Thermally induced chirp studies on spectral broadening of semiconductor laser diode arrays

Spectral-width broadening has many factors. Diode lasers are not always monochromatic due to several broadening mechanisms, widening the energy distribution of emitted photons. In this paper, we report the two main factors affecting time average spectral-width broadening of a laser diode array (LDA)-a transient rise of the active region temperature of an LDA due to injection current, and the temperature and stress nonuniform distribution of different emitters within an LDA. We find that temperature and stress nonuniformity broadens the spectral width by almost 0.1-1.0 nm as a function of different operating conditions, while the thermally induced chirp that is attributed to injection current plays a more signification role in spectral-width broadening.