Highly attenuating external cavity for picosecond-tunable pulse generation from gain/Q-switched laser diodes

The authors analyze in detail the behavior of gain/Q-switched Fabry-Perot laser diodes coupled to a highly attenuating, selective external cavity. Radical differences are shown as compared to the case of strong external feedback used in mode locking. A strong analogy with the case of pulsed lasers with a small quasi-monochromatic injection signal is indicated. Strong chirping is observed in single-mode emission, leading to tunable picosecond pulses after compression. Experiments are carried out on two types of devices. Picosecond pulses with very high tunability (40 nm) and repetition rates (>10 GHz) are obtained from 1.3- mu m gain-switched laser diodes, the minimum pulsewidth being 2.5 ps.<
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