Tunability of notch angles in quantum cascade microlasers with highly deformed spiral resonators

We study the mode spectra and lasing thresholds of spiral-shaped quantum cascade lasers with a deformation in the range of 10%-45% with respect to the radius and with various notch angles. We observe that the initial lasing wavelength and the threshold of a laser are correlated with each other, and they can be jointly tuned by both the deformation coefficient and notch angle. The dependence of the cavity loss on the deformation coefficient is analyzed via the measured lasing thresholds and frequency dependent gain coefficients. Moreover, we achieve single mode emission by tuning the notch angle and deformation coefficients.