共查询到20条相似文献,搜索用时 31 毫秒
1.
Alexandr A. Bogdashov Yury V. Rodin 《International Journal of Infrared and Millimeter Waves》2007,28(8):627-638
Particle Swarm Optimization (PSO) is an effective, simple and promising method intended for the fast search in multi-dimensional
space [Kennedy and Eberhart, "Particle Swarm Optimization", Proc. of the 1995 IEEE International Conference on Neural Networks, 1995]. Besides special testing problems a number of engineering tasks of electrodynamics were solved by the PSO successfully
[Robinson and Rahmat-Samii, "Particle Swarm Optimization in Electromagnetics", IEEE Trans. Antennas Propag., 2004; Jin and
Rahmat-Samii, "Parallel Particle Swarm Optimization and Finite-Difference Time-Domain (PSO/FDTD) Algorithm for Multband and
Wide-Band Patch Antenna Designs", IEEE Trans. Antennas Propag., 2005]. On the other hand, the scattering matrix technique
is a fast and accurate method of mode converter analysis. We illustrate PSO by a number of converter designs developed for
high-power microwaves control: a matching horn for output maser section, a corrugated converter of linear-polarized hybrid
modes, a TE01 mitre bend. 相似文献
2.
The measurement of the spectral width of ultrashort light pulses using a Fabry–Pérot interferometer (FPI) is investigated.
It is shown, numerically and experimentally, that the measured width critically depends on the pulse properties (such as pulse
shape, pulse duration, frequency chirp and wavelength) and on the properties of the FPI (such as the mirror spacing and the
mirror reflectivities). The obtained results are of particular importance if the spatial length of the short light pulses
is comparable or even shorter than the distance between the FPI mirrors. The derived guideline indicate that the actual spectral
width of the ultrashort light pulses is measured with good accuracy only if the finesse F≥40 and the round trip time of the
light pulses inside the Fabry–Pérot interferometer is approximately one to three times the pulse duration.
Received: 17 December 1999 / Revised version: 14 April 2000 / Published online: 5 July 2000 相似文献
3.
E. Granot S. Sternklar D. Schermann Y. Ben-Aderet M.H. Itzhaq 《Applied physics. B, Lasers and optics》2006,82(3):359-362
We use the spectral ballistic imaging technique to measure the impulse response of a Fabry–Pérot etalon with less than 0.2 ps
temporal resolution. The results show excellent agreement with the theoretical predictions and negligible noise. Comparison
to the Kramers–Kronig method along with its limitations is also presented.
PACS 42.65.Re; 07.60.Ly; 42.30.Kq 相似文献
4.
A very sensitive optomechanical sensor to detect femtometer-level displacements in the position of one of the cavity mirrors
in a Fabry–Pérot interferometer was constructed and characterized. We use a high-reflectivity coated, non-tilting out-of-plane
mode high-Q mechanical silicon oscillator as a rear mirror in the Fabry–Pérot interferometer. The benefit of our novel oscillator,
if compared to traditional torsional, flexural and many bulk acoustic mode oscillators, is that the action of weak forces
is observed to cause only pure linear translation of the moving mirror without any tilting or deformation of the mirror surface.
This non-tilting behavior allows, in principle, more precise optical mode stabilization, use of very short optical cavities
and studies of short-range interactions between parallel surfaces. The resonance frequency and Q value of the high-reflectivity
coated silicon oscillator are f0=27.5 kHz and Q=19000 at low pressure (p=0.1 mbar) and at room temperature. The finesse of the optical cavity is . The sensitivity of the displacement measurement is Δxmin=5 fm with a 1 Hz bandwidth. The prospects of reaching the standard quantum limit in an interferometric displacement measurement
using a macroscopic oscillator are discussed.
PACS 78.70.-g; 07.10.Cm; 07.60.Ly 相似文献
5.
2 ) nonlinear crystal is reported. The device uses a standing-wave dual-resonator scheme to enhance both near-infrared lasers.
For 7 mW of 778.2-nm and 275 mW of 842.5-nm input powers, 40 nW of 10.2-μm radiation is generated by a preliminary setup.
