<p>This study investigates two types of photonic crystal structures: those with fixed lengths and those with variable lengths. A comparison is made between dielectric/dielectric and dielectric/plasma photonic crystals. We employ a novel asymmetric layer arrangement that we have recently developed. The analysis examines the effects of various parameters—such as the number of layers, the smallest unit length of the proposed crystal, the magnitudes of the dielectric constants, the plasma density, and the incident angle of the electromagnetic wave—on the transmission spectra, the width and position of band gaps, and the omnidirectional band gaps. The transfer matrix method is used to calculate the transmission coefficient and to identify band gap regions in the designed structures. We demonstrate that our new proposal for a one-dimensional photonic crystal arrangement results in a tunable structure, yielding different values for optical band gaps, band gap widths, and omnidirectional band gaps.</p>