SIMULATION OF THE ELECTRIC FIELD STRENGTH DISTRIBUTION IN AN ALL-OPTICAL LOGIC COMPARATOR BASED ON THE GaAs PHOTONIC CRYSTAL

Abstract

Photonic crystals, semiconductor structures with a photonic band gap, are of great interest to the scientific community. They represent a new class of optical materials with spatial periodic modulation of permittivity with a period close to the wavelength of radiation. Interest in these structures is explained by their importance for fundamental studies of the interaction of radiation with matter and the potential for creating next-generation optoelectronic devices. This paper presents the results of modeling a compact optical logic comparator based on a GaAs photonic crystal operating in the second transparency window of an optical fiber (wavelength of 1.3 μm). The model comparator is a medium with two input and two output optical channels. When radiation is input to one of the comparator inputs, the corresponding output channel transmits radiation, indicating a logical one. In the absence of signals on the input channels or when signals are input to both input channels, both output channels do not transmit radiation, indicating logical zeros. The channels in the comparator are created using intersecting waveguides formed in a two-dimensional GaAs photonic crystal, which consists of a set of cylindrical GaAs crystals (pillars) with a diameter of 130 to 170 nm, embedded in a vacuum medium with a period of 450 to 750 nm. To ensure attenuation of electromagnetic waves introduced into the comparator in both input channels, defective GaAs pillars with a smaller diameter are embedded at the intersection of the waveguides. The influence of the diameter and period between the GaAs photonic crystal pillars on the propagation patterns of electromagnetic radiation in the optical comparator medium is studied. Based on the analysis of the ratio of signal intensity levels at the inputs and outputs of the device, it is established that the optimal diameter of the GaAs pillars and the distance between them, at which the structure best meets the requirements of the logic comparator, is 155 and 600 nm, respectively.