a method for generating radiation in a range of desired wavelengths in a direction of emission is provided . according to the method , initial radiation is produced by a radiation source , the wavelengths thereof including the desired range , and the initial radiation is filtered in such a way as to substantially eliminate the initial radiation beams having a wavelength outside the desired range . the inventive method is characterized in that the filtering is carried out by setting up a controlled distribution of the refractive index of the beams in a control region through which the initial radiation passes , in such a way as to selectively deviate the beams of the initial radiation according to the wavelength thereof and to recover the beams having desired wavelengths . the invention also relates to an associated device .