A μW-level range output power is expected after optimization of the device optical components. This compact tunable source
will allow Fabry–Pérot high-resolution Doppler-free spectroscopy of spherical molecules, such as OsO4 or SF6, in the 9–11 μm range as an alternative source to frequency-stabilized CO2 lasers.
Received: 17 March 1998 相似文献
6.
Si/SiO2 Fabry–Pérot microcavities with a silicon nanocrystal (Si-nc) active spacer have been realized using a novel process based
on a reactive magnetron sputtering of a pure silica target. Spectral, spatial and temporal behaviours of the quantum dots
confined inside the resonator are detailed. Compared with a reference sample, the spectral and spatial emission distributions
are significantly narrowed and the forward emission intensity is enhanced. Time resolved photoluminescence measurements also
revealed an increase of the spontaneous emission rate.
PACS 42.70.Qs; 78.55.-m; 78.66.-w 相似文献
7.
G. F. Iriarte 《Journal of nanoparticle research》2011,13(4):1737-1745
Artificial nanostructures (Samuelson et al., Physica E 21:560–567, 2004; Xia et al., Adv Mater 15:353–389, 2003) show promise for the organization of functional materials (Huck and Samuelson, Nanotechnology 14:NIL_5–NIL_8, 2003) to create nanoelectronic (Mizuta and Oda, Science 279:208–211, 2008) or nano-optical devices (Mazur et al.; Tanemura et al., Synthesis, Optical Properties and Functional Applications of ZnO
Nano-materials: A Review, 1–3:58–63, 2008). However, in most manufacturing recipes described so far, nanostructures are synthesized in solution and/or uncontrolled
deposition results in random arrangements; this makes it difficult to measure the properties of attached nanodevices or to
integrate them with conventionally fabricated microcircuitry. Here, we describe a fully CMOS compatible process technology
for mass manufacture of polysilicon nanowires by the CVD (chemical vapor deposition) method. The large scale production of
nanowires could successfully be synthesized on silicon (100) substrates. However, the method presented here can successfully
be employed with all technologically useful substrates with good adhesion for silicon such as SiO2, diamond-like carbon or III–V semiconductors. This opens up the possibility for the fabrication of strain-sensitive and defect-sensitive
optoelectronic devices on the optimum III–V substrate (Fonstad et al.). Finally, scanning electron microscopy (SEM) was used
to characterize the as-synthesized nanowires and energy-filtered transmission electron microscopy (EFTEM) and scanning transmission
electron microscopy (STEM) analysis were used to determine the nanowire composition. 相似文献
8.
F. Kalkum M. Peter G. Barbastathis K. Buse 《Applied physics. B, Lasers and optics》2010,100(1):169-172
Using plasmonic resonances of metal films, enhanced transmission of light through sub-wavelength holes has been demonstrated.
Here we show that external resonances can be employed as well: the transmission of 1.5-μm wavelength light through 600-nm
holes is enhanced by a factor of 20 using a Fabry–Pérot arrangement. The maximal enhancement factor is determined by the limited
reflectivity of metal surfaces. It seems promising to combine both effects—plasmonic resonances plus tailored photonic-crystal
structures on top of the metal film—in order to realize efficient sub-wavelength light sources as they are required for, e.g.,
advanced spectroscopy and lithography. 相似文献
9.
A low-finesse Fabry–Pérot interferometer is used to determine long and fast displacements. Two corner cube reflectors form
the traveling-wave cavity and one beam splitter couples the input collimated laser beam. Given the retro-directive property
of corner cube reflectors, the cavity operates at the edge of stability over an extended scanning range. The in-line scheme
with a single fixed optical component makes the proposed interferometer robust and easy to align and use. These characteristics
are particularly useful in applications running in noisy environments, such as in on-field absolute gravimetry. Experimental
data showing the performances reached in a transportable ballistic gravimeter are also presented. 相似文献
10.
We investigated the 13CD3I isotopomer of methyl iodide as a source of TeraHertz laser radiation using the optical pumping technique. We used a pulsed
waveguide CO2 laser as the pump laser and an open Fabry–Pérot cavity for new laser line generation. We discovered 18 new laser lines with
wavelengths ranging from 308.4 to 1132.7 μm, plus two lines previously assigned to 12CD3I. All of the lines were characterized in wavelength, pump frequency offset, optimum pressure of operation, and relative polarization
and intensity. 相似文献
11.
