Optical Waveguide Materials Research Articles

Dynamic Dipole Moment of Luminescent Liquid Crystals Enabled Highly Efficient Active Waveguide Materials Design and Synthesis

AbstractOrganic optical waveguide materials have attracted considerable attention for their promising applications in photonic and optoelectronic devices. However, for most materials, excellent light‐loss properties at high temperature cannot be obtained due to many factors. Consequently, realizing efficient optical waveguide materials that perform well at elevated temperatures remains a significant challenge. In this study, relying on the luminescent properties and self‐assembly properties of luminescent liquid crystals (LLCs), successfully fabricated materials are present for highly efficient active optical waveguides. A systematically synthesized set of LLCs with different structures is named according to the substituent type and the position of the cyano group, namely α‐DECN, α‐DEEOCN, β‐DECN, and β‐DEEOCN. Notably, α‐DECN and β‐DECN reveal hexagonal columnar phase, while α‐DEEOCN and β‐DEEOCN exhibit smectic phase. Optical waveguide experiments have revealed that the obtained LLCs showed highly efficient optical waveguide behavior, where the lowest light loss reached 0.15 dB mm−1 at room temperature. Remarkably, these LLCs show even lower light loss at high temperatures, with the light loss reaching 0.11 dB mm−1 as the lowest point. Further experimental results indicate that this phenomenon is attributed to the change in the dipole moment of these molecules. This research forms a significant groundwork for advanced exploration in optical waveguide material.

Laser Glass deposition of single-mode glass fibers for the fabrication of chip-scale photonic circuits

The use of glass, particularly fused silica (FS), instead of polymers or semiconductors as optical waveguide material is advantageous due to broadband transmission, reduced propagation losses, and enhanced thermal and mechanical stability. In this contribution, laser glass deposition for the chip-scale fabrication of FS-based optical waveguides is investigated. We use a CO2 laser with emission at a wavelength of 10.6 µm to weld conventional single-mode glass fibers onto a FS substrate, with the aim of maintaining the waveguide properties of the fibers. Synchronized translational and rotational axis movements allow for positioning of the waveguides in arbitrary geometries. Furthermore, a CO2 laser-based cleaving method is introduced, which facilitates on-chip creation of waveguide end facets for optical coupling. An analysis of the cleave geometry in dependence on process parameters as well as optical coupling losses are presented. Coupling losses of 0.88 dB for a laser-cleave and propagation losses of 0.56 dB/cm for a 10 cm on-chip welded fiber were achieved. The results pave the way for on-chip integration of fiber-based systems like lasers, sensing devices or optical communication networks.

Design and optical waveguide behavior of full-color emitting materials with adjustable band gap

Optical waveguide materials that span the entire visible spectrum is paramount for the efficacious operation of photon transmission devices in many contexts. Notably intriguing is the use of manipulating the band gap to finely modulate chromatic diversity within the luminous material. In this context, we synthesized three distinct organic small molecules, employing carbazole's inherent proclivity as the electron donor, while engaging thiophene, pyrimidine, and fluorenone as adept electron acceptor moieties. Evidently, our investigation unveiled a remarkable metamorphosis in the emitted fluorescence, wherein the chromatic spectrum transitions from blue to green, and subsequently to orange, as the electron acceptor group's capacity for electron absorption diminishes. Interestingly, the three materials manifest an inherent propensity for facile preparation into one-dimensional nanostructures, characterized by smooth surfaces, concurrently exhibiting commendable performance as optical waveguides. Our findings deepen a comprehensive understanding of the design of materials with the full visible spectrum, which might lead to innovations in the design of photonic integrated structures.

