Three-dimensional Photonic Crystals Research Articles

Structurally colored silica photonic crystal coatings modified by Ce or Eu rare-earth dopants

Recently three-dimensional photonic crystal (PC) materials with inverse opal morphology are very popular due to their high application capacity. The structural color that is one of these popular application areas attracts attention with fadeless bright color, low toxicity and eco-friendly features. With this respect, silica based inverse opal photonic crystals were deposited on borosilicate glass substrates and the effect of the cerium (Ce) and europium (Eu) dopants on the properties of these coatings were investigated in detail. Thermal, structural and physical properties were characterized via differential thermal analysis (DTA-TGA), x-ray photoelectron spectroscopy (XPS), x-ray diffractometer (XRD), scanning electron microscope (SEM), UV spectrophotometer (UV–vis) and optical microscope (OM), respectively. The results reveal that the ordered porous honeycomb like morphology surrounds the entire 3-D structure. Periodically ordered photonic crystal morphologies are achieved at the coatings with the lowest dopant ratios. SiO2 based PC coatings possess blue and purple structural colors. It was found that the photonic band gap value was red-shifted by Ce doping in the coating while blue-shifting by Eu doping.

Local density of optical states in the three-dimensional band gap of a finite photonic crystal

A three-dimensional (3D) photonic band gap crystal is an ideal tool to completely inhibit the local density of optical states (LDOS) at every position in the crystal throughout the band gap. This notion, however, pertains to ideal infinite crystals, whereas any real crystal device is necessarily finite. This raises the question as to how the LDOS in the gap depends on the position and orientation inside a finite-size crystal. Therefore, we employ rigorous numerical calculations using finite-difference time-domain (FDTD) simulations of 3D silicon inverse woodpile crystals filled with air or with toluene, as previously studied in experiments. We find that the LDOS versus position decreases exponentially into the bulk of the crystal. From the dependence on dipole orientation, we infer that the characteristic LDOS decay length $\ell_{\rho}$ is mostly related to far-field dipolar radiation effects, whereas the prefactor is mostly related to near-field dipolar effects. The LDOS decay length has a remarkably similar magnitude as the Bragg length for directional transport, which suggests that the LDOS in the crystal is dominated by vacuum states that tunnel from the closest interface towards the position of interest. Our work leads to design rules for applications of 3D photonic band gaps in emission control and lighting, quantum information processing, and in photovoltaics.

Reflectivity of three-dimensional GaAs photonic band-gap crystals of finite thickness

We study the optical reflectivity of three-dimensional (3D) photonic band gap crystals with increasing thickness. The crystals consist of GaAs plates with nanorod arrays that are assembled by an advanced stacking method into high-quality 3D woodpile structures. We observe intense and broad reflectivity peak with stop bands that correspond to a broad gap in the photonic band structures. The maximum reflectivity quickly reaches high values even for a few crystal layers. Remarkably, the bandwidth of the stop bands hardly decreases with increasing crystal thickness, in good agreement with FDTD simulations. This behavior differs remarkably from the large changes observed earlier in weakly interacting 3D photonic crystals. The nearly constant bandwidth and high reflectivity are rationalized by multiple Bragg interference that occurs in strongly interacting photonic band gap crystals, whereby the incident light scatters from multiple reciprocal lattice vectors simultaneously, in particular from oblique ones that are parallel to a longer crystal dimension and thus experience hardly any finite size effects. Our new insights have favorable consequences for the application of 3D photonic band gap crystals, notably since even thin structures reveal the full band gap functionality, including devices that shield quantum bits from vacuum fluctuations.

Fabrication of cotton fabrics with both bright structural colors and strong hydrophobicity

In order to achieve the coloration and hydrophobicity of cotton fabrics through one-step processing, this study utilized a vertical deposition method to fabricate polystyrene (PSt) photonic crystals on cotton fabrics. The morphological changes of cotton fabrics, the arrangement of photonic crystals and structural color effects, and the changes of hydrophobicity of cotton fabrics were investigated. Moreover, the possible mechanism of hydrophobicity was proposed. The results shows that the original gaps existed between adjacent fibers of cotton fabrics are obviously filled by the three-dimensional photonic crystals after the vertical deposition, the resultant cotton fabrics presented bright and iridescent structural colors and strong hydrophobicity. Specifically, a kind of multi-layered structure of water droplets-photonic crystal layers-fabrics was essentially presented, and the strong hydrophobicity was due to the PSt microspheres that made up the photonic crystals itself had good hydrophobicity and the own structure of photonic crystals was rough.

