雪崩倍增低温砷化镓高功率光电导太赫兹辐射源研究

In the proposal, a low-temperature-grown GaAs (LT-GaAs) photoconductive antenna device will be developed to generate sub-ps electric pulse and terahertz (THz) radiation with high electrical field source, and the physical mechanism of carrier avalanche multiplication of LT-GaAs biased by high electrical field and triggered by fs laser, preparation of photoconductive antenna chip and the integral insulation will be fully investigated. By analysing the transient constraint condition and the cascade process of optical excitation charge domain (OECD) in LT-GaAs biased by high electrical field from the generation to the quencher, the avalanche multiplication caused by photo-induced collision ionization and with the expression form of OECD, and the transient distribution and transport mechanism in the LT-GaAs triggered by fs laser with nJ pulse energy will be found.The distribution of electrical field in an on-state LT-GaAs chip will be improved by optimizing the performance of LT-GaAs material, and a mature scheme will be obtained to generate THz radiation with high electrical field from a LT-GaAs antenna by controlling the carrier avalanche multiplication using the quench mode of OECD. And LT-GaAs photoconductive antennas will be fabricated with the time-domain pulse width of less than 0.6 ps, the average power of 60 mW, the signal-to-noise ratio of higher than 20000 and the bandwidth of 0.1-10.0 THz.

围绕能产生亚皮秒电脉冲及强太赫兹（THz）电磁辐射的高功率低温砷化镓（LT-GaAs）光电导天线器件，对飞秒激光触发强电场偏置下LT-GaAs的载流子雪崩倍增机制、光电导天线芯片制备和整体绝缘进行深入研究。通过分析强电场下LT-GaAs内光激发电荷畴从产生到猝灭的瞬态约束条件和级联过程，认识在nJ量级飞秒激光作用LT-GaAs时，因光致碰撞电离引起的、以光激发电荷畴为表现形式的载流子雪崩倍增行为，以及载流子瞬态分布及输运的物理机制，通过改进LT-GaAs芯片材料的性能来改善触发导通瞬态过程中LT-GaAs芯片内电场的分布，得出成熟的利用光激发电荷畴的猝灭模式来控制并调节LT-GaAs产生具有载流子雪崩倍增机制的强THz辐射的方案，研制出时域脉冲宽度小于0.6ps、辐射THz电磁波平均功率大于60mW、信噪比高于20000、频带宽度0.1-10.0THz的LT-GaAs 光电导天线器件。

研究了产生亚皮秒电脉冲及强太赫兹（THz）电磁辐射的高功率低温砷化镓（LT-GaAs）光电导天线器件，通过理论与实验，得出飞秒激光触发强电场偏置下LT-GaAs的载流子雪崩倍增机制、雪崩倍增猝灭的物理机制，以及低温砷化镓光电导辐射源（LT-GaAs PCA）在飞秒激光触发条件下因光激发电荷畴猝灭模式所呈现出的瞬态载流子雪崩倍增机制的物理解释及有关实验结果。获得了强电场偏置下用LT-GaAs PCA产生强THz辐射时芯片内部载流子瞬态分布及输运的物理规律。改善了触发导通瞬态过程中LT-GaAs PCA芯片电场的分布，达到抑制闪络和防止丝状电流的形成。通过LT-GaAs PCA的材料处理、结构设计、制备工艺等，实现了用nJ量级的飞秒激光脉冲触发LT-GaAs PCA进入雪崩倍增工作模式，实验重复性及稳定性良好，也是目前国际上弱光触发LT-GaAs PCA雪崩倍增的最小值；掌握了LT-GaAs PCA雪崩倍增猝灭的客观规律，已实现在1.25 ns时间内使得LT-GaAs PCA从雪崩倍增状态猝灭，这个结果能够使LT-GaAs PCA在80 MHz重复频率的飞秒激光脉冲下工作。研制出时域脉冲宽度约0.6ps、单次触发辐射THz电磁波平均功率约数十mW、信噪比高于20000、频带宽度0.1-4.0THz的具有雪崩倍增机制的LT-GaAs PCA器件。