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1.
On the output characteristics of a semiconductor optical amplifier driven by an ultrafast optical time division multiplexing pulse train 总被引:1,自引:0,他引:1
A comprehensive theoretical analysis of a semiconductor optical amplifier (SOA) that is subject to an ultrafast optical time division multiplexing pulse stream is presented with the help of a simple but efficient model developed for this purpose. The model combines the necessary set of mathematical equations with the appropriate simplifying assumptions to describe in the time domain gain saturation and recovery for the case of multiple incoming pulses. In this manner, analytical expressions can be obtained for the power and chirp profile of the amplified pulses, essentially extending the work that has been performed for a single pulse only. This allows to identify the critical operational parameters and to investigate and evaluate their effect on these two output characteristics. The derived simulation curves are thoroughly studied to specify the limitations imposed on the SOA small signal gain and carrier lifetime as well as on the full-width at half-maximum (FWHM) and energy of the input pulses and, based on a series of logical arguments, to extract useful rules concerning their selection so as to achieve improved performance with respect to the practical applications of all-optical switching and pulse compression. The obtained results indicate that due to the continuous insertion of pulses, the requirements for the SOA small signal gain and the input pulse energy are stringent than those for the case of isolated pulse amplification. The combination of these two parameters determines also the regime in which the amplifier must be biased to operate in order to ensure distortionless pulse amplification and enhanced chirp for efficient pulse compression and it has been found that low saturation is necessary for the former case whilst heavy saturation for the latter. The scopes of the corresponding requirements for the carrier lifetime and the FWHM are also tight but to a less extent and can be simply satisfied with the available photonics technology. These results are in good agreement with the available experimental data essentially proving the validity and robustness of the model. The model can be thus applied to predict the behavior of more complex all-optical circuits of enhanced functionality in which the SOA is the basic functional device. 相似文献
2.
We consider a recently developed method to analyze the angular structure of pulsed acoustic fields in an underwater sound channel. The method is based on the Husimi transform that allows us to approximately link a wave field with the corresponding ray arrivals. The advantage of the method lies in the possibility of its practical realization by a vertical hydrophone array crossing only a small part of the oceanic depth. The main aim of the present work is to find the optimal parameter values of the array that ensure good angular accuracy and sufficient reliability of the algorithm to calculate the arrival angles. Broadband pulses with central frequencies of 80 and 240 Hz are considered. It is shown that an array with a length of several hundred meters allows measuring the angular spectrum with an accuracy of up to 1 degree. The angular resolution is lowered with an increase of the sound wavelength due to the fundamental limitations imposed by the uncertainty relation. 相似文献
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We show analytically and numerically that a practically realizable first-order optical Hilbert transformer (OHT) can simultaneously function as a negative/positive first-order temporal optical differentiator (OD) in the stopband and a broadband ±90° phase shifter in the passbands. An integrated-optic OHT based on a four-tap finite impulse response filter is designed using the Remez iteration algorithm and is numerically verified. 相似文献
4.
A single atom in free space can have a strong influence on a light beam and a single photon can have a strong effect on a
single atom in free space. Regarding this interaction, two conceptually different questions can be asked: can a single atom
fully absorb a single photon and can a single atom fully reflect a light beam. The conditions for achieving the full effect
in either case are different. Here we discuss related questions in the context of an optical resonator. When shaping a laser
pulse properly it will be fully absorbed by an optical resonator, i.e., no light will be reflected and all the pulse energy
will accumulate inside the resonator before it starts leaking out. We show in detail that in this case the temporal pulse
shape has to match the time-reversed pulse obtained by the cavity’s free decay. On the other hand a resonator, made of highly
reflecting mirrors which normally reflect a large portion of any incident light, may fully transmit the light, as long as
the light is narrow band and resonant with the cavity. The analogy is the single atom—normally letting most of the light pass—which
under special conditions may fully reflect the incident light beam. Using this analogy we are able to study the effects of
practical experimental limitations in the atom-photon coupling, such as finite pulses, bandwidths, and solid angle coverage,
and to use the optical resonator as a test bed for the implementation of the quantum experiment. 相似文献
5.
A.C. Selden 《Optics Communications》1973,7(1):55-56
Intensity structure in the spectrum of a noisy pulse is derived for the case of stationary phase. It is the frequency analogue of temporal intensity fluctuations present in incoherent light. Its relevance for laser mode-locking is briefly considered. 相似文献
6.
