Silicon Photonics: Fundamentals and Devices

8.1 Introduction

A (silicon) photodetector is a solid-state transducer that is used for converting light energy into electrical energy [1, 2]. This conversion of the transduced incident light into an electronic representation allows for a diversity of applications because processing, storing, or transmitting electronic images 3 now becomes relatively easy and fast with modern semiconductor integrated circuits and electronic systems. As an example, compared to the earlier photographic methods, solid-state imagers allow for much faster viewing of the images and their easier manipulations since they are in digital format [4–11]. As historical information, we note that some of the earliest digital images of the Apollo and Explorer space missions opened new horizons for digital-imaging technologies. This was further solidified by later deep-space pictures from the Hubble space telescope. In fact, in the past four decades, digital imaging has opened up fantastic new horizons in space explorations and in science.

Another major application of photodetectors is in optical fiber communications systems – the high-speed communications technology that currently brings information to us over long distances [1, 2]. The basic components of an optical fiber communications systems are the transmitter, the transmission medium, and the photoreceiver, and these are schematically shown in Figure 8.1. In the transmitter, there is also an optical encoder, through which the information signal in electronic ...