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Robust low-loss optical fiber joints are a prerequisite in all-fiber devices. Joining structurally dissimilar fibers, such as microstructured optical fibers, is a timely challenge, as they are beco...

Here, we report a nanocomposite with excellent photothermal performance promising for photothermal treatment. This nanocomposite is prepared by linking Au nanorods (NRs) to NaGdF4:18% Yb3+, 2%Er3+@...

An analysis model for an optical waveguide microcantilever sensor is developed combining the optical and mechanical models. An improved optical waveguide microcantilever sensor with a buffer is provided and taken as an example to explore using the analysis model. A systematic and detailed discussion about the couplers for the input waveguide to optical waveguide cantilever and the optical waveguide cantilever to the output waveguide of the improved waveguide cantilever sensor is presented. The sensitivity of an improved optical waveguide cantilever sensor is evaluated by analyzing the input/output waveguide, buffer, microcantilever, and gap. An improved optical waveguide microcantilever sensor by adding a buffer shows a sensitivity of $5.7\times 10^{-4}nm^{-1} $ , which is improved by 51.3%, compared with a conventional optical waveguide microcantilever sensor. The design of an optical waveguide cantilever sensor is a trade-off of different design parameters. These will be helpful for the study of an optical waveguide cantilever sensor.

All-perovskite tandem solar cells have great potential to realize the efficiency beyond the Shockley-Queisser efficiency limitation of single junction solar cells. Here we investigate the photon redistribution effect induced by introduction of the optical coupling layer in two terminal (2 T) tandem solar cells. In this work, it is shown that the introduction of the optical coupling layer could not only reduce the reflection loss, but also would affect the redistribution of the absorbed photons in the tandem device due to the optical interference effect, which will disturb the previous balance and complicate the optical modulation. This photon redistribution phenomenon is systemically investigated by combining the optical and electrical aspects. By considering the coupling effect beyond the antireflection function after introducing the optical coupling layer, the new current match could be achieved, which would obviously improve the device performance further. Various materials such as LiF, MgF2, Al2O3, ZnO have been adopted as the optical coupling layer and it is demonstrated that this phenomenon is universal for all the cases. The improvement brought by photon redistribution effect may be even more obvious than antireflection function. Through analyzing the inner optical mechanism and modulating the structure, a higher performance can be achieved by carefully considering the optical coupling effect.

This research concerns a design and construction of a bone mineral density (BMD) and bone mineral content (BMC) measurement system based on dual energy X-ray absorptiometry (DEXA). An indirect X-ray detector is designed by optical coupling CMOS sensor with image on the intensifying screen. A dedicated microcontroller X-ray apparatus is used as an X-ray source to capture two energy level X-ray of middle phalanges bone of middle finger. The captured image is processed based on modified Beer-Lambert law to compute bone mineral density. Bone mineral content is also computed by determining the area of the phalanges bone using active contour. The designed bone mineral density (BMD) and bone mineral content (BMC) measurement system is low-cost and hence can be distributed at district hospital for screening purposes of Osteoporosis of the elderly. Compared with BMD measured from commercial model, BMD measurement of our system acquires linear relation with R2 equals 0.969. The mean square error between the normalized BMD value and that of the commercial model is 0.0000981.

We demonstrate the bandwidth enhancement of optical 90° hybrid based on $2\times 4$ MMI coupler for the silicon-on-insulator platform, without adding any fabrication complexity. By optimizing the width of the conventional $2\times 4$ MMI coupler, our design achieves an operating bandwidth of 72 nm.

