Optical Waveguides Research Articles

Hierarchically Responsive Alternating Nano‐Copolymers with Tailored Interparticle Bonds

AbstractSelf‐assembly of inorganic nanoparticles (NPs) is an essential tool for constructing structured materials with a wide range of applications. However, achieving ordered assembly structures with externally programmable properties in binary NP systems remains challenging. In this work, we assemble binary inorganic NPs into hierarchically pH‐responsive alternating copolymer‐like nanostructures in an aqueous medium by engineering the interparticle electrostatic interactions. The polymer‐grafted NPs bearing opposite charges are viewed as nanoscale monomers (“nanomers”), and copolymerized into alternating nano‐copolymers (ANCPs) driven by the formation of interparticle “bonds” between nanomers. The resulting ANCPs exhibit reversibly responsive “bond” length (i.e., the distance between nanomers) in response to the variation of pH in a range of ~7–10, allowing precise control over the surface plasmon resonance of ANCPs. Moreover, specific interparticle “bonds” can break up at pH≥11, leading to the dis‐assembly of ANCPs into molecule‐like dimers and trimers. These dimeric and trimeric structures can reassemble to form ANCPs owing to the resuming of interparticle “bonds”, when the pH value of the solution changes from 11 to 7. The hierarchically responsive nanostructures may find applications in such as biosensing, optical waveguide, and electronic devices.

Hierarchically Responsive Alternating Nano-Copolymers with Tailored Interparticle Bonds.

Self-assembly of inorganic nanoparticles (NPs) is an essential tool for constructing structured materials with a wide range of applications. However, achieving ordered assembly structures with externally programmable properties in binary NP systems remains challenging. In this work, we assemble binary inorganic NPs into hierarchically pH-responsive alternating copolymer-like nanostructures in an aqueous medium by engineering the interparticle electrostatic interactions. The polymer-grafted NPs bearing opposite charges are viewed as nanoscale monomers ("nanomers"), and copolymerized into alternating nano-copolymers (ANCPs) driven by the formation of interparticle "bonds" between nanomers. The resulting ANCPs exhibit reversibly responsive "bond" length (i.e., the distance between nanomers) in response to the variation of pH in a range of ~7-10, allowing precise control over the surface plasmon resonance of ANCPs. Moreover, specific interparticle "bonds" can break up at pH≥11, leading to the dis-assembly of ANCPs into molecule-like dimers and trimers. These dimeric and trimeric structures can reassemble to form ANCPs owing to the resuming of interparticle "bonds", when the pH value of the solution changes from 11 to 7. The hierarchically responsive nanostructures may find applications in such as biosensing, optical waveguide, and electronic devices.

Coherent interface between optical and microwave photons on an integrated superconducting atom chip

Sub-wavelength arrays of atoms exhibit remarkable optical properties, analogous to those of phased array antennas, such as collimated directional emission or nearly perfect reflection of light near the collective resonance frequency. We propose to use a single-sheet sub-wavelength array of atoms as a switchable mirror to achieve a coherent interface between propagating optical photons and microwave photons in a superconducting coplanar waveguide resonator. In the proposed setup, the atomic array is located near the surface of the integrated superconducting chip containing the microwave cavity and optical waveguide. A driving laser couples the excited atomic state to Rydberg states with strong microwave transition. Then the presence or absence of a microwave photon in the superconducting cavity makes the atomic array transparent or reflective to the incoming optical pulses of proper frequency and finite bandwidth.

All-Optical XOR, AND, OR, NOT, NOR, NAND, and XNOR Logic Operations Based on M-Shaped Silicon Waveguides at 1.55 μm.

