Fig. 4. Lasing behaviour of the corner state.

a Pump-power dependence of the corner state for the cavity with a=360nm, D=222nm and g=30nm, on a logarithmic scale. The inset shows the enlarged curve around the threshold on a linear scale. Squares represent the experimental data, and the line represents the fitted result obtained with the semiconductor laser model. β is estimated as approximately 0.25. The lasing threshold is approximately 1µW. b Linewidths of the corner state as a function of pump power. The inset shows the normalized PL spectra for different pump powers. The unit of pump power is µW. The linewidth shows a clear narrowing. The linewidths and intensities are both extracted by fitting the high-resolution spectra with Lorentz peak functions