A NOVEL TECHNIQUE FOR MAKING GRATING DEMULTIPLEXERS IN INTEGRATED-OPTICS

A new technique is proposed for making phase diffraction gratings for integrated optics. The ion-exchange technique in glass is used, the grating is obtained by performing the ion exchange through a periodic mask photolithographically printed in aluminium. The required modulation of the index of refraction is obtained by introducing consecutively two different ions, Ag+and K+, inside the glass slide. The opto-geometric parameters of the phase diffraction grating are theoretically determined to obtain good wavelength demultiplexing properties at λ1= 0.6328 µm and λ2= 0.5145 µm. An experiment is performed where an incident light beam with two wavelengths, λ1and λ2, is directed on the grating with an angle of incidence such that all the diffracted energy is transferred to the first order of diffraction for λ1and to the zeroth order for λ2. The same device could easily be designed for wavelengths of interest in telecommunications systems. © 1990 IOP Publishing Ltd.