超低温下掺Er^(3+)玻璃的相干拍频调制效应研究  

Study of Coherent-Beat Modulation in Er^(3+)-Doped Glass at Ultra-Low Temperature

作　　者：李玉琼[1] 张扬[1] 沈建琪[1] 

机构地区：[1]上海理工大学理学院,上海200093

出　　处：《光学学报》2011年第11期237-240,共4页Acta Optica Sinica

摘　　要：采用非相干光时延四波混频(TDFWM-IL)实验装置,在7K温度下,利用波长为800nm的飞秒脉冲激光,观测到掺Er3+玻璃的光子回波效应,发现信号随延时变化的拍频调制结构。根据TDFWM-IL多能级理论,运用其非均匀加宽占主导时的公式拟合实验结果,从最佳拟合获得的退相时间T2=300fs,这与由相干控制实验测得的相一致。并且研究了调制参数c对相干拍频调制结构的影响。发现样品光子回波拍频调制结构的出现是在低温下,受体系多个激发态子能级相干效应影响。当样品温度逐渐升高,相干拍频调制结构消失,此时样品的光子回波图像特征类似于TDFWM-IL二能级系统。从而为研究低温下稀土材料的相干瞬态光谱提供了一个新的理论依据。The photon echo of the Er2 03 -doped TeO2-Nb2Os-ZnO glass is observed on the time-delay four-wave mixing with incoherent light （TDFWM-IL） experimental setup, at the temperature 7K and with the femtosecond pulse laser of 800 nm wavelength. Moreover, the interference-beat modulation of signal intensity versus delay time is found in the experiment. According to the multi-level theory of TDFWM-IL, the experimental result is fitted with the theoretical formula when the inhomogeneous broadening is dominant. The dephasing time T2- 300 fs is gotten when the fitting is the best . Then the influence of the modulation parameter c on the structure of beat frequency modulation is studied. It is found that the photon echo beat frequency modulation structure appeares at the ultralow temperature, because it is affected by the coherent effect of the coherent excited states of many sub-levels. When the temperature gradually increases, the coherent-beat modulation structure disappeares, then the feature of the photon echo is similar to the TDFWM-IL two-level system. Thus a new theoretical basis for the coherent transient spectroscopy study of the rare earth materials at low temperature is provided.

关 键 词：非线性光学 光子回波 相干拍频调制 非相干光时延四波混频 超低温 掺Er3+碲酸盐玻璃 

分 类 号：O482.3[理学—固体物理]