Conventional Photonic Crystals Research Articles

Limitations in design and applications of ultra-small mode volume photonic crystals

Ultra-small mode volume nanophotonic crystal cavities have been proposed as powerful tools for increasing coupling rates in cavity quantum electrodynamics systems. However, their adoption in quantum information applications remains elusive. In this work, we investigate possible reasons why, and analyze the impact of different low mode volume resonator design choices on their utility in quantum optics experiments. We analyze band structure features and loss rates of low mode volume bowtie cavities in diamond and demonstrate independent design control over cavity-emitter coupling strength and loss rates. Further, using silicon vacancy centers in diamond as exemplary emitters, we investigate the influence of placement imprecision. We find that the benefit on photon collection efficiency and indistinguishability is limited, while the fabrication complexity of ultra-small cavity designs increases substantially compared to conventional photonic crystals. We conclude that ultra-small mode volume designs are primarily of interest for dispersive spin-photon interactions, which are of great interest for future quantum networks.

Metal-organic framework photonic crystals with bidisperse particles-based brilliant structural colors and high optical transparency for elaborate anti-counterfeiting

Photonic crystals (PCs) have attracted great interest and wide applications in displays, printing, anti-counterfeiting, etc. However, two main challenges significantly hinder their applications: 1) the tradeoff between high optical transparency across the whole visible range and brilliant colors requiring a large refractive index contrast (Δn), and 2) the way of regulating structural colors by altering tens of different sizes. To address these issues, a new type of metal–organic framework (MOF)-based transparent photonic crystal (TPC) has been fabricated through self-assembling MOF particles into three-dimensional ordered structures which were then infiltrated by polydimethylsiloxane (PDMS). Compared to conventional PCs, these TPCs exhibit 1) both brilliant forward iridescent structural colors and high transmittance (>75 %) across the whole visible spectra range, and 2) conveniently adjustable colors based on bidisperse particles. The unique color-generating mechanism of the light diffraction by each plane lattice and the small Δn between MOF particles and PDMS are the keys to TPCs’ characteristics. Moreover, the prepared invisible anti-counterfeit labels can reversibly hide-reveal patterns with elaborate and exchangeable color contrast in a non-destructive way, showing potential applications in anti-counterfeiting, information encryption, and optical devices.

Defect modes in defective one dimensional parity-time symmetric photonic crystal

The introduction of defect layers into one-dimensional parity-time (PT) symmetric photonic crystals gives rise to resonances within the photonic bandgaps. These resonances can be effectively explained by our generalized temporal coupled mode theory. The scattering properties and dispersion relation of defect modes exhibit distinct characteristics compared to conventional one-dimensional Hermitian photonic crystals with defect layers. By tuning the non-Hermiticity or other model parameters, the modulus of the generalized decay rate can be reduced, consequently, the electric field concentrated within the defect layer strengthens. This arises due to the unique band structure of one-dimensional PT-symmetric photonic crystals, which differs significantly from that of traditional one-dimensional Hermitian photonic crystals. Furthermore, the interaction between multiple resonances is investigated through the introduction of multiple defect layers. Our study not only provides insights into resonance phenomena in defective non-Hermitian systems but also contributes to the design of relevant optical resonance devices.

The transmittance properties of the one-dimensional gyroidal superconductor photonic crystals

Abstract In this study, the transfer matrix method is used to analyze the optical properties of a layered structure, {Air(SrTiO3/BSCCO)20Substrate}, consisting of air, SrTiO3, BSCCO (bismuth strontium calcium copper oxide) bilayers, and a substrate. This paper aims to investigate the transmittance spectra of two proposed one-dimensional (1D) structures, including a conventional superconductor photonic crystal (PC) and a gyroidal superconductor PC at infrared (IR) wavelengths. A comprehensive analysis has been carried out to provide useful insights into the optical properties and the behavior of the proposed structure, highlighting the impact of many parameters, such as refractive index, filling fraction, and layer thickness. The numerical findings showed that the permittivity of the BSCCO superconductor of a gyroidal geometry takes a different response compared to the conventional one. Notably, the filling fraction and refractive index of the host material have a significant control on both real and imaginary parts of the gyroidal BSCCO permittivity through the considered wavelengths. Thus, the proposed design provides high transmittivity outside the obtained photonic band gap compared to the conventional one. We believe that the designed one-dimensional gyroidal BSCCO photonic crystals could act as an efficient reflector through near IR for optoelectronics and energy applications.

