Amorphous Photonic Structures Research Articles

Additive Mixing and Conformal Coating of Noniridescent Structural Colors with Robust Mechanical Properties Fabricated by Atomization Deposition.

Artificial structural colors based on short-range-ordered amorphous photonic structures (APSs) have attracted great scientific and industrial interest in recent years. However, the previously reported methods of self-assembling colloidal nanoparticles lack fine control of the APS coating and fixation on substrates and poorly realize three-dimensional (3D) conformal coatings for objects with irregular or highly curved surfaces. In this paper, atomization deposition of silica colloidal nanoparticles with poly(vinyl alcohol) as the additive is proposed to solve the above problems. By finely controlling the thicknesses of APS coatings, additive mixing of noniridescent structural colors is easily realized. Based on the intrinsic omnidirectional feature of atomization, a one-step 3D homogeneous conformal coating is also readily realized on various irregular or highly curved surfaces, including papers, resins, metal plates, ceramics, and flexible silk fabrics. The vivid coatings on silk fabrics by atomization deposition possess robust mechanical properties, which are confirmed by rubbing and laundering tests, showing great potential in developing an environmentally friendly coloring technique in the textile industry.

Tunable Amorphous Photonic Materials with Pigmentary Colloidal Nanostructures

Amorphous photonic structures using pigmentary α-Fe2O3/SiO2 core–shell nanoparticles are succesfully fabricated. The resulting non-iridicent brilliant colors can be manipulated by shell thickness, particle concentration, and external electrical stimuli using electrophoretic deposition process. Fully reversible and instantaneous color changes as well as noticeable difference between transmitted and reflected colors is observed.

Rapid fabrication of robust, washable, self-healing superhydrophobic fabrics with non-iridescent structural color by facile spray coating

An amorphous photonic structure dyeing system has been fabricated which endows non-iridescent color fabrics with color-tunable, robust, washable, self-healing and superhydrophobic properties by spray coating technique and heat treatment.

Optimization of TM modes for amorphous slab lasers.

We perform a numerical study of two-dimensional amorphous photonic structures consisting of dielectric rods in a close-packed honeycomb-like structure, with nearest-neighbor rods joined by dielectric veins of various widths. For vein widths comparable to the rod radius, the in-plane Q factors for the transverse magnetic (TM) modes are enhanced by around two orders of magnitude, due to the presence of short-range order in the amorphous lattice, even though the density of states has a weak dip rather than a prominent gap. Such structures may be useful for realizing multi-mode random quantum cascade lasers, which lase in the TM polarization.

A humidity sensitive two-dimensional tunable amorphous photonic structure in the bivalve ligament of Meretrix linnaeus.

A humidity sensitive two-dimensional tunable amorphous photonic structure (2D TAPS) in the bivalve ligament of Meretrix linnaeus (LML) was reported in this paper. The structural color and microstructure of LML were investigated by reflection spectra and scanning electron microscopy, respectively. The results indicate that the LML has complex structural colors from blue to orange in the wet state from ventral to dorsal, which are derived from the aragonite fiber diameter increases continuously from ventral to dorsal of the ligament. The reflection peak wavelength of the wet LML can blue-shift from 522 nm to 480 nm with the air drying time increased from 0 to 60 min, while the reflectivity decreases gradually and only a weak reflection peak at last, relevant color changes from green to light blue. The structural color in the LML is produced by a two-dimensional amorphous photonic structure consists of aligned aragonite fibers and proteins, in which the diameters of the aragonite fiber and the inter-fiber spacing are 104±11 nm and 126±16 nm, respectively. Water can reversibly tune the reflection peak wavelength and reflectivity of this photonic structure, and the regulation achieved through dynamically tune the degree of order and lattice constant of the ligament in the different wet states.

Photonics: Using Cuttlefish Ink as an Additive to Produce ­Non‐iridescent Structural Colors of High Color Visibility (Adv. Mater. 32/2015)

Non-iridescent structural colors of high color visibility are produced by amorphous photonic structures, in which natural cuttlefish ink is used as an additive to break down the long-range order of the structure. The color hue and its spectral purity can be tuned by adjusting the diameter of the polystyrene (PS) spheres and the proportion of ink particles, as demonstrated by X. H. Liu, L. Shi, J. Zi, and co-workers on page 4719.

Using cuttlefish ink as an additive to produce -non-iridescent structural colors of high color visibility.

Non-iridescent structural colors of high color visibility are produced by amorphous photonic structures, in which -natural cuttlefish ink is used as an additive to break down the long-range order of the structures. The color hue and its spectral purity can be tuned by adjusting the diameter of the polystyrene (PS) spheres and the proportion of ink particles.

A humidity sensitive two-dimensional tunable amorphous photonic structure in the outer layer of bivalve ligament from Sunset Siliqua.

A humidity sensitive two-dimensional tunable amorphous photonic structure (2D TAPS) in the outer layer of bivalve ligament from Sunset Siliqua (OLLS) was reported in this paper. The structural color and microstructure of OLLS were investigated by reflection spectra and scanning electron microscopy, respectively. The results indicate that the reflection peak wavelength of the wet OLLS blue-shifts from 454 nm to 392 nm with the increasing of air drying time from 0 to 40 min, while the reflectivity decreases gradually and vanishes at last, relevant color changes from blue to black background color. The structural color in the OLLS is produced by a two-dimensional amorphous photonic structure consisting of aligned protein fibers, in which the diameter of protein fiber and the inter-fiber spacing are 101 ± 12 nm. Water can reversibly tune the reflection peak wavelength and reflectivity of this photonic structure, and the regulation achieved through dynamically tuning the interaction between inter-fiber spacing and average refractive index.