Silicon waveguides are essential to integrated photonics, which is where optical and electronic components are coupled together on a single silicon chip. These waveguides allow for the integration of signal processing and optical transmission, which advances data centers, telecommunications, and other optical applications. Thus, our study involves the simulation of essential all-optical logic operations, namely XOR, AND, OR, NOT, NOR, NAND, and XNOR, and utilizes M-shaped silicon optical waveguides at a wavelength of 1.55 μm. This simulation is conducted through Lumerical FDTD solutions. The suggested waveguide comprises four identical slots, configured in the shape of the letter 'M', and all of which are formed of core silicon and silica cladding. These logic operations work based on constructive and destructive interferences that are caused by phase changes in the input optical beams. The contrast ratio (CR) is employed to quantitatively and comparatively assess the degree to which the target logic operations are efficiently executed. The simulation results indicate that, compared to other reported designs, the considered logic functions constructed using the proposed waveguide can be implemented with higher CRs. The outcomes of this paper can be utilized regarding the implementation of optoelectronic combinational logic circuits of enhanced functionality.

Single-layer waveguide with compound metasurfaces for highly efficient and chromatic-aberration-free augmented reality near-eye displays

Augmented reality (AR) near-eye displays seamlessly integrate virtual information with real world, in which the optical waveguide is the key component functioned as a coupler. Due to strong chromatic aberration, independent waveguides are always indispensable to separate the three primary colors that inevitably brings larger and thicker appearance. To address this, this paper proposes a new chromatic-aberration-free single-layer waveguide for AR displays by integrating a double-layer grating metasurface (MS) and the covered cylindrical MSs. The double-layer grating MS breaks through the limitations on a narrow wavelength band, enabling high diffraction efficiency for incident light deflection across the entire visible spectrum. Further, the cylindrical MSs provide accurate control over incident angles, not only overcoming the challenge of total reflection but also effectively eliminating chromatic aberration. Design results show that the proposed structure achieves an impressive diffraction efficiency of over 80 % for blue and green light and over 90 % for red light with an outstanding diffraction angular difference lower than 2.5 deg. Real-time ray tracing simulation demonstrates the capability of the designed AR engine to achieve high-resolution full-color imaging. The compound MSs enable precise light and color control for a single-layer waveguide coupler with exceptional diffraction efficiency and minimal chromatic aberration, which show great potential for cutting-edge AR applications.

Investigation of the molecular switching process between spin crossover states of triazole complexes as basis for optical sensing applications.

With the advent of the first laser sources and suitable detectors, optical sensor applications immediately also came into focus. During the last decades, a huge variety of optical sensor concepts were developed, yet the forecast for the future application potential appears even larger. In this context, the development of new sensor probes at different scales down to the atomic or molecular level open new avenues for research and development. We investigated an iron based triazole molecular spin-crossover complex changing its absorption characteristics significantly by varying environmental parameters such as humidity, temperature, magnetic or electric field, respectively, with respect to its suitability for a new class of versatile molecular sensor probes. Hereby, besides the investigation of synthesized pure bulk material using different analyzing methods, we also studied amorphous micro particles which were applied in or onto optical waveguide structures. We found that significant changes of the reflection spectra can also be obtained after combining the particles with different types of optical waveguides.The obtained results demonstrate the suitability of the material complex for a broad field of future sensor applications.

Wavelength multiplexing system based on ring resonators

Wavelength Division Multiplexing, WDM, is a technology developed for applications in telecommunications with the purpose of combining numerous wavelength signals into one single fibre. The aim of this research is the characterization of WDM systems of ring resonators with planar optical waveguides. The optical responses for different configurations, dimensions, and materials are analysed by doing a parametric study both considering analytical expressions and a Finite Element Tool. The results are from add-drop topologies with one, two and three rings. The main difference between topologies with the same parameters is the number of resonance wavelengths, which is higher due to the increase in the number of ring-shaped waveguides. It is concluded that adjusting the rings’ dimensions, the resonant wavelengths are tuned. Furthermore, the higher the rings’ radius the lower is the free spectral range, that can take values from 40 nm to 90 nm. Then, the number of resonant peaks in a wavelength range may change. Also, 1500–5000 describes the values computed for the quality factor, whereas the full width at half maximum varies within some units of nanometres. For models with different core materials, the higher transmittances decrease with lower core refractive indexes and the resonance width increases. These are new degrees of freedom to tune the response of the device that can definitely work as optical wavelength multiplexer, having losses from 20% to 40% considering the transmitted optical power.

