Optical modes in mesoscopic quantum cascade ring lasers

We present lasing spectra of mesoscopic rings processed from a GaAs-based quantum cascade material. The emission properties are investigated for various inner ring radii. Small inner radii leave the spectra unaffected, whereas large inner radii shift the spectra to smaller wavelengths. To obtain insight into the spatial distribution of the optical modes, we performed simulations with a finite-difference time-domain method.