Fabrication of step filter for miniature wavelength-division device based on photolithography

The combinatorial etching technique based on photolithography has been used to fabricate step filters in this paper, in order to eliminate the size limit and shadow effect of mechanical masks. A step filter with 16 × 1 channels for miniature wavelength-division device has been fabricated successfully. The width of a filter element is only 90μm and the total size of the wavelength-division device is less than 2 mm. The filter channels distribute from 632.4 nm to 739.6 nm with bandwidth narrower than 2.9 nm and transmittance higher than 70%. The filter element size of the step filter can be as small as in micro scale and the shadow effect of mechanical masks can be decreased to micro or sub-micro scale. Such step filters match with CCD completely and can be used as miniature wavelength-division device to compose a miniature spectral system for space applications etc.