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Dispersive self-Q-switching in self-pulsating DFB lasers



IEEE Journal of Quantum Electronics 33 (1997), Nr.2, S.211-18
ISSN: 0018-9197
Fraunhofer HHI ()
clocks; distributed feedback lasers; laser frequency stability; laser modes; laser theory; laser tuning; laser variables measurement; q-switching; semiconductor device models; semiconductor device testing; semiconductor lasers; dispersive self-q-switching; self-pulsating dfb lasers; distributed feedback sections; additional phase tuning section; dispersive self-q-switching mechanism; high-frequency self-pulsations; single-mode type; transparency current density; operating conditions; critical detuning; bragg wavelengths; electronic wavelength tuning; current-induced heating; electrical phase-control section; two-section dfb lasers; optical clocks

Self-pulsations reproducibly achieved in newly developed lasers with two distributed feedback sections and with an additional phase tuning section are investigated. The existence of the dispersive self-Q-switching mechanism for generating the high-frequency self-pulsations is verified experimentally for the first time. This effect is clearly distinguished from other possible self-pulsation mechanisms by detecting the single-mode type of the self-pulsation and the operation of one section near the transparency current density using it as a reflector with dispersive feedback. The operating conditions for generating this self-pulsation type are analyzed. It is revealed that the required critical detuning of the Bragg wavelengths of the two DFB sections is achieved by a combination of electronic wavelength tuning and current-induced heating. The previous reproducibility problems of self-pulsations in two-section DFB lasers operated at, in principle, suited current conditions are discussed, and the essential role of an electrical phase-control section for achieving reproducible device properties is pointed out. Furthermore, it is demonstrated that phase tuning can be used for extending the self-pulsation regime and for optimizing the frequency stability of the self-pulsation. Improved performance of the devices applied as optical clocks thus can be expected.