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类型 基础研究 预答辩日期 2018-01-17
开始(开题)日期 2016-03-02 论文结束日期 2017-12-05
地点 田家炳楼205 论文选题来源 国家自然科学基金项目     论文字数 6.5 (万字)
题目 相干诱导低维微纳结构光学非线性增强及其应用
主题词 非线性光学,低维微纳结构,四波混频,超Raman散射,高阶边带
摘要 作为光与物质相互作用的基本范畴,量子相干和干涉效应可以有效地控制和改变相干介质的线性和非线性光学响应,同时产生诸如,电磁诱导透明、相干布居捕获、光群速减慢、光学非线性增强等物理现象。近些年来,以量子相干和干涉效应为基础的诸多非线性光学现象也已经受到了人们的普遍重视和广泛研究,其中包括光学双稳态与多稳态、光学孤子、四波混频及多波混频过程、受激Raman散射、高阶边带以及光学频梳等。对这些光学现象进行深入研究不仅有助于理解非线性光学的本质,而且有利于预言和发现新的潜在的应用。 一般而言,相干介质中的光学非线性主要表现为:当相干介质在强的激光场驱动下,介质中的带电粒子发生光学跃迁或者重新分布,以至于介质中的电偶极矩不仅与光场振幅有关,还会受到光场振幅高阶项的影响。而能否表现出足以观测的光学非线性,很大程度取决于相干介质内部的组成结构。如何寻找和制备出具有理想的光学非线性的新材料,一直都是学术界的研究热点。近期的研究表明,随着相干介质尺寸和维度的减小,其量子效应和非线性光学特性将明显加强。在化学气相沉积(CVD)、分子束外延生长(MBE)、脉冲激光沉积(PLD)等晶体生长技术逐渐成熟的背景下,具有特定光学非线性响应的低维微纳结构也已经被合理地设计和制备。于是,在特定的低维微纳结构中进行特定光学非线性应用的研究已经成为人们追求和探索的新目标。 在本论文中,我们依据不同低维微纳结构所对应的特定光学非线性,对其进行了深入的研究工作。具体内容包含:在半导体量子阱异质结构中实现高效的四波混频、在强磁场驱动下的石墨烯中观测到电磁诱导透明和超Raman散射现象以及它们之间的竞争关系、在腔光力系统中实现高效的高阶边带和边带压缩效应。 1)在一个包含连续体的非对称四能级量子阱中,利用一束弱探测场和两束强控制场耦合量子阱带内能级跃迁,从而产生高效的四波混频方案。在稳态的条件下,利用Schr\"odinger和Maxwell方程组,我们推导出关于探测场、四波混频场、以及与它们相关的相移、线性吸收、群速特性和混频波转换效率的精确表达式。我们的研究结果表明,连续体所诱导的Fano干涉不仅使四波混频场在量子阱介质中保持超低的群速(约$10^{-4}c$),而且还可以极大地提高四波混频场的效率,其中最大效率可以达到{35\%}。此外,在Fano干涉效应的影响下,产生的混频波能够在介质中维持更远的传播距离(至少50 $\mu m$)。 接着,利用同样的方法,另一个高效的四波混频方案在五能级半导体量子阱系统中被发现。当五能级量子阱系统中的一个基态和两个相邻激发态之间发生交叉耦合时,该系统会同时产生两个四波混频的跃迁路径,以至于产生的四波混频效率也相应地提高两倍,最高可达60{\%}。更重要的是,通过选取优化的偶极矩的比,最大的四波混频效率可以支持至少100 $\mu m$的长距离传播。 2)强磁场驱动下的单层石墨烯拥有奇特的电子和光学性质,具体包括线性的色散关系、无质量的Dirac低能电子、电子态的手征性和特殊的带内跃迁选择定则。基于这些的理论背景,我们提出一种有效的太赫兹检测方案。该太赫兹探测技术主要是建立在电磁诱导透明效应的基础上,利用这种量子破坏性干涉带来的不同光学回复,从而达到太赫兹检测的目的。另一方面,由于强磁场驱动下的石墨烯Landau能级具有可调性,我们的研究结果展示出该太赫兹检测技术可覆盖广阔的频率带宽($0.36 THz - 11.4 THz$)。该方案的提出不仅可以促进固态光学探测装置的发展,也为相干光学和非线性光学的应用提供了基本素材。 3)同样是利用强磁场驱动下的单层石墨烯。基于其良好的光电性能,我们观测到关于超Raman散射和电磁诱导透明之间的竞争关系。该课题从理论的角度,运用量子力学的方法求解Schr\"odinger和Maxwell方程组,最终得到石墨烯系统的线性极化率、非线性极化率以及超Raman场的解析表达式。通过缀饰态理论分析,我们发现该超Raman散射过程和电磁诱导透明效应之间存在明显的竞争关系。利用这种竞争关系,我们可以通过抑制石墨烯中的电磁诱导透明效应,得到高效的超Raman散射过程。 4)在一个二次耦合的光力系统中,实现可控的双声子高阶边带放大效应。在超越传统的线性化近似方法下,我们完整地计算了Heisenberg-Langevin公式中的非线性微扰项,从而得到透射的探测场以及二阶边带振幅的解析表达式。我们的数值模拟结果表明:机械振子的泵浦场和控制场的失谐量不但可以改变探测场的透射光,而且能够增强双声子高阶边带的振幅。另外,当控制场较强的情况下,该双声子高阶边带还展现出明显的相敏依赖效应。从应用的角度来看,该双声子高阶边带可以被用做光学频梳和芯片级别的光学通信。 5)在一个内置二阶非线性的腔光力机械系统中,利用一束弱探测场和一束强控制场诱导系统产生高阶边带的正交压缩。在光力耦合诱导的非线性过程中,该方案涉及到非线性的压缩过程以及压缩态之间的态转移。研究结果表明:二阶非线性强度和控制场的失谐量不仅可以调制非线性压缩和压缩态转移过程,还可以优化高阶边带谱的振幅和压缩度。此外,当二阶非线性强度接近理论的临界值时,一个优化的高阶边带的压缩效应可以被实现。 总之,本论文的研究有利于加深了人们对低维微纳结构中非线性光学特性的认识和理解。这些研究对非线性光谱学,太赫兹科学,精密测量等学科和领域的发展具有一定的参考价值。
英文题目 Enhanced optical nonlinearity and related applications in coherence low-dimension micro-nano structure
英文主题词 Nonlinear optics, Low-dimension micro-nano structure, Four-wave mixing, Hyper-Raman scattering, Higher-order sidebands
英文摘要 Quantum coherence and interference effects, that are the fundamental phenomena of the light-matter interaction, can effectively change and control the linear and nonlinear optical responses in quantum coherent media. Simultaneously, they also lead to some interesting phenomena such as electromagnetically induced transparency, coherence population trapping, low group velocity of light pulses and enhanced high order nonlinearities. Based on these quantum coherence and interference effects, the nonlinear optical phenomena including optical bistability and multistability, optical soliton, four-wave and multi-wave mixing processes, stimulated Raman scattering, higher-order sidebands and optical combs have attracted considerable attention and have been widely studied. The further research for these optical phenomena not only is conducive to understand better the essence of nonlinear optics, but also is beneficial to further predict and discover the new potential applications. Generally, the optical nonlinearity in coherence medium refers to: when the coherence medium is driven by some strong laser fields, the charged particles in coherence medium experience an intersubband optical transition or redistribution, so that the electric dipole moment of coherence medium is related to the amplitude of the electric field as well