H. Ghafourishiraz et Cyj. Chu, ANALYSIS OF THE SPECTRAL LINEWIDTH OF 3-CAVITY SEMICONDUCTOR-LASER DIODES, Fiber and integrated optics, 13(1), 1994, pp. 1-16
The spectral linewidth for a semiconductor laser diode coupled to two
external cavities (known as a three-cavity laser diode) is studied in
the article. A closed-form expression for the linewidth of this laser
is derived by analyzing the number of photons in the laser cavity. It
is found that, because of the optical feedback provided by the externa
l cavities, rite photon lifetime becomes longer than that of a solitar
y Fabry-Perot (FP) laser, hence reducing the value of the spectral lin
ewidth. Our theoretical investigations reveal that the linewidth of a
three-cavity laser can be reduced further by using external mirrors wi
th high reflectivities and using anti-reflection (AR) coatings on the
laser diode facets. We have also studied the effects of uncertainties
in the linewidth enhancement factor alpha due to optical feedback and
found that such uncertainties have negligible effects on the validity
of our results.