  In this study, we used parallel plane mirror resonator analogy to design
all-dielectric optical resonator that is performed with the objective-first
inverse design algorithm. Confinement of the light is succeeded via predefined
objective function to create symmetric mirror regions for the fundamental
transverse-electric polarization mode. The algorithm creates bandgap in random
structure to obtain resonance peak at the desired wavelength without any
intuitive scanning of the parameter space. The first order mode is confined on
the cavity region at pre-defined wavelength. The obtained structure is analysed
by using the two-dimensional finite-difference time-domain method. The proposed
structure has a compact configuration with a footprint of $13.394 \times 0.592
\mu m^2$.
