Kenneth Järrendahl - Profile on Academia.edu (original) (raw)

Papers by Kenneth Järrendahl

Research paper thumbnail of Linear Birefringent Films of Cellulose Nanocrystals Produced by Dip-Coating

Nanomaterials

Transparent films of cellulose nanocrystals (CNC) are prepared by dip-coating on glass substrates... more Transparent films of cellulose nanocrystals (CNC) are prepared by dip-coating on glass substrates from aqueous suspensions of hydrolyzed filter paper. Dragging forces acting during films’ deposition promote a preferential alignment of the rod-shaped CNC. Films that are 2.8 and 6.0 µm in thickness show retardance effects, as evidenced by placing them between a linearly polarized light source and a linear polarizer sheet in the extinction configuration. Transmission Mueller matrix spectroscopic ellipsometry measurements at normal incidence as a function of sample rotation were used to characterize polarization properties. A differential decomposition of the Mueller matrix reveals linear birefringence as the unique polarization parameter. These results show a promising way for obtaining CNC birefringent films by a simple and controllable method.

Research paper thumbnail of Electrical peculiarities in Al/Si/Ge/…/Ge/Si and Al/SiGe/Si structures

Electrical peculiarities in Al/Si/Ge/…/Ge/Si and Al/SiGe/Si structures

Applied Surface Science, 2002

The current–voltage (I–V) and capacitance–voltage (C–V) behaviour of different Si/Ge multilayers ... more The current–voltage (I–V) and capacitance–voltage (C–V) behaviour of different Si/Ge multilayers and SiGe single layers prepared on p-type Si substrates by magnetron sputtering and annealing, has been studied in the temperature range of 80–320K by using Al Schottky contacts as test structures. Although a significant influence of the microstructure of the Si/Ge multilayers and SiGe layers was obtained on the

Research paper thumbnail of Ion implanted dopants in GaN and AlN: Lattice sites, annealing behavior, and defect recovery

Journal of Applied Physics, 2000

The recovery of structural defects in gallium nitride ͑GaN͒ and aluminum nitride ͑AlN͒ after impl... more The recovery of structural defects in gallium nitride ͑GaN͒ and aluminum nitride ͑AlN͒ after implantation of 111 In ϩ and 89 Sr ϩ in the dose range ͑0.1-3͒ 10 13 cm Ϫ2 and ion energies of 60-400 keV has been investigated as a function of annealing temperature with emission channeling ͑EC͒ and perturbed ␥␥ angular correlation spectroscopy. The implanted In and Sr atoms occupied substitutional sites in heavily perturbed surroundings of point defects after room temperature implantation. No amorphization of the lattice structure was observed. The point defects could be partly removed after annealing to 1473 K for 10-30 min. Lattice site occupation of implanted light alkalis, 24 Na ϩ in GaN and AlN as well as 8 Li ϩ in AlN, were also determined by EC as a function of implantation and annealing temperature. These atoms occupied mainly interstitial sites at room temperature. Lithium diffusion and the occupation of substitutional sites was observed in GaN and AlN at implantation temperatures above 700 K. A lattice site change was also observed for sodium in AlN, but not in GaN after annealing to 1073 K for 10 min.

Research paper thumbnail of Sum decomposition of Mueller-matrix images and spectra of beetle cuticles

Spectral Mueller matrices measured at multiple angles of incidence as well as Mueller matrix imag... more Spectral Mueller matrices measured at multiple angles of incidence as well as Mueller matrix images are recorded on the exoskeletons (cuticles) of the scarab beetles Cetonia aurata and Chrysina argenteola. Cetonia aurata is green whereas Chrysina argenteola is gold-colored. When illuminated with natural (unpolarized) light, both species reflect left-handed and near-circularly polarized light originating from helicoidal structures in their cuticles. These structures are referred to as circular Bragg reflectors. For both species the Mueller matrices are found to be nondiagonal depolarizers. The matrices are Cloude decomposed to a sum of non-depolarizing matrices and it is found that the cuticle optical response, in a first approximation can be described as a sum of Mueller matrices from an ideal mirror and an ideal circular polarizer with relative weights determined by the eigenvalues of the covariance matrices of the measured Mueller matrices. The spectral and image decompositions are consistent with each other. A regression-based decomposition of the spectral and image Mueller matrices is also presented whereby the basic optical components are assumed to be a mirror and a circular polarizer as suggested by the Cloude decomposition. The advantage with a regression decomposition compared to a Cloude decomposition is its better stability as the matrices in the decomposition are determined a priori. The origin of the depolarizing features are discussed but from present data it is not possible to conclude whether the two major components, the mirror and the circular polarizer are laterally separated in domains in the cuticle or if the depolarization originates from the intrinsic properties of the helicoidal structure.

