Continuously tunable laser diodes: longitudinal versus transverse tuning scheme

The operating principles and performances of the two most powerful approaches to monolithic tunable laser diodes-the longitudinally integrated three-section (3S) distributed Bragg reflector (DBR) laser and the transversely integrated tunable twin-guide (TTG) distributed feedback (DFB) laser-are described and compared. Both laser configurations are capable of being continuously tuned over several nanometers. The practically useful tuning range strongly depends on structure geometry parameters and is limited by either the required amplification or the tuning densities. It is shown that, with comparable parameters, the useful continuous tuning range of the TTG-DFB laser is 30% larger than that of the 3S-DBR laser. Wide-range continuous tuning of the TTG-DFB laser requires only a single control current, which is particularly advantageous for the manufacture and design of the wavelength control circuitry