共查询到20条相似文献,搜索用时 531 毫秒
1.
Kyeong-Sik Min Young-Hee Kim Daejeong Kim Dong Myeong Kim Seong-Ik Cho Jin-Hong Ahn Jin-Yong Chung 《Current Applied Physics》2003,3(6):507-510
A new CMOS negative charge pump scheme is proposed in this paper. This new pump scheme can generate output current which is 80% larger than the conventional pump with the sacrificial 10% area penalty. This new pump is regarded to be suitable to sub-1-V-VCC DRAMs with the negative-word-line (NWL) scheme, where the dynamic current consumption is expected to be very large. 相似文献
2.
This paper presents an idea of using residual pump power for implementation of low-noise and high-gain L-band erbium-doped fiber amplifiers (EDFAs). A single pump laser is employed to pump the first-stage EDFA, which serves as a low-noise preamplifier, in the proposed three-stage EDFA system. The residual pump power unabsorbed by the preamplifier is directed to pump the subsequent EDF. Experimental results show that gain enhancement of up to 8 dB with respect to conventional EDFAs can be achieved by using the proposed low-noise EDFA. 相似文献
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4.
We investigate the effect of pump area on lasing modes in an active random medium. Considering the structure characteristics in a real experimental system, the random medium is divided into two regions, i.e. pump and non-pump areas. The dependence of lasing modes on the pump area is qualitatively explained by means of the model in which the lasing is ascribed to the interaction of the complex localized modes in the active random medium with local aperiodic quasi-structure with appropriate pump light. There exist different pump sizes for lasing with different modes. As the pump size decreases in this random system, the pump threshold of the lasing modes increases. There are different lasing modes in different excitation regions in this random system. This gives us some information about the dependence of lasing modes on pump areas in active random media. 相似文献
5.
This paper presents an investigation of self-focusing of elliptical laser beam in collisionless plasma and its effect on stimulated Brillouin scattering. The pump beam interacts with a pre-excited ion-acoustic wave leading to Brillouin back-scattered process. The transverse intensity gradient of a pump beam generates a ponderomotive force, which modifies the background plasma density profile in a direction transverse to pump beam axis. This modification in density effects the incident laser beam, ion-acoustic wave and back-scattered beam. Non-linear differential equations for the beam width parameters of pump laser beam, ion-acoustic wave and back-scattered beam are set up and solved numerically. It is observed from the analysis that the focusing of waves enhances the SBS back-reflectivity. 相似文献
6.
A homogeneously broadened unidirectional ring laser can emit in several longitudinal modes for large enough pump and cavity length because of Rabi splitting induced gain. This is the so called Risken-Nummedal-Graham-Haken (RNGH) instability. We investigate numerically the properties of the multi-mode solution. We show that this solution can coexist with the single-mode one, and its stability domain can extend to pump values smaller than the critical pump of the RNGH instability. Moreover, we show that the multi-mode solution for large pump values is affected by two different instabilities: a pitchfork bifurcation, which preserves phase-locking, and a Hopf bifurcation, which destroys it. 相似文献
7.
For Mössbauer studies at very low temperatures, the target holder kept at 11°K with the help of a closed He cycle Mössbauer shroud, has to be insulated by evacuating the outside enclosure surrounding the shroud. The target is kept in thermal contact with the cryostat cold finger through He gas at atmospheric pressure. This provides a vibrationless thermal contact between the two. The evacuation of the outside chamber has to be vibration free which can be accomplished by means of a suitable ion pump which is totally vibration free. However, use of Vac-ion pump here could not be made successful because the pump did not work at all after little pumping. To find out the cause of pump's failure, RGA was employed which showed the presence of He gas in the outside chamber at the time of purging of He gas in the internal chamber. The pump, however, worked efficiently again when the dry N2 gas purged in place of Helium. This points out that totally vibration free Vac-ion pumps cannot be used for evacuation of such cryostats. Here, diffusion pump was used subsequantly taking extra precautions to minimise the vibrations. 相似文献
8.