Dynamic photonic crystal in a colloidal quantum-dot solution: formation, structure analysis, and dimensionality switching.

We demonstrated, for the first time, to the best of our knowledge, a simple method to create three-dimensional (3D) dynamic photonic crystal (PhC) with controllable lattice symmetry through the interference of four non-coplanar laser beams in a non-linear optical medium [colloidal solution of CdSe/ZnS quantum dots (QDs)]. 3D dynamic PhC was formed due to the periodically changing refraction and absorption of resonantly excited excitons in the colloidal solution of QDs. The formation of dynamic PhC was confirmed by the observed self-diffraction of the laser beams on the dynamic structure which they have created. Tuning of the PhC dimensionality to the two-dimensional (2D) and one-dimensional (1D) was done through the reduction of the number of interfering beams to three and two, respectively, and by controlling the polarization of interacting beams. Physical processes responsible for the observed self-action effects that arise in CdSe/ZnS QDs are discussed in detail.

Finite-size scaling of the density of states inside band gaps of ideal and disordered photonic crystals

We study the density of states (DOS) in band gaps of ideal and disordered three-dimensional photonic crystals of finite size. The ideal crystal is a diamond lattice of resonant point scatterers (atoms) whereas the disordered one is obtained from it by displacing the scatterers by random distances in random directions. We find that DOS inside a band gap of the ideal crystal decreases as the inverse of the crystal size. Disorder narrows the band gap and DOS exhibits enhanced fluctuations near the new band edges. However, the average DOS still exhibits the same scaling with the crystal size within the remaining band gap. A phenomenological explanation of this scaling suggests that it should hold for one- and two-dimensional photonic crystals as well.

Area scalable and period manipulable three-dimensional optically induced photorefractive photonic periodic crystal or aperiodic quasicrystal

Abstract We experimentally investigate the formation of area-scalable three-dimensional (3D) photonic periodic crystal and aperiodic quasicrystal in an iron doped lithium niobate photorefractive material by multi-wedge prisms assisted compact and versatile single step optical induction approach. The induced large-area lattice microstructures are analyzed and verified by plane wave guiding, Brillouin-zone spectroscopy, far field diffraction pattern imaging, angle-dependent transmission spectra. Our technique can be easily expanded for the larger area of photonic periodic crystal or aperiodic quasicrystal microstructures. We also demonstrate experimentally and theoretically the manipulation to the period of 3D photorefractive photonic lattices by engineered vertex angle of multi-wedge prisms. The intensity analyses of interference light fields show that (1) the 3D photonic lattice has not only different Z-axis longitudinal structure, but also different X–Y front structure to the corresponding 2D photonic lattice, and (2) there exist three sets of sub-lattices which are mutually nested to form the 3D triangle photonic crystal.

Rotational Periodicity Display of the Tunable Wettability Pattern in a Photoswitch Based on a Response Bilayer Photonic Crystal.

Although the forward diffraction of the three-dimensional (3D) photonic crystal is easily applied to a photoswitch, backward diffraction rainbows are rarely reported. The first rotational photoswitch based on a bilayer 3D photonic crystal with backward diffractions similar to those of two-dimensional photonic crystals was fabricated by vertically combining different thicknesses of nanoparticle templates. When rotating the bilayer photonic crystal, the opening or closing of the rotational photoswitch shows periodic reproducibility values of 30 and 60°. Different periods are regulated by the thickness and scattering effect of the top layer. Moreover, invisible patterns can be encoded and erased by changing the wettability via pH. Because of the decreasing of the refractive index differentials, it will be revealed rapidly when immersed in water. The revealed pattern can be periodically turned on and off by rotating the bilayer photonic crystal. It has great application prospects in optical prism, warning board, anti-counterfeiting, steganography, watermarking, and complex information coding.

Core-shell silica-rhodamine B nanosphere for synthetic opals: from fluorescence spectral redistribution to sensing.