Design of uncomplicated triangular core PCF for enhanced non-linearity applications

An innovative design of Photonic Crystal Fibre (PCF) for enhanced non-linearity applications using simulation with the Finite Element Method (FEM) is presented. The PCF is a kind of fibre optic waveguide that has air-holes along the entire length of the optical fibre, which exploits its exclusive features of being continuously single-moded and having a modifiable spot-size and dispersion properties for various linear and non-linear applications. This proposed triangular core PCF is made of silica material with a refractive index of 1.445 and features three large air-holes placed 120° apart in the core, each with a refractive index of 1.00. The air-holes have a pitch length of 6.03 μm and a radius of 2.86 μm, and the wavelength of operation is 1.55 μm. The proposed PCF design has a large diameter to pitch ratio (d/Λ) of up to 0.95, resulting in a reduced spot-size of just above 1.00 μm2. This indicates that the proposed triangular core PCF design could be used to enhance non-linearity applications. This study introduces a novel structure that simplifies construction by employing three strategically positioned large air-holes in the cladding, thus achieving the necessary properties for guiding light through the core. This streamlined approach overcomes complexities associated with previous designs from the literature, hence, offering a practical solution for effective light guidance while minimising construction difficulties. This inventive proposed PCF design can be fabricated using the Stack and Draw process or the slurry casting method.

Polychromatic photonic Floquet-Bloch oscillations.

Photonic Floquet-Bloch oscillations (FBOs), a new type of Bloch-like oscillations in photonic Floquet lattices, have recently been observed as a typical discrete self-imaging effect. Here, we theoretically investigate the spectral range of approximate photonic Floquet-Bloch oscillations in arrays of evanescently coupled optical waveguides and show the adjustability of the spectral range. At an appropriate amplitude of the Floquet modulation, we have demonstrated approximate photonic FBOs over a broad spectral range, termed "polychromatic photonic Floquet-Bloch oscillations," which manifest as approximate self-imaging of polychromatic beams. Furthermore, by designing the functional form of the Floquet modulation, we can cascade two polychromatic photonic FBOs and further enhance the performance of polychromatic self-imaging. Our results provide a simple and novel mechanism for achieving polychromatic self-imaging in waveguide arrays and may find applications in polychromatic beam shaping and broadband optical signal processing.

Compact and efficient lossy mode resonant refractive index sensor for aqueous environment

A very short length high sensitivity, large figure of merit and very high resolution integrated-photonic refractometer for aqueous environment operating in visible region of wavelength is proposed. The sensor design depends on the periodic coupling of the guided dielectric optical waveguide mode field and the lossy mode field of the conducting indium-tin-oxide thin film. Various layer thicknesses can be optimized to provide power transfer to the lossy layer and lossy mode resonance, resulting in a strong guided mode power absorption in the lossy layer occurs. The sensor has been designed to operate in both the TE and TM polarizations with different optimized layer frthicknesses. The optimized thicknesses are different for TE and TM polarizations. The obtained numerical results show that a spectral sensitivity of 2200 nm/RIU/2645 nm/RIU for TE/TM mode could be achieved with a very high resolution. Also, the sensors can operate in power interrogation mode with a maximum sensitivity nearly 5 × 107 dB RIU−1.

