Performance Of Optical Waveguides Research Articles

Organoboron Polymorphs with Different Molecular Packing Modes for Optical Waveguides.

Organoboron compounds offer a new strategy to design optoelectronic materials with high fluorescence efficiency. In this paper, the organoboron compound B-BNBP with double B←N bridged bipyridine bearing four fluorine atoms as core unit is facilely synthesized and exhibits a narrowband emission spectrum and a high photoluminescence quantum yield (PLQY) of 86.53 % in solution. Its polymorphic crystals were controllable prepared by different solution self-assembly methods. Two microcrystals possess different molecular packing modes, one-dimensional microstrips (1D-MSs) for H-aggregation and two-dimensional microdisks (2D-MDs) for J-aggregation, owing to abundant intermolecular interactions of four fluorine atoms sticking out conjugated plane. Their structure-property relationships were investigated by crystallographic analysis and theoretical calculation. Strong emission spectra with the full width at half maximum (FWHM) of less than 30 nm can also be observed in thin film and 2D-MDs. 1D-MSs possess thermally activated delayed fluorescence (TADF) property and exhibit superior optical waveguide performance with an optical loss of 0.061 dB/μm. This work enriches the diversity of polymorphic microcrystals and further reveals the structure-property relationship in organoboron micro/nano-crystals.

Crystal Engineering-Driven Sunlight Responsiveness and Flexible Waveguide Transmission.

Here, a barbituric acid derivative containing pyrene rings (DPPT) was successfully synthesized, and two types of crystals were prepared by using crystal engineering methods. Orange sheet-like crystals (DPPT-O, observed in visible light), prepared in a DCM/CH3OH solution, exhibited brittleness and weak fluorescence emission, along with sunlight-induced bending and fracturing. Red needle-like crystals (DPPT-R, also observed in visible light), synthesized in a DCM/CH3CN solution, demonstrated elastic properties, strong fluorescence emission, and excellent optical waveguide performance (with an optical loss coefficient of 0.23-0.30 dB mm-1). Single-crystal data analysis revealed that the stacking arrangement of molecules critically influenced the elasticity of the crystals, while the reaction cavity size regulated the photomechanical properties of the crystals. This study achieved effective control over sunlight responsiveness and flexible optical waveguide transmission for the first time, providing innovative insights for the application of homogeneous organic polycrystalline molecular crystals in this field.

Toward a10 dB net-gain waveguide amplifier in an Er3+-Yb3+ co-doped phosphate glass.

High-gain materials and high-quality structures are the two main conditions that determine the amplification performance of optical waveguides. However, it has been hard to balance each other, to date. In this work, we demonstrate breakthroughs in both glass optical gain and optical waveguide structures. We propose a secondary melting dehydration technique that prepares high-quality Er3+-Yb3+ co-doped phosphate glass with low absorption loss. Additionally, we propose a femtosecond laser direct-writing technique that allows controlling the cross section, size, and mode field of waveguides written in glass with high accuracy, leveraging submicron-resolution multi-scan direct-writing optical waveguide technology, which is beneficial for reducing insertion loss. As a proof of concept demonstration, we designed and fabricated two kinds of waveguides, namely, LP01- and LP11-mode waveguides in the Er3+-Yb3+ co-doped phosphate glass, enabling insertion loss as low as 0.9 dB for a waveguide length of 2 mm. Remarkably, we successfully achieved an optical amplification for both the waveguides with a net gain of >7 dB and a net-gain coefficient of >3.5 dB/mm, which is approximately one order of magnitude larger than that in the Er3+-Yb3+ co-doped phosphate glass fabricated by the traditional melt-quenching method. This will open new avenues toward the development of integrated photonic chips.

Adaptive penalty method with adam optimizer for enhanced convergence in optical waveguide mode solvers.

