实验研究了具有pn结结构的碲镉汞光电二极管的双光子吸收.激发光源采用了皮秒红外脉冲激光.尽管入射光子能量仅为碲镉汞材料带隙的60%左右, 在光电二极管两电极端仍然观察到了显著的光伏响应信号.利用线性关系拟合双对数坐标系下光伏响应与入射光强的关系, 发现两者呈现二次幂函数增强趋势, 表明这种光伏响应是一种典型的双光子吸收过程.通过调节光电二极管两端的反向偏压, 空间电荷区内的双光子吸收系数可比耗尽层外的强致130倍, 这种双光子吸收系数的场致增强现象可归因为双光子吸收的FK效应所致.对比空间电荷区内外双光子吸收产生的光生载流子数量, 证实空间电荷区内的双光子吸收会强烈地影响器件的光伏响应.

An experimental study of two photon absorption(TPA) in the HgCdTe pn junction detectors was reported. The excitation light source was a picosecond pulsed infrared laser. Even the incident photon energy was about 60% of HgCdTe(MCT) bandgap, an obviously photo-response was still observed. Quantification dependence of the peak amplitude on the incident intensity presented a slope of 2 by linear fitting to the experimental data in log-log coordinate, which indicated that the photo-response exhibited a quadratic power dependence on the incident intensity, suggesting a typical TPA process. The two photon absorption coefficient(TPAC) inside the space charge region(SCR) is as high as 130 times that of outside the depletion region which can be attributed to the TPA Franz-keldysh effect.