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41.
用于投影显示的分色合色膜系的消偏振设计 总被引:3,自引:3,他引:0
由于斜入射时,光学薄膜存在一定的偏振效应,将产生S-和P-偏振光的光谱分离.在Philips棱镜系统中,分色合色膜系通常分色时对S-光应用,合色时则对P-光应用.从提高光能利用率、减少杂散光和增加系统对比度等因素综合考虑,要求分色合色膜系的S-和P-偏振光的分离尽可能小.新设计方法采用宽带法布里-珀罗薄膜干涉滤光片中心波长两侧的干涉带作为长波通或短波通截止滤光片,可实现S-和P-偏振分量的分离几乎为零. 相似文献
42.
C. Mavroyannis 《Applied physics. B, Lasers and optics》2003,76(1):75-81
Analytical expressions of the spectral functions have been derived for a number of induced excitations that occur near the
difference-frequency generation in a four-level atomic system interacting with three laser fields. The spectral heights and
subnatural line widths of the induced peaks depend on the intensities of the laser fields involved. The maximum heights of
the induced peaks take positive, zero and negative values, indicating that the processes of absorption (attenuation), dark
resonance and stimulated emission (amplification) are likely to occur near the difference-frequency generation, respectively.
Received: 15 March 2002 / Revised version: 17 June 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +1-613-954-5242 相似文献
43.
The backscattered fluorescence of nitrogen from filaments generated by intense ultra-fast Ti:sapphire laser pulses propagating
in air is studied. The backscattered fluorescence from N2 molecules and ions show an exponential increase with increasing filament length, indicating amplified spontaneous emission.
Received: 11 October 2002 / Revised version: 3 December 2002 / Published online: 26 February 2003
RID="*"
ID="*"Corresponding author. Fax: +1-418/6562-623, E-mail: qluo@phy.ulaval.ca 相似文献
44.
Fabrication of planar gratings by direct ablation using an ultrashort pulse laser in a common optical path configuration 总被引:4,自引:0,他引:4
K. Venkatakrishnan N.R. Sivakumar B. Tan 《Applied Physics A: Materials Science & Processing》2003,76(2):143-146
Planar gratings have wide applications and to date, many methods for the fabrication of gratings have been reported. Ultrashort
pulse lasers have been used for the machining of gratings primarily because they allow direct ablation and the manufacturing
of sub-wavelength structures. In this paper, we present a novel direct ablation technique for the fabrication of planar gratings
which makes use of the interference of ultrashort pulses in a common optical path configuration. This technique of grating
fabrication not only simplifies the optical setup, but also immunizes the system to extraneous and inherent vibrations, thus
enabling the manufacturing of planar gratings of good edge acuity. We have successfully fabricated planar gratings on a copper
substrate.
Received: 6 November 2001 / Accepted: 4 March 2002 / Published online: 10 September 2002
RID="*"
ID="*"Corresponding author. Fax: +65/77-904-674, E-mail: mvenkata@ntu.edu.sg 相似文献
45.
T.?KunertEmail author R.?Schmidt 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,25(1):15-24
In Rydberg atoms subject to static and harmonic collinear electric fields, intrashell transition can be induced by the first
order perturbation from a small perpendicular electric or magnetic field, or by effects of the second order in the major fields.
Both mechanisms lead to resonances that are suppressed under certain conditions, and high-frequency interference oscillations
in case of non-adiabatic field switching. Recent measurements of microwave ionization signals show very rich and fascinating
structures similar to the ones predicted for intrashell mixing. We show that the observed ionization structures may be explained
by diabatic electric-field ionization and the consistent use of perturbation theory for intrashell mixing. In particular,
the dominant oscillation frequency is successfully interpreted in terms of interference between first and second order transition
amplitudes. New predictions are provided. The present approach gives a comprehensive picture of intrashell transitions, which
may be tested in future experiments designed to observe such transitions directly.