Two pulsed Fabry–Pérot quantum cascade lasers (QCL) have been employed for the simultaneous measurement of two analytes in
aqueous solutions. Two laser beams (1393 and 1080 cm-1) were combined by an optical system of parabolic mirrors and a ZnSe-beam splitter. Measurements were made in transmission
using a 41 μm CaF2-flow cell and a mercury-cadmium-telluride (MCT) detector. Using glucose and sodium acetate as model analytes, the measurements
show the potential of dual QCL absorption spectroscopy for analyte specific detection and background compensation. The use
of the two lasers gives quantitative information about the analytes, even when they show overlapping absorption bands typically
found in condensed phase.
PACS 42.55.Px; 42.62.Fi 相似文献
12.
J.L. Zhou L. Xia X.P. Cheng X.P. Dong P. Shum 《Applied physics. B, Lasers and optics》2008,91(1):99-103
A novel method of generating tunable microwave signals in the photonic domain is proposed. Eighteen pairs of stable dual-wavelength
single longitudinal mode lasings are achieved by incorporating a fiber Bragg grating based Fabry–Pérot filter and a tunable
fiber grating into a fiber ring cavity. The frequency of the generated microwave signal obtained by beating the dual-wavelength
laser with a photodetector can be tuned simply through configuring the working wavelength of the laser. A series of microwave
frequencies of 9.4885, 9.572, 9.7111, 9.8498, 9.9598 and 10.0712 GHz are generated experimentally. The proposed method is
useful in applications such as wireless access networks, sensor networks, radio-over-fiber systems and software-defined radio.
PACS 41.20.-q; 42.55.Wd; 41.81.-i 相似文献
13.
Quantum computational logics have recently stirred increasing attention (Cattaneo et al. in Math. Slovaca 54:87–108, 2004; Ledda et al. in Stud. Log. 82(2):245–270, 2006; Giuntini et al. in Stud. Log. 87(1):99–128, 2007). In this paper we outline their motivations and report on the state of the art of the approach to the logic of quantum computation
that has been recently taken up and developed by our research group. 相似文献
14.
The measurement of relative intensities in CO2 combination bands spectrum is performed using wavelength modulation spectroscopy (WMS) and a DFB (distributed feedback) diode
laser operating at 1.6 μm. The diode laser is stabilized with an external Fabry–Pérot interferometer and absorption spectroscopy
is performed in a multipass gas cell. A spectrum containing spectral lines of both 13CO2 and 12CO2 isotopic species is recorded. The variation of laser power during frequency scanning and the line shape are taken into account
to accurately extract line intensities from experimental data. The isotopic concentration ratio is deduced from the intensity
ratio. Both ratios are measured with an accuracy of about 0.5% in pure CO2.
Received: 9 June 2000 / Published online: 8 November 2000 相似文献
15.
2 and two diode lasers as pump sources are presented. A single-mode Fabry–Pérot-type tunable diode laser (TDL) and an external-cavity
diode laser (ECL) were combined to generate radiation in the mid-infrared region near 7.2 μm. With a TDL at a wavelength of
approximately 1290 nm and an ECL emitting between 1504 and 1589 nm it was possible to carry out spectroscopic experiments
concerning SO2 at five different phasematching points between 1350 and 1400 cm-1 by fixing the wavelength of one pump laser and tuning the wavelength of the other. With an input power of 8 mW for the single-mode
Fabry–Pérot-type diode laser and 6 mW for the external-cavity laser an output power of about 10 nW was generated. Using the
tuning capabilities of the external-cavity laser a spectral region up to 5 cm-1 could be covered within one scan. Measurements of SO2 absorption lines at low pressure demonstrate the high-resolution features of the spectrometer. Moreover, these data provide
new direct experimental phasematching data for the rarely investigated spectral region at 7.2 μm.
Received: 27 October 1997/Revised version: 8 May 1998 相似文献
16.