We demonstrate optical frequency division of an octave-spanning large repetition rate microcomb to an electronically-detectable frequency in an all-silicon nitride dual microcomb platform

We demonstrate the first reported integration of III-V waveguides (GaAs/Al0.4Ga0.6As) with SiN x waveguides via heteroepitaxial III-V-on-silicon growth. We achieve efficient optical coupling (-2.5 dB loss/transition) at 1550 nm and low threading dislocation density $(4\times 10^{6}\text{cm}^{-2})$ , suitable for fabrication of high-performance optoelectronic devices. © 2021 Massachusetts Institute of Technology

A unique combination of microlens and pillar on the facet of single mode fiber is proposed and examined to achieve high coupling efficiency to small spot size of silicon photonics. Pillar and microlens are fabricated by Self-Written Waveguide (SWW) method and dipping method, respectively using UV-curable resin.

One of the main approaches of design and manipulation of the quantum emitters’ radiative properties is based on proper control of optical modes of the surrounding quantum emitter environment, leading to, in its ultimate case, to a strong regime of the emitter - environment interaction. In this Letter, we present the realization of a mesoscopic physical system (Au SPASER nanoparticle with polydopamine shell containing dye molecules Cy 7.5) in which the strong optical coupling regime allows: (i) to get rid of dye molecules quenching, (ii) to suppress photobleaching of dye molecules and (iii) to get a great enhancement of dye molecules fluorescence. We have reduced the rate of fluorescence quenching of dye molecules in PDA by 1000 times and increased the fluorescence emission rate of dye molecules by 30 time, thus preparing bright, nanoscale and biocompatible fluorescent probes suitable for bio-sensing applications. As an example of practical use of the probe, we demonstrate direct detection of single SARS-CoV-2 viral particle via fluorescence measurements of the probes attached to the viral particle through the antibodies.

We report a novel 355 nm multi-spectral FLIm/ 1310 nm swept-source OCT intravascular imaging catheter system with improved performance. A free-form reflective distal optics enables uncompromised UV and NIR beam focusing. Adoption of an air bearing rotary collimator (100 rps) provides stable optical coupling (single mode transmission: 70+/-2% ); the integration of solid-state multi-spectral FLIm detection within motor drive benefits both FLIm acquisition speed (30 kHz point measurement rate) and signal quality (6x reduction in lifetime standard deviation). We anticipate that this system will complement OCT’s well known capabilities with improved inflammation quantification and extracellular matrix characterization of intravascular lesions.

In order to meet the increasing demand for data transmission over short distances of up to 100 m, the Optical Assembly and Connection Technology for ComponentIntegrated Bus Systems (OPTAVER) research group, funded by the German Research Foundation (DFG), developed a process for the additive manufacturing of three-dimensional optical waveguides. The research group focuses on design and modeling, simulation, and manufacturing polymer optical waveguides to produce 3D-Opto-Mechatronic-Integrated Devices (3D-Opto-MID). Inside 3D-Opto-MID, an optical coupler is presented based on an asymmetrical coupling principle. This paper reviews the entire process chain and the corresponding research results of the OPTAVER process.

We report a hybrid flip-chip-integrated laser attach technology on a monolithic SiPh platform. Efficient laser-to-PIC butt-coupling with optical power up to 11dBm was demonstrated through a combination of precise mechanical stops and optical alignment features.

Van der Waals heterostructures of monolayer crystals are promising platforms for novel electronic, photonic and spintronic devices [1] - [2] . Fine control of the stacking rotation angle, i.e. the twist angle θ, allows to tailor their electronic and optical properties. In twisted bilayer graphene (tBLG), interlayer coupling leads to a complex subband electronic structure and van Hove singularities (vHs) with θ-dependent energy position [3] .

Self-written waveguides are an established solution to connect different optical elements with each other. They minimize coupling losses and enable a rigid connection. Furthermore, their characteristics enable a usage as thermal sensing element simultaniously.

The optical fiber microtips can be utilized as a unique platform for various applications, including optical coupling, sensing, beam shaping and optomechanical systems. Here, we fabricate a polymer microtip between two SMFs and the whole device is integrated in a V-groove which is portable and reusable. Characteristics of the microtip bridge will be discussed. This integrated portable device can be used in various coupling and sensing applications.