In situ growth of AuNPs with a nanocavity on the surface of optical fibre for development of SPR sensor

Gold nanoparticles (AuNPs) integrated within optical fibres show great potential as sensor materials in the field of sensing, utilizing the Surface Plasmon Resonance (SPR) principle. This study presents a straightforward, cost-effective, and replicable approach for producing permanent in-situ embedding of AuNPs with nanocavities on the surface of optical fibres. The process involves chemical vapour etching (CVE), followed by gold sputtering and isothermal heat treatment. The analysis conducted using High-Resolution Transmission Electron Microscopy (HRTEM) and Energy-Dispersive X-ray Spectroscopy (EDX), confirmed the presence of nearly spherical AuNPs embedded on the surface of the optical fibre, with an average diameter of 60 ± 5 nm. Additionally, the detection of two distinct plasmon absorption peaks at 567 ± 5 nm and 620 ± 5 nm using a Fibre Optic Spectrometer further validated the presence of AuNPs. To verify the existence of nanocavities surrounding the AuNPs, Field Emission Transmission Microscopy (FESEM) was employed, along with subjecting the AuNPs embedded fibre to three different NaCl solutions of varying concentrations. The results supported the presence of a nanocavity encapsulating the AuNPs. A proposed mechanism was put forth to explain the spectral behaviour resulting from the creation of the nanocavity. This specialty optical fibre is expected to have broad applications in the development of SPR-based chemicals and biosensors, as it facilitates close interaction between the AuNPs and analytes through the nanocavity surrounding the AuNPs on the fibre surface. The fabrication process demonstrated excellent repeatability, with strong adhesion of AuNPs to the optical fibre surface, and no leaching even after repeated use. Thus, we believe that this fabrication method is an exceptional technique for permanently incorporating AuNPs into various glass-based optical waveguide materials for SPR-based sensing applications.

An Ultra-Low-Loss Waveguide Based on BIC Used for an On-Chip Integrated Optical Gyroscope

The development of integrated optical technology and the continuous emergence of various low-loss optical waveguide materials have promoted the development of low-cost, size, weight, and power optical gyroscopes. However, the losses in conventional optical waveguide materials are much greater than those in optical fibers, and different waveguide materials often require completely different etching processes, resulting in severely limited gyroscope performance, which is not conducive to the monolithic integration of gyroscope systems. In this paper, an ultra-low-loss Archimedean spiral waveguide structure is designed for an on-chip integrated optical gyroscope by using the high Q value and low-loss optical characteristics of the bound state in the continuum (BIC). The structure does not require the etching of high-refractive-index optical functional materials, avoiding the etching problem that has been difficult to solve for a long time. In addition, the optical properties of the BIC straight and the BIC bent waveguide are simulated using the finite element method (FEM) to find the waveguide structural parameters corresponding to the BIC mode, which is used to design the integrated sensing coil and analyze the gyroscope performance. The simulation results show that the gyroscope’s sensitivity can reach 0.6699°/s. This research is the first time a BIC optical waveguide has been used for an integrated optical gyroscope, providing a novel idea for the monolithic integration of optical gyroscopes.

Large Cation Engineering in Organic Antimony Halides for Low‐Loss Active Waveguide

AbstractActive waveguides have attracted growing attention as a basic component of miniaturized and integrated photonic devices. However, most optical waveguide materials suffer from severe self‐absorption, which greatly increases the optical loss. Therefore, developing highly efficient red‐emitting materials with large Stokes shift and negligible self‐absorption is of great interest. Herein, this work proposes a strategy to achieve both large Stokes shifts and high photoluminescence quantum yield (PLQY) in organic metal halide via large cation engineering. Two zero‐dimensional antimony(III) chlorides, (TMA)2SbCl5 and (TMAA)2SbCl5, are designed and synthesized by screening the ligands with different cationic volumes. Experimental and theoretical results reveal that the large cation can promote the self‐trapped excitons emission and improve stability. Benefiting from the large Stokes shift (291 nm) and high PLQY (98.3%), the as‐prepared (TMAA)2SbCl5 microplate exhibits efficient active waveguide with low loss coefficient of 6.07 × 10−3 dB µm−1. This work not only develops a novel active waveguide material, but also provides insights into the role of organic cation, which will provide new inspiration for the exploitation of excellent luminescent metal halides and photonic devices.

The Development and Progression of Micro-Nano Optics.

