High performance blocking filters for the region 1 micro to 20 micro

Area of Science:

• Optics and Photonics
• Materials Science
• Infrared Technology

Background:

• Continuous short-wave infrared (SWIR) blocking is crucial for various optical systems.
• Existing filter technologies may have limitations in rejection, transmission, or cutoff sharpness.
• Semiconductor absorption edges offer unique optical properties for filter design.

Purpose of the Study:

• To describe a novel set of filters for continuous SWIR blocking.
• To detail the design and performance of specific filters at 2.6, 5.5, and 12 micrometers.
• To explore the optimization of multilayer filter design.

Main Methods:

• Utilized semiconductor edges in filter sequences for SWIR blocking.
• Employed multilayer designs combined with semiconductor absorption edges.
• Analyzed filter performance regarding rejection, transmission, and cutoff characteristics.
• Applied principles analogous to electric circuit filter synthesis for multilayer design.

Main Results:

• Achieved >10^3 rejection in the stop region for each filter.
• Demonstrated >70% transmission over one octave with a square cutoff.
• Established cutoff points at approximately two-thirds octave intervals.
• Detailed specific filter designs at 2.6, 5.5, and 12 micrometers.

Conclusions:

• The described semiconductor edge filters effectively provide continuous SWIR blocking.
• The filter designs offer high performance metrics suitable for demanding optical applications.
• Multilayer design principles can be effectively adapted from electric circuit theory for optical filters.