Suppression of Coherence Collapse in Semiconductor Fano Lasers

We show that semiconductor Fano lasers strongly suppress dynamic instabilities induced by external optical feedback. A comparison with conventional Fabry-Perot lasers shows orders of magnitude improvement in feedback stability and in many cases even total suppression of coherence collapse, which is of major importance for applications in integrated photonics. The laser dynamics are analyzed using a generalization of the Lang-Kobayashi model for semiconductor lasers with external feedback, and an analytical expression for the critical feedback level is derived.

Figure 1

(a) Schematic of Fabry-Perot laser. (b) RIN in decibels as function of external reflectivity and on-chip distance to the external mirror for the FP laser. (c) Schematic of Fano laser. (d) RIN as function of external reflectivity and on-chip distance to the external mirror for the Fano laser.

Figure 2

(a) RIN as function of the external power reflectivity in decibels with $L_D=3\mathrm{cm}$ for a Fabry-Perot laser (stars) and Fano lasers with increasing nanocavity $Q$ factors (circles, triangles, squares). Solid lines are guides to the eye. (b) Numerical (red circles) and analytical (black line) critical feedback level as function of the total quality factor of the nanocavity.

Figure 3

Fano laser relaxation oscillation angular frequency (full black, left axis) and damping rate (dashed black, left axis), and ratio of energy stored in the nanocavity relative to the laser cavity (blue, right axis), all as a function of the total quality factor. (Inset) Simulated field distribution during lasing (logarithmic scale). Note the bright spots in the nanocavity.