MODE SELECTION AND SPATIAL HOLE BURNING SUPPRESSION OF A CHIRPED GRATING DISTRIBUTED FEEDBACK LASER

A new kind of distributed feedback (DFB) laser with a linearly chirped grating is proposed and investigated theoretically for the first time. The eigenmodes of the chirped grating DFB (CG-DFB) and the field intensity distribution are calculated. With a suitable cavity length and chirp factor, the threshold gain difference to the next competence mode can be very large and will keep the single longitudinal mode stable. The chirp factor can be chosen to make the field intensity distribution quite uniform and at the same time keep the threshold gain difference large. This behavior effectively suppresses spatial hole burning and hence makes CG-DFB lasers that are stable single mode at high power, and with a narrow linewidth.