Tom M. Evans Elham Doroodchi Behdad Moghtaderi 《Journal of nanoparticle research》2011,13(9):4395-4396
This brief communication provides a response to Murshed et al. (J Nanopart Res 12:2007–2010, 2010). We acknowledge that three of the equations in our original article (Doroodchi et al. J Nanopart Res 11:1501–1507, 2009) contained minor typographical errors. However, we confirm that these misprinted equations have no bearing on the results
presented within that article. In addition, we would like to clarify that we do not challenge the methodology of Leong et
al. (J Nanopart Res 8:245–254, 2006). Instead, we repeated their analysis using a more general form for the temperature field with continuity imposed across
the particle–nanolayer–liquid interfaces and found that the solution reduces to the Renovated-Maxwell model. 相似文献
17.
O. Frazão J.M. Marques J.L. Santos M.B. Marques J.M. Baptista 《Applied physics. B, Lasers and optics》2007,86(3):555-558
In this work, a Brillouin fibre laser sensor for strain and temperature discrimination is presented. The fibre laser sensor
consists of a Fabry–Pérot cavity with 20 m of optical fibre between two Bragg gratings. For the strain measurement, the 20 m
were split in half and in 10 m a pre-tension was applied originating two Brillouin peaks. For the temperature measurement
all of the sensing head was heated. The resolutions achieved were ±1 με and ±1 °C for strain and temperature measurements,
respectively.
PACS 42.81.-I; 42.55.Wd; 42.65.Es 相似文献
18.
We analyze the large-time behavior of various kinetic models for the redistribution of wealth in simple market economies introduced
in the pertinent literature in recent years. As specific examples, we study models with fixed saving propensity introduced
by Chakraborti and Chakrabarti (Eur. Phys. J. B 17:167–170, 2000), as well as models involving both exchange between agents and speculative trading as considered by Cordier et al. (J. Stat.
Phys. 120:253–277, 2005) We derive a sufficient criterion under which a unique non-trivial stationary state exists, and provide criteria under which
these steady states do or do not possess a Pareto tail. In particular, we prove the absence of Pareto tails in pointwise conservative
models, like the one in (Eur. Phys. J. B 17:167–170, 2000), while models with speculative trades introduced in (J. Stat. Phys. 120:253–277, 2005) develop fat tails if the market is “risky enough”. The results are derived by a Fourier-based technique first developed
for the Maxwell-Boltzmann equation (Gabetta et al. in J. Stat. Phys. 81:901–934, 1995; Bisi et al. in J. Stat. Phys. 118(1–2):301–331, 2005; Pareschi and Toscani in J. Stat. Phys. 124(2–4):747–779, 2006) and from a recursive relation which allows to calculate arbitrary moments of the stationary state. 相似文献
19.
Y.H. Wang Y.C. Qu W.J. Zhao D.M. Ren X.Y. Hu 《Applied physics. B, Lasers and optics》2008,92(2):237-241
We present a single longitudinal mode (SLM) TEA CO2 laser oscillation by using a three-mirror resonator with a Fabry–Pérot etalon. The etalon was inserted in the optical path
taken out from the main resonator of the CO2 laser for protecting the etalon from damage on the surface. A modified numerical model of the three- mirror resonator was
investigated for design the laser. SLM pulse from the TEA CO2 laser was achieved, and the experimentally measure values were found to have good agreement with the numerical model. The
maximum pulse energy of reliable SLM emission is obtained in excess of 200 mJ at 9.57 μm. The reliability of producing SLM
pulses was higher than 90%, and there was no damage on the etalon
PACS 42.55.Lt; 42.60.Fc 相似文献
20.
D. Barat J. Angellier A. Vicet Y. Rouillard L. Le Gratiet S. Guilet A. Martinez A. Ramdane 《Applied physics. B, Lasers and optics》2008,90(2):201-204
We report on Fabry–Pérot semiconductor lasers and single frequency distributed feedback lasers based on GaInAsSb/AlGaAsSb
quantum wells. The laser structures were grown by molecular beam epitaxy on GaSb substrates. The devices were etched either
by wet process or by inductively coupled plasma (ICP) process. Electron-beam lithography was used to deposit a metal Bragg
grating on each side of the laser ridge to fabricate the DFB lasers. The devices all operate in the continuous wave regime
at room temperature with a single frequency emission above 2.6 μm and good tuning properties, making them well adapted to
tunable diode laser absorption spectroscopy.
PACS 42.55.Px; 42.62.Fi 相似文献