Research paper thumbnail of Chirality-induced polarization effects in the cuticle of scarab beetles: 100 years after Michelson

Philosophical Magazine, 2012

Research paper thumbnail of Optical Mueller matrix modeling of chiral Al(x)In(1− x)N nanospirals

Thin Solid Films, Nov 28, 2014

a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Chiral nanostructures Muell... more a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Chiral nanostructures Mueller matrix spectroscopic ellipsometry Anisotropy Optical modeling High degree of circular polarization

Research paper thumbnail of Polarizing properties and structural characteristics of the cuticle of the scarab Beetle Chrysina gloriosa

Thin Solid Films, Nov 28, 2014

Polarizing properties and structural characteristics of the cuticle of the scarab Beetle Chrysina... more Polarizing properties and structural characteristics of the cuticle of the scarab Beetle Chrysina gloriosa, 2013, Thin Solid Films. http://dx.a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Scarab beetle Near-circular polarization Mueller-matrix spectroscopic ellipsometry

Research paper thumbnail of Curved-Lattice Epitaxial Growth of In(x)Al(1-x)N Nanospirals with Tailored Chirality

Nano letters, Nov 26, 2014

Chirality, tailored by external morphology and internal composition, has been realized by control... more Chirality, tailored by external morphology and internal composition, has been realized by controlled curved-lattice epitaxial growth of InxAl1-xN nanospirals. The curved morphology of the spiral segments is a result of a lateral compositional gradient while maintaining a preferred crystallographic growth direction, implying a lateral gradient in optical properties. Individual nanospirals show an asymmetric core-shell structure with curved basal planes. Mueller matrix spectroscopic ellipsometry shows that the tailored chirality is manifested in the polarization state of light reflected off the nanospirals.

Research paper thumbnail of Evidence for a dispersion relation of optical modes in the cuticle of the scarab beetle Cotinis mutabilis

Optical Materials Express, Nov 5, 2014

Variable angle Mueller matrix spectroscopic ellipsometry is used to study the properties of light... more Variable angle Mueller matrix spectroscopic ellipsometry is used to study the properties of light reflected from the exoskeleton (cuticle) of the scarab beetle Cotinis mutabilis. For unpolarized incident light, the ellipticity and degree of polarization of the reflected light reveal a lefthanded helical structure in the beetle cuticle. Analysis of the spectral position of the maxima and minima in the interference oscillations of the Mueller-matrix elements provides evidence for a dispersion relation similar to that of optical modes in chiral nematic liquid crystals calculated within a two-wave approximation. Additionally, a structural model for the cuticle of C. mutabilis is derived from the properties of the optical modes for nonattenuated propagation or selective reflection.

Research paper thumbnail of Chiral nanostructures producing near circular polarization

Optical Materials Express, Jun 19, 2014

Optical properties of chiral nanostructured films made of Al 1−x In x N using a new growth mechan... more Optical properties of chiral nanostructured films made of Al 1−x In x N using a new growth mechanism -curved-lattice epitaxial growth -are reported. Using this technique, chiral films with rightand left-handed nanospirals were produced. The chiral properties of the films, originating mainly from an internal anisotropy and to a lesser extent from the external helical shape of the nanospirals, give rise to selective reflection of circular polarization which makes them useful as narrow-band near-circular polarization reflectors. The chiral nanostructured films reflect light with high degree of circular polarization in the ultraviolet part of the spectrum with left-and right-handedness depending on the handedness of the nanostructures in the films.

Research paper thumbnail of Exploring optics of beetle cuticles with Mueller-matrix ellipsometry

Spectroscopic Mueller-matrix ellipsometry at variable angles of incidence is applied to beetle cu... more Spectroscopic Mueller-matrix ellipsometry at variable angles of incidence is applied to beetle cuticles using a small (50 -100 μm) spot size. It is demonstrated how ellipticity and degree of polarization of the reflected light can be derived from a Mueller matrix providing a detailed insight into reflection properties. Results from Cetonia aurata, Chrysina argenteola and Cotinis mutabilis are presented. The use of Mueller matrices in regression analysis to extract structural and optical parameters of cuticles is briefly described and applied to cuticle data from Cetonia aurata whereby the pitch of the twisted layered structure in the cuticle is determined as well as the refractive indices of the epicuticle and the exocuticle.

