Parameters such as waveguide thickness, grating periodicity, grating depth and duty cycle have been studied to achieve a supernotch filter at 785 nm, with a bandwidth of less than 2 nm and an optical density of more than 5.
As PC's grating period Λ, grating depth dg, and fill factor are important parameters to the final performance of PC-based nanofluidic sensor, maintaining the fabricated results conform to the designed structure parameters is of key importance.
Eigenvalue method were used to solve the equations and numerical solutions to the diffraction efficiency of each transmitted waves P q were figured out [21], which are sensitive to the profile parameters of the grating, such as duty cycle f, period d, the grating depth h and the substrate thickness H. Therefore, P q can be numerically solved by the structure parameters.
Robustness of this correlation scheme to variations such as the change of waveguide thickness or grating depth modifying the Fano resonance shape, is another asset.
What may sound enchanting to one choreographer may be as grating as car alarms to another.
The PC-based nanofluidic structure, with Si3N4 as its guided mode layer and SiO2 as its substrate, has a grating period Λ 400 nm, Si3N4 thickness d0 450 nm, and grating depth dg 350 nm.
a AFM image of Si3N4 grating depth and profile.
The final optimized results were shown as follows: PC period Λ was 400 nm, Si3N4 thickness d0 was 450 nm, and grating depth dg was 350 nm.
The proposed PC based nanofluidic structure, as shown in Fig. 3a, has a period Λ = 400 nm, fillfactor ff = 0.5, UV curable polymer grating depth h = 120 nm, and coated TiO2 depth t = 70 nm.
Fig. 3 a PC-based nanofluidic sensor structure: grating pitch Λ, gap distance d, TiO2 depth t, master wafer grating depth h.
