Non-polarizing broadband multilayer reflectors in fish

Area of Science:

• Optics
• Biomimetics
• Materials Science

Background:

• Non-polarizing dielectric multilayer reflectors are crucial optical components with applications in optical fibers, waveguides, and LEDs.
• Existing synthetic non-polarizing reflectors have limitations and do not mimic natural optical mechanisms.

Purpose of the Study:

• To analyze a biological non-polarizing optical mechanism in fish "silver" multilayer reflectors.
• To investigate the structural and optical properties of guanine crystal arrangements in fish stratum argenteum.
• To explore the potential of this biological mechanism for synthetic optical devices.

Main Methods:

• Analysis of broadband guanine-cytoplasm "silver" multilayer reflectors from three fish species.
• Examination of birefringent guanine crystal populations and their optic axis orientations.
• Investigation of the optical properties related to Brewster's angles and polarization neutralization.

Main Results:

• Identified two distinct populations of birefringent guanine crystals in fish stratum argenteum.
• Observed optic axes oriented parallel and perpendicular to the crystal's long axis, respectively.
• Demonstrated that this arrangement neutralizes reflection polarization by managing interfacial Brewster's angles.

Conclusions:

• The fish reflective mechanism achieves non-polarizing reflection through a unique arrangement of birefringent guanine crystals.
• This biological design is distinct from current synthetic non-polarizing mirrors, notably lacking refractive index contrast with the environment.
• The mechanism presents a viable model for manufacturing and implementing in novel synthetic optical devices.