Stable single-mode operation of distributed feedback lasers with wirelike active regions

A stable single-mode operation mechanism in distributed feedback (DFB) lasers with wirelike active regions was theoretically investigated by taking into account "gain matching" between standing wave profiles of each resonant mode and periodic active regions. As a result, it was clarified that the resonant modes at the longer wavelength side of the stopband have higher modal gain than those at the shorter wavelength side and that the oscillation takes place at the longer wavelength side resonant mode nearest to the stopband. The influence of the cleaved facet with respect to the grating phase was also analyzed. The measured spectral properties of buried heterostructure GaInAsP/InP DFB lasers consisting of wirelike active regions, such as a subthreshold gain spectrum and the lasing wavelength with respect to the stop band, agreed well with theoretical results. Finally, it was confirmed that a stable single-mode operation was preserved even after a room temperature continuous wave aging of 7300 h at bias current of around 10× the threshold.