Three optical multi-color filters are modelled in the current work. They are composed of defective photonic crystals of two layers A and B and a defect layer C which is selected as silver Ag. The three multi-color filters have the structures (ABA)(ABAC)(N)(ABA), (ABAC)(N)ABA, and (ABAC)(N)(BAB). The transmission spectra of the filters are investigated for different values of coupled defects (N). It is found that the three filters have several filtering channels. These channels are directly related to the number of coupled defects. In the multi-color filters (ABA)(ABAC)(N)(ABA), (ABAC)(N)ABA, and (ABAC)(N)(BAB), the number of filtering channels is equal to N + 1, N and N - 1, respectively. With the increase of N, the resonant peaks are blue shifted. These filters can be used effectively in pre-amplification, radio tuning to a specific frequency, tone control in audio systems, equalization and signal processing circuits.
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