Fig. 1
From: Tunable narrow-band single-channel add-drop integrated optical filter with ultrawide FSR
Design of the FSR-free ADF. a Schematic 3D view of the ADF based on three coupled waveguides with a central grating-assisted F-P cavity. b Top view of the filter consisting of Bragg grating mirrors, tapered grating, and point-defects cavity, indicated within the dashed white rectangle in a. c Cross-section of the coupling region of the filter, indicated by the dashed orange line in a. d Top-view SEM image of the filter