Research paper thumbnail of Polarization of Light Reflected from Chrysina Gloriosa Under Various Illuminations

Materials Today: Proceedings, 2014

When illuminated with unpolarized light, the scarab beetle Chrysina gloriosa, reflects left-hande... more When illuminated with unpolarized light, the scarab beetle Chrysina gloriosa, reflects left-handed near-circularly polarized light for a broad range of angles of incidence and wavelengths in the visible. It is, however, known that light scattered from the sky, reflected on water or transmitted through leaves often is linearly polarized. In this study we have analysed the polarization of light reflected on this beetle when illuminated with different polarization states of light. We have also analysed how the response would be with a polarization-sensitive detector. The reflected irradiance is shown to be highest when the incident light is s-polarized or left-handed polarized and the detector is unpolarized (or vice versa). In the case in which both, the source and the detector, are polarized, the irradiance is highest when both are s-polarized. On the contrary the visibility is low when the source is s-polarized and the detector is p-polarized.

Research paper thumbnail of Comparison and analysis of Mueller-matrix spectra from exoskeletons of blue, green and red Cetonia aurata

Thin Solid Films, Nov 28, 2014

a b s t r a c t a r t i c l e i n f o Available online xxxx

Research paper thumbnail of Polarizing Natural Nanostructures

Polarizing Natural Nanostructures

Springer Series in Surface Sciences, 2014

ABSTRACT A brief description of the polarizing environment we are living in and the possibilities... more ABSTRACT A brief description of the polarizing environment we are living in and the possibilities for some animals to detect this polarization is made. This is followed by a presentation of how animals and plants generate polarized light, usually through reflection from micro- and nanostructures. Special attention is made to scarab beetles reflecting light with a high degree of circular polarization. Finally some comments on the biological aspects of polarization are made.

Research paper thumbnail of Cuticle structure of the scarab beetle Cetonia aurata analyzed by regression analysis of Mueller-matrix ellipsometric data

Optics Express, 2013

Since one hundred years it is known that some scarab beetles reflect elliptically and near-circul... more Since one hundred years it is known that some scarab beetles reflect elliptically and near-circular polarized light as demonstrated by Michelson for the beetle Chrysina resplendens. The handedness of the polarization is in a majority of cases left-handed but also right-handed polarization has been found. In addition, brilliant colors with metallic shine are observed. The polarization and color effects are generated in the beetle exoskeleton, the so-called cuticle. The objective of this work is to demonstrate that structural parameters and materials optical functions of these photonic structures can be extracted by advanced modeling of spectral multi-angle Mueller-matrix data recorded from beetle cuticles. A dual-rotating compensator ellipsometer is used to record normalized Mueller-matrix data in the spectral range 400 -800 nm at angles of incidence in the range 25-75 • . Analysis of data measured on the scarab beetle Cetonia aurata are presented in detail. The model used in the analysis mimics a chiral nanostructure and is based on a twisted layered structure. Given the complexity of the nanostructure, an excellent fit between experimental and model data is achieved. The obtained model parameters are the spectral variation of the refractive indices of the cuticle layers and structural parameters of the chiral structure.

Research paper thumbnail of Symmetries and relationships between elements of the Mueller matrix spectra of the cuticle of the beetle Cotinis mutabilis

Thin Solid Films, Nov 28, 2014

Symmetries and relationships between elements of the Mueller matrix spectra of the cuticle of the... more Symmetries and relationships between elements of the Mueller matrix spectra of the cuticle of the beetle Cotinis mutabilis, 2013, Thin Solid Films. http://dx.a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Structural color Left-handed polarized light Mueller matrix Scarab beetles

Research paper thumbnail of Fano interference in supported gold nanosandwiches with weakly coupled nanodisks

Optics express, Jan 31, 2012

We studied the far-field optical response of supported gold-silica-gold nanosandwiches using spec... more We studied the far-field optical response of supported gold-silica-gold nanosandwiches using spectroscopic ellipsometry, reflectance and transmittance measurements. Although transmittance data clearly shows that the gold nanodisks in the sandwich structure interact very weakly, oblique reflectance spectra of s- and p-polarized light show clearly asymmetric line-shapes of the Fano type. However, all experimental results are very well described by modeling the gold nanodisks as oblate spheroids and by employing a 2 × 2 scattering matrix formulation of the Fresnel coefficients provided by an island film theory. In particular, the Fano asymmetry can be explained in terms of interference between the scattered waves from the decoupled nanodisks in the spectral range limited by their respective plasmon resonances. We also show that the reflectance and ellipsometry spectra can be described by a three-layer system with uniaxial effective dielectric functions.

