Frequency-tunable semiconductor lasers

Recent advances in frequency-tunable semiconductor lasers are reviewed. They are classified into hybrid and monolithic tunable lasers. Monolithic tunable lasers based on distributed Bragg reflector or distributed feedback laser structures are most attractive for practical applications. The device structures and the tuning characteristics are described, with emphasis on the tuning range, spectral linewidth and frequency-switching time. Recent system experiments using monolithic tunable lasers in an optical communication area are also described.An Invited Paper