Abstract
High speed photodetectors operating at a telecommunication band (from 1260 to 1625 nm) have been well studied with the development of an optical fiber communication system. Recent innovations of photonic systems have raised new requirements on the bandwidth of photodetectors with cutoff wavelengths from extended short wavelength infrared (eSWIR) to long wavelength infrared (LWIR). However, the frequency response performance of photodetectors in these longer wavelength bands is less studied, and the performances of the current high-speed photodetectors in these bands are still not comparable with those in the telecommunication band. In this paper, technical routes to achieve high response speed performance of photodetectors in the extended short wavelength infrared/mid wavelength infrared/long wavelength infrared (eSWIR/MWIR/LWIR) band are discussed, and the state-of-the-art performances are reviewed.
Highlights
Semiconductor photodetectors convert incident light into electrical current with advantages in reliability and fast response speed
Compared to solid core silica fiber, hollow core photonic bandgap fiber which operates at 2 μm wavelength with lower nonlinearity and ultra-low latency [2], together with the thulium doped fiber amplifier which provides wide wavelength demultiplexing (WDM) bandwidth [3], can potentially enable the higher capacity of optical communication system at around 2 μm [4,5,6,7,8]
It is noted that uni-traveling carrier (UTC) photodiodes can be used for high power application in the near infrared band, which indicates these MWIR UTC photodiodes may be potentially used in an optical heterodyne technique with a powerful local oscillator as well. The bandwidth of this first MWIR UTC device is lower than expected with such a thin absorber layer; the potential reason may be due to low mobility of InAs/GaSb and InAs/AlSb SLs especially in the carrier transport direction [104,105]
Summary
Semiconductor photodetectors convert incident light into electrical current with advantages in reliability and fast response speed. Compared to solid core silica fiber, hollow core photonic bandgap fiber which operates at 2 μm wavelength with lower nonlinearity and ultra-low latency [2], together with the thulium doped fiber amplifier which provides wide wavelength demultiplexing (WDM) bandwidth [3], can potentially enable the higher capacity of optical communication system at around 2 μm [4,5,6,7,8] These raise the demands for high-speed photodetector functioning in the 2-μm band. Thanks to the very close lattice constant between HgTe and CdTe, it is possible to grow Hg1−xCdxTe alloy with cut-off wavelength from 1 to 30 μm [19] These HgCdTe photodetectors can absorb the IR radiation across the fundamental energy gap, and have high quantum efficiency due the large optical absorption coefficient. QDIPs generally have a low quantum efficiency and absorption coefficient due to the small fill factor of QDs and inhomogeneous broadening of the self-assembled QDs [37]
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