We propose a cutting-edge penalty method for optical waveguide mode solvers, integrating the Adam optimizer into pseudospectral frequency-domain (PSFD) frameworks. This strategy enables adaptable boundary fluctuations at material interfaces, significantly enhancing numerical convergence and stability. The Adam optimizer, an adaptive algorithm, is deployed to determine the penalty coefficient, greatly improving convergence rates and robustness while effectively incorporating boundary conditions into the interfaces of subdomains. Our solver evaluates the numerical performance of optical waveguides by calculating effective indices of standard benchmark waveguides with high accuracy. This method diminishes numerical boundary errors and provides a marked increase in convergence speed and superior accuracy when compared to conventional methods and even metaheuristic optimization methods, all while maintaining the inherent global spectral accuracy of the PSFD.

Ligand-protected metal nanoclusters as low-loss, highly polarized emitters for optical waveguides.

Photoluminescent molecules and nanomaterials have potential applications as active waveguides, but such a use has often been limited by high optical losses and complex fabrication processes. We explored ligand-protected metal nanoclusters (LPMNCs), which can have strong, stable, and tunable emission, as waveguides. Two alloy LPMNCs, Pt1Ag18 and AuxAg19-x (7 ≤ x ≤ 9), were synthesized and structurally determined. Crystals of both exhibited excellent optical waveguide performance, with optical loss coefficients of 5.26 × 10-3 and 7.77 × 10-3 decibels per micrometer, respectively, lower than those demonstrated by most inorganic, organic, and hybrid materials. The crystal packing and molecular orientation of the Pt1Ag18 compound led to an extremely high polarization ratio of 0.91. Aggregation enhanced the quantum yields of Pt1Ag18 and AuxAg19-x LPMNCs by 115- and 1.5-fold, respectively. This photonic cluster with low loss and high polarization provides a generalizable and versatile platform for active waveguides and polarizable materials.

Eyebox uniformity optimization over the full field of view for optical waveguide displays based on linked list processing.

Eyebox uniformity is an important indicator to evaluate the performance of optical waveguide displays. However, there is currently no standard design approach that achieves ideal uniformity over the full field of view (FOV) within the eyebox. Here, a novel method for eyebox uniformity optimization based on linked list processing is proposed. The linked list processing method can fast record the light trajectory and calculate the optimal numerical diffraction efficiency distribution of the coupler. We use the linked list method for an L-shaped diffractive optical waveguide and solve the matched coupler structure by combining rigorous coupled-wave analysis (RCWA) and the simplex method. By building the model on LightTools and demonstrating the illuminance uniformity, the feasibility of the method is verified. In the FOV range of 15°× 15°, the eyebox uniformity reaches 0.9 at the central viewing angle and the overall eyebox uniformity is 0.617.

Optical Isomerization and Photo-Patternable Properties of GeO2/Ormosils Organic-Inorganic Composite Films Doped with Azobenzene

GeO2/organically modified silane (ormosils) organic-inorganic composite films containing azobenzene were prepared by combining sol-gel technology and spin coating method. Optical waveguide properties including the refractive index and thickness of the composite films were characterized by using a prism coupling instrument. Surface morphology and photochemical properties of the composite films were investigated by atomic force microscope and Fourier transform infrared spectrometer. Results indicate that the composite films have smooth and neat surface, and excellent optical waveguide performance. Photo-isomerization properties of the composite films were studied by using a UV–Vis spectrophotometer. Optical switching performance of the composite films was also studied under the alternating exposure of 365 nm ultraviolet light and 410 nm visible light. Finally, strip waveguides and microlens arrays were built in the composite films through a UV soft imprint technique. Based on the above results, we believe that the prepared composite films are promising candidates for micro-nano optics and photonic applications, which would allow directly integrating the optical data storage and optical switching devices onto a single chip.