Sabrina Pickartz Carsten Brée Uwe Bandelow Shalva Amiranashvili 《Optical and Quantum Electronics》2017,49(10):328
We study to which extent a fiber soliton can be manipulated by a specially chosen continuous pump wave. A group velocity matched pump scatters at the soliton, which is compressed due to the energy/momentum transfer. As the pump scattering is very sensitive to the velocity matching condition, soliton compression is quickly destroyed by the soliton self-frequency shift (SSFS). This is especially true for ultrashort pulses: SSFS inevitably impairs the degree of compression. We demonstrate numerically that soliton enhancement can be restored to some extent and the compressed soliton can be stabilized, provided that SSFS is canceled by a second pump wave. Still the available compression degree is considerably smaller than that in the Raman-free nonlinear fibers. 相似文献
9.
《Heat Recovery Systems and CHP》1987,7(3):203-212
This work was concenned with building and testing a prototype heat pump which incorporated thermochemical energy storage. The heat pump was designed to utilise the cheap ‘Economy 7’ electric tariff. Ammonia was used as the refrigerant and ambient air as a heat source. This heat pump featured two-stage compression and incorporated a liquidised CaCl2 absorbent. The use of a liquidised absorbent system improved the heat and mass transfer and simplified the construction of the generator/absorber of the heat pump. Both heat pumping and regeneration phases were demonstrated. Experimental tests on liquidised absorbent systems are described together with an analysis of the results. 相似文献
10.
Measurement of stimulated Brillouin scattering (SBS) threshold based on waveform variation of SBS optical limiting
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This paper proposes a method for measuring the stimulated
Brillouin scattering (SBS) threshold based on waveform variation of
SBS optical limiting. The output waveforms for different pump power
densities are numerically simulated, and validated in the Nd:YAG
seed-injected laser system. The results indicate that SBS does not
take place in the case of a low pump power density and thus the
output power scales up linearly with pump power. Once the pump power
density exceeds the SBS threshold, SBS takes place and thereby the
energies are transferred from pump to Stokes. As a result, a small
shoulder appears in the trailing edge of the output waveform, which
provides another method to determine the SBS threshold. 相似文献
11.
基于四能级受激准分子宽带泵浦碱金属激光器(XPAL)的工作机理建立了连续波半导体激光器泵浦的四能级XPAL理论模型,该模型基于速率方程,考虑泵浦光线宽与伴峰吸收线宽,采用迭代算法求解,主要用于分析半导体激光器连续泵浦四能级XPAL系统的泵浦阈值特性。讨论了温度、蒸气室长度、泵浦光线宽、输出耦合率和惰性气体粒子数密度对泵浦阈值的影响,结果表明激光器存在一个最佳温度可以使泵浦阈值达到最小,且在最佳温度附近较大范围内泵浦阈值不会有较大变化。除此之外,对蒸气室长度、输出耦合率、泵浦光线宽和惰性气体粒子数密度的分析表明,相较于惰性气体粒子数密度,其他参数的变化对泵浦阈值的影响较小。而较高的惰性气体粒子数密度可以有效提升增益介质对泵浦光的吸收从而降低阈值。 相似文献
12.
R. Rebhi P. Mathey M. Grapinet H.-R. Jauslin S. Odoulov 《Applied physics. B, Lasers and optics》2008,91(3-4):583-589
This paper describes the effect of pump waves misalignement on the performance of the semilinear photorefractive coherent oscillator with the reflection gratings. The oscillation intensity and its modulation frequency are calculated numerically for different misalignement angles, coupling strengths and pump intensity ratios. It is shown that a small angular detuning of the pump wave, less than one milliradian, extends the range of pump ratios and the range of coupling strengths for which a non-degenerate oscillation occurs. The results of experiments with the BaTiO3-based semilinear oscillator are in qualitative agreement with the calculated data. 相似文献
13.