Wavelength-independent light extraction enhancement by nanostructures for scintillators with broadband emission

Conventional photonic crystals with a single period are capable of enhancing the light output of scintillators based on the partial elimination of internal total reflection. However, the enhancement often comes along with a strong wavelength dependence, leading to a severe spectrum distortion. Here, the nanostructures for wavelength-independent light extraction enhancement, namely, multi-size spherical nanostructures, are designed and fabricated. The nanostructure can efficiently outcouple the scintillation light and at the same time significantly weaken the wavelength dependence. The light output of the scintillators with the nanostructures obtains noticeable enhancement with a ratio of 1.7, having weak wavelength dependence, which is in contrast to the enhancement by single-periodic photonic crystals. In addition to the applications on the scintillators, we anticipate that these wavelength-independent light output enhancement schemes could be expanded to other important fields, such as white light-emitting diodes and display devices.

Self-Destructive Structural Color Liquids for Time-Temperature Indicating.

Vaccines are undoubtedly a powerful weapon in our fight against global pandemics, as demonstrated in the recent COVID-19 case, yet they often face significant challenges in reliable cold chain transport. Despite extensive efforts to monitor their time-temperature history, current time-temperature indicators (TTIs) suffer from limited reliability and stability, such as difficulty in avoiding human intervention, inapplicable to subzero temperatures, narrow tracking temperature ranges, or susceptibility to photobleaching. Herein, we develop a class of structural color materials that harnesses dual merits of fluidic nature and structural color, enabling thermal-triggered visible color destruction based on triggering agent-diffusion-induced irreversible disassembly of liquid colloidal photonic crystals for indicating the time-temperature history of the cold chain transport. These self-destructive structural color liquids (SCLs) exhibit inherent irreversibility, superior sensitivity, tunable self-destructive time (minutes to days), and a wide tracking temperature range (-70 to +37 °C). Such self-destructive SCLs can be conveniently packaged into flexible TTIs for monitoring the storage and exposure status of diverse vaccines via naked-eye inspection or mobile phone scanning. By overcoming the shortcomings inherent in conventional TTIs and responsive photonic crystals, these self-destructive SCLs can increase their compatibility with cold chain transport and hold promise for the development and application of the next-generation intelligent TTIs and photonic crystals.

Direct ink writing of three-dimensional Al2O3/polydimethylsiloxane photonic crystal heterostructures for terahertz frequencies

The photonic crystal heterostructures with multi-bandgap could manipulate multiple optical signals simultaneously, and have important applications in various multi-channel optical or optoelectronic devices. However, due to the limitations of materials and structure complexity, photonic crystal heterostructures for terahertz frequencies are rarely reported. Here, we report a facile and efficient approach to fabricate terahertz photonic crystal heterostructures (TPCHs) via direct ink writing (DIW) 3D printing technology. Al2O3/polydimethylsiloxane (PDMS) composite ink suitable for DIW has been developed. Al2O3/PDMS TPCHs with different structural parameters have been fabricated by DIW 3D printing. The results of simulation and experiments demonstrate that these TPCHs exhibit some special optical properties, such as bandgap deepening and dual-bandgap, compared with the conventional three-dimensional terahertz photonic crystals (3D-TPCs). The optical properties of TPCHs could be accurately regulated by varying the lattice constant of their compositional 3D-TPCs. The DIW 3D printing technology offers a new opportunity to create TPCHs with tailored photonic behavior for novel terahertz functional devices.

Angle-insensitive topological interface states in hybrid one-dimensional photonic crystal heterostructures containing all-dielectric metamaterials.

Topological interface states (TISs) in conventional one-dimensional (1D) photonic crystal (PhC) heterostructures strongly shift toward higher frequencies as the incident angle increases. This strong blueshift property of TISs intensively limits the operating angle ranges of TISs. Herein, we design two angle-insensitive photonic bandgaps (PBGs) in two hybrid 1D PhCs containing all-dielectric metamaterials. By cascading these two hybrid 1D PhCs to construct a hybrid 1D PhC heterostructure, we achieve an angle-insensitive TIS under transverse magnetic polarization. Empowered by the angle-insensitive property of the PBGs, the angular tolerance of the TIS reaches 69.65°, which is much higher than those of the TISs in conventional 1D PhC heterostructures. In addition, the angle-insensitive property of the TIS is robust against the layer thickness. Our work provides a viable route to achieving TISs with high angular tolerances and would facilitate the applications of photonic topological states.

Tunable and controllable multi-channel time-comb absorber based on continuous photonic time crystals.