Photonic crystals are a unique tool to modify the photoluminescence of light-emitting materials. A variety of optical effects have been demonstrated by infiltrating opaline structures with photoactive media. On the other hand, the fabrication of such structures includes complex infiltration steps, that often affect the opal lattice and decrease the efficiency of light emission control. In this work, silica nanospheres were directly functionalized with rhodamine B to create an emitting shell around the dielectric core. Simple tuning of the microsphere preparation conditions allows selecting the appropriate sphere diameter and polydispersity index approaching 5%. These characteristics allow facile self-assembling of the nanospheres into three-dimensional photonic crystals whose peculiar density of photonic states at the band-gap edges induces spectral redistribution of the rhodamine B photoluminescence. The possibility to employ the new stable structure as sensor is also investigated. As a proof of principle, we report the variation of light emission obtained by exposure of the opal to vapor of chlorobenzene.

Synthesis and properties of SiO2 photonic crystals modified by DNA

Background: Photonic crystals are structures characterized by periodic modulations of the refractive index with a period commensurate with the wavelength. This periodicity is associated with the existence of a complete band gap in the spectrum of the electromagnetic states of the crystal. The stop zone is called the band gap for the highlighted direction in the crystal. Globular photonic crystals are called three-dimensional photonic crystals, which consist of the same diameter globules. The pores between the globules in the opal allow one to change the refractive index and optical contrast of the material. The task of controlling the stop-zone frequency limits of a globular photonic crystal without changing its physical structure is of practical interest. The easiest way to control the stop-zone parameters is to fill the pores of the photonic crystals with materials with different refractive indices, for example, DNA. Control of the optical parameters of a globular photonic crystal can be used for the creation of optical detectors, sensors, test systems, a quantum biocomputer as well as analyzing and studying a conformational state of DNA. Objectives: the creation of SiO2 globular photonic crystals modified by DNA and studying of the influence of DNA on their optical properties. Materials and Methods: Ethyl alcohol, distilled water, ammonium hydroxide, tetraethoxysilane and DNA were used to synthesize SiO2 photonic crystals. Aqueous DNA solution was used to infiltrate the photonic crystals. We used a visible range spectroscopy for optical experiments and a finite-difference time-domain (FDTD) method for numerical calculations. Results: SiO2 globular photonic crystals modified by DNA were synthesized with 195 nm globules. The reflection spectra of the obtained photonic crystals were measured. A red-shift of the stop-zone maximum after the infiltration of photonic crystals with DNA molecules was found. The electric field distribution was calculated for the photonic crystal with 200 nm globules. Conclusions: FDTD calculations in the linear mode show that the presence of point defects in the structure of the photonic crystal influences the amplification of the local electric field in the interglobular space of the photonic crystal, which houses the DNA molecule at infiltration. The DNA infiltration into the pores of a photonic crystal changes the effective refractive index of the system by 5.99%. Synthesis SiO2 photonic crystals with DNA leads to the formation of a more ordered structure at the macro levels. Thus, DNA serves as a template-like structure for photonic crystals to be assembled on. In this case, the effective refractive index of the system increases by 6.01%.

Investigation on the three-dimensional magnetized plasma photonic crystals with function dielectric under magneto-optical Faraday effect

In this paper, the dispersion features of three-dimensional (3D) magnetized plasma photonic crystals with function dielectric arranged by the simple-cubic lattices which are called the function magnetized plasma photonic crystals (FMPPCs) are investigated in theory by the plane wave expansion method under the magneto-optical Faraday effect. The configuration of such FMPPCs is that the function dielectric spheres are inserted into the magnetized plasma. The relative dielectric constant of function dielectric sphere is space-depended. The parameters of FMPPCs effects on the photonic band gaps (PBGs) for the right and left circular polarization waves also are studied. The computed results demonstrate that the obtained PBGs can be tailored by those parameters as mentioned above. The larger PBGs can be achieved in the 3D FMPPCs with the spherical filler compared with those FMPPCs with the cubic filler, when their filling factors are same. The right and left circular polarization waves also can be splitted when the the parameters of FMPPCs are large enough.

Distributed feedback organic lasing in photonic crystals.

Considerable research efforts have been devoted to the investigation of distributed feedback (DFB) organic lasing in photonic crystals in recent decades. It is still a big challenge to realize DFB lasing in complex photonic crystals. This review discusses the recent progress on the DFB organic laser based on one-, two-, and three-dimensional photonic crystals. The photophysics of gain materials and the fabrication of laser cavities are also introduced. At last, future development trends of the lasers are prospected.

