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Showing papers on "Bend radius published in 2018"


Journal ArticleDOI
TL;DR: In this paper, a geometric deformation-based index-shift-based approach is proposed to tune a diode laser with a low-confinement silicon nitride-based ring resonator.
Abstract: Typical integrated optical phase tuners alter the effective index. In this paper, we explore tuning by geometric deformation. We show that tuning efficiency, Vπ L, improves as the device size shrinks down to the optimal bend radius, contrary to conventional index-shift based approaches where Vπ L remains constant. We demonstrate that this approach is capable of ultra-low power tuning across a full FSR in a low-confinement silicon nitride based ring resonator of 580 μm radius. We demonstrate record performance with VFSR = 16 V, Vπ L = 3.6 V dB, Vπ Lα = 1.1 V dB, tuning current below 10 nA, and unattenuated tuning response up to 1 MHz. We also present optimized designs for high confinement silicon nitride and silicon based platforms with radius down to 80 μm and 45 μm, respectively, with performance well beyond current state-of-the-art. Applications include narrow-linewidth tunable diode lasers for spectroscopy and non-linear optics, optical phased array beamforming networks for RF antennas and LIDAR, and optical filters for WDM telecommunication links.

61 citations


Journal ArticleDOI
TL;DR: A novel single-polarization single-mode double-ring hollow-core anti-resonant fiber with two single-Polarization regions (1545-1553 nm and 1591-1596 nm) is proposed and exhibits high-performance bend resistance.
Abstract: A novel single-polarization single-mode double-ring hollow-core anti-resonant fiber with two single-polarization regions (1545–1553 nm and 1591–1596 nm) is proposed. Single-polarization guidance is achieved by coupling a polarized fundamental mode and silica mode by using different tube thicknesses. Specifically, when the wavelength is 1550 nm, only a single x-polarized fundamental mode with a low loss of 0.04 dB/m is propagated by a polarization extinction ratio of 17662 and minimum higher-order mode extinction ratio of 393 by optimizing the structural parameters. Furthermore, this fiber also exhibits high-performance bend resistance. The x-polarized FM loss is as low as 0.11 dB/m with single-polarization single-mode guidance when the proposed fiber was bent at a bend radius of 8 cm toward the x-direction.

50 citations


Journal ArticleDOI
TL;DR: In this paper, the authors analyzed movement track of bending die based on the principle of free bending technology and analyzed distribution characteristics of equivalent stress and strain on tube and bending die during different stages of the free bending process.

44 citations


Journal ArticleDOI
TL;DR: In this article, a new spherical connection of the bending die to the guide was designed through geometric derivation, which can lead to a greater deflection of the bend die, to realize the bending ratio of down to R/D0 = 2.5.
Abstract: In tube free-bending, the connection of the bending die to the guide has a great influence on the stability of mechanical movement and the forming limit of the bent tube. The general connection of the bending die to the guide cannot realize the continuous stable movement of the bending die. Spherical connection of the bending die to the guide can guarantee a continuous changed tipping of the bending die, but has a limited minimal bending ratio (ratio of bending radius to tube outer diameter) of R/D0 ≥ 3 depending on the geometrical constrains. In this paper, a new spherical connection of the bending die to the guide was designed through geometric derivation, which can lead to a greater deflection of the bending die, to realize the bending ratio of down to R/D0 = 2.5. Based on the designed spherical connection, the bending ratio of down to R/D0 = 2.43 and R/D0 = 2.78 of brass tube were realized in the finite element simulation and bending test respectively. And with the analytical model, simulation model and experimental bending results, the forming characteristics of bent tube with small bending radii based on the spherical connection structure were investigated. The main results show that the equivalent stress, displacement of the strain neutral layer (NL) increase with the decrease of bending radius, and the wall thickness thinning in outer bend shows little differences under tight and big bending radii due to the increased axial thrust.

