Currently,supra-wavelength periodic surface structures(SWPSS)are only achievable on silica dielectrics and silicon by femtosecond(fs)laser ablation,while triangular and rhombic laser induced periodic surface structure...Currently,supra-wavelength periodic surface structures(SWPSS)are only achievable on silica dielectrics and silicon by femtosecond(fs)laser ablation,while triangular and rhombic laser induced periodic surface structures(LIPSS)are achievable by circularly polarized or linear cross-polarized femtosecond laser.This is the first work to demonstrate the possibility of generating SWPSS on Sn and triangular and rhombic LIPSS on W,Mo,Ta,and Nb using a single linearly polarized femtosecond laser.We discovered,for the first time,SWPSS patches with each possessing its own orientation,which are completely independent of the light polarization direction,thus,breaking the traditional rules.Increasing the laser power enlarges SWPSS periods from 4–6μm to 15–25μm.We report a maximal period of 25μm,which is the largest period ever reported for SWPSS,~10 and~4 times the maximal periods(2.4μm/6.5μm)of SWPSS ever achieved by fs and ns laser ablation,respectively.The formation of triangular and rhombic LIPSS does not depend on the laser(power)or processing(scan interval and scan methodology)parameters but strongly depends on the material composition and is unachievable on other metals,such as Sn,Al,Ti,Zn,and Zr.This paper proposes and discusses possible mechanisms for molten droplet generation/spread/solidification,Marangoni convection flow for SWPSS formation,and linear-to-circular polarization transition for triangular and rhombic LIPSS formation.Reflectance and iridescence of as-prepared SWPSS and LIPSS are characterized.It was found that besides insufficient ablation on W,the iridescence density of Ta-,Mo-,Nb-LIPSS follows the sequence of melting temperatures:Ta>Mo>Nb,which indicates that the melting temperature of metals may affect the regularity of LIPSS.This work may inspire significant interest in further enriching the diversity of LIPSS and SWPSS.展开更多
The morphological structure and optical properties of the wings of 14 species of Morphidae have been investigated. Most of the scales of the iridescent species of Morphidae （Lepidoptera） present a very particular st...The morphological structure and optical properties of the wings of 14 species of Morphidae have been investigated. Most of the scales of the iridescent species of Morphidae （Lepidoptera） present a very particular structure. The ground scales, responsible for the major part of the optical properties, are covered by a very regular set of longitudinal ridges. The ridges themselves are constituted by a superposition of lamellae that act locally as a multilayered structure. This very specific morphology leads to both interferences and diffraction effects. The first one is responsible of the brilliant blue coloration of the males, while the second one diffracts this colored light at a very large angle. These two phenomena give to the butterfly a very effective long-range communication system. The morphological characteristics of the scales of the various species are presented in detail. Two types of optical measurement were performed on the iridescent wings of 14 different species of Morphidae： spectroscopic measurements under various incidences and gonioscopic measurements for a given incidence angle and wavelength. The first allows a determination of the index of refraction of the cuticular material. The second leads to the drawing of spatial diffraction maps. It shows that most of the reflected light is diffracted laterally over a very large angle （90° 〈 0 〈 120°, according to the different species） and that this repartition depends of the polarization of incident light. As predicted by previous calculations, the dissymmetric structure of the ridge is responsible for the separation of the polarization modes in the various diffraction orders.展开更多
Femtosecond laser induced periodic surface structures(LIPSSs)are excellent biomimetic iridescent antireflective interfaces.In this work,we demonstrate the feasibility to develop tunable iridescent antireflective surfa...Femtosecond laser induced periodic surface structures(LIPSSs)are excellent biomimetic iridescent antireflective interfaces.In this work,we demonstrate the feasibility to develop tunable iridescent antireflective surfaces via simultaneous synthesis of functional metal-oxide nanomaterials,in situ deposition and hierarchical LIPSSs nanostructuring by means of femtosecond laser ablation(fs-LA)of tungsten(W)and molybdenum(Mo)in air.Adjusting the scanning interval from 1μm to 20μm allows the modulation of particle deposition rates on LIPSSs.Diminishing the scan interval enables a higher particle deposition rate,which facilitates the development of better UV-to-MIR ultrabroadband antireflective surfaces with a less pronounced iridescence.Through comparing the reflectance of hierarchical LIPSSs with different densities of loosely/tightly deposited particles,it is found that the deposited WO_(x)and MoO_(x)particle aggregates have high UV-to-MIR ultrabroadband absorbance,especially extraordinary in the MIR range.Loosely deposited particles which self-assembly into macroporous structures outperform tightly deposited particles for ultrabroadband antireflective applications.The presence of loosely deposited MoO_(x)and WO_(x)particle absorbers can cause up to 80%and 60%enhancement of antireflectance performances as compared to the tightly particle deposited LIPSSs samples.One stone of"fs-LA technique"with three birds of(particle generation,in situ deposition and LIPSS hierarchical nanostructuring)presented in this work opens up new opportunities to tune the reflectance and iridescence of metallic surfaces.展开更多
