Wavelength Tunable Laser Diodes and Their Applications

Abstract

Single mode laser diodes with an electronically tunable wavelength are among the key components needed for advanced applications in optical communications, measurement and sensing. In particular, these devices may be used as wavelength controllable transmitters in wavelength division multiplexing or as local oscillators in optical receivers using the coherent detection technique. Furthermore, distance measurements with a high accuracy and large repetition frequency as well as threedimensional viewing are feasible using the frequency modulated continuous wave radar technique in the optical domain. Also numerous measurement techniques in optoelectronics and fiber optics can be performed by means of wavelength tunable lasers. This paper reviews the recent progress made on electronically wavelength tunable laser diodes in the InGaAsP material system at 1.5 11m wavelength. The operation principles and technological approaches of the various device concepts are presented and the laser parameters relevant for anticipated applications, such as tuning range, spectral linewidth and wavelength access, are discussed.The continuous and discontinuous tuning modes are introduced, compared and the physical limitations with respect to the maximum tuning ranges are commented on. Particular attention is paid to device handling and the effort needed for wavelength control which are most important for practical applications.