Research paper thumbnail of Chirality-induced polarization effects in the cuticle of scarab beetles: 100 years after Michelson

Philosophical Magazine, 2012

Research paper thumbnail of Optical response of supported gold nanodisks

Optics Express, 2011

It is shown that the ellipsometric spectra of short range ordered planar arrays of gold nanodisks... more It is shown that the ellipsometric spectra of short range ordered planar arrays of gold nanodisks supported on glass substrates can be described by modeling the nanostructured arrays as uniaxial homogeneous layers with dielectric functions of the Lorentz type. However, appreciable deviations from experimental data are observed in calculated spectra of irradiance measurements. A qualitative and quantitative description of all measured spectra is obtained with a uniaxial effective medium dielectric function in which the nanodisks are modeled as oblate spheroids. Dynamic depolarization factors in the long-wavelength approximation and interaction with the substrate are considered. Similar results are obtained calculating the optical spectra using the island-film theory. Nevertheless, a small in-plane anisotropy and quadrupolar coupling effects reveal a very complex optical response of the nanostructured arrays.

Research paper thumbnail of Optical properties and switching of a rose bengal derivative studied by spectroscopic ellipsometry

Optical properties in terms of the complex-valued dielectric function were determined for spin-co... more Optical properties in terms of the complex-valued dielectric function were determined for spin-coated films of a Rose Bengal derivative using variable angle of incidence spectroscopic ellipsometry in the visible and infrared wavelength regions. In addition, the thickness and roughness of the films were determined and related to the solution concentration of Rose Bengal. Switching between two different oxidation states of the Rose Bengal derivative was investigated. The two states were chemically induced by exposure to vapors of hydrochloric acid and ammonia, respectively. A substantial and reversible change of the optical properties of the films was observed.

Research paper thumbnail of Linear Birefringent Films of Cellulose Nanocrystals Produced by Dip-Coating

Nanomaterials

Transparent films of cellulose nanocrystals (CNC) are prepared by dip-coating on glass substrates... more Transparent films of cellulose nanocrystals (CNC) are prepared by dip-coating on glass substrates from aqueous suspensions of hydrolyzed filter paper. Dragging forces acting during films’ deposition promote a preferential alignment of the rod-shaped CNC. Films that are 2.8 and 6.0 µm in thickness show retardance effects, as evidenced by placing them between a linearly polarized light source and a linear polarizer sheet in the extinction configuration. Transmission Mueller matrix spectroscopic ellipsometry measurements at normal incidence as a function of sample rotation were used to characterize polarization properties. A differential decomposition of the Mueller matrix reveals linear birefringence as the unique polarization parameter. These results show a promising way for obtaining CNC birefringent films by a simple and controllable method.

Research paper thumbnail of Electrical peculiarities in Al/Si/Ge/…/Ge/Si and Al/SiGe/Si structures

Electrical peculiarities in Al/Si/Ge/…/Ge/Si and Al/SiGe/Si structures

Applied Surface Science, 2002

The current–voltage (I–V) and capacitance–voltage (C–V) behaviour of different Si/Ge multilayers ... more The current–voltage (I–V) and capacitance–voltage (C–V) behaviour of different Si/Ge multilayers and SiGe single layers prepared on p-type Si substrates by magnetron sputtering and annealing, has been studied in the temperature range of 80–320K by using Al Schottky contacts as test structures. Although a significant influence of the microstructure of the Si/Ge multilayers and SiGe layers was obtained on the

Research paper thumbnail of Ion implanted dopants in GaN and AlN: Lattice sites, annealing behavior, and defect recovery