The coupling coefficient of a 2×1 optically coherent microcavity laser array can be experimentally determined. We show the extracted coupling coefficient varies for arrays depending on in-phase or out-of-phase coherent operation, in agreement with theory.

We present scalable 3D photonic waveguide interconnects fabricated using two-photon polymerization. Interconnects comprise optical waveguide couplers with 1.2μm diameter, and we characterize numerous branching topologies. Finally, we demonstrate a 225 input and 529 output interconnect.

A novel system based on a robust grid of standard low-cost Polymer Optical Fibres has been created which efficiently detects varying 2-dimensional pressure profiles at high speed. Unobtrusive body movement detection in bed is demonstrated with 25 profiles/s using an easy to manufacture 16×8 grid.

Optical couplers based on Multi-mode interference (MMI) were considered using Ti-diffused LiNbO 3 (Ti:LN) waveguides. Properties of MMI waveguides of Ti:LN were analyzed using the beam propagation method. An optical 90-degree hybrid of the MMI structure was designed and fabricated with the Ti:LN waveguides. We experimentally confirmed that the MMI coupler could operate as a 90-degree hybrid using the MMI waveguide part of 50 μm width and 2.13 mm length.

International audience; Owing to their energy level splitting in the meV range, large graphene quantum dots (size ~100 nm) are very attractive candidates for THz technology. Whereas their electronic properties have been widely studied by transport measurements, only very few works have been focused on their interaction with THz radiation. Here, we report a theoretical and experimental investigation of the optical properties at THz frequencies of large graphene quantum dots. Using a tight-binding modeling, we show the existence of spatially extended mixed-states that should couple efficiently to THz photons. Furthermore, we experimentally demonstrate THz optical absorption of an array of circular 75 nm-diameter graphene quantum dots at 4K and 300K.

A 16-channel silicon photonics transmitter module has been proposed and demonstrated. To prove the feasibility of the module design, it’s necessary to analyze optical coupling calculation, thermal effect, and high-speed signal integrity.

We proposed 1:9 and 1:99 optical power couplers based on inverse designed nano-pixel. Both couplers occupy a compact area of 2.88 × 2.88 μm2 with a low excess loss of 0.68 (1:9) / 0.41 dB (1:99) and a wide wavelength operation range of 1500-1600 nm.

In this paper, the room-temperature performance of different optical coupling materials post temperature exposure was tested. The tested couplers included OC431A-LVP, OG0010 optical grease, BLUESIL V-788, and SAINT-GOBAIN BC-630. This was done by subjecting the whole detector with newly applied optical coupling materials to a 2-h temperature exposure—ranging from −20 to 50 °C and then by letting it return to room temperature before collecting a spectrum from a Cs-137 source. The energy resolution at 662 keV was computed as the metric for evaluating the performance. Three trials were run at each coupler–temperature combination. Our results reveal that the performance of all coupling agents do indeed change with temperature after the 2-h exposure. Over all the tested temperature trials, the energy resolution ranged from 11.4 to 14.3% for OC431A-LVP; 10.2 to 14.6% for OG0010; 10 to 13.4% for BLUESIL V-788; and 9.8 to 13.3% for SAINT-GOBAIN BC-630. OC431A-LVP had the lowest variance over the full range, while BC-630 was the most constant for temperatures above 20 °C. Ultraviolet-visible (UV-Vis) spectra experiments were also performed on isolated optical coupling materials to measure the light absorption coefficient. The results show that the temperature-induced variance in light absorption coefficient of each optical coupling materials is one of the reasons for the variance in energy resolution performance. Our findings suggest the need for further investigation into this effect and the recommendation that optical coupling materials need to be selected for the task at hand with greater scrutiny.