41 citations


Journal ArticleDOI
Shibo Yan1, Shuqin Lou1, Xin Wang1, Tongtong Zhao1, Wan Zhang1 
TL;DR: In this paper, a hollow core anti-resonant THz fiber is proposed, which has a simple structure consisting of only ten Topas tubes and achieves high birefringence by introducing two large tubes.
Abstract: A novel high-birefringence hollow-core anti-resonant THz fiber is proposed in this paper. This fiber has a simple structure which consists of only ten Topas tubes. High birefringence is achieved by introducing two large tubes. The first two resonant frequencies are 1.44 and 2.88 THz by fixing tube thickness at 0.09 mm, which makes two low-loss transmission windows exist in the frequency range from 0.8 to 3.0 THz. The lowest loss is 2.10 dB/m occurring at 1.2 THz in the first transmission window and 1.68 dB/m at 2.34 THz in the second transmission window. By optimizing the structure parameters, high birefringence above 7 × 10−4 in the frequency range from 1.0 to 1.24 THz are obtained. The highest birefringence is up to 8.7 × 10−4 at 1.04 THz. Birefringence can be further increased to the order of 10−3 by adjusting the structure parameters at the cost of loss increasing and the bandwidth decreasing. In addition, bent performance of this fiber is also discussed. In addition, this fiber can keep good performance when it is bent for x-direction. At the bend radius of 15 cm, the loss and birefringence has a more slightly change in the first transmission window than the second transmission window. The first transmission window own much better bent-insensitive characteristics.

38 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of varying circumferential and angular position along the pipe bend, as well as the influence of the bend radius, is investigated via 3D finite element simulations.
Abstract: This paper investigates the reflection of the torsional T(0,1) mode from defects in pipe bends. The effect of varying circumferential and angular position along the pipe bend, as well as the influence of the bend radius, is investigated via 3D finite element simulations. The results show that the reflection expected from a small defect varies significantly with position, the minimum reflection coefficient being about 10% of that from a comparable defect in a straight pipe, while maxima of around four times the straight pipe value are seen. The areas of low detectability are mainly found on the bend intrados and those of high detectability close to its extrados; similar effects are seen in bends with radii varying from one to twenty pipe diameters. It is shown that the reflection from a defect at a given location is roughly proportional to the square of the von Mises stress produced by the transmitted wave at that position. This holds for defects such as circumferential cracks, the detailed subject of this investigation, and is also expected to be valid for corrosion patches; it will not hold for axial cracks. The results explain the low reflection seen from a simulated corrosion defect at a bend in a previous investigation.

32 citations


Journal ArticleDOI
TL;DR: In this article, a new model for predicting particle flow characteristics in dense phase pneumatic conveying systems is presented, where the domain of the solid phase is evenly divided by discrete grids, based upon which particle collision forces are solved.

28 citations


Journal ArticleDOI
TL;DR: A novel optical fiber displacement sensor based on composite interference established within a balloon-shaped bent multimode (BSBM) fiber structure is described and experimentally demonstrated and could be a realistic candidate in the high-accuracy displacement measurement field.
Abstract: A novel optical fiber displacement sensor based on composite interference established within a balloon-shaped bent multimode (BSBM) fiber structure is described and experimentally demonstrated. The BSBM fiber structure is realized by bending a straight single-mode–multimode–single-mode (SMS) fiber structure into a balloon shape using a length of capillary tube to fix the shape of the structure. Owing to the bend in the multimode waveguide, the original undistorted multimode interference pattern is changed, and an extra Mach–Zehnder interferometer is effectively introduced within the multimode fiber (MMF) section at a suitable bending radius. This established composite interference greatly improves the displacement sensing performance of the SMS fiber structure. A maximum displacement sensitivity of 0.51 dB/μm over the displacement range of 0–100 μm at the operating wavelength of 1564.7 nm is achieved experimentally. Based on its easy fabrication process, low cost, and high measurement sensitivity, the sensor of this investigation could be a realistic candidate in the high-accuracy displacement measurement field.

23 citations


Journal ArticleDOI
TL;DR: In this paper, a segmented cladding fiber (SCF) with resonant ring is proposed, and a high leakage loss ratio (>100) between the high-order modes and the fundamental mode can be achieved at wavelength 1.064μm.
Abstract: A novel design of segmented cladding fiber (SCF) with resonant ring is proposed in this paper. A high leakage loss ratio (>100) between the high-order modes (HOMs) and the fundamental mode can be achieved at wavelength 1.064 μm. The HOMs suppression is better than the traditional SCF. The numerical results show that the effectively single-mode operation with a mode area of 790 μm2 can be achieved at a bend radius of 15 cm. Besides, the fiber performance is insensitive to the bending orientation at the ranging of [−180°, 180°]. This fiber design shows great potential in developing compact high-power fiber lasers and amplifiers.