Journal of Applied Physics, 2000

The recovery of structural defects in gallium nitride ͑GaN͒ and aluminum nitride ͑AlN͒ after impl... more The recovery of structural defects in gallium nitride ͑GaN͒ and aluminum nitride ͑AlN͒ after implantation of 111 In ϩ and 89 Sr ϩ in the dose range ͑0.1-3͒ 10 13 cm Ϫ2 and ion energies of 60-400 keV has been investigated as a function of annealing temperature with emission channeling ͑EC͒ and perturbed ␥␥ angular correlation spectroscopy. The implanted In and Sr atoms occupied substitutional sites in heavily perturbed surroundings of point defects after room temperature implantation. No amorphization of the lattice structure was observed. The point defects could be partly removed after annealing to 1473 K for 10-30 min. Lattice site occupation of implanted light alkalis, 24 Na ϩ in GaN and AlN as well as 8 Li ϩ in AlN, were also determined by EC as a function of implantation and annealing temperature. These atoms occupied mainly interstitial sites at room temperature. Lithium diffusion and the occupation of substitutional sites was observed in GaN and AlN at implantation temperatures above 700 K. A lattice site change was also observed for sodium in AlN, but not in GaN after annealing to 1073 K for 10 min.

Research paper thumbnail of Sum decomposition of Mueller-matrix images and spectra of beetle cuticles

Spectral Mueller matrices measured at multiple angles of incidence as well as Mueller matrix imag... more Spectral Mueller matrices measured at multiple angles of incidence as well as Mueller matrix images are recorded on the exoskeletons (cuticles) of the scarab beetles Cetonia aurata and Chrysina argenteola. Cetonia aurata is green whereas Chrysina argenteola is gold-colored. When illuminated with natural (unpolarized) light, both species reflect left-handed and near-circularly polarized light originating from helicoidal structures in their cuticles. These structures are referred to as circular Bragg reflectors. For both species the Mueller matrices are found to be nondiagonal depolarizers. The matrices are Cloude decomposed to a sum of non-depolarizing matrices and it is found that the cuticle optical response, in a first approximation can be described as a sum of Mueller matrices from an ideal mirror and an ideal circular polarizer with relative weights determined by the eigenvalues of the covariance matrices of the measured Mueller matrices. The spectral and image decompositions are consistent with each other. A regression-based decomposition of the spectral and image Mueller matrices is also presented whereby the basic optical components are assumed to be a mirror and a circular polarizer as suggested by the Cloude decomposition. The advantage with a regression decomposition compared to a Cloude decomposition is its better stability as the matrices in the decomposition are determined a priori. The origin of the depolarizing features are discussed but from present data it is not possible to conclude whether the two major components, the mirror and the circular polarizer are laterally separated in domains in the cuticle or if the depolarization originates from the intrinsic properties of the helicoidal structure.

Research paper thumbnail of Chirality-induced polarization effects in the cuticle of scarab beetles: 100 years after Michelson

Philosophical Magazine, 2012

Research paper thumbnail of Optical Mueller matrix modeling of chiral Al(x)In(1− x)N nanospirals

Thin Solid Films, Nov 28, 2014

a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Chiral nanostructures Muell... more a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Chiral nanostructures Mueller matrix spectroscopic ellipsometry Anisotropy Optical modeling High degree of circular polarization

Research paper thumbnail of Polarizing properties and structural characteristics of the cuticle of the scarab Beetle Chrysina gloriosa

Thin Solid Films, Nov 28, 2014

Polarizing properties and structural characteristics of the cuticle of the scarab Beetle Chrysina... more Polarizing properties and structural characteristics of the cuticle of the scarab Beetle Chrysina gloriosa, 2013, Thin Solid Films. http://dx.a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Scarab beetle Near-circular polarization Mueller-matrix spectroscopic ellipsometry

Research paper thumbnail of Curved-Lattice Epitaxial Growth of In(x)Al(1-x)N Nanospirals with Tailored Chirality

Nano letters, Nov 26, 2014

Chirality, tailored by external morphology and internal composition, has been realized by control... more Chirality, tailored by external morphology and internal composition, has been realized by controlled curved-lattice epitaxial growth of InxAl1-xN nanospirals. The curved morphology of the spiral segments is a result of a lateral compositional gradient while maintaining a preferred crystallographic growth direction, implying a lateral gradient in optical properties. Individual nanospirals show an asymmetric core-shell structure with curved basal planes. Mueller matrix spectroscopic ellipsometry shows that the tailored chirality is manifested in the polarization state of light reflected off the nanospirals.

