A diffractive outcoupler, for use in a cavity of a laser, includes a surface phase grating for receiving radiation from a laser source and has rectangular grooves with a depth D, a first reflector located to receive a first diffracted portion of the radiation from the grating and to reflect the first diffracted portion back toward the grating, and a second reflector located to receive a second diffracted portion of the radiation from the grating and to reflect the second diffracted portion back toward the grating. The depth D of the grooves satisfies a relationship with the refractive index of the grating to permit transmission of the second harmonic of the radiation through the grating while causing portions of the first harmonic passing through the grooves and elevations of the grating to destructively interfere.