H. G. Schuster 《Zeitschrift für Physik B Condensed Matter》1978,31(1):99-104
The critical behaviour of noninteracting electrons in a disordered solid is investigated near the mobility edge. A two component “spin glass” order parameter which—in contrast to previous work—is gauge invariant, is introduced and it is shown by renormalization group arguments that the system can be mapped to anXY model. Using recent results on the jump in the spin wave stiffness of a two dimensionalXY model an universal exact minimum conductivity value \(\sigma _M = \frac{{e^2 }}{\hbar }\frac{1}{{\pi ^2 }}\) is found which agrees well with numerical predictions. An extrapolation of the proportionality between conductivity and spin wave stiffness to other spatial dimensions yields Wegner's power law, with an exponent related to theXY model. 相似文献
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The problem of terahertz radiation generation in a quadratic nonlinear medium by a nanosecond phase-modulated optical pulse possessing the properties of supercontinuum has been investigated. The possibility of generating both broadband and quasi-monochromatic terahertz signals has been demonstrated. The conditions have been revealed under which the generation efficiency of a phase-modulated nanosecond optical pulse is greater than that of a spectrally confined femtosecond signal. 相似文献
9.
A scheme for the construction of fiber laser systems for the generation of tunable ultrashort optical pulses is proposed.
The scheme is based on the self-Raman shift of the soliton frequency in dispersion-decreasing fibers with the subsequent spectral
broadening owing to the supercontinuum generation in a short highly nonlinear fiber and the compression in the corresponding
fiber compressor. An all-fiber laser system for the generation of ultrashort laser pulses in the wavelength range 1.6–2.0
μm is experimentally demonstrated. In particular, the shortest pulses with a duration of 24 fs are generated at wavelengths
of 1.8–1.9 μm, which corresponds to less than four optical cycles. 相似文献
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A high energy long pulse and low peak power at 365 nm ultra-violet laser is described. The laser at this wavelength is produced by the second harmonic generation of a flash-lamp pumped solid state Alexandrite laser. At optimum temperature, coherent 365 nm light of 186 mJ/pulse with 220 μs width is obtained without Q-switching. 相似文献
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Propagation of a frequency-modulated Gaussian pulse along an optical fiber with a gradient refractive index is studied. It is shown that, after propagating a certain distance, the pulse undergoes compression. If, at the point of maximum compression, the pulse intensity is exactly equal to the threshold intensity, then either a bright or dark vortex soliton can form. 相似文献
15.
Sørensen OW 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2005,174(2):335-337
Examples are shown of how the derivative of the response of an NMR pulse sequence with respect to a variable in that pulse sequence can be obtained by another pulse sequence. This approach holds the potential of being a tool for discovery of new pulse sequences or a means of understanding how some pulse sequences are related to each other. 相似文献
16.
We propose a new cesium (Cs) atomic clock whose microwave source is a 9.1926-GHz harmonically and regeneratively mode-locked erbium fiber laser rather than a quartz oscillator and a multiplexer. The repetition rate of the laser is directly locked to the Cs resonance, and the frequency stability evaluated by the Allan variance is 7.1 x 10(-12) for tau = 1 s. This new atomic clock provides not only a precise 1-s time standard after demultiplexing but also an optical pulse train with the same stability, which means that the ultrastable clock signal can be delivered throughout the world by means of optical fiber networks. 相似文献
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Alexandru Popescu 《Optics Communications》2006,264(2):475-481
We present our recent progress towards a practical implementation of a remote sensing measurement technique of oceanic temperature profiles. Our approach combines the advantages of fiber amplifiers with the high spectral resolution of Faraday anomalous dispersion optical filters. In this paper, we focus on the edge filter characteristics of an excited state Faraday anomalous dispersion optical filter at moderate pump powers as the receiver unit for the Brillouin-lidar. 相似文献
20.
V. I. Esipenko 《Radiophysics and Quantum Electronics》1999,42(3):257-268
We propose and analyze a method of direct statistical analysis for linear first-order systems with deterministic parameters.
We derive the one- and multi-dimensional (with arbitrary dimension n) probability density of a stochastic process at the output
of a linear system.
Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika,
Vol. 42, No. 3, pp. 287–300, March 1999. 相似文献