as the higher-order terms of the electric field amplitude. Therefore, whether the coherence medium possesses of an observable optical nonlinearity is determined by its internal structure. How to find and provide a novel material that owns a strong optical nonlinearity has been a research hotspot. According to the recent advance of low-dimension micro-nano structure, the quantum effect and the nonlinear optical effect are significantly enhanced when the size and dimension of the coherence media decrease. Under the condition of that the crystal-growth techniques including chemical vapor deposition, molecular beam epitaxy and pulsed laser deposition become mature gradually, the low-dimension micro-nano structure that has specific nonlinear optical response has been a worthy research object. In this thesis for the Doctorate, we have studied deeply the specific optical nonlinearity in the specific low-dimension micro-nano structure. More specifically, we have studied the enhanced four-wave mixing (FWM) in semiconductor quantum wells, the competition between electromagnetically induced transparency (EIT) and hyper-Raman scattering in graphene under an external magnetic field, the tunable higher-order sideband and quadrature squeezing of higher-order sideband spectrum in cavity optomechanics. The main contents are as follows: 1)We propose and analyze an efficient way to enhance four-wave mixing (FWM) signals in a four-subband semiconductor quantum well via Fano-type interference. By using Schr\"odinger-Maxwell formalism under the steady-state condition, we show the corresponding analytical expressions of the probe and generated FWM pulses, as well as their phase shifts, absorption coefficients, group velocities, and the related conversion efficiency, respectively. With the aid of interference between two excited subbands tunneling to the common continuum, we find that the efficiency of FWM field is found to be significantly enhanced, up to {35\%}. In addition, the FWM field can keep an ultraslow group velocity in the quantum well, which can be maintained for a certain propagation distance (i.e., $50 \mu m$). Then, using the similar approach, a high efficient four-wave mixing (FWM) scheme is proposed in five-subband semiconductor quantum wells (SQWs). With the aid of cross coupling between one ground state and two closely adjacent excited states, the efficiency of the generated FWM field is found to be significantly enhanced, up to {60\%}. More interestingly, a wide region of the maximum FWM efficiency is demonstrated as the ratio of transition dipole moments is within the values ranging from $1.1$ to $1.3$, which can be maintained for a certain propagation distance (i.e. 100 μm). 2)Monolayer graphene under a strong magnetic field has fascinating electronic and optical properties, such as linear dispersion relation, massless Dirac low-energy electrons, chiral character of electron states and special selection rules between Landau levels. Supported by these properties of graphene,we propose and analyze an efficient way to detect the terahertz (THz) signal in a magnetized graphene system via electromagnetically induced transparency. Such a scheme for THz signal detection mainly relies on the measurement of probe transmission spectra, in which the behaviors of a weak-probe transmission spectra can be controlled by switching on/off the THz signal radiation. Taking into account the tunable optical transition frequency between the Landau levels in graphene, our analytical results demonstrate that a broad frequency bandwidth of the THz signal radiation, ranging from 0.36 to 11.4 THz, can be inspected and modulated by means of an external magnetic field. As a consequence, the proposed magnetized graphene system performs a striking potential to utilize quantum interference in the design of optical solid-state devices. 