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In this study, we present the design of a photonic crystal (PC) structurewith a hexagonal lattice, where adjustments to the PC unit cell symmetry revealan all-angle self-collimation (SC) effect. By optimizing opto-geometricparameters, such as the rotational angle of auxiliary rods and adjacentdistances, we analyze the SC property in detail, leveraging group velocitydispersion (GVD) and third-order dispersion (TOD) characteristics. We alsoinvestigate the relationship between symmetry properties and their influence ondispersion characteristics. Through symmetry manipulation, we gain acomprehensive understanding of the underlying mechanisms governing lightcollimation and confinement in the proposed configurations. The PC structurewith a $C_1$ symmetry group exhibits all-angle SC effect within the range of$a/\lambda=0.652$ and $a/\lambda=0.668$ normalized frequencies, with abandwidth of $\Delta \omega/\omega_c = 2.4\%$. Further breaking the symmetry,transforming from $C_1$ to $C_2$ group symmetry, enhances the SC bandwidth to$\Delta \omega/\omega_c =6.5\%$ and reveals the perfect linear equi-frequencycontours (EFC) at two different frequency bands: all angle SC between$a/\lambda = 0.616$ and $a/\lambda = 0.656$ normalized frequencies in the 4thtransverse magnetic (TM) band and between $a/\lambda=0.712$ and$a/\lambda=0.760$ in the 5th TM band. Additionally, we propose acomposite/hybrid PC structure resembling $C_2$ group symmetry, where twoauxiliary rods are replaced by rectangular photonic wires with the samerefractive index and width equal to the diameter of auxiliary rods. This hybridstructure exhibits an all-angle SC effect with an operating bandwidth of$\Delta \omega/\omega_c =11.7\%$, displays near-zero GVD and TOD performanceand offers enhanced robustness against potential fabrication precision issues.

Enhanced self-collimation effect by low rotational symmetry in hexagonal lattice photonic crystals