Three-dimensional macroporous photonic crystal enhanced photon collection for quantum dot-based luminescent solar concentrator

A luminescent solar concentrator (LSC) is a photon managing device that can harvest, direct and concentrate solar light to small areas, enabling subsequent coupling to photovoltaic devices (PVs) for enhanced solar energy conversion. However, the intrinsic photon loss through the so-called escape cone of the LSCs significantly limits their light harvesting and concentrating performance. In this work, we introduce a facile and low-cost approach for the fabrication of a three-dimensional (3D) macroporous photonic crystal (PC) filter as an efficient photon reflector, which can be coated onto quantum dot (QD) based LSC devices. We demonstrate that by controlling the PC reflection band to match the emission profile of the QD emitters, the light trapping efficiency of the PC coated LSC (PC-LSC) can be significantly improved from 73.3% to 95.1% as compared to the conventional PC-free LSC due to the reduced escape cone photon loss. In addition, we have developed a simulation model that considers the PC reflector effect. Both experimental and simulation results show that the enhancement in LSC device performance induced by the PC reflector increases with increasing dimension. In fact, simulation data predicts a maximum of 13.3-fold enhancement in external quantum efficiency (EQE) and concentration factor (C factor) of the PC-LSC under more ideal conditions. Moreover, the simulation result offers insight into the relationship between photon output efficiencies and the geometric design of the PC-LSC. Our study sheds light on future design and fabrication of LSC devices with enhanced photon collection and concentrating efficiencies through novel and wavelength-selective photon reflectors.

Reconfiguration of three-dimensional liquid-crystalline photonic crystals by electrostriction.

Natural self-assembled three-dimensional photonic crystals such as blue-phase liquid crystals typically assume cubic lattice structures. Nonetheless, blue-phase liquid crystals with distinct crystal symmetries and thus band structures will be advantageous for optical applications. Here we use repetitive electrical pulses to reconfigure blue-phase liquid crystals into stable orthorhombic and tetragonal lattices. This approach, termed repetitively applied field, allows the system to relax between each pulse, gradually transforming the initial cubic lattice into various intermediate metastable states until a stable non-cubic crystal is achieved. We show that this technique is suitable for engineering non-cubic lattices with tailored photonic bandgaps, associated dispersion and band structure across the entire visible spectrum in blue-phase liquid crystals with distinct composition and initial crystal orientation. These field-free blue-phase liquid crystals exhibit large electro-optic responses and can be polymer-stabilized to have a wide operating temperature range and submillisecond response speed, which are promising properties for information display, electro-optics, nonlinear optics, microlasers and biosensing applications.

Efficient nonlinear beam shaping in three-dimensional lithium niobate nonlinear photonic crystals

Nonlinear beam shaping refers to spatial reconfiguration of a light beam at a new frequency, which can be achieved by using nonlinear photonic crystals (NPCs). Direct nonlinear beam shaping has been achieved to convert second-harmonic waves into focusing spots, vortex beams, and diffraction-free beams. However, previous nonlinear beam shaping configurations in one-dimensional and two-dimensional (2D) NPCs generally suffer from low efficiency because of unfulfilled phase-matching condition. Here, we present efficient generations of second-harmonic vortex and Hermite-Gaussian beams in the recently-developed three-dimensional (3D) lithium niobate NPCs fabricated by using a femtosecond-laser-engineering technique. Since 3D χ(2) modulations can be designed to simultaneously fulfill the requirements of nonlinear wave-front shaping and quasi-phase-matching, the conversion efficiency is enhanced up to two orders of magnitude in a tens-of-microns-long 3D NPC in comparison to the 2D case. Efficient nonlinear beam shaping paves a way for its applications in optical communication, super-resolution imaging, high-dimensional entangled source, etc.

Plasmonic-3D photonic crystals microchip for surface enhanced Raman spectroscopy

Plasmonic-dielectic hybrid substrates of Ag-islands on three-dimensional photonic crystals are fabricated through magnetron sputtering of silver onto hydrophobized silica photonic crystals, free from etching process. Without typical “hot-spots” such as nanogaps, significant Raman enhancements can be achieved, attributed to the enhanced electromagnetic field and scattering of the plasmonic nanoparticles as well as the enhanced light-matter interaction by the slow photon effects. The detection limit for adenine by the hybrid substrates reaches nM level, with a calculated enhancement factor of 1.13 × 107, which is three orders of magnitude higher than the conventional noble metal film over nanosphere (FON) control group. Furthermore, microchips based on the hybrid substrates are facilely achieved, enabling micro-detection through super hydrophobic concentration. The facile fabrication and effective Raman enhancements make the Ag-islands on 3D photonic crystals promising candidates in the field of chemical sensors, Raman mapping and bioassays.

