Development of shot Optical pulse generators using semiconductor lasers

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We have investigated mainly the following four topics to develope short optical pulse generators.(1) Coherent photon seeding of acitively mode locked laser diodesWe have applied the coherent photon seeding technique to actively mode locked laser diodes for the first time and successfully achieved a single longitudinal laser diode mode operation.We also proposed a modified fiber cavity for obtaining single longitudinal laser diode mode operation in active mode locking.It has been shown that if a fusion spliced plane is incorporated inside the single mode fiber cavity, the reflection from it can provide the feedback necessary for coherent photon seeding(2) Suppression of multiple pulse formation by gain quenchingWe have proposed a new method for obtaining high-power short optical pulses without trailing pulses from an actively mode-locked laser diode. To quench the residual optical gain, a part of the output is reflected back into the laser diode with the orthogonal polarization and the appropriate time delay. A numerical analysis using traveling-wave rate equations shows that trailing pulses caused by both the excess gain and the residual reflection at the laser diode facet are drastically suppressed.(3) Optical pulse generation by polarization self-switching in laser diodesOptical pulses with a continuously tunable repetition rate has been generated through a polarization self-switching effect in an external cavity laser diode modified by the insertion of a slightly tilted quater-wave retardation plate.(4) Mode-locking of an erbium doped fiber laser with an laser diode absorber amplifierWe have obtained self-Q-switching and self-mode-locking in an erbium doped fiber laser which has an InGaAsP LD as a saturable absorber.Active mode-locking using an LD modulator has been also achieved.