We propose the simulation and the fabrication of a photonic crystal (PhC) strain-sensitive structure, showing that the optical properties of photonic crystals can be used to realize sensing devices characterized by a high degree of compactness and good resolution. The force/pressure optical sensor has been realized by designing a bulk GaAs/AlGaAs photonic crystal microcavity operating in the wavelength range 1300-1400 nm. The simulations show that the resonant wavelength of the mode localized in the microcavity shifts its spectral position following a linear behaviour when a pressure ranging between 0.25 Gpa and 5 GPa is applied, thus allowing the possibility to achieve pressure resolution of 5.82 nm/GPa. High-resolution electron beam lithography technique followed by inductively coupled plasma process were used to transfer the designed geometry on the sample.