Y型四能级系统中Doppler展宽对VIC相关的双光子吸收的影响

利用数值计算结果讨论了Doppler展宽对Y型四能级原子系统中真空诱导相干 性(VIC)相关的双光子吸收的影响. 研究结果表明: 1)在无Doppler展宽的情况中, 不存在VIC时, 吸收曲线具有双峰结构并产生电磁感应透明(EIT)现象, 存在VIC时吸收曲线具有单峰结构而EIT现象不再发生; 2)在有Doppler展宽的情况中, 不管是否存在VIC, EIT现象都能发生; 不存在VIC时, 不管探测场和驱动场传播方向相同还是相反, 随Doppler展宽宽度D值的增大, 吸收先增大后减小, 吸收曲线逐渐从双峰结构变为单峰结构; 存在VIC时, 若探测场和驱动场传播方向相同, 随D值的增大, 吸收先增大后减小, 吸收曲线逐渐从单峰结构变为双峰结构; 若探测场和驱动场传播方向相反, 随D值的增大, 吸收单调减小, 但吸收曲线仍保持单峰结构.     

Doppler展宽的封闭原子系统中无反转增益的相位控制

研究了在具有自发辐射诱导相干性的Doppler展宽的封闭Λ型三能级系统中探测场和驱动场之间的相对位相对探测场无反转增益的控制作用. 研究结果表明: 1) 不管探测场和驱动场是同向传播还是反向传播, 驱动场是失谐还是共振,无反转增益总是随相对位相的改变而作周期性变化,周期为2π. 2) 驱动场共振时,无反转增益极大值随Doppler展宽值的增大而单调减小,且反向传播时比同向传播时减小的速度更快;驱动场失谐时,无反转增益的极大值随Doppler展宽值的增大不再单调地减小或增大. 在以上两种情况下,均可以通过调 关键词： 自发辐射诱导相干 相位控制 Doppler展宽 无反转增益     

Doppler展宽的封闭原子系统中无反转增益的相位控制

研究了在具有自发辐射诱导相干性的Doppler展宽的封闭Λ型三能级系统中探测场和驱动场之间的相对位相对探测场无反转增益的控制作用. 研究结果表明: 1) 不管探测场和驱动场是同向传播还是反向传播, 驱动场是失谐还是共振，无反转增益总是随相对位相的改变而作周期性变化，周期为2π. 2) 驱动场共振时，无反转增益极大值随Doppler展宽值的增大而单调减小，且反向传播时比同向传播时减小的速度更快；驱动场失谐时，无反转增益的极大值随Doppler展宽值的增大不再单调地减小或增大. 在以上两种情况下，均可以通过调     

开放的V型三能级系统中原子注入和退出速率对位相相关的无反转激光增益和强度空间演化的调制作用

利用数值计算结果, 研究了具有自发辐射诱导相干的开放V 型三能级原子系统中的传播效应. 研究表明: 改变探测场和驱动场之间的相对位相对无反转激光(LWI)增益和 强度随传播距离的变化即空间演化具有重要的影响; 而原子的注入速率比(S)和退出速率(r₀)的改变将对位相相关的LWI增益和强度的空间演化产生明显的调制作用. 在S(r₀)的一定取值范围内, S(r₀)的值越大, LWI增益和强度越大且强度达到极大值需要的传播距离越长; 相应封闭系统中LWI增益和强度的最大值及能产生增益的传播距离都小于开放系统. Doppler效应对LWI增益和强度的空间演化也具有明显的影响, 存在Doppler效应时得到的LWI增益和强度明显小于无Doppler效应时的值.     

