Study on the Phase Dynamics of Macroscopic Polarization by Nonlinear Interferomer

为了探索固体材料中超快相干三阶非线性响应的机理，我们开发了一种检测由光激发产生的宏观偏振相干运动的方法。通过这种方法，我们可以研究无机和有机材料中共振激发的激子和双激子的相相干性。1)非线性干涉仪我们提出了一种测量三阶非线性偏振相干性的方案，通过检测简并四波混频信号和参考光脉冲的干涉，这些参考光脉冲也来自同一光源，用于产生非线性偏振的相干激励。利用这一装置，我们检测到了非线性偏振的相干振荡。双激子在飞秒脉冲共振双光子激励下的相干振荡表明，双激子的相干振荡持续时间可达50皮秒。3)标量双激子波的更多参考我们观察了正交极化泵浦光束激发的两个双激子波的干涉。这表明双激子波具有标量波的性质。据我们所知，这是第一次观测到固体中的标量波干涉。4) GaAs量子阱中双激子相干性的检测我们将上述方法应用于不具有稳定双激子态的二维量子阱激子。我们清楚地观察到2-f相干振荡在3皮秒内衰减。5)二维激子在无烟煤晶体中的自由感应衰减通过相干泵浦探测光谱，我们观察到了无烟煤晶体中表面激子的相干振荡信号。我们研究了表面激子的协同辐射衰变的作用，即二维激子的超辐射衰变。6)激子-腔耦合系统的简并四波混频我们研究了嵌入半导体微腔的二维量子阱中激子的线性耦合对相干非线性光学响应的影响。我们观察到光子在腔内的强约束增强了相干非线性响应。在强激子-光子耦合的情况下，腔极化子的形成影响激子偏振的相干振荡。我们在弱相互作用玻色子模型的基础上建立了一个理论模型来描述这种现象。少

In order to explore the mechanism of ultrafast coherent third order nonlinear responses in solid materials, we have developed a method to detect the coherent motion of macroscopic polarization created by the optical excitation. By this method, we can investigate phase coherence of resonantly excited excitons and biexcitons in inorganic and organic materials.1)Nonlinear InterferometerWe have proposed a scheme to measure the coherence of third-order nonlinear polarization by detecting the interference of degenerate four-wave mixing signal and reference optical pulses which were also from the same light source used to create coherent excitation of nonlinear polarization. With this set-up, we have detected the coherent oscillation of nonlinear polarization.2)Observation of Coherent Oscillation of Biexcitons in CuClThe coherent oscillation of biexcitons under the resonant two-photon excitation by femtosecond pulses has shown that the coherent oscillation continues up to 50 picosecond.3)Inte … More rference of Scalar Biexciton WavesWe have observed the interference of two biexciton waves which were excited by the orthogonally polarized pump beams. This indicates that the biexciton wave has the scalar wave nature. This is, to the best of our knowledge, the first time observation of scalar wave interference in solids.4)Detection of two-exciton coherence in GaAs quantum wellWe have applied the above methods to the 2D quantum well excitons which do not have stable biexciton state. We have clearly observed 2-f coherent oscillation which decays within 3 picosecond.5)Free Induction Decay of 2D Excitons in Anthracence crystalsBy using the coherent pump-probe spectroscopy, we have observed coherent oscillation signal of surface excitons in an anthracence crystal. We have examined the role of cooperative radiation decay of surface excitons, which is known as superradiative decay of 2D excitons.6)Degenerate Four Wave Mixing of Exciton-Cavity Coupled SystemWe have studied the linear exciton-photon coupling effect on the coherent nonlinear optical responses of excitons in 2D quantum well embedded in a semiconductor microcavity. We have observed that the strong confinement of photons inside the cavity enhances the coherent noonlinear responses. In the case of strong exciton-photon coupling, the formation of cavity polartons affects the coherent oscillation of excitonic polarization. We have developed a theoretical model to describe such phenomena based on the weakly interacting boson model. Less