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151.
We present a new algorithm for the evaluation of the quasi-periodic Green function for a linear array of acoustic point sources such as those arising in the analysis of line array loudspeakers. A variety of classical algorithms (based on spatial and spectral representations, Ewald transformation, etc.) have been implemented in the past to evaluate these acoustic fields. However as we show, these methods become unstable and/or impractically expensive as the frequency of use of the sources increases. Here we introduce a new numerical scheme that overcomes some of these limitations allowing for simulations at unprecedentedly large frequencies. The method is based on a new integral representation derived from the classic spatial form, and on suitable further manipulations of the relevant integrands to render the integrals amenable to efficient and accurate approximations through standard quadrature formulas. We include a variety of numerical results that demonstrate that our algorithm compares favorably with several classical methods both for points close to the line where the poles are located and at high-frequencies while remaining competitive with them in every other instance. 相似文献
152.
H. Ahmad A.A. Latif S.F. Norizan M.Z. Zulkifli S.W. Harun 《Optics & Laser Technology》2011,43(3):550-554
A dual-wavelength ytterbium doped fiber laser with a narrowest spacing of 0.53 nm and widest spacing of 12.2 nm at 1064 nm is presented in this paper. An arrayed waveguide grating (AWG) together with an optical channel selector (OCS) have also been incorporated in the proposed setup that works as a switchable mechanism giving 23 different wavelength tunings. Producing an average output power of ?8 dB m and side mode suppression ratio (SMSR) of 59.65 dB, this dual-wavelength fiber laser is quite stable with an output power variance as low as 0.47 dB giving it an advantage due to its switching ability and stable dual-wavelength output powers. 相似文献
153.
In this paper, a novel configuration of a wavelength converter is set forth by utilizing a semiconductor optical amplifier (SOA) as a nonlinear gain medium to generate a four-wave mixing (FWM) effect by using a dual wavelength bi-erbium-doped fiber laser that uses an Arrayed Waveguide Grating (AWG) together with two optical channel selector (OSC) as selective elements to function as a dual wavelength switchable pump power. The four-wave mixing (FWM) is produced with a wavelength detuning of 7 nm from the pump and signal which used is as the converted signal at wavelength 1532.8 nm or 1534.5 nm for transferring data from the input signal at wavelength 1547.0 nm. Thus, even though the conversion efficiency is as low as −43 dB, it is still possible for applications as a wavelength converter. 相似文献
154.
A new highly selective, reversible, chromogenic, and fluorogenic chemosensor (4) based on thiazole-coumarin moieties for quantification of copper ions in aqueous-DMSO was designed and synthesized. The mechanism of fluorescence was based on ICT, which was modified by the introduction of an electron-donating diethylamino group making it chromogenic and increasing the binding affinity. The selectivity toward copper ions was not affected by the presence of representative alkali metals, alkali earth metals, or other transition metals. 相似文献
155.
We demonstrate a multi-wavelength erbium-doped fiber laser (EDFL) using erbium gain and four-wave mixing (FWM) effect in a piece of erbium-doped fiber (EDF) with high erbium ion concentration. The EDF has a pump absorption rate of 24.6 dB/m at 979 nm and is bi-directionally pumped by 980-nm laser diodes. FWM effect redistributes the energy of different oscillating lines and causes multi-wavelength operation. The laser generates more than 22 lines of optical comb with a line spacing of approximately 0.10 nm at the 1569-nm region using only 1.5-m-long EDF. 相似文献
156.
A first time O band Brillouin fiber laser is demonstrated and compared with the C band Brillouin fiber laser. By utilizing
a 20 km True wave fiber (TWF), the experiment demonstrated four Brillouin lines generated from the simple set-up of Brillouin
fiber laser. We compared the threshold between the Brillouin pump wavelength at 1310 nm which represent O band region and
1550 nm for C band region. It shows that the Brillouin threshold at O band region is smaller that C band. The channels spacing
between these two bands are also different, where O band have 12.72 GHz spacing while 1550 nm have 10.25 GHz spacing. 相似文献
157.
