Independently tunable omnidirectional multichannel filters based on the fractal multilayers containing negative-index materials

We propose and demonstrate an independently tunable omnidirectional multichannel filter by combining the advantages of the independently tunable filtering properties of fractal structures and the omnidirectional resonant modes of one-dimensional photonic crystals containing negative-index materials. Compared to the conventional multichannel filters, each channel of the proposed filter can be tuned separately, and the frequency position of the filter is insensitive to the incident angle of light. It thus provides a simple way for designing omnidirectional multichannel filters with specific channels.