Research paper thumbnail of Evidence for a dispersion relation of optical modes in the cuticle of the scarab beetle Cotinis mutabilis

Optical Materials Express, Nov 5, 2014

Variable angle Mueller matrix spectroscopic ellipsometry is used to study the properties of light... more Variable angle Mueller matrix spectroscopic ellipsometry is used to study the properties of light reflected from the exoskeleton (cuticle) of the scarab beetle Cotinis mutabilis. For unpolarized incident light, the ellipticity and degree of polarization of the reflected light reveal a lefthanded helical structure in the beetle cuticle. Analysis of the spectral position of the maxima and minima in the interference oscillations of the Mueller-matrix elements provides evidence for a dispersion relation similar to that of optical modes in chiral nematic liquid crystals calculated within a two-wave approximation. Additionally, a structural model for the cuticle of C. mutabilis is derived from the properties of the optical modes for nonattenuated propagation or selective reflection.

Research paper thumbnail of Chiral nanostructures producing near circular polarization

Optical Materials Express, Jun 19, 2014

Optical properties of chiral nanostructured films made of Al 1−x In x N using a new growth mechan... more Optical properties of chiral nanostructured films made of Al 1−x In x N using a new growth mechanism -curved-lattice epitaxial growth -are reported. Using this technique, chiral films with rightand left-handed nanospirals were produced. The chiral properties of the films, originating mainly from an internal anisotropy and to a lesser extent from the external helical shape of the nanospirals, give rise to selective reflection of circular polarization which makes them useful as narrow-band near-circular polarization reflectors. The chiral nanostructured films reflect light with high degree of circular polarization in the ultraviolet part of the spectrum with left-and right-handedness depending on the handedness of the nanostructures in the films.

Research paper thumbnail of Exploring optics of beetle cuticles with Mueller-matrix ellipsometry

Spectroscopic Mueller-matrix ellipsometry at variable angles of incidence is applied to beetle cu... more Spectroscopic Mueller-matrix ellipsometry at variable angles of incidence is applied to beetle cuticles using a small (50 -100 μm) spot size. It is demonstrated how ellipticity and degree of polarization of the reflected light can be derived from a Mueller matrix providing a detailed insight into reflection properties. Results from Cetonia aurata, Chrysina argenteola and Cotinis mutabilis are presented. The use of Mueller matrices in regression analysis to extract structural and optical parameters of cuticles is briefly described and applied to cuticle data from Cetonia aurata whereby the pitch of the twisted layered structure in the cuticle is determined as well as the refractive indices of the epicuticle and the exocuticle.

Research paper thumbnail of Polarization of Light Reflected from Chrysina Gloriosa Under Various Illuminations

Materials Today: Proceedings, 2014

When illuminated with unpolarized light, the scarab beetle Chrysina gloriosa, reflects left-hande... more When illuminated with unpolarized light, the scarab beetle Chrysina gloriosa, reflects left-handed near-circularly polarized light for a broad range of angles of incidence and wavelengths in the visible. It is, however, known that light scattered from the sky, reflected on water or transmitted through leaves often is linearly polarized. In this study we have analysed the polarization of light reflected on this beetle when illuminated with different polarization states of light. We have also analysed how the response would be with a polarization-sensitive detector. The reflected irradiance is shown to be highest when the incident light is s-polarized or left-handed polarized and the detector is unpolarized (or vice versa). In the case in which both, the source and the detector, are polarized, the irradiance is highest when both are s-polarized. On the contrary the visibility is low when the source is s-polarized and the detector is p-polarized.

Research paper thumbnail of Comparison and analysis of Mueller-matrix spectra from exoskeletons of blue, green and red Cetonia aurata

Thin Solid Films, Nov 28, 2014

a b s t r a c t a r t i c l e i n f o Available online xxxx

Research paper thumbnail of Polarizing Natural Nanostructures

Polarizing Natural Nanostructures

Springer Series in Surface Sciences, 2014

ABSTRACT A brief description of the polarizing environment we are living in and the possibilities... more ABSTRACT A brief description of the polarizing environment we are living in and the possibilities for some animals to detect this polarization is made. This is followed by a presentation of how animals and plants generate polarized light, usually through reflection from micro- and nanostructures. Special attention is made to scarab beetles reflecting light with a high degree of circular polarization. Finally some comments on the biological aspects of polarization are made.