Angle dependent colors, such as iridescenee, are produced by structures present on flower petals changing their visual appearanee. These colors have been proposed to act as signals for plantinsect communication. Howev...Angle dependent colors, such as iridescenee, are produced by structures present on flower petals changing their visual appearanee. These colors have been proposed to act as signals for plantinsect communication. However, there is a paucity of behavioral data to allow for interpretations of how to classify these colors either as a signal or a cue when con sidering the n atural con ditions under which pollination occurs. We sampled flowers from 6 plant species across various viewpoints looking for changes in the visual appearanee of the petals. Spectral characteristics were measured with different instruments to simulate both the spectral and spatial characteristics of honeybee's vision. We show the presenee of color patches produced by angle dependent effects on the petals and the calyx of various species;however, the appearance of the angle dependent color patches significantly varies with viewpoint and would only be resolved by the insect eye at close distances. Behavior experiments with honeybees revealed that pollinators did not use angle dependent colors to drive behavior when presented with novel flower presentations. Results show that angle dependent colors do not comply with the requirements of a signal for plant-pollinator communication since the information transmitted by these colors would be unreliable for potential, free-flying pollination vectors. We thus classify angle dependent colors produced by micro- and ultra-structures as being a cue (a feature which has not evolved for communication), and observe no evidence supporting claims of these angle dependent colors having evolved as visual signal.展开更多
Male Lawes’s Parotia,a bird of paradise,use the highly directional reflection of the structurally colored,brilliant-silvery occipital feathers in their courtship display.As in other birds,the structural coloration is...Male Lawes’s Parotia,a bird of paradise,use the highly directional reflection of the structurally colored,brilliant-silvery occipital feathers in their courtship display.As in other birds,the structural coloration is produced by ordered melanin pigmentation.The barbules of the Parotia’s occipital feathers,with thickness,3 μm,contain 6–7 layers of densely packed melanin rodlets(diameter,0.25 μm,length,2 μm).The effectively,0.2 μm thick melanin layers separated by,0.2 μm thick keratin layers create a multilayer interference reflector.Reflectance measurements yielded peak wavelengths in the near-infrared at,1.3 μm,i.e.,far outside the visible wavelength range.With the Jamin-Lebedeff interference microscopy method recently developed for pigmented media,we here determined the refractive index of the intact barbules.We thus derived the wavelength dependence of the refractive index of the barbules’melanin to be 1.7–1.8 in the visible wavelength range.Implementing the anatomical and refractive index data in an optical multilayer model,we calculated the barbules’reflectance,transmittance and absorptance spectra,thereby confirming measured spectra.展开更多
文摘Currently,supra-wavelength periodic surface structures(SWPSS)are only achievable on silica dielectrics and silicon by femtosecond(fs)laser ablation,while triangular and rhombic laser induced periodic surface structures(LIPSS)are achievable by circularly polarized or linear cross-polarized femtosecond laser.This is the first work to demonstrate the possibility of generating SWPSS on Sn and triangular and rhombic LIPSS on W,Mo,Ta,and Nb using a single linearly polarized femtosecond laser.We discovered,for the first time,SWPSS patches with each possessing its own orientation,which are completely independent of the light polarization direction,thus,breaking the traditional rules.Increasing the laser power enlarges SWPSS periods from 4–6μm to 15–25μm.We report a maximal period of 25μm,which is the largest period ever reported for SWPSS,~10 and~4 times the maximal periods(2.4μm/6.5μm)of SWPSS ever achieved by fs and ns laser ablation,respectively.The formation of triangular and rhombic LIPSS does not depend on the laser(power)or processing(scan interval and scan methodology)parameters but strongly depends on the material composition and is unachievable on other metals,such as Sn,Al,Ti,Zn,and Zr.This paper proposes and discusses possible mechanisms for molten droplet generation/spread/solidification,Marangoni convection flow for SWPSS formation,and linear-to-circular polarization transition for triangular and rhombic LIPSS formation.Reflectance and iridescence of as-prepared SWPSS and LIPSS are characterized.It was found that besides insufficient ablation on W,the iridescence density of Ta-,Mo-,Nb-LIPSS follows the sequence of melting temperatures:Ta>Mo>Nb,which indicates that the melting temperature of metals may affect the regularity of LIPSS.This work may inspire significant interest in further enriching the diversity of LIPSS and SWPSS.
