title: A shape-anisotropic reflective polarizer in a stomatopod crustacean.
abstract: Many biophotonic structures have their spectral properties of reflection 'tuned' using the (zeroth-order) Bragg criteria for phase constructive interference. This is associated with a periodicity, or distribution of periodicities, parallel to the direction of illumination. The polarization properties of these reflections are, however, typically constrained by the dimensional symmetry and intrinsic dielectric properties of the biological materials. Here we report a linearly polarizing reflector in a stomatopod crustacean that consists of 6-8 layers of hollow, ovoid vesicles with principal axes of ~550 nm, ~250 nm and ~150 nm. The reflection of unpolarized normally incident light is blue/green in colour with maximum reflectance wavelength of 520 nm and a degree of polarization greater than 0.6 over most of the visible spectrum. We demonstrate that the polarizing reflection can be explained by a resonant coupling with the first-order, in-plane, Bragg harmonics. These harmonics are associated with a distribution of periodicities perpendicular to the direction of illumination, and, due to the shape-anisotropy of the vesicles, are different for each linear polarization mode. This control and tuning of the polarization of the reflection using shape-anisotropic hollow scatterers is unlike any optical structure previously described and could provide a new design pathway for polarization-tunability in man-made photonic devices.
authors.affiliation: School of Biological Sciences, University of Bristol, Tyndall Avenue, Bristol, BS8 1TQ, UK.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Jordan
authors.affiliation: School of Biological Sciences, University of Bristol, Tyndall Avenue, Bristol, BS8 1TQ, UK.|Bristol Centre for Functional Nanomaterials, School of Physics, HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, BS8 1TL, UK.
authors.forename: David
authors.initials: D
authors.lastname: Wilby
authors.affiliation: Department of Life Sciences, National Cheng Kung University, Tainan City 70101, Taiwan, Republic of China.
authors.forename: Tsyr-Huei
authors.initials: TH
authors.lastname: Chiou
authors.affiliation: School of Biological Sciences, University of Bristol, Tyndall Avenue, Bristol, BS8 1TQ, UK.
authors.forename: Kathryn D
authors.initials: KD
authors.lastname: Feller
authors.affiliation: Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
authors.forename: Roy L
authors.initials: RL
authors.lastname: Caldwell
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, USA.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Cronin
authors.affiliation: School of Biological Sciences, University of Bristol, Tyndall Avenue, Bristol, BS8 1TQ, UK.|Bristol Centre for Functional Nanomaterials, School of Physics, HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, BS8 1TL, UK.
authors.forename: Nicholas W
authors.initials: NW
authors.lastname: Roberts
mesh_terms: D000818:Animals; D016880:Anisotropy; D003445:Crustacea / Q000033:anatomy & histology*; D008857:Microscopy, Interference; D055620:Optical Phenomena