Photonic Crystal Band Structure Calculation

This MATLAB program calculates the photonic crystal band structure using the widely-adopted plane wave expansion method. The algorithm expands the electromagnetic wave equations into Fourier series components, constructing a Hermitian eigenvalue problem that is solved using MATLAB's built-in eigensolvers. Key implementation features include periodic boundary condition handling through reciprocal lattice vectors, dielectric constant Fourier decomposition, and automatic band diagram plotting. The code efficiently handles complex unit cell geometries by discretizing the Brillouin zone and computing eigenfrequencies across high-symmetry points. The program includes visualization tools for generating publication-ready band structure diagrams, with customizable parameters for lattice constants, dielectric contrasts, and wave propagation directions. This computational tool provides researchers with robust capabilities for analyzing photonic band gaps and dispersion relations in various photonic crystal configurations, supporting applications in optical communications, sensing, and photonic integrated circuits.