Bristow M P
Appl Opt. 1998 Sep 20;37(27):6468-79. doi: 10.1364/ao.37.006468.
The application of photomultiplier gain modulation to the compression of wide-dynamic-range lidar signals is investigated in relation to the effect of the gain level on anode-signal linearity. Gain reduction is achieved by the coupling of modulation signals through either multidynode or focus-grid gating networks. This technique facilitates signal recovery and prevents detector nonlinearity and dynode damage caused by high near-field lidar signals. The measurements were performed in the current mode primarily on a 50-mm-diameter, 12-stage photomultiplier (EMI 9214) with a bialkali photocathode. With 3- or 4-dynode-based modulation made at a photomultiplier voltage of 1300 V and a gain of 1 x 10(7), signals of ~6 mA can be maintained at the 1% linearity limit from 100% to 0.2% modulation, corresponding to a 500-fold reduction in the lidar-signal dynamic range. A significant advantage to dynode modulation is that it preserves the shot-signal-to-noise ratio of the incoming signal, which is not true for focus-grid modulation or external predetection schemes such as controlled obscuration or Pockels-cell modulation that attenuate the as-yet unamplified signal.
研究了将光电倍增管增益调制应用于宽动态范围激光雷达信号压缩，并探讨了增益水平对阳极信号线性的影响。通过调制信号经多倍增极或聚焦栅极选通网络耦合来实现增益降低。该技术有助于信号恢复，并防止高近场激光雷达信号导致的探测器非线性和倍增极损坏。测量主要在电流模式下，使用直径50毫米、12级、带有双碱光电阴极的光电倍增管（EMI 9214）进行。在光电倍增管电压为1300 V、增益为1×10⁷的情况下，基于3或4个倍增极进行调制时，在100%至0.2%调制范围内，~6 mA的信号可维持在1%线性度极限，对应激光雷达信号动态范围降低500倍。倍增极调制的一个显著优点是它能保持入射信号的散粒信噪比，而聚焦栅极调制或诸如受控遮蔽或普克尔盒调制等外部预检测方案则不然，这些方案会衰减尚未放大的信号。
