26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Towards flatband lasing in bottom-up Kagome lattice photonic crystal lasers

Not scheduled

1h 30m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral COMMAD - Optoelectronic and Microelectronic Materials and Devices Parallel sessions

Description

Flatband lasers featuring near-dispersionless photonic bands offer a compelling pathway to overcome the band dispersion limitations inherent in conventional two-dimensional (2D) photonic crystals (PhCs) [1,2]. The near-zero photon group velocity in these bands generates an exceptionally large density of states across a broad range of in-plane wavevectors. This dramatically enhances light-matter interactions while enabling wide-angle far-field coupling for novel device functionalities. Among cavity architectures, the Kagome lattice PhC – a 2D corner-sharing triangular lattice – is uniquely advantageous. Its structure inherently induces geometric frustration and destructive interference, suppressing photon hopping between neighbouring unit cells [3,4]. However, experimental realisation remains hindered by the fabrication complexities of closely spaced nanopillars. Furthermore, the tight-binding approximation breaks down in practical devices due to non-negligible long-range coupling and uncontrolled scattering, severely degrading band flatness.

Here, we demonstrate a robust pathway towards realising flatband lasing in Kagome lattice PhCs. Diverging from typical monopolar modes, we utilise a dipolar “p-orbital” flatband mode supported by an array of elongated dielectric nanobars, which exhibits superior resilience against next-nearest-neighbour coupling [4]. At the designed flatband wavelength, the in-plane rotating electric fields perfectly cancel at the shared lattice corners, securing the defining dispersionless characteristics. Simulated bandstructures verify the presence of the flatband across the entire Brillouin zone, accompanied by two dispersive bands that form a Dirac cone at the K-point and a van Hove singularity at the M-point – both characteristics of a Kagome lattice. To implement this cavity design, we utilise selective area epitaxy to grow uniform arrays of InP nanostructures. This bottom-up approach circumvents the need for dry-etching, mitigating undesired scattering from sidewall roughness [5]. Each adjacent nanosheet is rotated by 60°, perfectly aligning with the crystallographic symmetry of their {10-10} sidewall facets. Key results detailing cavity design, fabrication methodologies, and optical characterisation will be presented.