Doppler展宽准Λ型四能级系统中传播效应的位相相关性

利用数值计算详细研究具有真空诱导相干的准Λ型四能级原子系统中探测场和驱动场之间的相对位相(Φ)对传播效应的影响。结果表明:通过选择Φ的取值可以获得更大的GWI和更长的存在无反转增益的传播距离,从而获得更高的LWI强度;Doppler展宽存在时,Doppler展宽宽度及探测场和驱动场传播方向对位相相关的GWI和LWI强度的空间演化有明显的调制作用。     

开放的非共振梯型无粒子数反转激光系统非线性增益与色散的研究

本文给出了开放的非共振ladder型三能级无粒子数反转激光系统的非线性精确解,利用数值计算结果讨论了系统各参量的变化对激光场的增益和色散的影响.作者得到以下结论:当探测激光场和驱动场都共振时,无论其他参量如何变化,色散为零.当仅有探测场失谐(驱动场失谐)时,增益和色散随探测场失谐(驱动场失谐)的变化曲线分别具有偶对称性和中心对称性,当探测场和驱动场皆失谐时,这种对称性消失;适当调节探测激光场或(和)驱动场的失谐可获得最大或较大的无粒子数反转激光增益和无吸收高色散.增益和色散(粒子数差绝对值)随原子注入速率之比的增加单调增加(单调减小),且原子退出速率越大增加(减小)得越快.在探测场和驱动场适当失谐的情况下,保持系统其他参量不变,非相干泵浦速率只有在一定范围内取值时,才能获得无粒子数反转激光增益,并存在一个增益极大值.改变探测场或驱动场Rabi频率对无粒子数反转激光增益的影响与非相干泵浦速率改变时的情况类似.     

飞秒激光参数对三态阶跃型分子Autler-Townes分裂的影响

利用三态模型和含时波包法, 研究了K₂分子在强飞秒泵浦-探测激光场中泵浦/探测场强、波长对光电子能谱Autler-Townes(AT)分裂的影响．通过分别改变两激光场的场强或者波长预测AT峰移和间距,并且首次量化了AT分裂的峰移和间距．光电子能谱在共振时显示为对称双峰,失谐时为非对称双峰。AT分裂间距随泵浦场强增大而增大,但不因探测场强改变而改变．     

射频驱动下电磁诱导透明窗口的分裂和增益的出现

在Λ型三能级系统的基础上引入两个共振射频场, 通过详细讨论系统的探测吸收特性随两个射频场Rabi频率取不同值时的变化规律, 得出电磁诱导透明(EIT)的分裂规律以及EIT上出现增益现象的产生条件.研究结果表明: 两个射频场对系统所起的控制作用不同, 控制基态精细结构能级之间跃迁的射频场对EIT的分裂起作用, 而控制激发态精细结构能级之间跃迁的射频场不会导致EIT的分裂; 而且, 只有当控制基态精细结构能级之间跃迁的射频场的Rabi频率大于控制激发态精细结构能级之间跃迁的射频场的Rabi频率时, 才能产生EIT与增益相叠加的新特性. 关键词： 射频场 电磁诱导透明 增益 精细结构能级     

与Λ型三能级原子非共振相互作用的SU(1,1)场的性质

导出了介质中双模SU(1,1)相干态场与Λ型三能级原子非共振相互作用系统的态函数,研究了场模失谐量、克尔介质以及原子初态对场的互关联函数和Mandel Q参量的影响.结果表明:失谐量将削弱光场两模的关联性,并影响场模光子数的统计分布;当SU(1,1)场两模间的光子数之差增大时,失谐量对它们产生的影响变得更弱,此时克尔效应的影响变得明显,它使两模的关联性和光子数的统计分布趋于稳定.     

稳态V型和A型无粒子数反转激光增益的比较研究

在相应参量取值相同的情况下,利用数值模拟的方法对比研究了封闭的V型和A型原子系统稳态增益随相干光场失谐量的变化规律.研究发现,这两种系统的稳态探测激光增益随探测激光场失谐量的变化曲线具有相似的形状,但数值上存在差异.这一现象与两种系统的原子相干性与粒子数分布的特点直接相关.另外,还发现驱动激光失谐及由于自发辐射诱导相干导致的原子相干性的增强能显著影响探测激光增益.     