Micro-Nano optics is one of the most active frontiers in the current development of optics. It combines the cutting-edge achievements of photonics and nanotechnology, which can realize many brand-new functions on the basis of local electromagnetic interactions and become an indispensable key science and technology of the 21st century. Micro-Nano optics is also an important development direction of the new optoelectronics industry at present. It plays an irreplaceable role in optical communication, optical interconnection, optical storage, sensing imaging, sensing measurement, display, solid-state lighting, biomedicine, security, green energy, and other fields. In this paper, we will summarize the research status of micro-nano optics, and analyze it from four aspects: micro-nano luminescent materials and devices, micro-nano optical waveguide materials and devices, micro-nano photoelectric detection materials and devices, and micro-nano optical structures and devices. Finally, the future development of micro-nano optics will be prospected.

Adaptable Optical Microwaveguides From Mechanically Flexible Crystalline Materials.

Flexible organic crystals (elastic and plastic) are important materials for optical waveguides, tunable optoelectronic devices, and photonic integrated circuits. Here, we present highly elastic organic crystals of a Schiff base, 1-((E)-(2,5-dichlorophenylimino)methyl)naphthalen-2-ol (1), and an azine molecule, 2,4-dibromo-6-((E)-((E)-(2,6-dichlorobenzylidene)hydrazono)methyl)phenol (2). These microcrystals are highly flexible under external mechanical force, both in the macroscopic and the microscopic regimes. The mechanical flexibility of these crystals arises as a result of weak and dispersive C-H⋅⋅⋅Cl, Cl⋅⋅⋅Cl, Br⋅⋅⋅Br, and π⋅⋅⋅π stacking interactions. Singly and doubly-bent geometries were achieved from their straight shape by a micromechanical approach using the AFM cantilever tip. Crystals of molecules 1 and 2 display a bright-green and red fluorescence (FL), respectively, and selective reabsorption of a part of their FL band. Crystals 1 and 2 exhibit optical-path-dependent low loss emissions at the termini of crystal in their straight and even in extremely bent geometries. Interestingly, the excitation position-dependent optical modes appear in both linear and bent waveguides of crystals 1 and 2, confirming their light-trapping ability.

Dedoping of phosphorus and tin via laser-induced nickel sphere migration in glass ceramics

Changes in the local composition of glass, which can locally control the optical properties of glass, are used to form optical waveguide materials, such as optical fibers. The authors have previously demonstrated the technique of metal sphere manipulation inside glass. In this method, the metal sphere moves toward a laser light source, absorbing the light and making the glass soft in the vicinity. In this paper, we report that the nickel sphere migration in glass ceramics dedoped phosphorus and tin from the trajectory of the sphere migration and condensed them in the nickel sphere. At the same time, nickel was doped in the trajectory of nickel sphere migration. The mechanisms of dedoping and incorporation are presented.

Optical Properties and Applications of Crystalline Materials

Optical Properties and Applications of Crystalline Materials

Low-Dimensional Organic Metal Halide Hybrids with Excitation-Dependent Optical Waveguides from Visible to Near-Infrared Emission.

Molecular luminescent materials with optical waveguide properties have wide application prospects in the fields of sensors, filters, and modulators. However, designing and synthesizing optical waveguide materials with unique morphology, high emissive efficiency, and tunable optical properties in the same solid-state system remains an open challenge. In this work, we report new types of morphological one-dimensional (1D) organic metal halide hybrid micro/nanotubes and micro/nanorods, which exhibit excitation-dependent optical waveguide properties from visible to near-infrared (NIR) regions with low-loss coefficient and high emissive efficiency during the propagation process. Strong intermolecular interactions within the hybrid systems could effectively reduce the nonradiative transition and improve quantum efficiency. Photophysical studies and theoretical calculations demonstrate that the color-tunable emission can be attributed to the coexistence of locally excited states and charge-transfer states. Utilizing excitation-dependent optical waveguide emission ranging from visible to NIR regions, we fabricate an optical wavelength converter to transfer short-wavelength into long-wavelength emission with multichannels. Furthermore, an optical logic gate system was designed based on the tunable emission properties of the 1D metal halide micro/nanotubes. Therefore, this work provides not only a facile process to synthesize 1D organic metal halide hybrids with excitation-dependent optical waveguide properties but also a new way to advance photofunctional logic computation at the micro/nanoscale.