Commercial couplers designed for 1550nm are conveniently adopted for realizing efficient Radio-over-Fiber links operating at 850nm on the standard G.652 single mode fiber. In particular, exploiting the mode filtering properties observed in these couplers when excited at 850nm, a multi-wavelength system over the standard G.652 fiber is obtained, opening the possibility to easily integrate in currently developed infrastructures such low cost systems operating in the first optical window.

A 2-point Haar transform (HT) building block (BB) in an indium phosphide (InP) integrated platform is proposed. The developed BB consists of a $2\times 2$ multimode interference (MMI) with two delay lines phase shifters to attain the expect operation from the 2-point HT BB. The simulation and experimental results of the MMI coupler output access waveguides are presented and discussed. A coupling ratio of 88:12 was achieved in the developed BB.

C-reactive protein (CRP) plays an important role in inflammation detection and disease monitoring. The optical biosensor is a highly sensitive and easy detection tool. The microfluidic self-driving optical sensors were fabricated with transparent glass material and used for the enhanced surface plasmon resonance (SPR) optical detection of the model protein CRP using Au nanoparticles (AuNPs) and a sandwich immune reaction. The 3D design of the chip was devised to improve the optical coupling efficiency and enable integration with a microfluidic control and rapid detection. The array of pre-fixed antibody modified by Au nanoparticles was used to achieve rapid antigen capture and improve the optical sensitivity. The Au nanoparticle amplification approach was introduced for the SPR detection of a target protein. CRP was used as a model target protein as part of a sandwich assay. The use of Au NP measurements to detect the target signal is a threefold improvement compared to single SPR detection methods.

We demonstrate adiabatically tapered fibers terminating in sub-micron tips that are clad with a higher-index material for coupling to an on-chip waveguide. This cladding enables coupling to a high-index waveguide without losing light to the buried oxide. A technique to clad the tip of the tapered fiber with a higher-index polymer is introduced. Conventional tapered waveguides and forked tapered waveguide structures are investigated for coupling from the clad fiber to the on-chip waveguide. We find the forked waveguide facilitates alignment and packaging, while the conventional taper leads to higher bandwidth. The insertion loss from a fiber through a forked coupler to a sub-micron silicon nitride waveguide is 1.1 dB and the 3 dB bandwidth is 90 nm. The coupling loss in the packaged device is 1.3 dB. With a fiber coupled to a conventional tapered waveguide, the loss is 1.4 dB with a 3 dB bandwidth extending beyond the range of the measurement apparatus, estimated to exceed 250 nm.

We propose a novel fabrication of total internal reflection spherical concave with polymer material by gray-tone optical lithography on printed circuit boards for vertical optical coupling between waveguides and optoelectronic devices.

Within a Brillouin-based bulk crystalline cavity optomechanical system, we demonstrate high quantum cooperativities as well as strong coupling between infrared light and high-frequency (12.7 GHz) bulk acoustic modes.

We demonstrate robust partially-automated characterization of evanescent coupling between a SNAP microresonator and a tapered optical fiber, and report coupling parameter profiles for two axial series along the taper’s longitudinal axis.

AIP Advances 10(11), 115016 - (2020). doi:10.1063/5.0030765, Published by American Inst. of Physics, New York, NY

We report non-trivial changes in the photoconductivity of organic semiconductor polarons when their optical transition is strongly-coupled to a microcavity mode. Our observations point to a change in the underlying photoinduced electron transfer process.

We present the analysis of the influence of fabrication imperfections on the optical, mechanical and optomechanical coupling characteristics in an optomechanical crystal nanobeam cavity. © 2020 The Author(s)

We proposed a new conceptual tiny optical engine. With optimization of direct optical coupling between PDs and PLC-AWG, the compact optics embedded optical receiver engine mounted on silicon interposer was applicable for 400G CWDM4 10km © 2020 The Author(s)

We present a compact, single microring resonator with a tunable coupler to measure waveguide losses. The method is demonstrated by extracting the propagation losses of 550 nm and 600 nm wide SOI rib waveguides.

