双光力诱导透明窗口的可调特性

提出一个杂化腔光力系统理论方案,利用两纳米机械振子间的库仑耦合作用实现弱探测光的双光力诱导透明窗口.研究边带可分辨区域和红失谐情况下双光力诱导透明窗口的可调特性.数值计算表明:两纳米振子间的库仑作用可有效地使单光力诱导透明窗口劈裂为双透明窗口.随着库仑耦合强度的增大,两透明窗口间的距离对称性地拉大;其次,光力腔衰减率的改变对两透明窗口的位置和深度无影响,仅对两透明窗口的宽度产生细微改变,测量精度可在坏腔情形下得到很好的保持;另外,仅增加参量放大器的非线性增益参量将使两透明窗口变宽,而引入驱动参量放大器的光场相位,利用相位匹配可以产生比空腔情形更加狭窄陡峭的双透明窗口,可用于比空腔情况更加精密的测量.     

相干反馈相位对腔光力系统中正交模劈裂的影响

强耦合是腔光力系统用于产生和观察许多宏观量子现象（如光力压缩态和纠缠态等）的基本条件,系统进入强耦合的明显标志是正交模劈裂。本文理论分析了加入光学参量放大器和相干反馈的光力系统中的正交模劈裂现象,并讨论分析了反馈回路的光学相位对正交模劈裂的影响。在不同参数情况下,如光学参量放大器参量增益、反馈分束器的反射系数和输入光功率等,模式位置和线宽随相移的变化。结果表明：在其他参数一定时,通过调节反馈相位,初始无模式劈裂的系统随相位变化出现模式劈裂并达到最大的模式间隔,从而从弱耦合进入强耦合状态。而且,多个参数的协同调节,可有效提高模式劈裂的程度。该研究为实验上增强光力耦合强度的实验调节提供了方便,可广泛用于光力系统的弱力灵敏探测以及宏观量子态产生与测量等。     

原子辅助光力系统中快慢光的量子调控

随着纳米科技以及半导体技术的迅猛发展,光力诱导透明、快慢光和光存储以及其他在光力系统中发现的量子光学和非线性光学效应成为人们目前研究的热点.本文将薄膜腔光力系统同被束缚在腔中的二能级冷原子系综相耦合,通过直接在薄膜振子上引入弱辅助驱动场来研究该原子辅助光力系统中原子和相位对量子相干性质及其快慢光的调控.经过分析发现,通过改变辅助驱动场的强度可直接实现对光力诱导透明窗口深度的调控,通过改变辅助场与探测场之间的相位差,可实现输出的探测场在"吸收"、"透明"和"增益"之间相互转换,进而对弱探测场进行动态调控实现光开关.与此同时,还发现系统的群延迟时间随相位差的改变呈周期性变化.通过调节相位差及原子数,不但可以改变群延迟时间,还可实现快慢光之间的相互转换.     

强耦合条件下内腔电磁诱导透明和正交模劈裂的研究

文章分析了Λ-型三能级原子与腔耦合系统在强耦合条件下,腔透射谱在随腔模失谐的变化情况。结果表明,改变腔模失谐不但对正交劈裂峰会产生频移,同时对内腔EIT峰也会产生频率推移,并且在单光子失谐时,推移程度也有所不同;当腔模失谐达到自由光谱区的一半时,内腔暗态极子模出现双峰结构。这一结果对研究基于原子腔系统的关联光场具有积极的意义。     

里德伯原子辅助光力系统的完美光力诱导透明及慢光效应

光力诱导透明是典型的量子相消干涉效应,在量子光学和量子信息处理当中具有广泛的应用.本文在里德伯原子系综镶嵌的复合光力学系统中考察了光力诱导透明现象以及由此产生的慢光效应.当考虑非旋转波近似的情况下,可以获得完美的光力诱导透明,即非常狭窄的理想透明窗口.在可分辨边带条件下,微腔品质越高,完美透明窗口中的慢光效应越明显.特别地,与其他原子相比,在实现超慢光方面里德伯原子的长寿命体现了其优越性.     