To date there have been many studies on multi-channel absorbers for conventional photonic crystals (PCs). However, the number of absorption channels is small and uncontrollable, which cannot satisfy applications such as multispectral or quantitative narrowband selective filters. To address these issues, a tunable and controllable multi-channel time-comb absorber (TCA) based on continuous photonic time crystals (PTCs), is theoretically proposed. Compared with conventional PCs with fixed refractive index (RI), this system forms a stronger local electric field enhancement in the TCA by absorbing externally modulated energy, resulting in sharp multi-channel absorption peaks (APs). Tunability can be achieved by adjusting the RI, angle, and time period unit (T) of the PTCs. Diversified tunable methods allow the TCA to have more potential applications. In addition, changing T can adjust the number of multi-channels. More importantly, changing the primary term coefficient of n1(t) of PTC1 can control the number of time-comb absorption peaks (TCAPs) in multi-channels within a certain range, and the mathematical relationship between the coefficients and the number of multiple channels is summarized. This will have potential applications in the design of quantitative narrowband selective filters, thermal radiation detectors, optical detection instruments, etc.

Magnetically Tunable One-Dimensional Plasmonic Photonic Crystals.

Integrating plasmonic resonance into photonic bandgap nanostructures promises additional control over their optical properties. Here, one-dimensional (1D) plasmonic photonic crystals with angular-dependent structural colors are fabricated by assembling magnetoplasmonic colloidal nanoparticles under an external magnetic field. Unlike conventional 1D photonic crystals, the assembled 1D periodic structures show angular-dependent colors based on the selective activation of optical diffraction and plasmonic scattering. They can be further fixed in an elastic polymer matrix to produce a photonic film with angular-dependent and mechanically tunable optical properties. The magnetic assembly enables precise control over the orientation of the 1D assemblies within the polymer matrix, producing photonic films with designed patterns displaying versatile colors from the dominant backward optical diffraction and forward plasmonic scattering. The combination of optical diffraction and plasmonic properties within a single system holds the potential for developing programmable optical functionalities for applications in various optical devices, color displays, and information encryption systems.

Graphene-Based Photonic-like Highly Integrated Programmable Electronic Devices.

Photonic-crystal-like devices and photonic-crystal-like microcavities in graphene are investigated theoretically. The results show that the size of the photonic-crystal-like device and the photonic-crystal-like microcavity is able to be scaled down to more than 2 orders of magnitude smaller than that of the realistic conventional photonic crystal with the same energy, due to the shorter optical-like transport wavelength in graphene. So, the graphene-based photonic-like devices offer a higher degree of integration than their conventional counterparts. By changing the applied voltage, the mutual conversion of photonic-like devices with different functions can be realized, while the performance of such photonic-like devices can be manipulated. Therefore, this kind of photonic-like device has high programmability and adjustability. And the photonic-like devices can be integrated with traditional microelectronic circuits. It will have important application prospects in photonic-like integrated circuits and photonic-like computing.

Tamm plasmon polariton with high angular tolerance in heterostructure containing all-dielectric elliptical metamaterials

Tamm plasmon polariton (TPP) in heterostructure composed of a metal layer and a conventional one-dimensional photonic crystal (1DPC) strongly shifts toward shorter wavelengths as the incident angle increases. Such angle-sensitive property of TPP greatly limits the operating angular width of TPP-based optical devices. Very recently, researchers found that the angle dependence of the photonic bandgap (PBG) in 1DPC containing all-dielectric elliptical metamaterials (EMMs) can be flexibly tuned from angle-sensitive to angle-insensitive. Herein, we propose a heterostructure composed of a metal layer and a 1DPC containing all-dielectric EMMs to achieve a TPP with high angular tolerance. The angular tolerance of the TPP reaches 30.8°, which is much larger than those of the reported TPPs in heterostructures composed of a metal layer and a conventional 1DPC. Our work provides a feasible route to expending the operating angular width of TPP-based optical devices, such as filters, absorbers, lasers, and sensors.

Geometric manifestation led optical beam shaping in one-dimensional photonic crystals

The transmission of light through a periodically stratified medium such as a photonic crystal (PC) results in acquiring a “quantized” geometric phase, which is also known as a “topological phase.” This gives rise to the possibility of structuring optical beams through an appropriate experimental design. In addition, the broad transmission spectral bands of a PC provides a versatile platform for structuring optical beams over broad spectral bandwidth. Here, we present a simple and flexible route to generate first-order Hermite–Gaussian, i.e., H G 01 or H G 10 , beams utilizing the light transmitted from conventional one-dimensional PCs and provide a theoretical insight using finite-difference time-domain (FDTD)-based simulations. We also show that the technique could be employed for achieving beam structuring in reflected light beams, and consequently, it provides a plausible route for wavefront shaping involving high optical power.

