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Our study shows that for the copropagating probing and driving fields, the gain without inversion doesn't monotonously decrease or increase with the increasement of Doppler width. When the driving field is resonant, at a suitable Doppler width, we can get a maximum value of the gain without inversion, which is much larger than that obtained when Doppler broadening is absent. 相似文献
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An analysis is made of the effect of Doppler broadening on gainwithout inversion (GWI) from different aspects in a closedlambda-type three-level system with an incoherent pump. It is shownthat, regardless of the driving field being on resonance or not, forthe counter- or co-propagating of the probe and driving fields (PDF),GWI does not monotonically decrease or increase with increasingDoppler width. Except for the case of counter-propagating PDF withoff-resonance driving field, at a suitable Doppler width one canobtain a gain maximum value much larger than that without Dopplerbroadening; especially in the situation of the resonant drivingfield, the co-propagating geometry leads to a larger GWI. Inaddition, for the counter-propagating geometry, when Doppler width islarger enough, GWI oscillation occurs, and the oscillation amplitudeand region increase with increasing Doppler width. These conclusionsare very different from that obtained in previous investigation(Lukin {it et al}, {it Laser Phys.} {bf 6} 436 (1996)). 相似文献
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We have studied the effect of the spontaneously generated coherence(SGC) on gain of lasing without inversion (LWI) in a closedthree-level $Lambda $-type atomic system with Doppler broadening. Itis shown that, regardless of the driving and probe fields being co-or counter-propagating, at a suitable value of the Doppler width, wecan obtain a much larger LWI gain with SGC than that without SGC; andthe region of the LWI gain spectrum with SGC is obviously larger thanthat without SGC. When the Doppler width takes a constant value, thegain does not monotonically decrease or increase with increasingstrength of SGC, the largest LWI gain can be obtained by adjustingstrength of SGC. Generally speaking, the co-propagating probe anddriving fields is favourable to obtain a larger LWI gain. 相似文献
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利用透射电子显微镜的电子能量损失谱研究了蓝宝石AlL和OK近边精细结构,给出了Al原子和O原子的电子数布居分析及不同分截面的比较.通过考虑一个原子在均匀固体中的电离来解释近边电离区中的元素效应.应用推广的Hückel分子轨道理论及反映了晶体变换对称性影响的布洛赫定理来计算电子从内层向价层的跃迁,从而解释了近边区域的化学效应.还考虑了附加的化学效应,这来自激发原子附近的原子产生的外行平面波弹性后向散射,由此产生电离区中的所谓延展精细结构.理论计算结果与实验得到的蓝宝石单相区电子能量损失谱符合较好.关键词： 相似文献
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AL L CORE EDGE FINE STRUCTURE IN Al, AlN AND α-Al2O3：A COMPARISON OF MICROELECTRON ENERGY LOSS SPECTRA WITH THEORY 
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下载免费PDF全文 The Al L near-edge fine structures of aluminum and its compounds with nitrogen and oxygen are studied using electron energy loss microspectroscopy in a transmission electron microscope. These edges are normalized to the same scattering cross section per Al atom per electronvolt. The cross section is calculated by using the Born approximation. The contributions to the cross section are from the valence shell crystal states obtained by using the extended Hückel band calculation and the ionization states obtained by using the electron gas model. The chemical effects in the ionization region are taken into account by in cluding the contributions from the elastic backscattering of outgoing plane waves by the atoms that neighbor the excited atoms. The results by theoretical calculation agree semiquantitatively with experimental results. 相似文献
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Our study shows that for the copropagating probing and driving fields, the gain without inversion doesn't monotonously decrease or increase with the increasement of Doppler width. When the driving field is resonant, at a suitable Doppler width, we can get a maximum value of the gain without inversion, which is much larger than that obtained when Doppler broadening is absent. 相似文献
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AL L CORE EDGE FINE STRUCTURE IN Al,AlN AND α-Al2O3：A COMPARISON OF MICROELECTRON ENERGY LOSS SPECTRA WITH THEORY 下载免费PDF全文
下载免费PDF全文 The Al L near-edge fine structures of aluminum and its compounds with nitrogen and oxygen are studied using electron energy loss microspectroscopy in a transmission electron microscope. These edges are normalized to the same scattering cross section per Al atom per electronvolt. The cross section is calculated by using the Born approximation. The contributions to the cross section are from the valence shell crystal states obtained by using the extended Hückel band calculation and the ionization states obtained by using the electron gas model. The chemical effects in the ionization region are taken into account by in cluding the contributions from the elastic backscattering of outgoing plane waves by the atoms that neighbor the excited atoms. The results by theoretical calculation agree semiquantitatively with experimental results. 相似文献
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给出了Al电子能量损失谱吸收边缘的理论解释、电子粒子数布居分析及不同散射分截面计算结果的比较.能量吸收边缘被归一化为每原子每电子伏的散射截面.对散射截面的贡献来自三个方面.第一是来自应用推广的Hückel带模型得到的电子从内层向价层的跃迁;第二是来自利用电子气模型得到的电离末态;第三是来自激发原子附近的原子产生的外行平面波弹性反向散射.理论计算结果与实验得到的电子能量损失谱符合较好.关键词： 相似文献