随着我国加快深海、深地资源的开发力度,对此类应用环境下的液体提升泵的可靠性提出了更高的要求。而泵内固体颗粒引起的磨损破坏是其中一个严重问题。本文基于DEM-CFD耦合方法,针对自开发的两级混流泵研究了颗粒在泵内部与流体相互作用下的流动特性和对泵的磨损规律,并基于该泵分析了不同颗粒形状、颗粒浓度下的运动特性和泵磨损分布,发现颗粒主要沿着叶轮工作面以及导叶凹面运动,且随着浓度增加,磨损速率会逐渐达到一个饱和值。本文分析探讨了颗粒在泵内的流动特性、颗粒与叶轮导叶发生碰撞的形式及磨损严重区域,对设计抗磨损多级混流泵提供了理论支撑。 相似文献
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15.
P. A. Prudkovskii 《JETP Letters》2018,107(12):749-752
The effect of pump depletion on the spectrum of twin beams, which appear in the process of collinear parametric down-conversion in a nonlinear crystal with an aperiodic domain structure and have a high degree of simultaneity, has been described. A system of equations describing the interaction of pump with all modes of scattered light simultaneously has been derived. It has been shown that pump depletion results in a noticeable broadening of the spectrum of twin beams for a quadratic-hyperbolic law of variation of the reciprocal lattice vector of the domain structure. The effect of narrowing of the coherent peak in the sum-frequency generation signal from twin beams has been demonstrated. This effect increases as the pump is depleted. 相似文献
16.
针对利用周期极化晶体实现的抽运光角度调谐准相位匹配(QPM)光学参量振荡器(OPO)进行了系统的理论分析,给出了描述QPM OPO中抽运光旋转角与三波波长关系的精确公式和近轴公式.研究发现,对信号光单谐振的情况而言,抽运光与空闲光沿晶体x轴的同侧出射,而对空闲光单谐振而言,抽运光与信号光沿晶体x轴的同侧出射.另外,信号光单谐振下信号光与空闲光间的夹角要大于空闲光单谐振下两者间的夹角.更重要的是,信号光单谐振时的波长调谐速度也较空闲光单谐振时的大.
关键词:
准相位匹配
空闲光单谐振光学参量振荡器
抽运光角度调谐
调谐速度 相似文献
17.
An analysis of the degenerate parametric amplifier including the quantisation of pump and signal modes is presented. It is shown that the fluctuations in one quadrature of the signal mode may be reduced at most by a factor of two. This is in contradistinction to analyses where the pump field is treated classically which overestimate the reduction in fluctuations possible. 相似文献
18.
This paper is an experimental work of the applied methodical character in which as an attempt to optimize a laser ignition
system a systematic study of the best incoupling geometry for the employed Nd:YAG laser was performed. The incoupling geometry
comprises the pump fiber and an aspheric collimating lens. In this context, the distance between pump fiber and collimating
lens was made continuously variable. The distance between fiber and lens primarily influences the diameter of the pump beam.
In this way, it is possible to control the pulse energy as well as the number of pulses generated within a pump cycle. Furthermore,
investigations to analyze the focal size dependence of plasma generation were carried out. As a result, it was found that
it is possible to reduce optical losses caused by plasma transmission by choosing an optimum focal volume. This experiment
was carried out for different pressures and focal volumes. 相似文献
19.
《Heat Recovery Systems and CHP》1988,8(3):279-287
Two major criteria for successful heat pump installations in process plants are the “appropriate placement” and “appropriate sizing” of the heat pump, consistent with the thermodynamics of the process. Failure to fulfil these conditions will result in the heat pump not achieving the anticipated savings and may even cause a net increase in process energy costs.This paper outlines a study in which the proven thermodynamics-based techniques of pinch technology were used to evaluate the scope for heat pumping in a range of industrial processes of significance in the United States. The procedures used in the study are presented together with the results obtained from the work. Implications for future heat pump applications in the United States are also described. 相似文献