Abstract
We study the luminosity function of Lyman Alpha Emitters (LAEs) at redshifts between z~6.5 in strong gravitational lensed (GL) fields by clusters of galaxies, using OSIRIS tunable filters (TFs) at the GTC. OSIRIS TFs enhance the emission line contrast, together with the total flux magnification produced by the lens, will be used to detect faint LAEs and to extend the low luminosity queue of the Luminosity Function (LF) of LAEs.