Analysis on the Light-Extraction Efficiency of GaN-Based Light-Emitting Diodes With Deep-Hole Amorphous Photonic Crystals Structures

We demonstrated that amorphous photonic crystals can effectively improve the light extraction efficiency of GaN-based light-emitting diodes (LEDs) by the Anderson localization effect. The finite-difference time-domain method was employed to analyze the frequency dependence of the light localization characteristics in the amorphous photonic crystals structure. Numerical studies revealed that the localization modes become most efficient at certain frequencies, owing to the confinement by short-range order. With the action of these strong localization modes, the light that propagated in the horizontal direction was redirected and propagated in the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm z}$</tex></formula> -direction. Compared with conventional LEDs, significant enhancement of the light extraction efficiency (5.83 times) was achievable from amorphous photonic crystals LEDs with optimized structural parameters. Finally, we analyzed the physical mechanisms by which amorphous photonic crystals can effectively improve light extraction.

Photonic band gaps in three-dimensional network structures with short-range order

We present a systematic study of photonic band gaps (PBGs) in three-dimensional (3D) photonic amorphous structures (PAS) with short-range order. From calculations of the density of optical states (DOS) for PAS with different topologies, we find that tetrahedrally connected dielectric networks produce the largest isotropic PBGs. Local uniformity and tetrahedral order are essential to the formation of PBGs in PAS, in addition to short-range geometric order. This work demonstrates that it is possible to create broad, isotropic PBGs for vector light fields in 3D PAS without long-range order.

Strong Light Confinement With Periodicity

Photonic crystals were proposed over two decades ago to realize strong light confinement via their perfect photonic bandgaps, but the expected ultrahigh-Q wavelength-sized cavities were achieved just recently in a slightly different system that has only a partial bandgap, more specifically, a modulated mode-gap cavity in a 2-D photonic crystal. It is now possible to store photons for over a nanosecond in a wavelength-sized volume for this type of cavity, which has not been realized in other systems. The same confinement mechanism has provided various interesting cavities including air-core cavities, index-modulation-induced cavities, and dynamic cavities. We discuss the impact and possible applications of the achieved strong light confinement. First, it has a strong impact on photonic integrated circuits and photonic network-on-chip (NoC) applications because these cavities enable us to realize tiny, low-power-consumption, and integratable photonic devices, which are hard to realize conventionally. It is next shown that an ultrahigh- Q cavity system constitutes an extreme slow-light medium. It is also shown that ultrahigh-Q cavities enable the adiabatic tuning of light, which makes it possible to manipulate optical signals very differently from conventional optics. Finally, other possible systems promising for strong light confinement are investigated, such as 1-D photonic crystals and photonic amorphous structures without any periodicity.

Lasing modes in polycrystalline and amorphous photonic structures

We systematically studied the lasing characteristics in photonic polycrystalline and amorphous structures. 2D arrays of air holes were fabricated in a GaAs membrane. InAs quantum dots embedded in the membrane provide gain for lasing under optical pumping. The lasing modes are spatially localized, and blue shift as the structural order becomes short ranged. Our three-dimensional numerical simulations reveal that the out-of-plane leakage of the lasing mode dominates over the in-plane leakage. The lasing modes in a photonic polycrystalline move away from the center frequency of the photonic band gap to reduce the out-of-plane leakage. In a photonic amorphous structure, the short-range order improves optical confinement and enhances the quality factor of resonances. Understanding the behavior of photonic polycrystalline laser and amorphous laser opens the possibility of controlling lasing characteristic by varying the degree of structural order.

Control of Lasing in Biomimetic Structures with Short-Range Order

We demonstrate lasing in photonic amorphous structures that mimic the isotropic nanostructures which produce noniridescent color in nature. Our experimental and numerical studies reveal that lasing becomes most efficient at certain frequencies, due to enhanced optical confinement by short-range order. The optimal lasing frequency can be tuned by adjusting the structure factor. This work shows that lasing in nanostructures may be effectively improved and manipulated by short-range order.

Structural coloration and photonic pseudogap in natural random close-packing photonic structures

Scales on the elytra of longhorn beetle Anoplophora graafi display diverse non-iridescent colors ranging from blue, green, yellow, and red to purple. By structural characterizations, optical measurements, and theoretical calculations, we found that the scale colors stem from an amorphous photonic structure possessing only short-range order: random close-packing of chitin nanoparticles. Our results showed that direction-independent photonic pseudogaps found in the photon density of states of the random close-packing photonic structure are the ultimate physical origin for non-iridescent coloration of scales. The color steering strategy of scales is ingenious, simply by varying the size of chitin nanoparticles. Revealed natural random close-packing photonic structures and the color steering strategy of scales could render valuable inspiration for the artificial fabrication and design of photonic structures and devices as well.

Two-dimensional amorphous photonic structure in the ligament of bivalve Lutraria maximum

Here we report a two-dimensional amorphous photonic structure (2D APS) discovered in the ligament of bivalve Lutraria maximum, based on scanning electron microscopy and fiber optic spectrometry combined with the image processing technology and pair correlation function analysis. This structure contains 70% in volume of parallel aragonite fibers embedded in a protein matrix. These fibers, in cross section, are hexagonal to polygonal with diameters of 194nm and are packed in short-range order with a nearest-neighbor distance of 202nm. Moreover, experimentally measured reflectance spectrum and theoretical predictions prove that this photonic structure gives rise to a golden structural color with the peak wavelength at about 650nm. We expect this unraveled structure may inspire the design and synthesis of a novel 2D APS.

Photonic gaps of amorphous photonic structures

Photonic gaps of amorphous photonic structures