Electrical tuning and mode locking of an external-cavity semiconductor laser with an ultrashort (0.4 mm) fiber-Bragg-grating (FBG) reflector are studied theoretically and experimentally. Evolution of electrical tuning of longitudinal modes in a laser with broad-bandwidth FBG is analyzed theoretically. Tuning over an 11.4-nm range was experimentally possible by mechanically changing the connectorized FBG reflector in the external cavity of a diode laser package. With a 40%-reflection FBG, the external cavity laser was mode locked and generated at < 50-ps optical pulses at (6.3 ± 0.3) GHz within a broad frequency range of 600 MHz. The authors have simulated the intensity-modulation response of this laser and have shown that the broad frequency range mode locking of these lasers is determined by a chirp-related resonance rather than an external cavity resonance. The theoretical analysis agrees with the experimental results.
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