Noise Properties and Time Response of Superlattice and Conventional Avalanche Photodiodes

在光波通信系统中，在光束上传递信息并例如通过光纤传输信息是一个方面。第二个同样重要的方面是在接收端提取信息。必须这样做，以便在复制原始信息时具有较小的失真。这样做的重要之处在于，在接收信号从光转换回电信号后，增加(放大)接收信号的强度。否则，总信号强度将太弱，不能用由总接收过程贡献的随机电信号(噪声)来完成。第二种方法是放大输入的光信号，而不是转换后的电信号，然而，至少在目前看来，以电子方式放大似乎更有利。原因有两个：在放大过程中增加了固有的噪声，以及可以产生的放大幅度。在这两个方面，电子放大都比现在更好。本提案涉及在伴随噪声最小的情况下对光学信息进行电子放大的重要方面。新型人工泰勒德电子材料有望提供比更传统的自然材料更好的性能。了解噪声的产生、材料设计和放大过程是至关重要的，也是当前工作的中心主题。

In a lightwave communications system imparting information on a lightbeam and transmitting it, for instance through a fiber, is one aspect. A second and equally important aspect is the extraction of the information at the receiving end. This must be done so as to have little distortion in the reproduction of the original information. Of importance in doing this is increasing the strength of (amplifying) the received signal after it has been converted from light back to an electrical signal. Otherwise the overall signal strength would be too feeble to complete with random electrical signals (noise) contributed from the overall receiving process. A second approach would be to amplify the incoming optical signal rather than the converted electrical signal, however, for the moment at least it appears more favorable to amplify electrically. The reason is two-fold: inherent noise added in the amplification process, and the amplification magnitude that can be produced. On both accounts, electrical amplification is superior up to the present. The present proposal deals with the important aspects of electrical amplification of optical information with a minimum of accompanying noise. New artificially taylored electronic materials promise to provide better performance than more conventional natural materials. Understanding the noise generation, the materials design, and amplification processes are crucial and are the central topics of the present effort.