强光下多像素光子计数器超动态范围的实验证明与机理分析

摘要

现有理论认为多像素光子计数器(MPPC)的动态范围由其雪崩的单元总数决定,如果一个MPPC的单元数为1 000,那么它同时能够探测到的光电子数最多为1 000个.只有激发光脉冲的宽度大于MPPC输出的雪崩脉冲的宽度时,MPPC的一个单元才可以发生多次雪崩,从而使能够探测到的光子数增加.文中利用皮秒短脉冲激光实验分析MPPC的动态范围特性.结果表明,即使入射光脉冲的宽度远小于MPPC输出的雪崩脉冲的宽度,在入射光强度较大时,MPPC输出信号的幅度也可以数倍于其单元总数等效的幅度.在MPPC正常工作时,MPPC的非高电场区(即所谓的死区)也有一定的增益,约为250,高场区的增益在105以上;MPPC的非高电场区应工作在雪崩光电二极管的线性模式.%Theoretically,the dynamic range of a Multi-Pixel Photon Counter(MPPC)is considered to be limited by the total number of pixels of MPPC.Thus the maximum detectable photoelectron number is equal to the total pixel number of MPPC.More avalanches could be triggered in a single pixel only if the width of the pulsed incident light is larger than that of the output avalanche pulse of MPPC.In this paper,the dynamic range characteristic of MPPC is analyzed with pico-second short laser pulses.The results show that when the intensity of the incident light is large,the amplitude of the output signal of MPPC is several times larger than that of the total number of pixels,even if the width of the incident light pulse is far smaller than that of the output avalanche pulse of MPPC.The non-high electrical field region in the MPPC also has its own gain but smaller than the gain in the high electrical field region.The gain in the non-high electrical field region is about 250,while the gain in the high electrical field region is about 105.The non-high electrical field region should be working in the linear mode avalanche photodiode (APD).