Photonic Polymer Research Articles

Monolithic integration of waveguide amplifiers and passive polymer photonic devices using photolithography

The monolithic integration of rare-earth-doped waveguide amplifiers with passive photonic devices has long been a subject of extensive research. Herein, we propose a method for active-passive monolithic integration based on polymer photonic integrated devices. The monolithic integration of passive devices with active waveguide amplifiers is achieved by spin-coating an active layer atop a passive polymer waveguide and subjecting specific regions of the active layer to selective photolithography. To validate the proposed monolithic integration scheme's impact on the performance of passive devices, performance tests were conducted on both passive and active-passive integrated 8-channel arrayed waveguide grating (AWG) devices. The crosstalk (CT) of the AWG devices before and after adding the active layer ranged from −12.04 dB to −14.72 dB and from −10.02 dB to −14.88 dB, respectively, with channel spacings of 9.29 nm and 8.80 nm, indicating consistent performance of the passive devices with the addition of the active layer. In a 0.5 cm-long active waveguide, internal net gain was achieved across all eight channels of the AWG, with a gain bandwidth ranging from 1518 nm to 1580 nm. Notably, an internal net gain of 9.5 dB was attained at 1527 nm. The successful integration of rare-earth-doped waveguide amplifiers with passive components on a monolithic chip has been achieved for the first time, requiring only two straightforward photolithography steps. This milestone not only preserves the inherent functionality of passive components but also enables effective signal amplification. This technological innovation holds the promise of fully harnessing the potential of rare-earth-doped waveguide amplifiers in the realm of photonic integrated circuits, thereby catalyzing significant breakthroughs and advancements in the field of optoelectronics.

In Situ Characterization of Thermal‐Induced Evolution of Structure/Optical Properties of Heterogeneous 3D Chiral Soft Photonic Crystal Polymer

AbstractPolymer stabilized blue phase (PSBP) liquid crystal has aroused wide attention due to its broad temperature range and potential applications in flexible display, multi‐mode monitor, and mirrorless laser based on its well‐compatible stability and multi‐responsiveness, such as electricity, humidity, and temperature. Temperature produces an important effect on the structure/optical properties of PSBP, but there lack of detailed investigation on thermal‐induced deformation and its influence on the optical performance of PSBP. Here, the thermal‐induced evolution of structure/optical properties of PSBP with different polymer content is in situ characterized by variable‐temperature ultra‐small‐angle X‐ray diffraction, Kossel diffraction, and polarized optical microscopy. A restricted deformation of PSBP cubic lattice is revealed by the shift of reflective wavelength and evolution of Kossel diagrams, which is mainly attributed to the thermal‐induced phase transition/separation of non‐polymerized components. The thermal stability of PSBP is improved by increased polymer content based on the limited deformation ability. This work is significant for the design of novel functional material, which paves the way for the preparation of photonic crystal soft materials with high stability and optical quality.

A comprehensive investigation of cholesteric liquid crystal interpenetrating polymer networks for metal ion sensor technology

This study outlines the fabrication process of a photonic polymer cholesteric liquid crystal (PCLC) engineered for dynamic response to external stimuli. The methodological framework includes the precise templating of PCLC onto an interpenetrating polymer network (IPN) following selective UV crosslinking and the careful removal of nonreactive mesogens. The sensor component of the PCLC film is composed of poly(acrylic acid) hydrogel. A key aspect of the process involves the formation of micro-holes through acetone treatment to enhance sensitivity. Additionally, functionalization with potassium hydroxide (KOH) improves the detection of calcium ions (Ca2+) by disrupting hydrogen bonds and facilitating the formation of potassium carboxylate salt. Combining the inherent properties of PCLC with the hydrogel’s responsiveness to metal ions results in a sophisticated sensor designed to detect Ca2+ ions through the modulation of PCLC pitch, creating distinct transmission bands. The manuscript provides a detailed quantitative analysis of stimulus-induced changes in PCLC wavelength, using measured spectra to refine and optimize process conditions. The resulting PCLC sensor demonstrates exceptional sensitivity (9.30 nm/mM) within the 1–15 mM Ca2+ ion concentration range, along with excellent specificity. This cost-effective, user-friendly, and colorimetric sensing modality holds significant promise for various applications in analytical chemistry.

