基于TiO_2纳米粒子薄膜的低阈值随机激光器的动力学研究

Dynamics of low-threshold random laser based on TiO_2 nanoparticle films

本文利用共轭聚合物(MEH-PPV)覆盖TiO_2纳米粒子薄膜制作随机激光器。随机TiO_2纳米粒子薄膜的激光辐射阈值比平面MEH-PPV薄膜的放大自发辐射阈值缩小了9倍。这是由于TiO_2纳米粒子诱导的多重散射造成的。进一步的飞秒荧光上转换实验表明,随机激光器中,光在增益介质里的停留时间有所增加,这直接证实了光在随机激光器结构中的多重散射引起光的传播路径增加。因此,这会促进更多的光发生辐射,从而降低随机激光器的阈值。

We have prepared random lasers with conjugated polymer（ MEH-PPV） coated on TiO2 nanoparticle films. The threshold of the lasing based on random TiO2 nanoparticle film is significantly reduced by a factor of9 in comparison with the amplified spontaneous emission（ ASE） threshold of the flat MEH-PPV film,which is caused by multiple scattering induced by TiO2 nanoparticles. Further investigation by femtosecond fluorescence up-conversion experiment reveals that the dwell time of light inside the gain medium is increased in the random laser device,which directly confirms that light travels longer path due to the multiple scattering in the random structure. So it stimulates the emission of more light and the threshold of the random laser is lowered.