Zero-cell photonic crystal nanocavity laser with quantum dot gain

We demonstrate laser oscillation in a hexagonal-lattice photonic crystal nanocavity using an InGaAs quantum dot gain material by optical pumping at 5 K. The cavity comprises a defect created by shifting several air holes in a two-dimensional photonic crystal slab structure without removing any air holes to achieve both small mode volume and a high cavity quality factor. The measured cavity quality factors and estimated mode volume for the nanocavity are ∼33 000 and 0.004 μm³ [0.23 (λ₀ /n)³]. The laser threshold is compared between the zero-cell and L3-type nanocavity lasers, and the zero-cell nanolasers are found to have lower thresholds of about one-third of the L3-type nanolasers. This result suggests that a higher Purcell factor of the zero-cell nanolaser is reflected as a lower laser threshold.