3)Similar to the graphene model in above terahertz signal detection,we propose and analyze the competetion between electromagnetically induced transparency and hyper-Raman scattering. By solving the Schr?dinger–Maxwell formalism, we derive explicitly analytical expressions for linear susceptibility, nonlinear susceptibility, and generated Raman electric field under the steady-state condition. Based on dressed-state theory, our results show a competition between EIT and hyper-Raman scattering, and the hyper-Raman process is totally dominant when multiphoton destructive interference is completely suppressed. 4)In a quadratically coupled optomechanical system, we propose an efficient scheme for the controllable amplification of two-phonon higher-order sidebands. Beyond the conventional linearized approximation, we derive analytical expressions for the output transmission of probe pulse and the amplitude of second-order sideband by adding the nonlinear coefficients into the Heisenberg-Langevin formalism. Using experimentally achievable parameters, we identify the conditions under which the mechanical pump and the frequency detuning of control field allow us to modify the transmission of probe pulse and improve the amplitude of two-phonon higher-order sideband generation. Furthermore, we also find that the higher-order sideband generation depends sensitively on the phase of mechanical pump when the control field becomes strong. The present proposal offers a practical opportunity to design chip-scale optical communications and optical frequency combs. 5)We propose an efficient scheme to generate quadrature squeezing of higher-order sideband spectrum in an optomechanical system. That is achieved by exploiting a well-established optomechanical circumstance, where a second-order nonlinearity is embedded into the optomechanical cavity driven by a strong control field and a weak probe pulse. Using experimentally achievable parameters, we demonstrate that the second-order nonlinearity intensity and the frequency detuning of control field allow us to modify the amplitude of higher-order sidebands and improve the amount of squeezing of higher-order sideband spectrum. Furthermore, when the second-order nonlinearity is nearly ’critical point’, an optimizing quadrature squeezing of higher-order sideband spectrum can be achieved. In conclusion, this thesis deepens our awareness and understanding of the characteristics of nonlinear optics in low-dimension micro-nano structure. These investigations may have some reference value for the developments of nonlinear spectroscopy, terahertz science, precision measurement.
学术讨论
主办单位时间地点报告人报告主题
物理学院杨文星课题组 2015年11月12日 田家炳楼南205 刘少鹏 电磁诱导透明、四波混频和古斯—汉欣位移
物理学院杨文星课题组 2016年05月30日 田家炳楼南203 刘少鹏 全量子理论—相干态与压缩态
物理学院杨文星课题组 2016年06月06日 田家炳楼南205 刘少鹏 全量子理论—量子关联性
东南大学物理学院 2016年10月21日 田家炳楼南203 刘少鹏 腔光力系统中的高阶边带及光学频梳的压缩问题
东南大学物理学院 2015年04月29日 田家炳楼南205 吕新友 Squeezed Optomechanics with Phase-Matched Amplification and Dissipation
东南大学物理学院 2016年04月17日 田家炳楼南205 熊豪 光力系统中的高阶边带产生效应
东南大学物理学院 2016年05月09日 田家炳楼南205 庄佑林 Quantum theory for pulse propagation in electromagnetically-induced-transparency media beyond the adiabatic approximation
物理学院杨文星课题组 2016年05月10日 田家炳楼北407 庄佑林 Quantum squeezing in EIT-based system
     
学术会议
会议名称时间地点本人报告本人报告题目
国家自然科学基金委数学物理科学部主办 2016年12月20日 华东交通大学,南昌,江西 腔光力学中的非线性光学增强及其应用
The Materials Research Society of Singapore (MRS-S) June 18-23, 2017 Suntec Singapore Effective hyper-Raman scattering via inhibiting electromagnetically induced transparency in monolayer graphene under an external magnetic field
     
代表作
论文名称
Giant enhanced four-wave mixing efficiency via two-photon resonance in symmetric quantum wells
Effective terahertz signal detection via electromagnetically induced transparency in graphene
Tunneling-induced giant Goos–Hanchen shift in quantum wells
Coherent control of the Goos-Hanchen shift via Fano interference
Effective hyper-Raman scattering via inhibiting electromagnetically induced transparency in monolaye
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
刘博 正高 教授 博导 南京信息工程大学
盛宇波 正高 教授 博导 南京邮电大学
郭昊 正高 教授 博导 东南大学
陈世华 正高 教授 博导 东南大学
周海清 正高 教授 博导 东南大学
喻小强 副高 其他 东南大学 秘书
      
答辩秘书信息
姓名职称工作单位备注
喻小强 副高 副教授 东南大学