Optical Waveguides in Organic Crystals of Polycyclic Arenes

AbstractOrganic crystals which can confine and guide optical waves on command are currently of considerable interest because of their tremendous potentials in broadband communications, optoelectronic devices, high‐capacity information storage, etc. Polycyclic arenes, with tunable molecular structures, packing modes, and photophysical properties, are a highly versatile class of organic materials, applicable as optical waveguide crystals. In this review, the optical waveguides of polycyclic arene‐based crystals are discussed, focusing on the molecular design, packing structures, crystal engineering, and the corresponding photonic properties. Moreover, several proof‐of‐concept devices are also shown. This review summarizes the current state of the art in this rapidly expanding field of research, which has become one of the key exploration areas of optical waveguiding materials.

Synthesis of polyurethane-imids and application in surface plasmon polaritons waveguide

The crosslinkable electro-optic (EO) polymers polyurethane-imides (PUI) were designed and synthesized with monomers azo chromophore, phenyl diisocyanate and aromatic dianhydrides. Molecular structure characteristics for the polymers were evidenced by nuclear magnetic resonance (1HNMR) and fourier transform infrared (FTIR) spectroscopy. PUI as cladding, the strip long-range surface plasmon polaritons (LRSPPs) waveguides were designed and fabricated. The LRSPPs waveguiding along 18-nm-thin and 8-µm-wide gold stripes buried in EO PUI polymers were characterized at the light wavelength of 1310 nm and 1550 nm. The results indicated that the PUI can be used as preparation surface plasmon polaritons EO polymer optical waveguide materials, due to the merits of crosslinkable property, thermal stability, good film-forming ability, high processability and low optical waveguide propagation loss in near-infrared wave band.

Crystal Engineering of a Hydrazone Molecule toward High Elasticity and Bright Luminescence.

Flexible luminescent crystals have attracted increasing attention on account of the potential application value in optical material fields. How to design crystals with high elasticity and bright luminescence is an urgent duty that material researchers want to effectuate. Crystal engineering could achieve different crystal materials with various functions based on one molecular structure. Therefore, crystal engineering provides a potential strategy to improve the properties of flexible crystals. In this paper, we gave a pioneer work to improve the properties of flexible luminescent crystals by designing on crystal structure. By disclosing the relationship of structure-property, our work extracted the advantages (elasticity or bright emission) of two inferior crystals and obtained three elastic bending crystals with outstanding emission behaviors. Notably, our work not only achieves the fabrication of flexible crystals based on crystal engineering aspect but also provides good candidates for flexible optical waveguiding materials.

Micromanipulation of Mechanically Compliant Organic Single-Crystal Optical Microwaveguides.

Flexible organic single crystals are evolving as new materials for optical waveguides that can be used for transfer of information in organic optoelectronic microcircuits. Integration in microelectronics of such crystalline waveguides requires downsizing and precise spatial control over their shape and size at the microscale, however that currently is not possible due to difficulties with manipulation of these small, brittle objects that are prone to cracking and disintegration. Here we demonstrate that atomic force microscopy (AFM) can be used to reshape, resize and relocate single-crystal microwaveguides in order to attain spatial control over their light output. Using an AFM cantilever tip, mechanically compliant acicular microcrystals of three N-benzylideneanilines were bent to an arbitrary angle, sliced out from a bundle into individual crystals, cut into shorter crystals of arbitrary length, and moved across and above a solid surface. When excited by using laser light, such bent microcrystals act as active optical microwaveguides that transduce their fluorescence, with the total intensity of transduced light being dependent on the optical path length. This micromanipulation of the crystal waveguides using AFM is non-invasive, and after bending their emissive spectral output remains unaltered. The approach reported here effectively overcomes the difficulties that are commonly encountered with reshaping and positioning of small delicate objects (the "thick fingers" problem), and can be applied to mechanically reconfigure organic optical waveguides in order to attain spatial control over their output in two and three dimensions in optical microcircuits.

