ALMA is the largest radio astronomical facility in the world providing high sensitivity between 35 and 950 GHz, divided in 10 bands with fractional bandwidths between 19 and 36%. Having a lifespan of at least 30 years, ALMA carries out a permanent upgrading plan which, for the receivers, is focused on achieving better sensitivity and larger bandwidths. As result, an international consortium works on demonstrating a prototype receiver covering currents Bands 2 and 3 (67 to 116 GHz) which corresponds to a fractional bandwidth of 54%. Here we present the preliminary design, implementation and characterization of suitable refractive optics. Results indicate an excellent performance in good agreement with simulations.