Gain enhancing due to quantum interference effect in an open four-level atomic system with Doppler broadening

The effect of vacuum-induced coherence (VIC) on the gain of lasing without inversion (LWI) is studied in an open four-level atomic system with Doppler broadening for both cases: co- and counter-propagating probe and driving fields. The results show that: (1) in general, for a fixed VIC strength, LWI gain decreases monotonously with the value of the Doppler broadening width increasing. Regardless of the Doppler broadening being obvious or not, the LWI gain much larger than that without VIC always can be gotten by choosing suitable VIC strength, i.e. values of two factors p₁ and p₂ which represent the VIC effect. (2) Varying p₁ or p₂ will produce remarkable different influence on the LWI gain, and the influence is closely related to the value of the Doppler broadening width. (3) In the case of counter-propagating probe and driving fields, when the Doppler broadening is large enough, gain oscillation occurs. For the same value of the Doppler broadening width, the oscillation amplitude increases with increasing values of strength of VIC. (4) The atomic exit and injection rates also can dramatically affect LWI gain. (5) The LWI gain for the co-propagating probe and driving fields is always larger than that for the counter-propagating probe and driving fields. (6) A much larger LWI gain in open system than that in the corresponding closed system can be obtained.     

Influence of Doppler broadening and spontaneously generated coherence on propagation effect in a quasi lambda-type four-level system

In this paper we study influences of Doppler broadening, spontaneously generated coherence, and other system parameters on propagation effect in a quasi lambda-type four-level atomic system. It is shown that when the Doppler broadening is present, generally speaking, the values of gain and intensity of lasing without inversion (i.e. the probe field) in the co-propagating probe and driving fields case are much larger than those in the counter-propagating case; considerably larger gain and intensity of lasing without inversion than those without the Doppler broadening can be obtained by choosing appropriate values of the Doppler broadening width and spontaneously generated coherence strength. The gain and intensity of lasing without inversion increase with the increase of spontaneously generated coherence strength; when spontaneously generated coherence is present, much larger gain and intensity of lasing without inversion than those in the case without spontaneously generated coherence can be obtained. Choosing suitable values of the probe detuning, Rabi frequencies of the driving and pump fields at the entrance of the medium also can remarkably enhance the gain and intensity of lasing without inversion.     

Phase-dependence of inversionless gain in a Doppler broadened open four-level system

The effect of the relative phase (?) between the probe and driving fields on the gain without inversion (GWI) in a Doppler broadened open quasi Λ-type four level atomic system with vacuum induced coherence (VIC) for both co- and counter-propagating probe and driving fields cases is studied. It is shown that: (1) GWI and the probe detuning region in which GWI exists are very sensitive to variation of the relative phase; when values of the other parameters keep unvarying, by adjusting value of ?, the largest GWI can be obtained. (2) The Doppler width (D) also has dramatically modulation role on the phase-dependent GWI. When value of D is smaller, the value of ? which corresponds to the largest value of GWI is about π, when value of D is large enough, it is about π/2. (3) GWI varies periodically with ? varying, the period is 2π, but the concrete variation rule is closely related to value of D. (4) In the co-propagating case we can obtain much larger GWI than that in the counter-propagating case.     

Phase modulation of propagation effect with Doppler broadening

This paper studies the propagation effect in a closed lambda-type three-level atomic system with Doppler broadening. It is shown that, Doppler broadening due to atomic motion and propagation effect associated with driving field depletion along the active medium decreases obviously the gain and output of the lasing without inversion （LWI）; the relative phase between the probe and driving fields has a remarkable modulation role to the propagation effect on LWI when Doppler broadening presents; by choosing suitable value of the relative phase, we can get the largest gain and output of LWI.     