Micromanipulation of Mechanically Compliant Organic Single‐Crystal Optical Microwaveguides

AbstractFlexible organic single crystals are evolving as new materials for optical waveguides that can be used for transfer of information in organic optoelectronic microcircuits. Integration in microelectronics of such crystalline waveguides requires downsizing and precise spatial control over their shape and size at the microscale, however that currently is not possible due to difficulties with manipulation of these small, brittle objects that are prone to cracking and disintegration. Here we demonstrate that atomic force microscopy (AFM) can be used to reshape, resize and relocate single‐crystal microwaveguides in order to attain spatial control over their light output. Using an AFM cantilever tip, mechanically compliant acicular microcrystals of three N‐benzylideneanilines were bent to an arbitrary angle, sliced out from a bundle into individual crystals, cut into shorter crystals of arbitrary length, and moved across and above a solid surface. When excited by using laser light, such bent microcrystals act as active optical microwaveguides that transduce their fluorescence, with the total intensity of transduced light being dependent on the optical path length. This micromanipulation of the crystal waveguides using AFM is non‐invasive, and after bending their emissive spectral output remains unaltered. The approach reported here effectively overcomes the difficulties that are commonly encountered with reshaping and positioning of small delicate objects (the “thick fingers” problem), and can be applied to mechanically reconfigure organic optical waveguides in order to attain spatial control over their output in two and three dimensions in optical microcircuits.

Reactive Ion Etching of Cytop and Investigation of Residual Microstructures

Reactive Ion Etching (RIE) of Cytop as the cladding material for optical waveguides and microfluidic channels is investigated. Different grades of Cytop (M, A and S), different mask materials including photoresist and metals, different RIE parameters, along with different substrate materials were investigated. Grass-like structure was observed at the bottom of etched channels, of height that depends on the etching process parameters. A comprehensive post-etch acid cleaning procedure was devised to effectively remove the grass structure. [2019-0232]

Wavelength-Conversion-Material-Mediated Semiconductor Wafer Bonding for Smart Optoelectronic Interconnects.

A new concept of semiconductor wafer bonding, mediated by optical wavelength conversion materials, is proposed and demonstrated. The fabrication scheme provides simultaneous bond formation and interfacial function generation, leading to efficient device production. Wavelength-converting functionalized semiconductor interfacial engineering is realized by utilizing an adhesive viscous organic matrix with embedded fluorescent particles. The bonding is carried out in ambient air at room temperature and therefore provides a cost advantage with regard to device manufacturing. Distinct wavelength conversion, from ultraviolet into visible, and high mechanical stabilities and electrical conductivities in the bonded interfaces are verified, demonstrating their versatility for practical applications. This bonding and interfacial scheme can improve the performance and structural flexibility of optoelectronic devices, such as solar cells, by allowing the spectral light incidence suitable for each photovoltaic material, and photonic integrated circuits, by delivering the respective preferred frequencies to the optical amplifier, modulator, waveguide, and detector materials.

Low-loss planar optical waveguides based on plasma deposited silicon oxycarbide

Silicon oxycarbide deposited by plasma enhanced chemical vapor deposition is investigated regarding its application as a material for optical waveguides. The dependence of the infrared absorption, the refractive index, and the surface roughness on the precursor gas flow ratios is studied by Fourier transform infrared spectroscopy, ellipsometry, and atomic force microscopy, respectively. Results show that the refractive index can be tuned over a significant wider range compared to silicon oxynitride. Fabricated waveguides with a refractive index contrast of 0.05 show waveguide attenuation from about 0.3 dB/cm to 0.4 dB/cm for wavelengths between 1480 nm and 1570 nm. These low values were achieved without using a high temperature annealing process.

Photoluminescence enhancement OF Er3+-DOPED ZnO/SiO2 nanocomposites fabricated through two-step synthesis

In this study, we demonstrated two processes for the fabrication of thin films comprising ZnO nanocrystals dispersed in a SiO2 matrix doped with Er3+ ions (Er3+-doped SiO2/ZnO nanocomposites). The thin films can be applied as SiO2 glasses for optical waveguide materials working at the 1.54 μm band. In the first process, the conventional sol–gel method was utilized to generate homogeneous materials wherein ZnO nanoparticles formed after heat treatment. In the second process, SiO2 and ZnO sols were separately prepared before the fabrication of Er3+-doped nanocomposites. Different fabrication conditions, such as doping concentration and heat treatment temperature, and the optical properties of the corresponding prepared films were presented. The optical properties of the two material systems were compared to propose and discuss different excitation mechanisms via the interaction between intermediate ZnO nanocrystals and Er3+dopants.