Research paper thumbnail of Cuticle structure of the scarab beetle Cetonia aurata analyzed by regression analysis of Mueller-matrix ellipsometric data

Optics Express, 2013

Since one hundred years it is known that some scarab beetles reflect elliptically and near-circul... more Since one hundred years it is known that some scarab beetles reflect elliptically and near-circular polarized light as demonstrated by Michelson for the beetle Chrysina resplendens. The handedness of the polarization is in a majority of cases left-handed but also right-handed polarization has been found. In addition, brilliant colors with metallic shine are observed. The polarization and color effects are generated in the beetle exoskeleton, the so-called cuticle. The objective of this work is to demonstrate that structural parameters and materials optical functions of these photonic structures can be extracted by advanced modeling of spectral multi-angle Mueller-matrix data recorded from beetle cuticles. A dual-rotating compensator ellipsometer is used to record normalized Mueller-matrix data in the spectral range 400 -800 nm at angles of incidence in the range 25-75 • . Analysis of data measured on the scarab beetle Cetonia aurata are presented in detail. The model used in the analysis mimics a chiral nanostructure and is based on a twisted layered structure. Given the complexity of the nanostructure, an excellent fit between experimental and model data is achieved. The obtained model parameters are the spectral variation of the refractive indices of the cuticle layers and structural parameters of the chiral structure.

Research paper thumbnail of Symmetries and relationships between elements of the Mueller matrix spectra of the cuticle of the beetle Cotinis mutabilis

Thin Solid Films, Nov 28, 2014

Symmetries and relationships between elements of the Mueller matrix spectra of the cuticle of the... more Symmetries and relationships between elements of the Mueller matrix spectra of the cuticle of the beetle Cotinis mutabilis, 2013, Thin Solid Films. http://dx.a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Structural color Left-handed polarized light Mueller matrix Scarab beetles

Research paper thumbnail of Fano interference in supported gold nanosandwiches with weakly coupled nanodisks

Optics express, Jan 31, 2012

We studied the far-field optical response of supported gold-silica-gold nanosandwiches using spec... more We studied the far-field optical response of supported gold-silica-gold nanosandwiches using spectroscopic ellipsometry, reflectance and transmittance measurements. Although transmittance data clearly shows that the gold nanodisks in the sandwich structure interact very weakly, oblique reflectance spectra of s- and p-polarized light show clearly asymmetric line-shapes of the Fano type. However, all experimental results are very well described by modeling the gold nanodisks as oblate spheroids and by employing a 2 × 2 scattering matrix formulation of the Fresnel coefficients provided by an island film theory. In particular, the Fano asymmetry can be explained in terms of interference between the scattered waves from the decoupled nanodisks in the spectral range limited by their respective plasmon resonances. We also show that the reflectance and ellipsometry spectra can be described by a three-layer system with uniaxial effective dielectric functions.

Research paper thumbnail of Chirality-induced polarization effects in the cuticle of scarab beetles: 100 years after Michelson

Philosophical Magazine, 2012

Research paper thumbnail of Optical response of supported gold nanodisks

Optics Express, 2011

It is shown that the ellipsometric spectra of short range ordered planar arrays of gold nanodisks... more It is shown that the ellipsometric spectra of short range ordered planar arrays of gold nanodisks supported on glass substrates can be described by modeling the nanostructured arrays as uniaxial homogeneous layers with dielectric functions of the Lorentz type. However, appreciable deviations from experimental data are observed in calculated spectra of irradiance measurements. A qualitative and quantitative description of all measured spectra is obtained with a uniaxial effective medium dielectric function in which the nanodisks are modeled as oblate spheroids. Dynamic depolarization factors in the long-wavelength approximation and interaction with the substrate are considered. Similar results are obtained calculating the optical spectra using the island-film theory. Nevertheless, a small in-plane anisotropy and quadrupolar coupling effects reveal a very complex optical response of the nanostructured arrays.

Research paper thumbnail of Optical properties and switching of a rose bengal derivative studied by spectroscopic ellipsometry

Optical properties in terms of the complex-valued dielectric function were determined for spin-co... more Optical properties in terms of the complex-valued dielectric function were determined for spin-coated films of a Rose Bengal derivative using variable angle of incidence spectroscopic ellipsometry in the visible and infrared wavelength regions. In addition, the thickness and roughness of the films were determined and related to the solution concentration of Rose Bengal. Switching between two different oxidation states of the Rose Bengal derivative was investigated. The two states were chemically induced by exposure to vapors of hydrochloric acid and ammonia, respectively. A substantial and reversible change of the optical properties of the films was observed.