## 3 Results and Discussion
Meanwhile, selective light scattering did result in a reduction of light intensity by about 5-10% in the whole spectrum, which was mainly caused by the back scattering of light within short wavelengths. Through further optical design, combined with the selective coating of specific areas of down-conversion dyes, it is believed that the scattered light with short wavelengths will also be fully utilized. As a result, the ratio of the light component can be simply controlled by changing the angle of incidence. Considering their selected light scattering properties, Al nanodents can be used as simple light filters for cheap white LEDs to reduce the damage caused by blue light. A far-field model based on FDTD simulation was used on quasi-ordered hexagonal close-packed Al nanodents to prove such angle-dependent selected light scattering, as shown in Figure 4. In this model, the scattering light was collected on a hemispherical surface (diameter of 1 m) with periodic boundary conditions. To better understand the light scattering direction, the direction of the incidence was defined along the Y axis, as shown in Figure 4. The scattered light distribution of the incidence was near the center of the hemispherical surface, presented by polar coordinates. As shown in Figure 4a-c, the scattering of light at a 450 nm wavelength greatly increased with the increment of the incidence angle. The scattering of light was mainly localized along the incident direction, which was along the Y axis. In contrast to light at a 450 nm wavelength, the scattering of light at 550 nm was relatively low, although it grew slightly with the increment of the incidence angle, as shown in Figure 4d-f. Obviously, the far-field simulations coincide well with our experiment observations. Figure 4: **(a–c)** Far-field simulations on Al nanodents with \(0^{\circ}\), \(15^{\circ}\), and \(30^{\circ}\) incidence angles at a 450 nm wavelength. (**d–f**) Far-field simulations on Al nanodents with \(0^{\circ}\), \(15^{\circ}\), and \(30^{\circ}\) incidence angles at a 550 nm wavelength. Figure 3: Scattering (incident direction) and output spectrum of the white LED on Al nanodents. (**a**) Scattering spectrum (incident direction) of the white LED light scattering on Al nanodents. (**b**) Output spectrum of the white LED light with incidence angles from \(30^{\circ}\) to \(70^{\circ}\). Near-field simulation was also carried out to better understand the selected scattering on Al nanodents. As shown in Figure 5, two light sources were chosen according to the two peaks of the white LED with 450 and 550 nm wavelengths. As shown in Figure 5a-c, no obvious near-field enhancement was found in Al nanodents under vertical incidence (angle of 0\({}^{\circ}\)) at both wavelengths of 450 and 550 nm and light was mainly localized in the holes of Al nanodents. Overall, the main difference of the two kinds of light lies in their penetration depth. As shown in Figure 5a-f, the penetration depth of light at the same wavelength increased with the increment of its incidence angle, and the penetration depth of light at a 450 nm wavelength was greater than that at a 550 nm wavelength with the same incidence angle. The selected light scattering of light can be attributed to the interaction between light and holes on the Al nanodents, and only provides efficient light coupling for lights with short wavelengths.