Trend and applications of tunable semiconductor lasers

Tunable semiconductor lasers have been under intense research interests for the past decades due to their vast applications in optical networks, optical characterization, and optical sensing. The required device characteristics can be very different for applying the tunable lasers to various areas. We classify the tunable lasers in terms of their tuning characteristics and switching speed. Four kinds of tunable lasers are described in this paper to manifest the application-dependent device structures and performance. The applications include the use of sampled grating based lasers to form multi-wavelength laser arrays, cascaded distributed-feedback lasers for multi-gas sensors, wavelength-selectable laser arrays for fast wavelength switching sources, and short cavity lasers for fault monitoring in passive optical networks.