OPTICAL Stark EFFECTS AND OPTICAL NONLINEARITY AT LOW-DIMENSIONALLY CONFINED EXCITONS IN LAYERED CRYSTALS

层状晶体中低维约束激子的光学斯塔克效应和光学非线性

• 批准号: 02452043
• 负责人: KARASAWA Tsutomu
• 金额: $ 4.29万
• 依托单位: Osaka City University of Science
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1990
• 资助国家: 日本
• 起止时间: 1990 至 1992
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-02452043/
• 关键词: Layered Crystals; Bismuth Iodide; Stacking Fault Exciton; Optical Stark Effect; Nonlinear Electric Susceptibility; Quantum Confined Effect; Degenerate Four-Wave-Mixing; Dephasing Process

In this study, several mechanisms of nonlinear optical responses have been clarified especially in the low-dimensionally confined exciton systems at stacking disorders in layered crystals. A theoretical research on basic processes in a highly excited exciton system has been done. Main results obtained are as follows: 1. Transient absorption spectra at the qusi two-dimensional exciton system localized at specific stacking fault in BiI_<delta> have been investigated up to the pico second time region by means of the pump-probe method. (1) The optical Stark effect by the pump-field was clearly observed. The spectral change was analyzed on the basis of "dressed exciton model". As a result, extraordinarily large non-linear susceptibility was obtained reflecting a large electric-dipole moment in this system. (2) It turns out that even after the pump-field, really excited high-density excitons interact with each other resulting in the spectral change characteristic in the two-dimensional syste … More m. (3) From the degenerate four-wave-mixing measurements, the dephasing mechanism was made clear: under the low excitation, the intra-band LA-phonon scattering governs the dephasing process, while for the high excitation, exciton-exciton scattering becomes dominant in the process. (4) Other nonlinear optical responses: the bi-exciton state coexists with the high density exciton phase, and the occurrence of bistability with respect to the density was observed.2. Besides the above results, we observed the induced Raman lines in BiI_3, and SBI_3 crystals. Furthermore, we found that under the hydrostatic pressure, a new exciton transition appears in SBI_3, which gives a new information on quantum confined exciton states.. We studied an electron-hole system in a direct gap semiconductor which is coherently excited by a high-intensity laser. Using a mean-field approximation, we have showed that the many body effects via the screened Coulomb interactions bring about the density bistability with respect to the frequency of the laser field, in which a low density state is regarded as the exciton gas and a high density state is the BCS state of electron-hole Cooper-pairs. Less

在本研究中，阐明了几种非线性光学响应机制，特别是在层状晶体中堆叠无序的低维受限激子系统中。对高激发激子系统的基本过程进行了理论研究。主要研究结果如下：1。用泵浦探针法研究了BiI_< δ >中特定层错处准二维激子系统在皮秒范围内的瞬态吸收光谱。(1)清楚地观察到泵场的光学斯塔克效应。根据“盛装激子模型”对光谱变化进行了分析。结果表明，该系统具有非常大的非线性磁化率，这反映了该系统具有较大的电偶极矩。(2)结果表明，即使在泵场作用后，真激发高密度激子之间的相互作用也会导致二维系统的光谱变化特征。(3)通过简并四波混频测量，明确了脱相机制：低激发下，带内la声子散射主导了脱相过程，而高激发下，激子-激子散射主导了脱相过程。(4)其他非线性光学响应：双激子态与高密度激子相共存，并观察到与密度相关的双稳性。除上述结果外，我们还观察到了BiI_3和SBI_3晶体的诱导拉曼线。此外，我们发现在静水压力下，SBI_3中出现了一个新的激子跃迁，给出了量子限制激子态的新信息。研究了高强度激光相干激发下直接间隙半导体中的电子-空穴系统。利用平均场近似，我们证明了通过屏蔽的库仑相互作用产生的许多体效应导致密度与激光场频率有关的双稳定，其中低密度态被认为是激子气体，高密度态被认为是电子-空穴cooper -对的BCS态。少

项目成果

S.Takeyama: "Magneto-optical effects of exciton in Bil_3 crystals under pulsed high magnetic fields.I.Indirect and direct excitons" Physical Review. B41. 4513-4523 (1990)

S.Takeyama：“脉冲高磁场下 Bil_3 晶体中激子的磁光效应。I.间接和直接激子”物理评论。

I.Akai: "Picosecond time resolved spectra of the optical Stark effects on the stacking fault excitons in Bil_3 crystals" Mol.Cryst.Liq.Cryst.218. 25-30 (1992)

I.Akai：“Bil_3 晶体中堆垛层错激子光学斯塔克效应的皮秒时间分辨光谱”Mol.Cryst.Liq.Cryst.218。

K. Oimatsu: "Excitonic polariton effects in an optical waveguide with a quantum well" J. Luminescence. 48/49. 721-724 (1991)

K. Oimatsu：“具有量子阱的光波导中的激子极化子效应”J. Luminescent。

M. Ichida: "Dephasing processes on the stacking-fault excitons in BiI_3" Physical Review. B 47. 1474-1482 (1993)

M. Ichida：“BiI_3 中堆垛层错激子的相移过程”物理评论。

T.Karasawa: "Ultrafast Nonlinear Optical Response and High Density Excitation Effects of the Stacking Fault Exciton in Bil_3" Appl.Phys.A.53. 480-490 (1991)

T.Karasawa：“Bil_3 中堆垛层错激子的超快非线性光学响应和高密度激发效应”Appl.Phys.A.53。