Limaçon-shaped micro-cavity lasers with directional emission and its performance

• We demonstrated a limaçon-shaped micro-cavity laser and compared its performance with an F–P cavity ridge laser.
• The micro-cavity laser shows a low threshold current density level.
• The Q factor of the micro-cavity laser was improved up to 1130 by two step etching.
• The micro-cavity laser shows a directional emission with far field 32°×66° at FWHM.
• The micro-cavity laser also shows good reliability.

We fabricated a limaçon-shaped semiconductor micro-cavity laser by using quantum cascade laser material. The device performance was investigated and compared to a traditional F–P cavity ridge laser prepared with the same material. From the experimental results, the threshold current density of the micro-cavity laser was about 36% lower than that of the F–P cavity ridge laser, and the quality factor was improved up to 1130 by combining dry etching to achieve smooth vertical sidewalls with wet etching. From the mode spacing, we confirmed the emission of whispering gallery type resonance mode at about 10 μm wavelength. From the far-field pattern results, we achieved a highly directional emission with parallel directional divergence angle of 32° and perpendicular divergence angle of 66° at full width of half maximum for the micro-cavity laser with a deformed factor of 0.42, which is similar to that of the F–P cavity ridge laser. Finally the reliability testing of the micro-cavity lasers was carried out.