ABSTRACT
The term ‘‘near-infrared’’ or NIR is most commonly used with reference to a wavelength spectral range
between 0.7 and 2.0mm. This portion of infrared is of paramount importance in several applications,
first among them are the optical communications with transmission windows located at 0.85, 1.3, and
1.55mm, corresponding to GaAs-based laser emission and to two minima in attenuation for standard
silica fibers, respectively. Moreover, wavelength division multiplexing for high-capacity links encourages
to using the whole interval between 1.3 and 1.6mm (S, C, and L bands). Due to the growing demand
for wideband internet and massive data transmission, applications have shifted from long-haul point-
to-point connections to local networks down to subscribers, softening the specifications and opening
entirely new markets [1]. In addition to communications, NIR spectroscopy is employed in remote
sensing of the environment, monitoring of industrial processes, biology, and medicine. For example,
water has absorption lines that allow to detect its content in the flora for fire prevention [2], various gas
species exhibit NIR absorption bands useful for emission or toxicity analysis [3]. In addition, NIR
spectroscopy has been exploited for DNA sequencing [4], brain activity mapping [5], and cancer
detection [6]. However, since optical fiber communications remain the main field driving research in
NIR detectors, this chapter will focus on NIR detectors on silicon from the receiver standpoint.