A simple strategy for increasing optical waveguide performance using spherical aberration

Femtosecond Laser Writing (FLW) has some advantages over competing techniques; it is a direct, highly flexible, and maskless process that can inscribe waveguides in almost any type of transparent material. FLW has proven to produce photonic integrated circuits with innovative design in a deterministic way for several applications, including quantum photonics and microfluidics. Although direct laser writing of waveguides has been extensively studied, there is still an intense search for methods to produce waveguides with lower losses and higher optical quality, because improvements in this sense will impact photonic research and technology. In this work, straight waveguides were directly inscribed into Eagle XG glass samples in a single process step at fabrication depths up to 370 µm. The propagation loss and the mode profile for single-mode waveguides were obtained. The laser pulse energy threshold that triggers the optical breakdown as a function of the depth was measured and used to study its relationship with the resulting waveguide optical properties. A trend between the waveguide losses and the observed pulse energy threshold for optical breakdown was found, which is connected with the microscope objective spherical aberration. It can be useful for finding the best conditions for producing low-loss waveguides. Compared to the waveguides written with the corrected pulses, propagation losses up to 2.5 times smaller were observed in our experiments when applying the strategy presented here. Therefore, by taking advantage of the inherent spherical aberration, the FLW technique can be made capable of much more at even higher intensities than previously possible.

Polymer-Coated Organic Crystals with Solvent-Resistant Capacity and Optical Waveguiding Function.

Recently, luminescent organic crystals have been widely studied as new optoelectronic materials. However, corrosion and dissolution of organic crystals by solvents have always been a great challenge for the application of organic crystals in various fields. In this work, we propose a general method of fabricating a solvent-resistant coating to prevent organic crystals from being corroded or dissolved by organic solvents. The coatings involved layer-by-layer assembly of poly(diallyldimethylammonium) (PDDA) and poly(styrenesulfonate) (PSS) onto crystals, followed by immersing the coated crystals into polyvinyl alcohol (PVA) aqueous solutions for 2 minutes. The coated crystals can remain intact over 24 h in common organic solvents without being damaged and even insoluble in dichloromethane for 5 days. Moreover, the thin and transparent coatings have little effect on the optical properties of crystals which still have excellent optical waveguide performance with the coatings.

Polymer‐Coated Organic Crystals with Solvent‐Resistant Capacity and Optical Waveguiding Function

AbstractRecently, luminescent organic crystals have been widely studied as new optoelectronic materials. However, corrosion and dissolution of organic crystals by solvents have always been a great challenge for the application of organic crystals in various fields. In this work, we propose a general method of fabricating a solvent‐resistant coating to prevent organic crystals from being corroded or dissolved by organic solvents. The coatings involved layer‐by‐layer assembly of poly(diallyldimethylammonium) (PDDA) and poly(styrenesulfonate) (PSS) onto crystals, followed by immersing the coated crystals into polyvinyl alcohol (PVA) aqueous solutions for 2 minutes. The coated crystals can remain intact over 24 h in common organic solvents without being damaged and even insoluble in dichloromethane for 5 days. Moreover, the thin and transparent coatings have little effect on the optical properties of crystals which still have excellent optical waveguide performance with the coatings.

Controlled Shape Evolution of Pure-MOF 1D Microcrystals towards Efficient Waveguide and Laser Applications.

MOF-based one-dimensional materials have received increasing attention in the nanophotonics field, but it is still difficult in the flexible shape evolution of MOF micro/nanocrystals for desired optical functionalities due to the susceptible solvothermal growth process. Herein, we report on the well-controlled shape evolution of pure-MOF microcrystals with optical waveguide and lasing performances based on a bottom-up and top-down synergistic method. The MOF microcrystals from solvothermal synthesis (bottom-up) enable the evolution from microrods via microtubes to nanowires through a chelating agent-assisted etching process (top-down). The three types of MOF 1D-microstructures with high crystallinity and smooth surfaces all exhibit efficient optical waveguide performance. Furthermore, MOF nanowire with lowest propagation loss served as low-threshold pure-MOF nanolasers with Fabry-Pérot resonance. These results advance the fundamental understanding on the controlled MOF evolution mechanism, and offer a valuable route for the development of pure-MOF-based photonic components with desired functionalities.

