Fourier-transform-limited, single-mode picosecond optical pulse generation by a distributed feedback InGaAsP diode laser

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Abstract
The first generation of bandwidth-limited, single-mode ultrashort optical pulses with excellent coherency from a distributed feedback InGaAsP diode laser at 1.3 μm by the method of strong rf modulation superimposed on the dc bias current is reported. It was realized only by the laser diode itself with no requirement of any other optical elements or external cavity or careful optical control. The measurement of time-bandwidth product of the generated coherent picosecond pulses at 500-MHz modulation gave the value of 0.38 for Lorentzian pulse shape with a full width at half-maximum of nearly 34 ps, which proved definitely the Fourier-transform-limited character. By changing the dc bias current from positive to negative, the pulse width was demonstrated to be continuously controllable over a range of approximately twice to three times depending upon the modulation frequency.