This paper presents an optical mean to probe carefully the strain field generated by a microindentation on -oriented GaAs sample, using micro-Raman spectroscopy and microphotoluminescence spectroscopy. Raman and photoluminescence signals recorded from the same point of the sample are directly compared. The frequency shift of the longitudinal and transverse optical phonons was analyzed in great detail, revealing unambiguously the presence of both compressive and tensile strains within the indented area. Outside the indentation fingerprint, the magnitude of strain deduced from luminescence measurements was found to be lower than the one determined by Raman scattering. The Raman spectra revealed significant variations of the optical phonons polarizability with the deformation. Finally, atomic force microscope images of the indented zone aid in the interpretation.