准Λ型四能级原子系统在弱场中的增益及电磁感应透明

利用数值模拟的方法讨论了稳态下准型四能级原子与两光场相互作用系统对探测场的增益以及与粒子数布居规律之间的关系。结果表明即使在场较弱的情况下,随着探测场和它所对应能级间跃迁频率失谐量的变化,系统在所有拉比频率相位为零时对探测光总会同时呈现三个增益峰和两个固定的产生电磁感应透明(EIT)现象的位置,并且当系统呈现电磁感应透明的同时,探测场所对应的高能级粒子数为零;而拉比频率相位的变化则会导致系统对探测光既有吸收也有增益,并且也呈现电磁感应透明现象,但仅仅相位的变化并不影响高能级的粒子数分布。值得注意的是该结果均在精确求解下所得。     

掺杂稀土离子晶体中的电磁感应光透明现象

对在掺杂稀土离子晶体中实现电磁感应光透明进行了实验研究。首先,以Er3＋∶YAG晶体为样品,用旋转波近似下的密度矩阵方程理论计算了探测场的吸收特性随Er3＋离子浓度的变化规律,结果表明：在探测场失谐Δp=0时,形成了一个对于探测光透明的窗口,从而在理论上论证了在掺杂稀土离子晶体中实现电磁感应光透明效应的可行性。设计了一个以Pr3＋∶Y2SiO5晶体为样品的实验激发方案,吸收光谱显示,当温度为6 K时其在共振吸收峰处可形成一个完全透明的窗口,实现了在掺杂离子晶体中的电磁感应光透明。实验还分析了工作温度、耦合场失谐对探测光透过率的影响,结果显示：当样品温度上升到15 K时,透明窗口消失;耦合场的失谐量越大,透射率越小。     

失谐对开放的四能级系统无粒子数反转激光的影响

提出开放的四能级双驱动场无反转激光系统的理论模型,由电偶极和旋转波近似得到其密度矩阵方程,讨论无反转激光产生的物理机制,利用数值计算结果分析探测场和驱动场失谐对系统无反转激光增益和粒子数差的影响.     

Phase control in an open Λ-type system with spontaneously generated coherence

This paper investigates the control role of the relative phase between the probe and driving fields on the gain, dispersion and populations in an open A system with spontaneously generated coherence （SGC）. It shows that by adjusting the value of the relative phase, a change from lasing with inversion to lasing without inversion can be realized; the values and frequency spectrum regions of the inversionless gain and dispersion can be obviously varied; high refractive index with zero absorption and electromagnetically induced transparency can be achieved. It is also found that when the driving field is resonant, the shapes of the dispersion and the gain curves versus the probe detuning are very similar if the relative phase of the dispersion lags π/2 than that of the gain, however for the off-resonant driving field the similarity will disappear; the gain, dispersion and populations are periodical functions of the relative phase, the modulation period is always 2π; the contribution of SGC to the inversionless gain and dispersion is much larger than that of the dynamically induced coherence.     

Phase control of probe response in an open ladder type system with spontaneously generated coherence

The control role of the relative phase between the probe and driving fields on the gain and dispersion in an open three-level ladder atomic system with incoherent pumping and spontaneously generated coherence is investigated. It is shown that by adjusting the value of the relative phase, the switching from lasing with inversion to lasing without inversion (LWI) can be realized; high index of the refraction with zero absorption can be achieved. It is also found that when the driving field is on resonance, the dispersion curve versus the probe detuning is very similar to the gain curve if the relative phase corresponding to the dispersion advances π/2 than that corresponding to the gain. LWI gain from the open system is obviously larger than that from corresponding closed system. When the incoherent pumping is absent, the open system can get LWI gain, moreover the gain is larger than that when the incoherent pumping presents for suitable value of the relative phase, but the corresponding closed system exhibits only absorption. In addition, manipulation effects of atomic exit and ratio of the injection rates on phase dependent gain are also analyzed.