and planar delocalization of CO2 after an intense linearly polarized femtosecond laser pulse excitation. The effects are measured by a polarization technique involving a perturbative probe that itself does not induce appreciable alignment. We show that this technique allows one to measure a signal proportional to -1/3, with theta the angle between the molecular axis and the laser polarization. Simulations that support this analysis allow one to characterize the experimentally observed alignment and planar delocalization quantitatively. 相似文献
5.
Amplitude and rotation of the ellipticity of harmonicsfrom a linearly polarized laser field
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We simulate the dynamic response of H2+ in a linearly polarized laser field by numerically solving the time-dependent Schrödinger equation. The elliptically polarized high-order harmonics generated by H2+ irradiated by the linearly polarized laser field are systematically investigated. The result shows that the amplitude and rotation of the ellipticity of harmonics are affected by the alignment angle and internuclear distance of the molecule. Analyzing the change in forces acted on the ionized electrons and the trajectories of the electrons, the phenomena are found to be due to the change in the direction of the total Coulomb forces from the two nuclei felt by the recollided ionized electrons in the direction perpendicular to the laser polarization direction. Based on the influence law, we can select the harmonics with a specific frequency band under different alignment angles and then synthesize the isolated attosecond pulses with different rotations, which can be continuously converted from right-handed circular polarization, linear polarization, and left-handed circular polarization by changing the alignment angle. This study provides a new possible approach to the real-time detection of molecular states by using attosecond pulses and obtaining more optimized harmonics with molecular properties. 相似文献
6.
We present for the first time to the best of our knowledge a computerized characterization and alignment scheme of an erbium
all-fiber laser passively mode-locked by nonlinear polarization rotation. This scheme can replace the common trial and error
alignment procedure with manual polarization controllers and therefore greatly reduce the time to start up an ultrashort pulsed
fiber laser. Based on the mode-locking maps generated by automated characterization we also demonstrate reproducible selection
of pulses with different pulse durations and central wavelengths. These settings were stable over several days allowing us
to choose that pulsed operation mode that is more advantageous for a specific application. 相似文献
7.
A. P. Voitovich A. Ch. Izmailov O. E. Kostik V. V. Mashko 《Journal of Applied Spectroscopy》1999,66(1):48-54
A calculation of the selective losses of a spectrometer based on a broad-band laser with an anisotropic three-mirror ring
resonator containing a two-photon-absorbing atomic gas medium with a light-induced resonance anisotropy has been performed.
The conditions under which laser radiation power resonances appear in the output radiation spectrum and the contribution of
different factors to their formation have been revealed. Possible ways of obtaining information on the polarization effects
induced by a powerful light wave in a medium at the frequencies of two-quantum transitions were investigated.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 48–53, January–February, 1999. 相似文献
8.
High-order harmonic generation from coherently rotating N2 and O2 molecules has been observed for different alignment angles in a pump and probe experiment using femtosecond laser pulses. The results obtained are in excellent agreement with those calculated using a recently developed theory, which represent the characteristic properties predicted for angle-dependent harmonic generation. It is shown that polarization geometry and alignment distribution play essential roles in potential applications to probe electronic structure and dynamics of molecular systems. 相似文献
9.
We propose a fundamental interconnection method using a polarization alignment system for waveguides having different spatial
modes. In addition, as an example for the verification of the fundamental operation, we demonstrate an interconnection between
a photonic crystal fiber and a laser that have obviously different spatial modes. The polarization alignment system operates
synergistically with a self-written waveguide formed with a double phaseconjugate mirror. This technique enables us to interconnect
a photonic crystal fiber with a laser source without complicated and time-consuming optical alignment. In this method, although
it is not necessary to perform an external control for interconnection, the waveguide most suitable for connection is formed
autonomously in a Sn2P2S6:Sb crystal developed for this purpose. There was a marked reduction in the polarization dependence of coupling efficiency,
compared with that observed using a stand-alone double phase-conjugate mirror. 相似文献
10.
We investigate strategies for field-free three dimensional molecular axis alignment using strong nonresonant laser fields under experimentally realistic conditions. Using the polarizabilites and rotational constants of an asymmetric top rotor molecule (ethene, C2H4), we consider three different methods for axis alignment of a Boltzmann distribution of rotors at 4 K. Specifically, we compare the use of impulsive kick laser pulses having both linear and elliptical polarization to the use of elliptically polarized switched laser pulses. We show that an enhanced degree of field-free three dimensional alignment of ground vibronic state molecules obtains from the use of two orthogonally polarized, time-separated laser pulses. 相似文献
11.