Cellulose Metamaterials with Hetero‐Profiled Topology via Structure Rearrangement During Ball Milling for Daytime Radiative Cooling

AbstractPassive radiative cooling is a zero‐energy consumption approach, which can dissipate heat to outer space by emitting infrared radiation through the transparency window. Traditional cooling materials, such as photonic films, metafabrics, and polymer foams, still suffer from complex preparation processes and high costs. In this work, it is reported that natural cellulose can be converted into a “green” optical metamaterial by rational structure reconfiguration at the micro/nano level via scalable ball milling technology for efficient daytime radiative cooling. Specifically, fine‐tuning the shearing kinetics in the mechanochemistry process, cellulosic optical metamaterial (COM) with ≈98% solar reflectivity and ≈0.97 infrared emissivity has been successfully achieved, which can break through the theoretical value of photonic crystals as well as the conventional synthetic optical materials. The COMSOL simulation reveals that the excellent optical properties of the cellulose metamaterial are explained by the “confined scattering” effect caused by the rearranged heterostructure at the micro/nano level. Outdoor tests demonstrat that the COM‐based coating exhibits a daytime radiative cooling efficiency of 5.7 °C in hot Nanjing. Meanwhile, the COM can be produced into different scattering materials via spray coating, freeze casting, and solution casting technology. This study will facilitate the development of scalable and sustainable optical metamaterials for mitigating energy consumption.

Bioinspired Stretchable Polymers for Dynamic Optical and Thermal Regulation

Elaborated optical and thermal modulatory systems are of great importance to the survival and evolution of organisms in nature. Inspired by these natural intelligent systems, researchers have made great efforts for developing stretchable polymers and exploring their applications in fields of communication, dynamic camouflage, thermal management, and others. Herein, an up‐to‐date account of the advancements in bioinspired stretchable polymers for dynamic optical and thermal regulation is provided. First, stretchable polymers for dynamic structural colors are presented, including cholesteric liquid crystal elastomers, photonic crystal elastomers, and emerging photonic polymers. Then stretchable polymers for dynamic infrared emissivity are introduced, which are achieved by stretch‐induced wrinkled‐flat surface or stretch‐induced cracked surface. Third, stretchable polymers for dynamic thermal management are discussed, focusing on tunable solar transmittance and dynamic radiative cooling. Moreover, the perspectives on the opportunities and challenges for future research directions of bioinspired stretchable polymers are presented at the end.

Molecularly imprinted photonic polymer for rapid visual detection of sulfamethoxazole in environmental water samples

AbstractSulfamethoxazole (SMX) has numerous adverse effects and is present in various water systems; thus, the development of a rapid and accurate analytical method to detect SMX in water systems is crucial for protecting the environment and human health. A sulfamethoxazole molecularly imprinted photonic polymer (MIPP‐SMX) capable of facile naked‐eye recognition of target molecules was synthesized using the dual‐functional monomers acrylamide and methacrylic acid. The color of the MIPP‐SMX changed from green to blue in water samples containing sulfamethoxazole (SMX) in the concentration range of 0.5–5.0 mM. Furthermore, a linear correlation existed between the detected Bragg diffraction peak shift Δλ and SMX concentrations in water ranging from 0.5 to 2.0 mM. The detection limit for SMX was 0.3 mM. A recovery rate of 91.9%–108.5% was achieved when the polymer sensor was used to detect SMX in river water samples, with a relative standard deviation of 4.9%–6.0%. The designed MIPP‐SMX enabled rapid visual detection of SMX in water samples. The proposed method represents a significant advancement in the visual detection of SMX in environmental water samples.

Incorporating amidine groups into photonic cholesteric polymer networks for food quality sensing

Concerns about food safety and food quality have been the driving forces behind the development of smart packaging and food quality sensors. Cholesteric liquid crystal polymers make an excellent candidate...

Recent progress in low‐swellable polymer‐based smart photonic crystal sensors

AbstractLow‐swelling polymers (LSPs) generally refer to materials with a low solvent absorption ratio or volume expansion rate at swelling equilibrium. LSPs with exceptional responsiveness could be upgraded to smart sensors with structural color self‐reporting by bridging photonic crystals (PCs). Based on the regulation of swelling to effective refractive index, lattice spacing, the order‐disorder arrangement of nanostructures, and incident/detection angle, the structural color feedback of smart photonic crystal sensors (SPCSs) can quantitatively and visually reveal the stimulus, which greatly promotes the interdisciplinary development of nanophotonic technology in the fields of chemical engineering, materials science, engineering mechanics, biomedicine, environmental engineering, etc. Herein, to clarify the role of the photonic structures and polymer molecules in high‐performance SPCSs, LSP‐based SPCSs are summarized and discussed, including general swelling mechanisms, color change strategies, structural design, and typical functional applications. It aims to figure out the combination rule between PC structures and LSPs, optimize the design of PC structures, and expound the corresponding structural color sensing mechanisms, inspiring the fabrication of next‐generation SPCSs. Finally, perspectives on future structural design and sensing applications are also presented. It is believed that SPCSs are multifunctional nanophotonic tools for the interdisciplinary development of numerous engineering fields in the future.