Compact, remote optical waveguide magnetic field sensing using double-pass Faraday rotation-induced optical attenuation

Compact, magnetic field, B sensing is proposed and demonstrated by combining the two Faraday rotation elements and beam displacement crystals within a micro-optical fiber circulator with a fiber reflector and ferromagnets to allow high contrast attenuation in an optical fiber arm. Low optical noise sensing is measured at λ=1550nm as a change in attenuation, α, of optical light propagating through the optical noise sensing rotators and back. The circulator’s double-pass configuration, using a gold mirror as a reflector, achieves a magnetic field sensitivity s=Δα/ΔB=(0.26±0.02)dB/mT with a resolution of ΔB=0.01mT, over a detection range B=0−89mT. The circulator as a platform provides direct connectivity to the Internet, allowing remote sensing to occur. The method described here is amenable to multisensor combinations, including with other sensor technologies, particularly in future integrated waveguide Faraday optical circuits and devices, extending its utility beyond point magnetic field sensing applications.

Designing of efficient optical waveguide using magnetic photonic crystal for communication application

Designing of efficient optical waveguide using magnetic photonic crystal for communication application

Liquid-Crystal Polarization Volume Gratings Technology and its Applications in Diffractive Optical Waveguides Systems for Augmented Reality

Liquid-Crystal Polarization Volume Gratings Technology and its Applications in Diffractive Optical Waveguides Systems for Augmented Reality

Singular transmission properties of electromagnetic waves in one-dimensional [formula omitted]-symmetric triangular optical waveguide networks

In this paper, the singular transmission properties of electromagnetic waves in one-dimensional PT-symmetric triangular finite periodic optical waveguide networks are investigated. We find that the transmission properties of electromagnetic waves differ significantly depending on whether the imaginary part of the system’s Bloch phase is zero or non-zero. Based on this, the generalized passbands and bandgaps of the PT-symmetric optical waveguide network are defined, and its generalized band structure is presented. Furthermore, we discover that electromagnetic waves incident within the frequency range of generalized bandgaps, where transmittance approaches zero, exhibit a reciprocal relationship between left and right reflectance. The system can generate interesting phenomena such as bidirectional total reflection, unidirectional super reflection, and unidirectional no reflection at these frequencies. It is also demonstrated that the frequency positions of these phenomena can be flexibly controlled by adjusting the length of the PT-symmetric waveguide and the imaginary part of its refractive index. These research findings offer a scientific basis for developing highly sensitive and multifunctional optical filters and laser reflectors.

Net gain in C+L band from LED pumped broadband emission in Er3+-doped oxyhalide tellurite glass

Expanding gain bandwidth into the L-band for erbium-doped fiber amplifiers (EDFAs) is a crucial strategy to overcome limitations in prevalent C-band focused commercial silica-based EDFAs, significantly boosting optical network transmission capacity. Herein, we synthesized Er3+-doped broadband near-infrared emission tellurite glasses utilizing the melt quenching process, systematically exploring the impact of ZnCl2 on the glass structure and optical properties. The 82TeO2–3Nb2O5–15ZnCl2–3Er2O3 (TNZ15) glass emerged as a standout candidate for broadband amplifiers around wavelength at 1.55 μm. With escalating ZnCl2 concentration, a discernible red shift in the emission peak wave lines was observed, accompanied by an expansion of the full width at half maximum (FWHM) from 98 nm to 106 nm. Noteworthy characteristics of all samples included exceptional thermal stability and elevated near-infrared (NIR) transmittance. Application of the Judd-Ofelt (J-O) theory facilitated the calculation of J-O parameter intensity, providing deeper insights into the optical behavior of the materials. Finally, the evaluation of TNZ15 planar optical waveguides, employing the vertical top pumping mode of two 980 nm LEDs, encompassed both the C-band (1530–1565 nm) and the L-band (1565–1625 nm). The results underscore the potential of TNZ15 glass as a promising gain material for broadband optical amplifiers and lasers, offering valuable insights into the development of next-generation optical amplification technologies.

