Characteristics of single-longitudinal-mode selection in short-coupled-cavity (SCC) injection lasers

Effective single-longitudinal-mode selection can be achieved in short-coupled-cavity (SCC) injection lasers consisting of a cleaved short-cavity laser (length
L
, refractive index
n
) with a short external resonator (spacing d). The mode-selectivity is due to the combined advantages of large gain-rolloff for the adjacent modes in the short ( cavity, and resonator-loss-modulation in the coupled cavity. This I paper discusses the theoretical considerations and experimental studies for the SCC lasers. The results show that for good single-longitudinal-mode operation, the resonator-loss modulation period factor
m
, given by the effective optical length ratio
nL/d
, should be between approximately three and eight, with typical short-cavity laser length
L
in the
40-100-\mu
m range and external resonator spacing
d
also in the
40-120- \mu
m range, depending on the specific
L
.