Angle-insensitive and solar-blind ultraviolet bandpass filter.

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Metal-dielectric filters are crucial for spectral selection.
• Achieving narrow passbands with angular insensitivity in the UV spectrum is challenging.

Purpose of the Study:

• To design and analyze a novel metal-dielectric stack ultraviolet (UV) bandpass filter.
• To investigate the role of reflection phase shifts in achieving subwavelength dielectric thicknesses and angular insensitivity.

Main Methods:

• Parametric evaluation of reflection phase shifts at metal-dielectric interfaces.
• Analysis of coupled Fabry-Perot resonances within subwavelength dielectric films.
• Modeling the total phase shift considering wave propagation and reflection phase contributions.

Main Results:

• The proposed filter effectively rejects visible light while allowing UV transmission.
• Nontrivial phase shifts enable coupled Fabry-Perot resonances with subwavelength dielectric layers.
• The filter exhibits relative insensitivity to the angle of incidence due to engineered phase shifts.

Conclusions:

• Metal-dielectric stacks offer a viable route for creating thin, angularly stable UV bandpass filters.
• Engineering dielectric thickness and metal plasma frequency allows tuning of filter passbands across the spectrum.
• The design principles provide valuable insights for future optical filter development.