Nonlinear and low-loss tantalum pentoxide based micro-ring resonator by ion-assisted electron-beam deposition

Tantalum pentoxide (Ta2O5) is a promising material for optical waveguide applications of photonics integration due to its excellent linear and nonlinear optical properties, such as high refractive index, large bandgap, and high nonlinearity. The quality of thin film deposition will then be critical for realizing optical waveguide devices and modules. In this work, an ion-assisted electron-beam evaporation system has been used to deposit such thin film. As low as 0.73 nm thickness roughness has been demonstrated in a 700 nm thick film, indicating it as a candidate for fabricating a low-loss waveguide. An optical waveguide-based ring resonator was made for examining the optical waveguide performance. Through the flat surface morphology, a low propagation loss of 1.4 dB/cm with an unloaded quality factor of 3 × 105 ring resonance has been realized. The nonlinear index of refraction (n2) in as-deposited Ta2O5 film was found to be in an order of magnitude of 10−14 cm2/W, which was also confirmed by both Z-scan technique and all-optical modulation technique. By such high bandgap properties, a nonlinear absorption threshold of few TW/cm2 was also observed for the first time. The measured device performances are comparable to the state-of-the-art results from up-to-date counterparts.

Application of bromocresol purple nanofilm and laser light to detect mutton freshness.

Optical waveguide gas sensor with bromocresol purple (BCP) nano-film (70-80nm) composited with silicone deposited on surface of K+-ion exchanged glass slide was fabricated and applied to detect amine gases released during mutton spoilage to test mutton freshness with the help of laser light (632m). Gas sensing measurements (output light intensity vs. time) proved its high selectivity and good sensitivity (0.01ppm) toward amines among volatile organic compounds. The optimal fabricating condition (2600rpm, 0.10% BCP, 5.17% silicone) was selected experimentally, displaying 1s and 12s response-recovery time toward gases released from mutton samples stored at 5°C and 25°C respectively. The sensing mechanism was explained by combination and competition of diffusion-reaction, considering deprotonating reaction of bromocresol purple molecules and molecular size of analyte gases in diffusion process. UV-vis spectroscopy was used to select the specific wavelength of laser light source in optical waveguide performance and to detect the total volatile basic nitrogen contents in mutton sample to confirm the practicability of as-prepared optical waveguide sensor in detecting mutton freshness. The fabricated sensor is able to detect 7.2mg/100g gases released from mutton decomposition, providing a simple, fast, and cheap method to detect meat freshness.

Fine Fabrication and Optical Waveguide Characteristics of Hexagonal tris(8-hydroxyquinoline)aluminum(Ⅲ) (Alq3) Crystal

Herein, we reported on the precise growth and optical waveguide characteristics of hexagonal tris(8-hydroxyquinoline)aluminum(Ⅲ) (Alq3) micro-crystals (MCs). The hexagonal Alq3 MCs were prepared using surfactant-assisted assembly growth with the help of cetyltrimethylammoniumbromide (CTAB), in which the crystallization occurred as a result of molecular assembly and packing. Also, we adjusted the molar ratio of Alq3 and CTAB for the control degree of crystallization. The formation and structure of Alq3 MCs were investigated using field-emission scanning electron microscopy and X-ray diffraction pattern experiments, respectively. The solid-state laser confocal microscope-photoluminescence spectra and charge-coupled device images for the Alq3 MCs were measured to study the luminescence efficiency and colors, respectively. The optical waveguide performance of the hexagonal Alq3 MCs was measured for each side direction. According to our results, crystalline Alq3 micro-crystals are promising materials for application to the development of optical communication devices.

Improvement of silicon waveguide transmission by advanced e-beam lithography data fracturing strategies

