Effect of Doppler broadening on gain in an open V-type inversionless lasing system

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.     

Inversionless gain enhancing due to Doppler broadening in a closed lambda-type system

An analysis is made of the effect of Doppler broadening on gain without inversion (GWI) from different aspects in a closed lambda-type three-level system with an incoherent pump. It is shown that, regardless of the driving field being on resonance or not, for the counter- or co-propagating of the probe and driving fields (PDF), GWI does not monotonically decrease or increase with increasing Doppler width. Except for the case of counter-propagating PDF with off-resonance driving field, at a suitable Doppler width one can obtain a gain maximum value much larger than that without Doppler broadening; especially in the situation of the resonant driving field, the co-propagating geometry leads to a larger GWI. In addition, for the counter-propagating geometry, when Doppler width is larger enough, GWI oscillation occurs, and the oscillation amplitude and region increase with increasing Doppler width. These conclusions are very different from that obtained in previous investigation (Lukin {\it et al}, {\it Laser Phys.} {\bf 6} 436 (1996)).     

Effect of spontaneously generated coherence on inversionless lasing gain in an atomic system with Doppler broadening

We have studied the effect of the spontaneously generated coherence (SGC) on gain of lasing without inversion (LWI) in a closed three-level $\Lambda $-type atomic system with Doppler broadening. It is shown that, regardless of the driving and probe fields being co- or counter-propagating, at a suitable value of the Doppler width, we can obtain a much larger LWI gain with SGC than that without SGC; and the region of the LWI gain spectrum with SGC is obviously larger than that without SGC. When the Doppler width takes a constant value, the gain does not monotonically decrease or increase with increasing strength of SGC, the largest LWI gain can be obtained by adjusting strength of SGC. Generally speaking, the co-propagating probe and driving fields is favourable to obtain a larger LWI gain.     

蓝宝石的近边精细结构和电子数布居分析

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：     

AL L CORE EDGE FINE STRUCTURE IN Al, AlN AND α-Al2O3：A COMPARISON OF MICROELECTRON ENERGY LOSS SPECTRA WITH THEORY

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.     

开放的无粒子数反转激光系统中原子响应的时间演化和光放大机制

研究了开放的Λ型无粒子数反转激光系统中原子响应的时间演化规律,阐明了该系统产生无粒子数反转光放大的机制.发现开放系统中原子响应的时间演化特征与封闭系统有显著的差 别.认为时间演化过程中振荡频率的改变和振荡的非谐性来源于系统中原子振子的随机相干性. 关键词： 开放 无粒子数反转激光 原子响应 随机相干性     

Effect of Doppler broadening on gain in an open V-type inversionless lasing system

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.     

有初始相干性注入的V型无粒子数反转激光系统的非线性增益分析和粒子数差振荡现象

本文给出了有初始相干性注入的V型无粒子数反转激光系统的非线性注解,分析了 系统参量变化对无粒子数反转激光增益和与探测场相互作用的两能级之间的粒子数差的影 响,我们发现伴随着驱动场Rabi频率的增加,粒子数差的变化表现出一个振荡行为,我们对这一新现象给出了解释。     

Al的能量吸收边缘和电子粒子数布居分析

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：     

A NONLINEAR ANALYTICAL AND NUMERICAL STUDY FOR AN OPEN SYSTEM WITH COHERENT OFF-RESONANCE FIELDS

An exact nonlinear analytical solution of an open V-type inversionless lasing system with two incoherent pump fields, off-resonant driving and probe fields is given. Through qualitative and quantitative comparison of the gain, dispersion and population differences of the linear and nonlinear cases, some conclusions concerning the Rabi frequencies of the driving and the probe fields are drawn and discussed in detail.