This paper presents the results of numerical simulation of the light-matter interaction in the GaAs-based photonic crystal (PhC). The study focuses on the coupled configurations of waveguides and hexagonal microcavities operating at a wavelength of 1.3 µm. A systematic investigation is conducted into the influence of the diameter of microcavity, its distance from the waveguide and the defect configuration on the distribution of the electric field strength within the PhC structure. It is shown that a spacing of 2 rows between the waveguide and 1.65-µm-diameter cavity allows achieving maximum electric field strength within the cavity. An introduction of a defect into the waveguide leads to a further increase in the electric field strength in the cavity, with an optimal radius of 209 nm.