Efficient thermal management and all-season energy harvesting using adaptive radiative cooling and a thermoelectric power generator

Passive daytime radiative cooling (PDRC) is useful for thermal management because it allows an object to emit terrestrial heat into space without the use of additional energy. To produce sub-ambient temperatures under direct sunlight, PDRC materials are designed to reduce their absorption of solar energy and to enhance their long-wavelength infrared (LWIR) emissivity. In recent years, many photonic structures and polymer composites have been studied to improve the cooling system of buildings. However, in cold weather (i.e., during winter in cold climates), buildings need to be kept warm rather than cooled due to heat loss. To overcome this limitation, temperature-responsive radiative cooling is a promising alternative. In the present study, adaptive radiative cooling (ARC) film fabricated from a polydimethylsiloxane/hollow SiO2 microsphere/thermochromic pigment composite was investigated. We found that the ARC film absorbed solar radiation under cold conditions while exhibiting radiative cooling at ambient temperatures above 40 °C. Thus, in outdoor experiments, the ARC film achieved sub-ambient temperatures and had a theoretical cooling power of 63.2 W/m2 in hot weather. We also demonstrated that radiative cooling with an energy harvesting system could be used to improve the energy management of buildings, with the thermoelectric module continuously generating output power using the ARC film. Therefore, we believe that our proposed ARC film can be employed for efficient thermal management of buildings and all-season energy harvesting in the near future.

Polymer Waveguide-Based Optical Sensors—Interest in Bio, Gas, Temperature, and Mechanical Sensing Applications

In the realization of photonic integrated devices, materials such as polymers are crucial. Polymers have shown compatibility with several patterning techniques, are generally affordable, and may be functionalized to obtain desired optical, electrical, or mechanical characteristics. Polymer waveguides are a viable platform for optical connectivity since they are easily adaptable to on-chip and on-board integration and promise low propagation losses <1 dB/cm. Furthermore, polymer waveguides can be made to be extremely flexible, able to withstand bending, twisting, and even stretching. Optical sensing is an interesting field of research that is gaining popularity in polymer photonics. Due to its huge potential for use in several industries, polymer waveguide-based sensors have attracted a lot of attention. Due to their resilience to electromagnetic fields, optical sensors operate better in difficult situations, such as those found in electrical power generating and conversion facilities. In this review, the most widely used polymer materials are discussed for integrated photonics. Moreover, four significant sensing applications of polymer-waveguide based sensors which include biosensing, gas sensing, temperature sensing and mechanical sensing have been debated.

High efficiency, lossless, large free-standing photonic bandgap polymer films

ABSTRACT Polarization selective photonic bandgaps are demonstrated as free-standing flexible films of chiral structure. Capability of large sizes, absence of defects and related high optical quality make the films adequate for imaging, optical communication, display, and other applications.

Bio-inspired thermal responsible liquid crystal actuators showing shape and color variations simultaneously

BackgroundInspired by butterflies, a series of photonic polymers and butterfly-shaped LC actuators were fabricated using a laser cutter that show reversible curling and color variations simultaneously. MethodsTo fabricate a polymer film that shows thermal actuation and color variation simultaneously, cholesteric liquid crystal films consisting of planar and focal-conic alignment layers were designed and fabricated. Significant findingsPhotonic polymers were synthesized via a one-step polymerization, which simultaneously show color variation and thermal actuation. The planar-co-focal conic construction of the fabricated liquid crystal films was confirmed using SEM. Upon heating, the planar-co-focal-conic constructed film is observed to curl from the bottom to top direction due to the shrinkage of the top planar layer being higher than that of the bottom focal-conic layer. Both thermally induced reversible U-shaped curling and helical actuations for the as-synthesized planar-co-focal conic films were successfully achieved. Butterfly-shaped LC actuators were fabricated using a laser cutter showing reversible curling and color variations simultaneously. These predesigned liquid crystalline actuators with planar-co-focal-conic layers are expected to show great potential for soft robotics and optical devices.