基于X射线衍射仪的X光晶体本征参量的标定

X光晶体本征参量的实验标定是准确鉴定X光晶体种类和品质,研制各种类型晶体谱仪,X光线谱定量测量和高分辨X光单能成像的基础.基于X射线衍射仪,通过制作平面晶体样品架,采取控制X射线管电源、滤波片选取和厚度控制等措施,极大地抑制了Cu-KJ3及韧致辐射,使X射线管光源Cu-Kα单能化,提出了用滤片作为光源单能化的判据.对X光线谱测量中常用的X光分光晶体季戊四醇[PET(002)]的晶格常量2d和Cu-Ka能点的积分衍射效率R.进行了标定方法研究,其标定值分别为(0.87425±0.00042)nm和(1.759±0.024)×10-4 Rad.基于X射线衍射仪的X光晶体本征参量的精密实验标定方法既快速高效,且十分方便和灵活.通过更换衍射仪的X射线管靶材,采取类似方法,可以标定其它能点的晶体积分衍射效率,可为X光晶体的本征参量库提供更多的标定数据.     

基于X射线衍射仪的X光晶体本征参量的标定

X光晶体本征参量的实验标定是准确鉴定X光晶体种类和品质,研制各种类型晶体谱仪,X光线谱定量测量和高分辨X光单能成像的基础.基于X射线衍射仪,通过制作平面晶体样品架,采取控制X射线管电源、滤波片选取和厚度控制等措施,极大地抑制了Cu-Kβ及韧致辐射,使X射线管光源Cu-Kα单能化,提出了用滤片作为光源单能化的判据.对X光线谱测量中常用的X光分光晶体季戊四醇的晶格常量2d和Cu-Kα能点的积分衍射效率R_c进行了标定方法研究,其标定值分别为(0.874 25±0.000 42)nm和(1.759±0.024)×10^-4 Rad.基于X射线衍射仪的X光晶体本征参量的精密实验标定方法既快速高效,且十分方便和灵活.通过更换衍射仪的X射线管靶材,采取类似方法,可以标定其它能点的晶体积分衍射效率,可为X光晶体的本征参量库提供更多的标定数据.     

用基于磁场的改进型有限差分法分析光波导的全矢量本征模

提出一种改进的有限差分法,用以求解全矢量磁场波方程,分析光波导承载的全矢量本征模.离散交叉项时,采用与波导结构无关的六点差分格式,考虑磁场分量的导数在芯包分界处的不连续性,比传统四点差分格式有更高的计算精度.分析阶跃型光纤、矩形和脊形光波导的全矢量本征模问题,给出全矢量基模的磁场分布及其归一化传播常数,揭示全矢量本征模的混合特性,所得结果与解析法、高精度模横向谐振法的结果吻合,验证了方法的收敛性与计算精度.     

各向同性介质界面本征模分析

分析了两个各向同性材料界面处的本征模,从另一个角度来分析解释了布儒斯特定律.当入射光与界面处的表面模匹配时,入射光的能量就会全部转移到界面的本征场上,如果电磁波在折射介质中为行波,界面的本征场又会在折射介质中激发新的电磁波,形成透射波,也就是布儒斯特定律描述的横电波或者横磁波的全透射现象,这也可以看作是一种光学共振现象.横磁波的全透射现象往往出现在两个具有相同磁导率的介质的界面处,而横电波的全透射现象则往往出现在两个具有相同介电常数的介质的界面处.     

利用PPKTP晶体半整块光学参量放大器产生1.5μm光通信波段明亮正交振幅压缩光

利用周期极化磷酸氧钛钾(PPKTP)晶体构成的半整块结构简并光学参量放大器获得了连续变量1.5μm光通信波段的明亮正交振幅压缩态光场。光学参量放大器工作于阈值以下反放大状态,阈值功率为220 mW。当780nm抽运光场功率为110 mW,1.5μm注入信号光场功率为115 mW时,下转换光场输出功率为80μW,实测的连续变量1.5μm明亮正交振幅压缩态光场的压缩度达3.0dB。     

Optomechanically induced amplification and perfect transparency in double-cavity optomechanics

We study optomechanically induced amplification and perfect transparency in a double-cavity optomechanical system. We find that if two control lasers with appropriate amplitudes and detunings are applied to drive the system, optomechanically induced amplification of a probe laser can occur. In addition, perfect optomechanically induced transparency, which is robust to mechanical dissipation, can be realized by the same type of driving. These results indicate important progress toward signal amplification, light storage, fast light, and slow light in quantum information processes.     

Perfect optomechanically induced transparency in two-cavity optomechanics

Here, we study the controllable optical responses in a two-cavity optomechanical system, especially on the perfect optomechanically induced transparency (OMIT) in the model which has never been studied before. The results show that the perfect OMIT can still occur even with a large mechanical damping rate, and at the perfect transparency window the long-lived slow light can be achieved. In addition, we find that the conversion between the perfect OMIT and optomechanically induced absorption can be easily achieved just by adjusting the driving field strength of the second cavity. We believe that the results can be used to control optical transmission in modern optical networks.     

