采用脉冲测试电路，测试了半绝缘GaAs光导开关(PCSS)在锁定工作模式下的偏置电场及触发光能阈值。测试结果表明，在一定光能范围内，电场阈值随光能阈值的增大类似于指数关系减小；激励光能在数10 μJ下，半绝缘光导开关偏置电场阈值为9 kV/cm。当激励光脉冲能量大于0.78 mJ时，光导开关在不同偏压下都不能工作于锁定工作模式而进入线性模式。依据实验测试结果，提出了高倍增偶极畴模型，给出了半绝缘GaAs光导开关的电场与光能阈值的计算结果，在实验误差范围内，理论分析与实验测试结果符合。

As for semi-insulating GaAs photoconductive semiconductor switch (PCSS) operated in lock-on mode, threshold conditions of biased electric field and optical excitation energy are measured by a pulsed circuit. Experimental results show that the field threshold has an analogy to inverse exponential dependence on the optical energy threshold. PCSS can be triggered into lock-on mode with 9 kV/cm when the optical energy is on the order of 10 μJ; and with the optical energy above 0.78 mJ, PCSS will be operated in linear mode but not lock-on mode for different voltages. On basis of the results, high-gain dipole domain model is proposed to analyze electric field and optical energy thresholds of the PCSS. The results from the experiments and calculation are in good agreement within the measurement error.