We present our work on integrated optic beam combiners devoted to mid-infrared applications in the field of stellar
interferometry, in particular for nulling interferometry, where high rejection ratios are needed. The main results obtained are the single-mode behavior of the waveguides at a central wavelength λ=3.39μm, in both TE and TM polarization, a high rejection ratio on the modulated signal (best value of 30dB) and low dispersion in wide-band configuration. In a second time, in order to improve the electro-optic response of the modulators, we have realized a photonic crystal inside one of the arms of the Y-junction. Theoretical results predict simultaneous TE and TM group index enhancement, which should give better electro-optic response, however, our preliminary experimental results do not show significant difference with the initial combiners. Perspectives on the future work will be presented.