Synthesis and characterization of fluorinated polyurethaneimide electro-optic waveguide material with novel structure

Abstract Structurally novel fluorinated polyurethaneimide (PUI) electro-optic polymer based on chromophore molecule b, diisocyanate MDI and anhydride BPAFDA was synthesized by stepwise polymerization of oligomer PUI with fluorinated aromatic diamines BATB and BATPP. Electro-optic (EO) PUI chain structure had the structure of polyimide and polyurethane chain segments, integrating the advantages of polyimide and polyurethane. The PUI possessed good film-forming property, a high glass transition temperature (T g = 193 °C) and good thermal stability (5 % weight loss temperature T d up to 320 °C). Y-Structured inverted ridge polymer optical waveguides were designed and fabricated using the PUI as the waveguide core material. The PUI had good optical performance with an EO coefficient (γ33) of 79 pm/V and 1.1 dB/cm optical propagation loss at a wavelength of 1550 nm. The results showed that the synthesized PUI met the performance requirements for the preparation of polymer optical waveguide devices and was suitable as a polymer electro-optic waveguide material.

Integrating Full-Color 2D Optical Waveguide and Heterojunction Engineering in Halide Microsheets for Multichannel Photonic Logical Gates.

Ensuring information security has emerged as a paramount concern in contemporary human society. Substantial advancements in this regard can be achieved by leveraging photonic signals as the primary information carriers, utilizing photonic logical gates capable of wavelength tunability across various time and spatial domains. However, the challenge remains in the rational design of materials possessing space-time-color multiple-resolution capabilities. In this work, a facile approach is proposed for crafting metal-organic halides (MOHs) that offer space-time-color resolution. These MOHs integrate time-resolved room temperature phosphorescence and color-resolved excitation wavelength dependencies with both space-resolved ex situ optical waveguides and in situ heterojunctions. Capitalizing on these multifaceted properties, MOHs-based two-dimensional (2D) optical waveguides and heterojunctions exhibit the ability to tune full-color emissions across the spectra from blue to red, operating within different spatial and temporal scales. Therefore, this work introduces an effective methodology for engineering space-time-color resolved MOH microstructures, holding significant promise for the development of high-density photonic logical devices.

Mechanical dicing of optical quality facets and waveguides in a silicon nitride platform

AbstractThe authors report a ductile dicing process for manufacturing optical‐quality facets in a multi‐layered silicon nitride platform without the need for polishing. A surface roughness (Sa) of 1.5 nm was achieved. This technique was extended to fabricate ridge waveguides, and the results and characterization are reported.

Thin-film lithium niobate electro-optic terahertz wave detector

The design, fabrication, and validation of a thin-film lithium niobate on insulator (LNOI) electro-optic (EO) time-domain terahertz (THz) wave detector is reported. LNOI offers unprecedented properties for the EO detection of freely propagating THz wave radiation pulses and transient electric fields because of the large EO coefficient of the material, engineering of the velocity matching of the THz wave and optical wave, and much reduced detector size. The proof-of-concept device is realized using thin-film lithium niobate optical waveguides forming a Mach–Zehnder interferometer with interferometer arms electrically poled in opposite directions. THz waves are coupled effectively to the fully dielectric device from free space without using antennas or plasmonics. The detection of THz waves with frequencies up to 800 GHz is successfully demonstrated. The detector allows for the detection of THz frequency electric fields up to 4.6 MV/m. The observed frequency response of the device agrees well with theoretical predictions.

Photo‐Induced Electric Field Effects on Water Droplets Generated in a LiNbO3 Opto‐Microfluidic Platform

AbstractIn this work, droplets elongation as a result of the photo‐induced photovoltaic electric field is presented and modeled. Moving water droplets are generated in microfluidics channels by means of a droplet‐based opto‐microfluidic platform integrated in lithium niobate (LN). A cross‐junction is engraved on the substrate as droplets generator, on top of which a z‐cut iron‐doped lithium niobate (Fe:LN) crystal is placed in order to build up photo‐induced electric field as a result of photovoltaic effect promoted upon suitable illumination. Droplets detection is realized by optical waveguides, designed in a Mach‐Zehnder Interferometer (MZI) configuration on the same substrate. The dynamics of droplet elongation is investigated, highlighting the impact of the photovoltaic electric field on the droplet dimension and surface tension.