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J. Eur. Opt. Society-Rapid Publ. 21, 24( 2025)
Figure
8. This figure shows the bandgap for the used sample sets compared to the thickness of the Ta 2 O 5 laminates. Samples were measured directly after coating and after annealing.
Figure
9. The refractive index at 550 nm compared to the thickness of the Ta 2 O 5 laminates for the same samples as in Figure 8. Samples were measured directly after coating and after annealing.
alternately. Each QNL layer consists of a multiple of laminate pairs made of Ta 2 O 5 and SiO 2. The thickness of the individual SiO 2 and Ta 2 O 5 laminates was calculated as SiO 2 = 1.36nmandTa 2 O 5 = 1.00 nm, resulting in a pair thickness of 2.36 nm. Each of the 20 QNL blocks in this optimized design has its own thickness, ranging from 47 nm to 60 nm, which results in a total QNL thickness of 1016 nm and thus approximately 430 laminate pairs within the design. These two designs were then coated using optical monitoring and subsequently measured with a spectrophotometer.
In Figure 10, the shortpass filter using QNL as the highrefractive-index material is shown in blue, while the one with Ta 2 O 5 is shown in red. The transmission spectra are illustrated with solid lines for both, and it can be seen that the design with QNL allows for a larger transparent range in the UV region until absorption( dotted line) prevents further use. This curve clearly shows that the chosen mixture is usable for an additional 20 nm into the shorter wavelength range. However, in the dashed reflection spectra, it is also evident that due to the lower refractive index, the width of the mirror region is significantly narrower compared to the Ta 2 O 5 based design.
As another experiment, a QNL mixture with a very low refractive index of n 1.6( QNL1) was chosen. This allowed for the creation of a very deep absorption edge. Using this, it became possible to design an antireflection coating with 6 layers at 266 nm. A quartz glass was coated on both sides with the design and measured using a photo spectrometer, as shown in Figure 11.
The spectrum is shown in blue, with the solid line once again representing the transmission in this case. It can be