Two-section semiconductor lasers subject to optical feedback

Two section semiconductor lasers are devices that can give bistability and self-pulsation by systematic, independent variation of the bias injection current to the two sections of the device [1]. These features are used in photonic switching and clock synchronisation applications. Recently, we observed the generation of a broadband, multi-mode output (> 2 THz) caused by modulation of a two section semiconductor laser [2]. This type of operation has not been reported previously to our knowledge. The two-section lasers are multi-mode (4-5 modes) in free-running operation (both sections tied together electrically). In this study the spectral output of a two-section laser subject to both optical feedback and differential bias to the absorber and laser section has been measured. There are features in common with both single section lasers subject to optical feedback [3] and two-section lasers subject to modulation [2].