Rugate notch filter fabricated by atomic layer deposition.

Area of Science:

• Materials Science and Engineering
• Optical Engineering
• Nanotechnology

Background:

• Rugate filters are periodic dielectric structures used for wavelength-selective filtering.
• Fabricating filters with precise refractive index control is crucial for achieving desired optical performance.
• Atomic Layer Deposition (ALD) offers atomic-level precision for thin-film fabrication.

Purpose of the Study:

• To demonstrate the fabrication of a Rugate notch filter using Atomic Layer Deposition (ALD).
• To achieve tailored refractive indices by controlling the TiO2/Al2O3 thickness ratio.
• To validate the filter's performance by comparing experimental and designed reflectance spectra.

Main Methods:

• Fabrication of a Rugate notch filter using Atomic Layer Deposition (ALD).
• Tailoring the refractive index by precisely regulating the thickness ratio of TiO2 and Al2O3 in nanoscale layers.
• Utilizing the equivalent refractive index method to discretize the continuously variable refractive index for iterative deposition.

Main Results:

• Successfully fabricated a Rugate notch filter with tailored refractive indices.
• Experimental reflectance spectrum closely matched the designed spectrum.
• Achieved an average reflectance of 86.7% in the 510-590 nm wavelength range.

Conclusions:

• ALD is an effective technique for fabricating Rugate notch filters with precise refractive index control.
• The proposed method of regulating TiO2/Al2O3 thickness ratio enables the design and realization of high-performance optical filters.
• The demonstrated filter exhibits excellent performance, suitable for various optical applications requiring specific wavelength filtering.