This paper reports a new fabrication method for a microactuated tunable optical filter based on porous silicon formation followed by electropolishing. This surface micromachining process generates in a single step a multilayered optical interference filter, releases it from the substrate and lifts it out of plane [1]. The filter can be tilted by a thermal bimorph actuator in order to tune the wavelength it transmits or reflects. The fabrication process uses only two photolithography levels on ordinary silicon p{sup}+ substrates. Large, flat, actuatable flip-up Bragg mirrors of porous silicon have been realized with a typical thickness of 30μm and areas ranging from 250μm by 750μm to 2400μm by 4000μm. Their capability to distinguish light sources with a wavelength separation of less than 20 nm in the visible is presented.
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