We will calculate the properties of chromatic plasmonic polarizers for color filtering and polarimetry, reproducing figures 2b, 2d, 3 of Ellenbogen et al to show the variation in the transmission spectrum as a function of polarization and the position of the dip in transmission as a function of the arm length of the cross-shaped structures of the array.
The file [[sp_filter_symm.ldev]] can be used to simulate an array of chromatic plasmonic polarizers (CPPs). The simulation file contains one unit cell of the periodic structure. The polarization angle of the source can be set in the model analysis group which is at the top of the Objects Tree. If set to 0 or 90 degrees, the group will automatically use either PEC or PMC boundary conditions on the plane of symmetries to reduce the simulation volume.
To obtain the polarization information required for figure 2, two simulations are necessary, as the results for arbitrary linear polarizations can be obtained by summing the results from two orthogonal polarizations with appropriate weighting. The simulations are performed by running the parameter sweep named figure2 in the Optimization and Sweeps window where the transmission spectrum is recorded as a result of the sweep.
To obtain information on the transmission minima as a function of the arm length of the cross structure to recreate figure 3, we use the figure3 sweep object which will record the transmission spectrum as a function of CPP horizontal length.
The results of the sweeps are already contained in the simulation file. However, you can re-run the parameter sweeps to refresh the results. The script file [[sp_filter_dgtd.lsf]] will then analyze the results and plot them as they are displayed in figures 2b, 2d and 3 of Ellenbogen et al.
We can see that there is good agreement with the published results. It is possible to improve the result by using a smaller mesh size (here we used a 15 nm mesh on the surface of the Al CPP) and by replacing the ITO with a better material model (here we used a dielectric with n=1.9). The result can be also be greatly improved if a more accurate version of the fabricated structure can be simulated. Also, it should be noted that the polarization angle definition was reversed between figures 2b and 2d of the publication.
Transmission over wavelength at different polarization angles
Transmission over wavelength and polarization angle
Minimum transmission wavelength as a function of arm length (L)
- Tal Ellenbogen et al, "Chromatic Plasmonic Polarizers for Active Visible Color Filtering and Polarimetry", Nano Lett.12(2):1026-31 (2012)
Photothermal Heating in Plasmonic Nanostructures