Photonic Liquid Crystal Polymer Absorbent for Immobilization and Detection of Gaseous Nerve Agent Simulants

Detection and sequestration of chemical warfare agents (CWAs), such as poisonous organophosphates, are highly desirable for both personal security and environmental protection. However, both sensing and absorption in a single device have been rarely reported. In this study, we describe a photonic absorbent based on a cholesteric liquid crystal polymer as a dual sensing and decontamination device for gas-type CWAs. Dimethyl methylphosphonate (DMMP) was used as a simulant compound. A blue reflective photonic polymer was fabricated that was able to detect DMMP vapor through absorption. Hydrogen bond interactions between DMMP and mesogenic carboxylic groups of the polymer allow selectivity and capture. A distinct optical change of the film from blue to bright green indicates the absorption of DMMP vapor molecules and confirms when full absorption of the polymer is achieved. The diffusion of DMMP vapor into the material was observed by the formation of a sharp boundary between swollen and unswollen material, as evidenced by scanning electron microscopy images and the structural color changes. In ambient conditions, DMMP molecules are retained in the photonic absorbent without release to the environment. Heating above approximately 60 °C releases the absorbed DMMP, leading to a reusable optical device. These results confirm the ability of photonic polymers to sense and immobilize dangerous vapor, paving the way for the realization of simple, battery-free optical devices able to simultaneously warn and protect.

Construction of highly efficient carbon dots-based polymer photonic luminescent solar concentrators with sandwich structure

The enhancement of photoluminescence (PL) emission and waveguide play a key role in improving the optical efficiency of luminescent solar concentrators (LSCs). In this work, to boosting PL emission and waveguide simultaneously, one photonic crystal (PC) structure (crystalline colloid arrays (CCAs)) was introduced into carbon dots (CDs)-based polymer LSCs. A sandwich-structured CDs-based polymer photonic LSC, comprising glass/CDs-based polymer PC film/glass, was created. First, CDs-based colloidal crystal suspensions were prepared by co-assembly of monodispersed p(MMA-NIPAm) colloids and multicolor-emitting CDs in HEMA monomer induced by the evaporation-driven assembly. The obtained suspensions not only had uniform PL and structural colors, but showed enhanced PL emission. Second, the above suspensions were sandwiched between two glass sheets and finally a photonic polymer LSC with sandwiched structure (25 × 25 × 1.8 mm3) were formed via one-step photopolymerization technique. Remarkably, the optimal CDs-based polymer photonic LSCs with sandwiched structure not only had high transparence at visible range (>60%), but exhibited PL emission enhancement (at least 2 times). Furthermore, the maximum external optical efficiency (η opt ) of 5.84% could be achieved based on yellow-emitting CDs-based polymer photonic LSC. The high external optical efficiency was mainly attributed to the PL emission enhancement and good PC waveguide.

Three-Dimensional Printed Planar Polymer Photonic Topological Insulator Waveguides and Their Robustness to Lattice Defects

Three-Dimensional Printed Planar Polymer Photonic Topological Insulator Waveguides and Their Robustness to Lattice Defects

Detection of progesterone in aqueous samples by molecularly imprinted photonic polymers.

A label-free molecular imprinted polymer (MIP) sensor was fabricated for the detection of progesterone in aqueous solutions, by polymerization inside the void spaces of colloidal crystals, which gave them photonic properties. The prepolymerization mixture was prepared fromacrylic acid as the functional monomer, ethylene glycol as thecross-linker agent, ethanol as solvent, and progesterone as the imprinted template. After polymerization, the colloidal crystal was removed by acid etching and the target eluted with a solvent. Material characterization included as follows: attenuated total reflectance-Fourier-transform infrared spectroscopy, dynamic light scattering, swelling experiments, and environmental scanning electron microscopy. MIPs were investigated by equilibrium binding, kinetics experiments, and UV-visible spectra to investigate Bragg diffraction peak shift that occurs with the rebinding at different progesterone concentrations in deionized water and 150-mM NaCl solutions. The MIP response was investigated with progesterone concentration in the 1-100μg L-1 range, with LOD of 0.5μg L-1, reaching the detected range of hormone in natural waters. Furthermore, hydrogel MIP films were successfully tested in various real water matrices with satisfactory results. Moreover, the MIP film exhibited good selectivity toward the progesterone hormone evidenced by a larger response than when exposed to structurally similar molecules. Computational studies suggested that size along with surface potential influenced the binding of analog compounds. Due to their ease of use and low cost, the sensors are promising as screening tools for the presence of progesterone in aqueous samples.

