A special sampling structure based on the double exposure technology is proposed to achieve dual-wavelength lasing in
the distributed feedback (DFB) fiber laser. This structure is composed of two grating pitches in one sampling period,
which could be realized by changing the fiber's length in the fabrication. And through employing an equivalent phase
shift, only a submicrometer-level precision is required for precise phase control. Then a stable dual-wavelength laser
with the spacing of 400pm is obtained in the experiment successfully. The output power is 30.46uW and the SMSR is
46dB under a pumped power of 146mw.
A complex-coupled DFB Laser with the sampled grating has been designed and fabricated. The +1<sup>st</sup> order reflection of
the sampled grating is utilized for laser single mode operation, which is 1.5387μm in the experiment. The typical
threshold current of the device is 30mA, and the optical output power is about 10mW at the injected current of 100mA.