Inreflectance: a new function for the optimization of multilayers with absorbing materials

Area of Science:

• Optics and Photonics
• Materials Science
• Thin Film Technology

Background:

• Multilayer optimization is crucial for controlling light-matter interactions.
• Existing methods for maximizing reflectance can be complex, especially for absorbing materials.

Purpose of the Study:

• To introduce and define a new optical magnitude, inreflectance, for optimizing multilayer reflectance.
• To demonstrate the utility of inreflectance in designing highly reflective multilayers.

Main Methods:

• Definition of inreflectance based on complex reflectance and refractive index.
• Sequential maximization of inreflectance for internal layers of a multilayer.
• Application of the method to multilayer design in the extreme ultraviolet (EUV) spectral range.

Main Results:

• Inreflectance maximization leads to multilayers with superior reflectance compared to traditional methods.
• Inreflectance differs from reflectance in absorbing media, offering distinct optimization pathways.
• Optimized layer thicknesses for inreflectance maxima are larger than those for reflectance maxima.

Conclusions:

• Inreflectance provides a novel and effective approach for multilayer optimization, particularly for achieving maximum reflectance.
• The inreflectance concept is applicable to designing multilayers with fixed and variable layer thicknesses.
• This new magnitude simplifies the design of high-performance optical coatings in spectral regions with material absorption, such as the EUV.