Liquid, Transparent, and Antideformable Thermochromic Photonic Crystals for Displays

AbstractThe conventional thermochromic photonic crystal (TPC) gels based on thermally responsive poly(N‐isopropyl acrylamides) can switch their reflection signals at different temperatures by changing their lattice distances or order degree. However, these TPC gels exhibit a poor sensing range of temperature (ΔT < 30 °C) and poor antideformation properties, significantly limiting their applications. Here, a new type of liquid and transparent TPC is fabricated through assembling silica particles into the mixture of ethanol and poly(ethylene glycol) diacrylate. Different from the conventional TPCs, these liquid TPCs can reversibly alter their reflectance and brightness by temperatures based on the variation of the refractive index contrast (Δn). The liquid TPCs show 1) the unique “off/on” characteristics, 2) outstanding shapeable and antideformable properties, and 3) a large ΔT (80 °C), high sensitivity (reflectance: 0.46% °C−1), fast responsive speed (reflectance: ≈4.75% s−1), and good reversibility (>30 times). It is shown that these TPCs are ideal candidates for visual hot warning labels and temperature‐based display units. This work opens a new avenue for developing advanced stimulus‐responsive photonic materials and upgrades the basic understanding of the color tuning mechanisms.

Photonic crystal based interferometric design for label-free all-optical sensing applications.

Optical sensing devices has a great potential in both industrial and biomedical applications for the detection of biochemicals, toxic substances or hazardous gases thanks to their sustainability and high-selectivity characteristics. Among different kinds of optical sensors based on such as fibers, surface plasmons and resonators; photonic crystal (PC) based optical sensors enable the realization of more compact and highly efficient on-chip sensing platforms due to their intriguing dispersive relations. Interferometric devices based on PCs render possible the creation of biochemical sensors with high sensitivity since a slight change of sensor path length caused by the captured biochemicals could be detected at the output of the interferometer via the interferences of separated beams. In this study, a new type of Mach-Zehnder Interferometer (MZI) using low-symmetric Si PCs is proposed, which is compatible with available CMOS technology. Intended optical path difference between the two MZI channels is provided by the periodic alignments of symmetry-reduced PC unit cells in the MZI arms. Unlike the conventional symmetrical PC based MZIs, Fano resonances exist for the proposed MZI design, i.e. transmission dips and peaks appear in the output spectrum, and the location of dip and peak frequencies in transmission spectra can be efficiently controlled by utilizing interference phenomenon. Exploiting this effect, any refractive index change at the surrounding medium could be distinctly observed at the transmission spectra. In the view of such results, it is convenient to say that the proposed MZI configuration is suitable for efficient optical sensing of toxic gases as well as liquids. The designed all-dielectric MZI system is numerically investigated in both spectral and spatial domains to analyze its interferometric tunability: an optical sensitivity of about 300 nm/RIU is calculated for gaseous analytes whereas that sensitivity value is around 263.2 nm/RIU in the case of liquid analytes. Furthermore, high quality factor of Q > 45000 is obtained at Fano resonances with Figure-of-Merit (FoM) value of FoM ∼ 8950 RIU-1(7690 RIU-1) in the case of gas analytes (liquid analytes), which is the indication of enhanced optical sensing performance of the proposed MZI design. Considering all the above-mentioned advantages, the proposed interferometric configurations based on low-symmetric PCs could be utilized for efficient photonic sensor applications that require controllable output power or sensing of gaseous and liquid substances.

Photonic Quasi-Crystal Fiber-Based Plasmonic Biosensor: a Platform for Detection of Coronavirus.

Since the coronavirus pandemic began, research groups worldwide developed diagnostic tests. One of the promising platforms for testing is an optical and plasmonic biosensor. Localized surface plasmon resonances owing to their highly concentrated field intensity provide highly sensitive devices. A beneficial approach to excite localized surface plasmon modes for field-based applications is using photonic crystal fibers while photonic quasi-crystals demonstrate a higher order of symmetry, the more isotropic Brillouin zone, and the easier achievement of photonic bandgap as compared with conventional photonic crystals. In this work, by exploiting a photonic quasi-crystal fiber, we are designing a surface plasmon resonance biosensor for the on-chip and real-time detection of coronaviruses. In our miniaturized design, a thin gold layer is employed on the outer layer of an air hole of a photonic quasi-crystal fiber with a 12-fold symmetry where the leakage of the fiber core mode can excite the surface plasmon resonance mode on the gold. According to three-dimensional finite-difference time-domain simulations, the proposed biosensor shows the sensitivity of 1172 nm/RIU in the detection of coronaviruses within the saliva. Moreover, the smallest detection limit obtained in the simulation is about 12 nm. These promising results altogether indicate that this reconfigurable and lab-on-a-chip platform can potentially be used in the detection of all kinds of coronaviruses.

