Large spontaneous emission factor (>0.1) in the photonic crystal monopole-mode laser

1.55-μm-InGaAsP photonic crystal lasers operating in the monopole mode of a triangular lattice defect cavity are realized by room-temperature optical pumping with a low threshold of $\text{<0.5\hspace{0.5em}}\mathrm{mW}.$ By analyzing rate equations and the light–light characteristic curve, we evaluate the spontaneous emission factor $\mathrm{(\beta )}$ of this laser to be larger than 0.1, an extremely high value for photonic crystal lasers. The achievement of this large β is attributed to the facts that the investigated monopole-mode laser operates at the peak of the spontaneous emission spectrum and it shows a single-mode operation in a wide spectral range. In addition, nonclamping of carrier density near threshold and the $\text{β>0.1}$ are confirmed by the investigation of carrier-density dependent wavelength blueshift of the lasing mode.