Triple Resonance Optical Filter with Three Ripples in Passband Area

The experiment on the Fabry–Perot (F–P) triple resonance optical filter is reported. Flat passband can be achieved owing to the three subtle ripples which appear in the passband. Furthermore the passband loss and width can be arbitrary tuned by changing the reflectivity of mirrors. In order to experimentally generate the triple resonance, it was required that the resonance frequencies of the three F–P single resonators, whose optical lengths were 300 µm, were matched within several GHz. The passband width of 26 GHz and the smallest loss of 0.2 dB were obtained. The sharp cutoff characteristic was also achieved successfully. 1.5–10 dB shape factor was evaluated at 0.60. These experimental data well coincide with the theoretical values.