Received 2 May 2002 / Received in final form 23 September 2002 Published online 21 January 2003
RID="a"
ID="a"e-mail: Valentin.Ostrovsky@pobox.spbu.ru
RID="b"
ID="b"e-mail: horsdal@ifa.au.dk 相似文献
46.
R. Unanyan S. Guérin B. W. Shore K. Bergmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(3):443-449
In traditional schemes of multilevel multilaser excitation, each laser pulse interacts with only one pair of states, and the
rotating wave approximation (RWA) is applicable. Here we study the population transfer process in a three-state system when
each of the two lasers interacts with each of the pair of states and when the Rabi frequencies characterizing the interaction
strengths of the system are comparable to or larger than the difference of the transition frequencies. We show that complete
and robust population transfer is possible under conditions more general than those hitherto considered necessary for stimulated
Raman adiabatic passage (STIRAP) or for successive π pulses. Using adiabatic Floquet theory we show that successful population transfer can be interpreted as adiabatic passage
by means of a transfer state which connects the initial and final states. The Floquet picture offers a convenient interpretation
of the population transfer as accompanied by multiple absorption of photons from or emission into the laser fields. 相似文献
47.
Edward R. Floyd 《Foundations of Physics》2007,37(9):1403-1420
The double slit problem is idealized by simplifying each slit by a point source. A composite reduced action for the two correlated
point sources is developed. Contours of the reduced action, trajectories and loci of transit times are developed in the region
near the two point sources. The trajectory through any point in Euclidean 3-space also passes simultaneously through both
point sources. 相似文献
48.
Margarita A. Deneva Pepa I. Uzunova Marin N. Nenchev 《Optical and Quantum Electronics》2007,39(3):193-212
We report (theory, experimental check) an improved approach for generation of a tunable, subnanosecond pulse (0.1–0.4 ns),
based on a single pulsation (“spike”) separation from the transient oscillations in a dye laser with active mirror (AMIR).
A pumping by 20–50 ns pulses from Q-switched Nd:YAG laser is considered. The separation is in original, two-spectral selective
channels cavity, where the forced by AMIR quenched generation at one of the wavelength stops initially started spiking generation
at the other wavelength after the first spike development. The AMIR quickly starts the quenching generation at a precisely
controlled moment and with necessary intensity thus assuring the desired separation. An advantage is a high reproducibility
of the separation for high (~250%) pump power fluctuations combined with tuning in large range (~20 nm). To obtain such an
operation we form ~1 ns leading front pump pulse by electrooptical temporal cutting of the input pump pulse and use an optical
delay line. This increases also a few times the power in the separated spike (to be ~100 kW). Our approach widens the combinations
of lasers for effective applications of spike separation technique (dye lasers excited by Q-switched solid-state or Cu-vapor
lasers). 相似文献
49.
T. Ferrus R. George C.H.W. Barnes N. Lumpkin D.J. Paul M. Pepper 《Physica B: Condensed Matter》2007,400(1-2):218-223
Sodium impurities are diffused electrically to the oxide-semiconductor interface of a silicon MOSFET to create an impurity band. At low temperature and at low electron density, the band is split into an upper and a lower sections under the influence of Coulomb interactions. We used magnetoconductivity measurements to provide evidence for the existence of Hubbard bands and determine the nature of the states in each band. 相似文献
50.
K. Jin Z. C. Wang Q. Zhang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):325-332
We study the absorption spectra of a degenerate V-type
atom, where a resonant driving field and a probe field drive
different branches of transitions and a dc field is applied to
drive the transition between two excited states. The effects of
vacuum induced coherence (VIC) on the absorption spectra are
investigated. It is demonstrated that in some special cases the
VIC can lead to the depression of absorption and narrow resonance.
The origin of these features are discussed. When the pump field
and the dc field have the same intensity, it is interesting to
find that the whole absorption spectrum comes mainly from the
absorptions induced by the interferences among different
transitions between dressed states. 相似文献