A low cost and large-scale synthesis of 3D photonic crystal with SP2 lattice symmetry

In this work, a novel lithographic method is proposed to prepare three-dimensional (3D) photonic crystal (PC) that is different from conventional top-down and bottom-up approaches. The method combines a 2D optical mask and off-the-axis double optical exposures to create a desirable 3D PC structure. Since the method uses only two optical exposures of a photo-resist layer, it is inherently a low-cost, high throughput and wafer-scale lithographic method. The method is implemented to make a slanted post 3D PC having the SP2 lattice symmetry. Three types of SP2 3D PC structures were successfully fabricated with a minimum feature size of d=1.5 μm over a large scale of 8x10 mm2, without any observable fabrication defects. The SP2 PCs are: (i) SU8 posts in air background, (ii) air pores in CdS background and (iii) Pt coated on SU8 SP2 templates. A spectroscopic study of the SP2 PCs shows select spectral regions of high reflectance, indicating the existence of a photonic stop band. This low-cost and large-scale method could enable broader technological impacts of 3D PC materials in areas such as thermo-photovoltaics and above room-temperature Bose-Einstein Condensation. Furthermore, this off-axis method could lead to the creation of an entirely new class of slanted-rod based photonic crystals, such as topological photonic crystal in 3D.

Polarization-dependent multiple Bragg diffraction in the high-energy region of three-dimensional photonic crystals

We have studied angle- and polarization-dependent multiple Bragg diffraction in the high-energy region of a three-dimensional photonic crystal, which is quite distinctive as compared to the low-energy region. We identify polarization-dependent prominent multiple Bragg diffraction at different angular ranges. The decrease and increase in the peak reflectivity of diffraction peaks confirm the energy exchange between them in the coupling region. The TE-polarized light interacts strongly with crystal compared to TM polarization in the high-energy region, which agrees with theory. The results are useful for designing devices with the selective tuning of Bragg diffracted wavelengths in a broad wavelength range for applications like optical switches, waveguides, and filters.

Optical properties and photonic density of states in one-dimensional and three-dimensional liquid-crystalline photonic crystals

ABSTRACT Complex optical investigations were performed in one-dimensional (cholesteric) and three-dimensional (Blue Phase II) liquid-crystalline photonic crystals. Spectra of optical transmission and luminescence in the range of the photonic stop band contain information about the local anisotropy, characteristics of the photonic stop band, photonic density of states. We determine the photonic density of states in one-dimensional and three-dimensional liquid-crystalline photonic crystals employing measurements of polarised luminescence. The width of the photonic band gap, density of states and the optical characteristics related to the density of states essentially change with temperature in one-dimensional cholesteric photonic crystal. Drastic transformation of the density of states was found at the transition from one-dimensional to three-dimensional (Blue Phase II) photonic crystal. The results of our investigations demonstrate the possibility to employ the applied method for various types of photonic structures.

Highly efficient GPU eigensolver for three-dimensional photonic crystal band structures with any Bravais lattice

A null-space free method with the FFT-based matrix–vector multiplications was proposed to solve the Maxwell equations that model the three-dimensional photonic crystals. The most time-consuming parts of this method were the FFT-based matrix–vector multiplications. In this article, we propose new mathematical formulas to compute the FFT-based matrix–vector multiplications and derive highly efficient algorithms on top of the NVIDIA GPU architecture. The resulting algorithms are approximately two- to threefold faster than the previous algorithms. We have successfully used a single NVIDIA Tesla P100 GPU to solve a set of generalized eigenvalue problems of 5,184,000 dimensions in 17 to 22 seconds for each problem. Furthermore, we ported the codes to a GPU cluster and achieved near linear scalability. To our knowledge, these GPU implementations of the proposed algorithms are the fastest implementations. The schemes can be applied to simulate a three-dimensional photonic crystal with all 14 Bravais lattices. These highly efficient schemes and codes raise possibilities for large-scale and near real-time numerical simulations for novel physical discoveries and engineering applications of photonic crystals.