Pure frequency modulation of a multielectrode distributed-Bragg-reflector (DBR) laser diode

Intensity-modulation suppressed frequency modulation (FM) is demonstrated over a 600-MHz bandwidth by using a three-electrode distributed-Bragg-reflector (DBR) laser diode (LD). A nonuniform carrier-density distribution in the active region is realized by two separated electrodes, whose push-pull modulation yields only a 0.7% intensity fluctuation per 1-GHz frequency deviation. This corresponds to a 20-dB FM purity improvement. A third electrode on the DBR region makes it possible to tune the wavelength simultaneously. Because of its wider modulation bandwidth, the LD is suitable for the lightwave oscillator in frequency-shift-keyed (FSK) transmissions and for linewidth reduction by electrical feedback.<
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