Dual-insensitive zero refraction based on annular photonic crystals

Over the past few years, zero refraction (ZR) represents an important breakthrough in field of distinctive dynamic optical beam tuning for double-zero-index (media with zero relative permittivity and permeability) photonic crystals (PCs). Because accidental ZR effects for conventional PCs is sensitive to the structural or refractive index parameters, how to enhance the robustness of ZR design is vital for applications. Here, we report a pioneering wave property that reveals a non-accidental Dirac-like cone dispersion composed of low- or high-energy bands, corresponding to dual-insensitive ZR effects for both transverse magnetic and transverse electric polarizations based on the same annular PCs. The performance of non-accidental ZR is simultaneously based on refractive index-insensitivity and structural- insensitivity, attributed to a satisfactory filling ratio.

Photo-Luminescent Photonic Crystals for Anti-Counterfeiting.

The conventional photonic crystals (PCs) are usually prepared by the self-assembly of silica or polystyrene particles. However, their applications are limited significantly due to the lack of the functions of the building blocks. Here, a new kind of photo-luminescent photonic crystals (PLPCs) with brilliant PL and structural colors were prepared by the self-assembly of dye-doped silica particles. The PL and structural colors of PCs can be well-controlled by altering the species of dyes and the size of the particles, respectively. Based on these advantages, PLPC patterns with encrypted information were fabricated through the combination of PLPCs and PCs with similar structural colors but diverse PL colors. These patterns can reversibly hide and display the encrypted information under sunlight and UV illumination, respectively. This work paves a new way for constructing functional PCs and will promote their applications in anti-counterfeiting, smart labels, and optical devices.

Block copolymer gyroids for nanophotonics: significance of lattice transformations

Abstract A gyroid crystal possesses a peculiar structural feature that can be conceptualized as a triply periodic surface with a constant mean curvature of zero. The exotic optical properties such as the photonic bandgap and optical chirality can emerge from this three-dimensional (3D) morphological feature. As such, gyroid crystals have been considered as the promising structures for photonic crystals and optical metamaterials. To date, several methods have been proposed to materialize gyroid crystals, including 3D printing, layer-by-layer stacking, two-photon lithography, interference lithography, and self-assembly. Furthermore, the discovery of Weyl points in gyroid crystals has further stimulated these advancements. Among such methods, the self-assembly of block copolymers (BCPs) is unique, because this soft approach can provide an easy-to-craft gyroid, especially at the nanoscale. The unit-cell scale of a gyroid ranging within 30–300 nm can be effectively addressed by BCP self-assembly, whereas other methods would be challenging to achieve this size range. Therefore, a BCP gyroid has provided a material platform for metamaterials and photonic crystals functioning at optical frequencies. Currently, BCP gyroid nanophotonics is ready to take the next step toward topological photonics beyond the conventional photonic crystals and metamaterials. In particular, the intrinsic lattice transformations occurring during the self-assembly of BCP into a gyroid crystal could promise a compelling advantage for advancing Weyl photonics in the optical regime. Lattice transformations are routinely considered as limitations, but in this review, we argue that it is time to widen the scope of the lattice transformations for the future generation of nanophotonics. Thus, our review provides a comprehensive understanding of the gyroid crystal and its lattice transformations, the relevant optical properties, and the recent progress in BCP gyroid self-assembly.

Chemical sensor based on the colorimetric response of porous silicon photonic crystal

In this article, the authors performed computer simulations and experimentally investigated the application of the colorimetric approach based on CIE1931 color space for characterization of the optical response of porous silicon (PS) based photonic crystals (PC). The colorimetric parameters as dominant wavelength (λdom) and excitation purity (EP) were determined and compared with conventional PC parameters as Bragg peak position λ0 and FWHM. The colorimetric parameters were obtained for PC with different sets of porosity values of bi-layers and the position of Bragg peak λ0(air). The PS sensor structures were fabricated by the method of electrochemical anodization of Si wafer. The colorimetric sensitivity of the PC sensors is higher for structure with smaller refractive indexes. Colorimetric parameters characterize the modification of the entire complex spectrum of the optical sensor as opposed to the conventional parameter as the Bragg peak position. The time dependences of colorimetric parameters on PC parameters during adsorption/desorption of ethanol are determined. The colorimetric approach for sensor characterization is preferable to develop the rapid not dispersive sensor systems as artificial tongue/nose with coordinate-dependent parameters of the spectrum.