In the maturing field of silicon photonics, advances continue in both design and process improvements. Waveguide propagation loss is strongly affected by sidewall roughness, and so for fabrication using e-beam lithography, loss is influenced by e-beam writing parameters. Here, the authors look specifically at fracturing strategies in data preparation for e-beam lithography, and find significant reduction in waveguide loss by utilizing advanced fracturing options. For our evaluation, the authors fabricate optical waveguides using a well-characterized, highly stable baseline fabrication process with hydrogen silsesquioxane resist exposed by a 100 kV electron beam, a high-contrast tetramethyl-ammonium hydroxide develop, and a Cl2 inductively coupled plasma etch. Using surface grating couplers for input and output, automated optical measurements are made by scanning input light in the region of the design wavelength of 1550 nm and measuring optical output power. The authors use a design cell containing grating couplers and both straight and curved waveguides with a range of lengths. The authors find a significant reduction in grating coupler insertion loss and waveguide loss along with increased uniformity by leveraging a new fracturing strategy implemented in the beamer pattern data processing software from GenISys, GmbH. Single line edge smoothing is an exposure strategy in which all feature edges are traced using a single-line shape (sometimes referred to as a single-pass line) while the bulk of the shape is then exposed with trapezoidal beam filling. The insertion loss for grating couplers written using single line edge smoothing shows a significant loss reduction of 1.2 dB as well as greatly improved uniformity. Both straight and curved waveguide losses were also reduced by use of single line edge smoothing, by 0.7 and 1.1 dB/cm, respectively. Here, the authors will discuss the likely mechanisms of this improvement as well as present additional device data using these new fracturing methods which represent a significant, incremental improvement in performance of optical waveguides written by e-beam lithography.

Fabrication and optical waveguide of Sn-catalyzed CdSe microstructures

Quasi-one-dimensional CdSe microstructures, including branched, needle-like and uniform microwires, have been successfully synthesized via a Sn-catalyzed thermal evaporation method. Possible growth mechanisms of these different CdSe microstructures are proposed. The optical properties of different CdSe microstructures were studied by the confocal optical microscope and obvious optical waveguide observed in the uniform microwire. The results indicate that efficient optical resonant cavities, dark excitons orientation not along the c axis and high crystallinity play a crucial role in optical waveguide performance of microstructure CdSe.

Research on Transmission Loss of Optical Waveguide in Three-Component Acceleration Seismic Geophone

The optical waveguides are produced in LiNbO3 substrate of three-component acceleration seismic geophone by lithography. Three-component acceleration seismic geophone detects changes in the external acceleration by detecting phase changes in the optical waveguides. The performance of optical waveguide directly affects the performance of three-component acceleration seismic geophone. Therefore, it is critical to measure and reduce the transmission loss of waveguides. The advantages and disadvantages of LiNbO3 crystal are introduced. The production process of Ti:LiNbO3 optical waveguide and its performance are presented. Some information about the types of transmission loss of optical waveguide and the measurement methods of optical waveguide loss are provided.

Environmental stability of PDMS-waveguides for electrical-optical circuit boards

The environmental stability of polydimethylsiloxane (PDMS)-based optical waveguides implemented in electrical-optical circuit boards has been tested against international standards. Temperature shock, moisture treatments, dry heat exposure as well as soldering float showed only a moderate impact on optical waveguide performance.

Hybrid Siloxane-Based Nano Building Blocks for Optical Applications: Optimization of the Synthetic Procedures by Spectroscopic Analysis

Diphenylsilanediol (DPDO) reacts with triethoxysilane (TREOS) in anhydrous conditions and in the presence of pyridine, to form complex mixtures of linear and cyclic condensation products which were identified by 29Si NMR and ATR/FTIR spectroscopies. The distribution of products can be varied by modifying the reaction conditions. Spectroscopic analysis allowed to identify the optimal reagents ratio and concentration for the production of hetero-condensation products minimizing the number of residual –OH groups whose presence would affect the performance of optical waveguides based on the synthesised nano building blocks.

Stress effects on the performance of optical waveguides

Stresses can cause anisotropic and inhomogeneous distribution of the refractive index. Their effects on the performance of optical waveguides have been observed in photoelectric devices. In this paper, the photo-elastic relation and wave equations for inhomogeneous and anisotropic waveguides are reviewed. The effective refractive indexes and mode shapes of planar waveguides under different stress states are obtained analytically. It is found that stress can affect the optical performance; different stress states play different roles: high stress value can change the cutoff thickness, which may induce multimode; in-plane stress causes birefringence, which may induce polarization shift and polarization dependent loss; stress concentration can change the mode shape, which may induced large transition loss; and pure shear stress has little effects on the effective refractive index.