A novel type of digital optical spectrometer on chip is proposed and first results of their fabrication and characterization are reported. The devices are based on computer-designed digital planar holograms which involves millions of lines specifically located and oriented in order to direct the output light into the designed focal points according to the wavelength. Spectrometers were fabricated on silicon dioxide and hafnium dioxide planar waveguides using electron beam lithography and dry etching. The optical performances of the first devices with up to 1000 channels for a central wavelength of 660 nm are reported.