Fig. 2: Lasing threshold reduction.

Continuous-wave (CW) current-voltage-power characteristics measured at room temperature with a short-cavity QCL where highly reflective metallic coatings are applied on both laser facets. The blue line and dots show the results where no apertures are patterned on the coatings. The orange line and dots show the results measured when a 950-nm-diameter circular hole is created in the metal layer of the coating on the front side. The green line and dots display the measured results when an additional 950-nm-diameter circular hole is milled in the Au film of the back-facet high-reflectivity coating. In these characterizations, the measuring step is 0.3 mA. A reduction of the threshold current is shown by the movement of the current-voltage kinks toward the left, and are more clearly displayed in the left inset, where the measurements are conducted using a finer current step of 0.1 mA. In total, the threshold dissipation power is reduced by over 25%. The laser is single-mode at the threshold, as shown in the right inset, where the spectral resolution of the measurement is 0.075 cm⁻¹. ⓒ 2021 IEEE. Figure 2 is reprinted, with permission, from ref. ²⁰.