We present an optical signal coupling scheme for slab waveguide surface grating coupler sensors. The proposed solution is based on the use of polymer microlenses. In this work we analyze two types of compact polymer lenses: the aspheric plano-convex lenses and Fresnel lenses. The feasibility of the proposed scheme is demonstrated by the experimental investigation into the optical signal coupling to the test structure of TiO2-SiO2 slab waveguide surface grating coupler using both types of lenses.

The acousto-optical response of a microtoroidal optomechanical microresonator with optically compensated damping factor is measured and analyzed. We demonstrate that the large optical quality factor combined with the enhanced acoustic response due to radiation pressure make optomechanical microresonators excellent candidates as sensitive acousto-optical transducers with extremely low power consumption.

We investigate the influences of ridge-waveguide shape and width on performances of InP-based coupled ridge waveguide laser arrays emitting at $2.1~\mu \text{m}$ . Four devices with different shapes and widths of ridge elements are fabricated. The trapezoid ridges reduce the optical losses at regions between ridge elements in the trapezoid devices, thus enhances the optical coupling between ridge elements and lead to larger coherent output powers compared with the rectangular ones. Meanwhile, narrower ridges with the same shape give a stronger optical confinement to the lateral modes in every single ridge and improve the overall modal and far-field characteristics of the device. The results show that the trapezoid and narrower ridges can lead to a comprehensive improvement in the performances of the coupled ridge waveguide laser arrays emitting at $2.1~\mu \text{m}$ .

Two-dimensional two-period gradual Photonic Crystals (PhCs) structure arrays were designed by double-cone interference method (3+3), and the effects of different polarization combinations of inner and outer cone beams on the double-cone interference were studied. By adding a beam of light in the third dimension to the double-cone interference, umbrella-like double-cone interference and inverted umbrella-like double-cone interference are constructed, and the formed three-dimensional PhCs is observed to study the periodicity of the photonic structure. This structure is very important for optical coupling and light integration.

A Silicon photonics platform operating at 100 Gbit/s (53Gbaud-PAM4) per lane is demonstrated. Integration of 60 GHz High-Speed Photodiode and efficient High-Speed Phase Modulator into a 400G-DR4 3D test chip is shown. Extension towards 400G-FR4 is addressed by the introduction of a SiN layer allowing wideband fiber to the chip optical coupling and polarization management.

This paper presents the analysis and development of an evanescent waveguide sensor system, based on a hydrogenated amorphous silicon (a-Si:H) photodiode and a double ion-exchanged waveguide diffused in a borosilicate BK7 glass substrate. The a-Si:H sensor is a p-doped/intrinsic/n-doped diode, with a metal top electrode and an indium tin oxide (ITO) transparent bottom contact. Simulations on the confinement of a monochromatic light in a channel waveguide and its coupling into a thin-film photodetector were performed using COMSOL Multiphysics. The system design considers a deep investigation on refractive index and thickness of the ITO layer, which are key parameters for the optical coupling optimization between the waveguide and the photodetector. The first prototype was made using standard microelectronics techniques: physical and chemical vapor deposition of the thin films of the structure, wet and dry etching of the different materials, and photolithography for the thin-film pattern definition. The electrooptical characterization of the fabricated device shows the effectiveness of the optical coupling and suggests its use for on-chip detection in lab-on-chip applications.

We present optical coupling schemes for silicon integrated photonics circuits that account for the challenges in large-scale data processing systems such as those used for emerging big data workloads. Our waveguide based approach allows to optimally exploit the on-chip optical feature size, and chip- and package real-estate. It further scales well to high numbers of channels and is compatible with state-of-the-art flip-chip die packaging. We demonstrate silicon waveguide to polymer waveguide coupling losses below 1.5 dB for both the O- and C-bands with a polarisation dependent loss of

We design a temporary optical coupler to obtain high injection and extraction efficiencies while keeping the bending loss low with the aim of realizing optical cable re-routing without service interruption. The temporary optical coupler injects/extracts signal lights into/from a fiber by using fiber bending. The extraction efficiency is improved by using a double-clad fiber or a graded-index fiber for light injection and extraction while the injection efficiency is maintained compared with that of a conventional temporary optical coupler that uses a single-mode fiber. This improvement enables us to realize an optical cable re-routing operation support system that requires no service interruption.