Multilayer Polymer Photonic Aegises Against Near-Infrared Solar Irradiation Heating.

Preventing solar heating is nowadays of paramount interest in energy savings and health preservation. For instance, in building thermalization solar heating consumes an excess of energy leading to harmful CO2 emissions, while in food and beverage packaging it may lead to variation of organoleptic properties or even health issues. The phenomenon is attributed to the large presence of moieties with highly absorbing vibrational overtones and combination bands in the near-infrared spectral region that induces heating in water, moisture, and in polymers used in packaging. Thus, reducing and controlling the light absorbed by these materials with effective low-cost passive systems can play a major role in energy saving and health preservation. In this work, different polymer dielectric mirrors are reported, made of poly(N-vinylcarbazole) and either cellulose acetate or poly(acrylic acid), and able to selectively reflect near-infrared radiation while maintaining high transparency in the visible range. To this end, simple, tandem, and superperiodic mirrors are used to shield radiation impinging on samples of water and paraffin, demonstrating shielding efficiencies up to 52% with respect to unshielded references, promising a new paradigm to solve thermal management issues.

A molecularly imprinted photonic polymer based on an inverse opal structure for sensing D-dimer at the point-of-care

Accurate and timely diagnosis of venous thromboembolism (VTE) is crucial to prevent related morbidity and mortality. This work reports a label-free sensor for D-dimer, a biomarker of VTE. The sensor is based on the synergy between the colloidal crystal templating method and the molecular imprinting technique. The design of the photonic molecularly imprinted polymer (PMIP) is focused on the preparation of an inverse opal structure, resulting from silica infiltration in a poly(methyl methacrylate) photonic crystal template, followed by a calcination stage that removes the sacrificial colloidal crystal. The molecularly imprinted polymer in the inverse opal structure is then synthesized in the presence of the template molecule, the peptide D-dimer. After D-Dimer removal, the PMIP consists in a three-dimensional highly ordered structure, where nanocavities complementary to the D-dimer in shape and binding features are distributed. The PMIP showed a linear response to D-dimer in synthetic urine, exhibiting a decrease in the reflectance intensity with increasing D-dimer concentrations, ranging from 22.5 ng mL−1 to 1450.0 ng mL−1. The PMIP material demonstrated a limit of detection of 15.5 ng mL−1 and was selective for D-dimer in the presence of fibrinopeptide B, another prospective VTE biomarker in urine. Moreover, the sensor was reusable up to five times without losing its recognition ability. Overall, a novel PMIP material is described for successful recognition of D-Dimer. Considering the clinical relevance of D-dimer detection, the sensor is envisioned as a promising low-cost test for urinalysis.

Controllable Synthesis of Centrosymmetric/Noncentrosymmetric Phases for the Family of Halogen-Based Photonic Coordination Polymers to Enhance the Phase-Matching Second-Harmonic-Generation Response.

The nonlinear-optical (NLO) materials with second-harmonic-generation (SHG) response need to crystallize in the noncentrosymmetric space group. It is very difficult to control the synthetic conditions to solely form a noncentrosymmetric phase for the materials with noncentrosymmetric and centrosymmetric conformations. Herein, we found that the temperature and halogen anion play an important role during the formation procedure of the pure noncentrosymmetric or centrosymmetric phase for the halogen-based family of coordination polymers to yield hybrid materials with a phase-matching SHG response as well as inherit the primary excellent photonic property of organic linkers. Our results provide a good choice for the design and construction of novel materials with a particular photonic property.

Multicolor photonic patterns through an intensity-controlled single photopolymerization step.

The UV intensity during photopolymerization allows control over the structural color of a cholesteric liquid crystal (CLC) polymer photonic coating in a single step. Simultaneously, the glass transition temperature (Tg) of the polymer can be tuned by the applied UV intensity. Most likely the low intensity photopolymerization increases the inhibition time, leading to in situ formation of polymer fragments through oxygen inhibition. The formation of polymer fragments changes the matrix during the inhibition time, which results in a color change before the polymer network is formed. Additionally, these fragments inside the network act as a plasticizer, effectively lowering the Tg. This method can be combined with temperature responsive properties based on shape memory to fabricate photonic coatings with multiple, responsive colored patterns. The presented work allows for new functionalities in responsive photonic polymers as multiple colors and response temperatures can be incorporated in a single polymerization step.