Generation of multiple-pitch gratings in WDM devices by using a single computer-generated phase mask

Use of a single computer-generated phase mask (CGPM) for monolithic fabrication of submicronmeter multiple-pitch gratings is proposed. The CGPM is a computer-generated Fourier hologram generating multiple diffracted beams with equal intensity from a single incident beam. The submicronmeter grating periods differing by as little as a few angstroms are estimated with basis of the multiple diffraction angles. As a result of preliminary experiment, an array of nine gratings has been achieved by using a CGPM with 2-μm minimum feature size. Limit of the CGPM period due to increase in wavelength spacing of WDM devices is also discussed.