An efficient 21 cm Bismuth-based erbium doped fiber amplifier (Bi-EDFA) operating in both C- and L-band wavelength regions
is proposed and demonstrated. The proposed Bi-EDFA uses the gain medium with an erbium ion concentration of 6300 ppm in conjunction
with a double-pass configuration. Compared to conventional silica-based erbium-doped fiber amplifiers (Si-EDFAs) with the
same amount of Erbium ions, the Bi-EDFA provides a higher attainable gain as well as a greater amplification bandwidth ranging
from 1525 to 1620 nm. The proposed Bi-EDFA achieved a flat-gain of around 23 dB with gain variation of ±3.5 dB within the
wavelength region from 1530 to 1565 nm at the maximum pump power of 150 mW. The corresponding noise figures are obtained at
an average of 6 dB. 相似文献
158.
The m-machine no-wait flowshop scheduling problem with the objective of minimizing total completion time subject to the constraint that the makespan value is not greater than a certain value is addressed in this paper. Setup times are considered non-zero values, and thus, setup times are treated as separate from processing times. Several recent algorithms, an insertion algorithm, two genetic algorithms, three simulated annealing algorithms, two cloud theory-based simulated annealing algorithms, and a differential evolution algorithm are adapted and proposed for the problem. An extensive computational analysis has been conducted for the evaluation of the proposed algorithms. The computational analysis indicates that one of the nine proposed algorithms, one of the simulated annealing algorithms (ISA-2), performs much better than the others under the same computational time. Moreover, the analysis indicates that the algorithm ISA-2 performs significantly better than the earlier existing best algorithm. Specifically, the best performing algorithm, ISA-2, proposed in this paper reduces the error of the existing best algorithm in the literature by at least 90% under the same computational time. All the results have been statistically tested. 相似文献
159.
Dark pulse emission in nonlinear polarization rotation-based multiwavelength mode-locked erbium-doped fiber laser 总被引:1,自引:1,他引:0
We experimentally show dark pulse generation in all-normal dispersion multiwavelength erbium-doped fiber laser(EDFL) with a long cavity of figure-of-eight configuration. The EDFL generates a stable multiwavelength laser with 0.47 nm spacing at 24 m W threshold pump power, while the number of lines obtained increases with the pump power. A dark pulse emission is observed as the pump power is increased above 137 m W, with fundamental repetition rate of 29 k Hz and pulse width of 2.7 μs. It is observed that the dark pulse train can be shifted to second-, third-, and fourth-order harmonic dark pulses by carefully adjusting the polarization controller. For the fundamental dark pulse, the maximum pulse energy of 32.4 n J is obtained at pump power of 146.0 mW. 相似文献
160.
S.M.Azooz F.Ahmad H.Ahmad S.W.Harun B.A.Hamida S.Khan A.Halder M.C.Paul M.Pal S.K.Bhadra 《中国光学快报(英文版)》2015,(3):14-17
We propose and demonstrate a passively mode-locked fiber laser operating at 1951.8 nm using a commercial thulium-doped fiber(TDF) laser, a homemade double-clad thulium–ytterbium co-doped fiber(TYDF)as the gain media, and a multi-walled carbon nanotube(MWCNT) based saturable absorber(SA). We prepare the MWCNT composite by mixing a homogeneous solution of MWCNTs with a diluted polyvinyl alcohol(PVA) polymer solution and then drying it at room temperature to form a film. The film is placed between two fiber connectors as a SA before it is integrated into a laser ring cavity. The cavity consists of a 2 m long TDF pumped by a 800 nm laser diode and a 15 m long homemade TYDF pumped by a 905 nm multimode laser diode. A stable mode-locking pulse with a repetition rate of 34.6 MHz and a pulse width of 10.79 ps is obtained when the 905 nm multimode pump power reaches 1.8–2.2 W, while the single-mode 800 nm pump power is fixed at 141.5 m W at all times. To the best of our knowledge, this is the first reported mode-locked fiber laser using a MWCNT-based SA. 相似文献