Photonic crystals (PhCs) and plasmonic nanostructures offer the unprecedented capability to control the interaction of light and biomolecules at the nanoscale. Based on PhC and plasmonic phenomena, a variety of analytical techniques have been demonstrated and successfully implemented in many fields, such as biological sciences, clinical diagnosis, drug discovery, and environmental monitoring. During the past decades, PhC and plasmonic technologies have progressed in parallel with their pros and cons. The merging of photonic crystals with plasmonics will significantly improve biosensor performances and enlarge the linear detection range of analytical targets. Here, we review the state-of-the-art biosensors that combine PhC and plasmonic nanomaterials for quantitative analysis. The optical mechanisms of PhCs, plasmonic crystals, and metal nanoparticles (NPs) are presented, along with their integration and potential applications. By explaining the optical coupling of photonic crystals and plasmonics, the review manifests how PhC-plasmonic hybrid biosensors can achieve the advantages, including high sensitivity, low cost, and short assay time as well. The review also discusses the challenges and future opportunities in this fascinating field.

We aim to study the properties of the output probe field (OPF) in a system composed of two coupled-optical cavities. Two fields such as strong pump and a weak probe field drives the left cavity whereas the right-side cavity is coupled to mechanical oscillation via photothermal effect. The two cavities are coupled with optical coupling strength $J$. Single photothermally induced transparency (PTIT) in a single cavity is realized via thermal effect (Sci. Adv. 6, eaax8256 (2020)). Following the idea, we report double PTIT in coupled-cavities system. The control of single to double PTIT is realized in the proposed system by properly adjusting the coupling strength $J$. We further show the enhancement of slow light by adjusting the coupling strength ($J$) between the cavities. Our proposed scheme facilitates experiments to investigate photothermal effects in an array of optomechanical systems.

16-fold enhancement of spontaneous emission rate of a single new color center in diamond is achieved using a high-quality factor photonic crystal nanocavity for efficient spin-photon interfaces.

There are many optical detection and sensing methods used today that provide powerful ways to diagnose, characterize, and study materials. For example, the measurement of spontaneous Raman scattering allows for remote detection and identification of chemicals. Many other optical techniques provide unique solutions to learn about biological, chemical, and even structural systems. However, when these systems exist in a highly scattering or turbid medium, the optical scattering effects reduce the effectiveness of these methods. In this article, we demonstrate a method to engineer the geometry of the optical interface of a turbid medium, thereby drastically enhancing the coupling efficiency of light into the material. This enhanced optical coupling means that light incident on the material will penetrate deeper into (and through) the medium. It also means that light thus injected into the material will have an enhanced interaction time with particles contained within the material. These results show that, by using the multiple scattering of light in a turbid medium, enhanced light–matter interaction can be achieved; this has a direct impact on spectroscopic methods such as Raman scattering and fluorescence detection in highly scattering regimes. Furthermore, the enhanced penetration depth achieved by this method will directly impact optical techniques that have previously been limited by the inability to deposit sufficient amounts of optical energy below or through highly scattering layers.

A MEMS-based mid-infrared (MIR) chip-to-chip optical coupling technique, optical quilt packaging (OQP), is described. Numerical simulations are performed to predict performance and establish fabrication tolerances. The OQP fabrication process is described in detail and MIR inter-chip optical coupling between two waveguide arrays joined by OQP is characterized. The coupling loss between Ge-on-Si passive MIR waveguides is found to be ~ 4.1 dB, which is the lowest butt-coupling loss reported between two chips.