We present a project to study the luminosity function of Lyman Alpha Emitters (LAEs) at redshifts between z~3 and z~6.5 in gravitational strong lensed fields by clusters of galaxies, using OSIRIS tunable filters at the GTC.

OSIRIS tunable filters can be tuned to bandwidhts of about 15 angstroms, that is very useful to enhance the emission line contrast. This feature, along 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 of LAEs. Results will be compared with other studies of the Luminosity Function of LAEs.

New strong lensed LAEs found in our study will be also used to perform or refine gravitational lens models for the cluster of galaxies, and the mass luminosity relation in the core of the cluster.

Preliminary results will be presented.