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401.
402.
Spectrum evolutions of spontaneous and pump-depleted stimulated Brillouin scatterings in liquid media 下载免费PDF全文
A theoretical model for calculating spontaneous and stimulated
Brillouin scattering(SBS) spectra is described. An empirical formula
for the Stokes output spectral linewidth, a function of spontaneous
Brillouin linewidth and the exponential gain coefficient, is
obtained by the calculated data fitting. The formula holds true for
two cases involving pump undepletion and depletion. The lineshape
change from spontaneous to highly pump-depleted SBS spectra is also
investigated. The result shows that for the pump power below the SBS
threshold, the Stokes output spectral lineshape evolves from
Lorentzian to approximately Gaussian as the pump power increases.
For the pump power near or beyond the threshold, the SBS spectrum is
in the form of a steady Gaussian profile, and the spectral linewidth
comes to a certain value about 7 times narrower than the spontaneous
one. The theoretical results are experimentally demonstrated by
using several common liquid media. 相似文献
403.
We present the results of study of the influence of the transmitted-laser linewidth on the measurement sensitivity and error
of a double-edge incoherent wind lidar. The quantitative relationship between the transmitted-laser linewidth and the full
width at a half maximum (FWHM) of the backscattered spectrum was simulated using the Monte Carlo method, because such relationship
cannot be given by an analytic formula. The quantitative relationship was fitted using a quadratic fit and was further employed
for calculating the measurement sensitivity and error. The FWHM of the backscattered spectrum increased from 3.884 GHz to
5.407 GHz, while the transmitted-laser linewidth increased from a monochromatic one to 2 GHz. The measurement greatly suffered
from the broadening of the transmitted-laser linewidth. The measurement sensitivity decreased from 0.0031 to 0.0019 and the
measurement error increased from 0.326 m/s to 0.524 m/s, while the signal-to-noise ratio and laser shots were both 1000. 相似文献
404.
研究了掺铒光纤环形腔激光器(EDFRL)的注入锁定现象,提出了一种实现可调谐的单纵模EDFRL波长及功率稳定的新方法,即利用注入锁定技术向法布里-珀罗可调滤波器结合复合腔结构的EDFRL腔内注入低功率的连续光,使某一纵模在注入连续光的基础上起振.这个纵模在对增益介质的竞争中可以稳定地占据优势,从而与注入信号发生锁定,实现激光器输出光谱的稳定.实验得到激光器在1527.4~1561.9 nm范围内波长可调,输出功率>0.6 dBm,信噪比(SNR)>43 dB;输出光波长与功率抖动分别<0.01 nm和≤0.02 dB,且线宽约为1.4 kHz. 相似文献
405.
406.
Jean-Marcel Colmont Linh Nguyen François Rohart 《Journal of Molecular Spectroscopy》2007,246(1):86-97
Collisional relaxation has been considered for millimeter lines of carbon monoxide at room temperature. Accurate measurements of carbon dioxide- and rare gases-broadened widths have been performed on the J = 3 ← 2 rotational line of 12CO by using a video-type spectrometer. Measurements of nitrogen-, oxygen-, and xenon-broadened widths of the J = 5 ← 4 rotational line of 13CO were also carried by using a frequency-modulated spectrometer. A lineshape study performed on all the investigated binary systems provide confirmation that Voigt profile is not a suitable model to analyse experimental lines in the millimeter-waves region. On one hand, using this profile in the low pressure range, i.e. in the Doppler regime, the retrieved collisional linewidths do not follow a linear variation with the perturbing gas pressure. On the other hand, regardless of the pressure, lineshapes exhibit a narrowed profile. An accurate analysis of the pressure dependence of relaxation rates show that the Galatry profile is not appropriate and that experimental lineshapes are actually Speed Dependent Voigt profiles. Accurate broadening parameters were retrieved from this profile and compared to previous reported values and predictions calculated from the Robert-Bonamy formalism. Finally a variation of the ratio of relaxation speed dependence to broadening parameters versus relative masses of the collision partners is presented. 相似文献
407.
实验与理论研究了外光注入种子脉冲有效压缩增益开关DFB激光器光谱线宽的注入时间窗口.发现只有在增益开关光脉冲建立之前约100 ps的时间窗口内,注入种子脉冲方可以有效压缩增益开关DFB半导体激光器光谱线宽, 并且线宽随着注入光强度的增加而减小,可产生低啁啾的近变换极限的超短光脉冲.实验证实,在此时间窗口内注入种子脉冲,增益开关DFB激光器的光谱线宽从0.46 nm压缩至0.08 nm,时间带宽积从2.46降低至0.70.同时理论研究了增益开关DFB半导体激光器的光谱线宽压缩与种子脉冲的注入时间及强度的关系. 相似文献
408.
提出利用布里渊放大技术对水中微弱光散射信号进行频谱选择性光放大的方法.根据频率失谐布里渊放大理论模型,分析了Stokes种子光的线宽及频率失谐对布里渊放大的影响,研究了种子光放大率随水温及其功率密度变化的规律,理论和实验符合较好.研究表明,相同频率失谐时,线宽较大的种子光信号放大率更高.选取20℃的CS2为放大介质,不同温度海水产生的Stokes种子光信号均能得到有效的布里渊放大.相同抽运光功率密度情况下,种子光的放大率随其功率密度的增加而减小,当种子光能量约为5μJ时,其放大率达102以上. 相似文献
409.
B. H. Robinson C. Mailer A. W. Reese 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,138(2):199-209
We present a method of simulating the EPR spectra of spin labels in liquids using direct convolution of hyperfine splitting with Lorentzian linewidths. The aim is to simulate the experimental lineshape by considering all spectrometer characteristics as well as inhomogeneous and homogeneous linewidth effects. A major advance in this method is the correction for the broadening produced by Zeeman modulation commonly used to obtain EPR signals; this allows experimenters much more freedom to optimize their experimental conditions for the best signal-to-noise ratio. Microwave power broadening (saturation) effects on the EPR lines are significant even at very low observer levels. Successful simulation requires that all contributions from unresolved hyperfine splittings be explicitly included. Inhomogeneous broadening is dealt with by including all spins that interact with the electron (as a set of superhyperfine interactions); there is no "effective Gaussian" to substitute for the correct superhyperfine interactions. The effects of spin exchange on the linewidth and lineshape can be observed and must be taken into account in order to extract the fundamental linewidths. 相似文献
410.