A comparative study of the beats of circular polarization generated by anisotropic atomic collisions is carried out on the basis of theoretical calculations for the states J=1, 3/2, and 2 of neon atoms and ions excited by monochromatic laser radiation in xenon atmosphere. Contributions made by ordinary alignment and higher polarization moments (octupole orientation and dodecapole alignment) in the collisional generation of orientation and the signal of beatings of circular polarization are compared. 相似文献
12.
Levesque J Mairesse Y Dudovich N Pépin H Kieffer JC Corkum PB Villeneuve DM 《Physical review letters》2007,99(24):243001
High harmonic emission in isotropic gases is polarized in the same direction as the incident laser polarization. Laser-induced molecular alignment allows us to break the symmetry of the gas medium. By using aligned molecules in high harmonic generation experiments, we show that the polarization of the extreme ultraviolet emission depends strongly on the molecular alignment and the orbital structure. Polarization measurements give insight into the molecular orbital symmetry. Furthermore, molecular alignment will allow us to produce attosecond pulses with time-dependent polarization. 相似文献
13.
Hong-Zhao Zheng 《Optics Communications》2010,283(7):1394-1396
It is revealed that the phase-shift and polarization properties of laser beam reflected from a photonic crystal (PC) are sensitive to the surface-layer thickness of the PC. A continuous variation of λ/4 in surface-layer thickness produces a continuous change of π in the phase-shift. Besides, in the case of an asymmetric coupled-defect PC, various polarization patterns including linearly polarization in different directions, circular polarization, and different elliptical polarizations, will appear simultaneously within one laser beam. In this paper, a PC with modified surface-layer thickness is designed to induce incoherent laser irradiation with random phase at the focus point of the reflected field. This scheme will satisfy the increasing requirements for incoherent laser irradiation. 相似文献
14.
Magnetization curves of untreated and laser scribed GO FeSi steels were measured for 19 different frequencies from 0.05 to 500 Hz and for four polarizations from 1.4 to 1.7 T. From hysteresis loops, hysteresis losses were separated and frequency-dependent anomaly factors were calculated. Frequency-dependent anomaly factors for all measured polarizations can be very well described by an empirical equation. This behavior can be explained by the fact that an increase in polarization at a fixed magnetizing frequency corresponds to an increase of magnetizing frequency at a fixed polarization. Both an increase in frequency and an increase in polarization activate a higher number of domain walls in the magnetization process. The power losses can be described only by the frequency dependence of the anomaly factor and by the additional knowledge of hysteresis loss. 相似文献
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《Comptes Rendus de l''Academie des Sciences Series IV Physics》2000,1(5):639-645
The cw oscillation of a tunnel laser is demonstrated. The high losses encountered in tunneling systems are here compensated for by a high gain amplifying medium for barrier widths between 0 and λ/2. For a first particular angle of incidence, the TM frequency remains invariant when the total length of the laser is varied. For a higher value of the incidence angle, the frequency associated with the TE polarization increases while the frequency associated with the TM polarization undergoes a negative variation when the total length of the laser is reduced. 相似文献
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Direct observability of polarization moments of a higher order—octupole orientation of atomic angular momenta (κ=3) and their hexadecapole alignment (κ=4)—from polarization of quadrupole radiation is discussed. The case when atoms are excited through dipole absorption of light producing orientation or alignment of angular momenta with κ=1 or 2 and higher polarization moments are induced by collisions with a beam of particles is considered. It is shown that differences in the laws of transformation of polarization moments of various ranks κ in rotations of coordinate axes allow us to select the pure contribution of the higher polarization moment under study from the signal of polarization of quadrupole emission by excluding the contribution of orientation or alignment with κ=1 or 2. Optimum systems of coordinate axes for the observation of octupole orientation from circular polarization of light and for the observation of hexadecapole alignment from linear polarization of light, in which the pure contribution of the higher polarization moment under study to polarization of quadrupole emission reaches its maximum, are calculated. 相似文献
19.
Gavrielides A Erneux T Sukow DW Burner G McLachlan T Miller J Amonette J 《Optics letters》2006,31(13):2006-2008
The square-wave response of edge-emitting diode lasers subject to a delayed polarization-rotated optical feedback is studied in detail. Specifically, the polarization state of the feedback is rotated such that the natural laser mode is coupled into the orthogonal, unsupported mode. Square-wave self-modulated polarization intensities oscillating in antiphase are observed experimentally. We find numerically that these oscillations naturally appear for a broad range of values of parameters, provided that the feedback is sufficiently strong and the differential losses in the normally unsupported polarization mode are small. We then investigate the laser equations analytically and find that the square-wave oscillations are the result of a bifurcation phenomenon. 相似文献