【摘要】 本文报导了用非相干光时间延迟四波混频方法测得Ti₂O超微粒子的扩散系数和载流子复合时间分别为0.016cm²/s和1.08ns.两个光栅衰减时间分别是1.07ns和0.56ns.讨论了引起两个光橱衰减时间不同的原因.更多还原

【Abstract】 In this paper we propose a new method, which allows us to extract the carrier recombination time, diffusion coefficient and the decay time of the grating from the experimental results.According to the theory of laser-induced dynamic gratings and the phase-matching condition, we have obtained equations ( 7 )-(10). So the decay time of grating, the carrier recombination time and the diffusion coefficient can be derived from relative intensities of the constant background and the two peaks around τ= 0 and τ=-T in TDFWM-IL.Using the second harmonic of a Q-Swithed NdsYAG laser with τe= 28 ps, seting T= 230ps and θ= 7.5°, we have measured Is(τ) for TiO2 ultrafine particles in the organosols as shown in Fig. 3. The intensity of the τ= -T peak is much weaker than that of the τ= 0 peak. This phenomenon can not be attributed to carrier diffusion because the size of the ultrafine particle is much smaller than the period of the two gratings, carriers are effectively confined in the particles. We attribute I, (-T)/I,(0)<1 to the Brownian movement, which delocalize the excited particle makes the small period grating suffer more serious deterioration than the large period one. By Eq. (7)-(10) we have got T11= 1.07ns, T12=0.56ns, TR=1.08ns, and D=0.016cm2/s. In Fig. 3,the two peaks are symmetric about τ=0 and τ=-T, respectively, with a constant background and separated by T= 230 ps, just as the theory predicted.更多还原