文摘The morphological structure and optical properties of the wings of 14 species of Morphidae have been investigated. Most of the scales of the iridescent species of Morphidae （Lepidoptera） present a very particular structure. The ground scales, responsible for the major part of the optical properties, are covered by a very regular set of longitudinal ridges. The ridges themselves are constituted by a superposition of lamellae that act locally as a multilayered structure. This very specific morphology leads to both interferences and diffraction effects. The first one is responsible of the brilliant blue coloration of the males, while the second one diffracts this colored light at a very large angle. These two phenomena give to the butterfly a very effective long-range communication system. The morphological characteristics of the scales of the various species are presented in detail. Two types of optical measurement were performed on the iridescent wings of 14 different species of Morphidae： spectroscopic measurements under various incidences and gonioscopic measurements for a given incidence angle and wavelength. The first allows a determination of the index of refraction of the cuticular material. The second leads to the drawing of spatial diffraction maps. It shows that most of the reflected light is diffracted laterally over a very large angle （90° 〈 0 〈 120°, according to the different species） and that this repartition depends of the polarization of incident light. As predicted by previous calculations, the dissymmetric structure of the ridge is responsible for the separation of the polarization modes in the various diffraction orders.
基金supported by the National Natural Science Foundation of China(Grant Nos.50425204,50272032&90401012)the Ministry of Sciences and Technology of China through 973-Project(Grants 2002CB61306&2001CB6104).
文摘Femtosecond laser induced periodic surface structures(LIPSSs)are excellent biomimetic iridescent antireflective interfaces.In this work,we demonstrate the feasibility to develop tunable iridescent antireflective surfaces via simultaneous synthesis of functional metal-oxide nanomaterials,in situ deposition and hierarchical LIPSSs nanostructuring by means of femtosecond laser ablation(fs-LA)of tungsten(W)and molybdenum(Mo)in air.Adjusting the scanning interval from 1μm to 20μm allows the modulation of particle deposition rates on LIPSSs.Diminishing the scan interval enables a higher particle deposition rate,which facilitates the development of better UV-to-MIR ultrabroadband antireflective surfaces with a less pronounced iridescence.Through comparing the reflectance of hierarchical LIPSSs with different densities of loosely/tightly deposited particles,it is found that the deposited WO_(x)and MoO_(x)particle aggregates have high UV-to-MIR ultrabroadband absorbance,especially extraordinary in the MIR range.Loosely deposited particles which self-assembly into macroporous structures outperform tightly deposited particles for ultrabroadband antireflective applications.The presence of loosely deposited MoO_(x)and WO_(x)particle absorbers can cause up to 80%and 60%enhancement of antireflectance performances as compared to the tightly particle deposited LIPSSs samples.One stone of"fs-LA technique"with three birds of(particle generation,in situ deposition and LIPSS hierarchical nanostructuring)presented in this work opens up new opportunities to tune the reflectance and iridescence of metallic surfaces.
文摘Angle dependent colors, such as iridescenee, are produced by structures present on flower petals changing their visual appearanee. These colors have been proposed to act as signals for plantinsect communication. However, there is a paucity of behavioral data to allow for interpretations of how to classify these colors either as a signal or a cue when con sidering the n atural con ditions under which pollination occurs. We sampled flowers from 6 plant species across various viewpoints looking for changes in the visual appearanee of the petals. Spectral characteristics were measured with different instruments to simulate both the spectral and spatial characteristics of honeybee's vision. We show the presenee of color patches produced by angle dependent effects on the petals and the calyx of various species;however, the appearance of the angle dependent color patches significantly varies with viewpoint and would only be resolved by the insect eye at close distances. Behavior experiments with honeybees revealed that pollinators did not use angle dependent colors to drive behavior when presented with novel flower presentations. Results show that angle dependent colors do not comply with the requirements of a signal for plant-pollinator communication since the information transmitted by these colors would be unreliable for potential, free-flying pollination vectors. We thus classify angle dependent colors produced by micro- and ultra-structures as being a cue (a feature which has not evolved for communication), and observe no evidence supporting claims of these angle dependent colors having evolved as visual signal.
基金This study was financially supported by AFOSR/EOARD (grant FA8655-08-1-3012).
文摘Male Lawes’s Parotia,a bird of paradise,use the highly directional reflection of the structurally colored,brilliant-silvery occipital feathers in their courtship display.As in other birds,the structural coloration is produced by ordered melanin pigmentation.The barbules of the Parotia’s occipital feathers,with thickness,3 μm,contain 6–7 layers of densely packed melanin rodlets(diameter,0.25 μm,length,2 μm).The effectively,0.2 μm thick melanin layers separated by,0.2 μm thick keratin layers create a multilayer interference reflector.Reflectance measurements yielded peak wavelengths in the near-infrared at,1.3 μm,i.e.,far outside the visible wavelength range.With the Jamin-Lebedeff interference microscopy method recently developed for pigmented media,we here determined the refractive index of the intact barbules.We thus derived the wavelength dependence of the refractive index of the barbules’melanin to be 1.7–1.8 in the visible wavelength range.Implementing the anatomical and refractive index data in an optical multilayer model,we calculated the barbules’reflectance,transmittance and absorptance spectra,thereby confirming measured spectra.