强耦合光机械腔中的简正模式分裂和冷却

研究由辐射压力与驱动Fabry-Perot光学腔相耦合而产生的腔光机械动力学行为. 通过量子朗之万方程具体研究了机械振子的涨落光谱、机械阻尼与共振频移和基态冷却. 随着输入激光功率的增加,振子的涨落光谱呈现简正模式分裂的现象,并且数值模拟结果和实验结果相符合. 同时推导了有效机械阻尼和共振频移. 红移边带导致了机械模的冷却,蓝移边带引起了机械模的放大. 此外,引入一种近似机制来研究振子的基态冷却,并且考虑在解析边带机制下简正模式分裂对机械振子冷却的影响. 最后,数值讨论了初始浴温度、输入激光功率和机械品质因数这三个因素对机械振子冷却的影响. 关键词： 腔光机械 辐射压力 简正模式分裂 冷却     

Ideal optomechanically induced transparency generation in a cavity optoelectromechanical system

The ideal optomechanically induced transparency effects of an output probe field are investigated in a cavity optoelectromechanical system, which is composed of an optical cavity, a charged mechanical resonator, and a charged object.Although the charged mechanical resonator damping rate is nonzero, the ideal optomechanically induced transparency can still appear due to the non-rotating wave approximation effect in the system. The location of optomechanically induced transparency dip can be controlled via the Coulomb coupling strength. In addition, we find that both the transparency window width and the maximum dispersion curve slope are closely related to the optical cavity decay rate.     

Tunable optomechanically induced transparency and fast–slow light in a loop-coupled optomechanical system

We theoretically explore the tunability of optomechanically induced transparency(OMIT) phenomenon and fast–slow light effect in a loop-coupled hybrid optomechanical system in which two optical modes are coupled to a common mechanical mode. In the probe output spectrum, we find that the interference phenomena OMIT caused by the optomechanical interactions and the normal mode splitting(NMS) induced by the strong tunnel coupling between the cavities can be observed. We further observe that the tunnel interaction will affect the distance and the heights of the sideband absorption peaks. The results also show that the switch from absorption to amplification can be realized by tuning the driving strength because of the existence of stability condition. Except from modulating the tunnel interaction, the conversion between slow light and fast light also can be achieved by adjusting the optomechanical interaction in the output field. This study may provide a potential application in the fields of high precision measurement and quantum information processing.     

Entanglement of movable mirror and cavity field enhanced by an optical parametric amplifier

A scheme to generate entanglement in a cavity optomechanical system filled with an optical parametric amplifier is proposed. With the help of the optical parametric amplifier, the stationary macroscopic entanglement between the movable mirror and the cavity field can be notably enhanced, and the entanglement increases when the parametric gain increases.Moreover, for a given parametric gain, the degree of entanglement of the cavity optomechanical system increases with increasing input laser power.     

Enhancement of electromagnetically induced transparency cooling by an optical cavity

We theoretically investigate an enhanced electromagnetically induced transparency （EIT） cooling method by introduc- ing a high finesse cavity. We find that the quantum destructive interference that is induced by the EIT effect and the cavity coupling can eliminate all of the heating effects in the cooling process by choosing appropriate parameters. Compared with the EIT cooling scheme, a lower final temperature can be obtained under the same conditions in our scheme.     

Einstein——Podolsky——Rosen entanglement in time-dependent periodic pumping non-degenerate optical parametric amplifier

The solution of the time-dependent periodic pumping non-degenerate optical parametric amplifier (NOPA) is derived when the pump depletion is considered both above and below thresholds. Based on this solution, the quantum fluctuation calculated shows that a high entanglement and a good squeezing degree of the parametric light beams are achieved near and above thresholds. We adopt two kinds of pump fields: (i) a continuously modulated pump with a sinusoidal envelope; (ii) a sequence of laser pulses with Gaussian envelopes. We analyse the time evolution of continuous variable entanglement by analytical and numerical calculations, and show that the periodic driven pumping also improves the degree of entanglement. The squeezing and Einstein-Podolsky-Rosen (EPR) entanglement by using the two pumping driven functions are investigated from below to above the threshold regions, the tendencies are nearly the same, and the Gaussian driven function is superior to that of the sine driven function, when the maximum squeezing and the minimum variance of quantum fluctuation are considered. In the meantime, the generalization of frequency degenerate OPA to frequency non-degenerated OPA problem is investigated.