20 citations


Proceedings ArticleDOI
01 Jun 2018
TL;DR: A flexible fan-out wafer-level packaging (FOWLP) process for heterogeneous integration of high performance dies in a flexible and biocompatible elastomeric package (FlexTrateTM) was used to assemble >600 dies with co-planarity and tilt < 1µm, average die-shift of 3.28 µm with? < 2.23 µm.
Abstract: A flexible fan-out wafer-level packaging (FOWLP) process for heterogeneous integration of high performance dies in a flexible and biocompatible elastomeric package (FlexTrateTM) was used to assemble >600 dies with co-planarity and tilt <1µm, average die-shift of 3.28 µm with ? < 2.23 µm. We have also engineered a novel corrugated topography of a stress buffer layer for metal interconnects on FlexTrateTM to mitigate the buckling phenomenon of metal films deposited on elastomeric substrates. Corrugated interconnects were then tested for their mechanical bending reliability and have shown less than 0.4% change in resistance after bending at 1 mm radius for 1,000 cycles. Finally, we demonstrate integration of an array of 25 dielets interconnected in a daisy chain configuration at 40 µm interconnect pitch.

19 citations


Journal ArticleDOI
27 Apr 2018
TL;DR: In this article, a full-vectorial finite difference method was used to compare the optical power distribution and bending loss of etching, proton exchange (PE), and strip-loaded waveguides.
Abstract: Waveguides formed by etching, proton-exchange (PE), and strip-loaded on single-crystal lithium niobate (LN) thin film were designed and simulated by a full-vectorial finite difference method. The single-mode condition, optical power distribution, and bending loss of these kinds of waveguides were studied and compared systematically. For the PE waveguide, the optical power distributed in LN layer had negligible change with the increase of PE thickness. For the strip-loaded waveguide, the relationships between optical power distribution in LN layer and waveguide thickness were different for quasi-TE (q-TE) and quasi-TM (q-TM) modes. The bending loss would decrease with the increase of bending radius. There was a bending loss caused by the electromagnetic field leakage when the neff of q-TM waveguide was smaller than that of nearby TE planar waveguide. LN ridge waveguides possessed a low bending loss even at a relatively small bending radius. This study is helpful for the understanding of waveguide structures as well as for the optimization and the fabrication of high-density integrated optical components.

Journal ArticleDOI
Xiao Wang1, Jianhua Liu1, Shaoli Liu1, Peng Jin1, Tianyi Wu1, Wang Zhi1 
TL;DR: A stereo vision based method that can measure the bend radius automatically without artificial operations and show good performance in terms of precision and reliability, even when lacking corresponding points or with incomplete edges.

Journal ArticleDOI
TL;DR: In this paper, an ultrasonic technique for accurate temperature measurement by tracking the time-of-flight of reflected guided wave modes from appropriately spaced notch reflectors is proposed, while using the reflection from a bend is used as a reference.
Abstract: This paper reports the feasibility of using an ultrasonic waveguide sensor for distributed temperature measurement in two different case studies, that is: 1) skin temperature of a solid structure (pipe) and 2) fluid (water). This technique improves upon the conventional multiple thermocouples approach for multi-level temperature measurements. The range of temperatures is from room temperature to maximum utility temperature for the two case studies (85 °C for water and 200 °C for pipe). Using the interaction of the propagating ultrasonic waves in a thin rodlike waveguide with intentionally designed geometric discontinuities (bends, axisymmetric, non-axisymmetric notches, and so on), the localized information on the temperature is extracted. An ultrasonic technique for accurate temperature measurement by tracking the time-of-flight of reflected guided wave modes from appropriately spaced notch reflectors is therefore proposed here, while using the reflection from a bend is used as a reference. Using a finite element model approach, the notch size and/or the bend radius were selected in order to reduce mode conversion effects as well as to obtain uniform amplitudes of the reflected signals from these designed discontinuities. The numerical results were experimentally validated for the L(0,1) wave mode using a stainless steel waveguide sensor. This paper is of interest to industrial applications including mould cooling jacket temperature monitoring during the steel manufacturing process as well as for furnace wall temperature measurements in petrochemical industries.

Journal ArticleDOI
TL;DR: In this paper, a new method was proposed to predict the U-R relationship for the arbitrary power hardening aluminum alloy (Al alloy) circular tube based on the U -R relationship of the reference material and the sensitivity analysis of material parameters, which may reduce many experimental works.
Abstract: The bending radius (R) of the bending component is defined by the deflection (U) of the bending die in the tube free-bending process. The U-R relationship is the key factor to obtain the precise geometry size of the complex bending tubular components. Therefore, this study aims at proposing a new method to predict the U-R relationship for the arbitrary power hardening aluminum alloy (Al alloy) circular tube based on the U-R relationship of the reference material and the sensitivity analysis of material parameters, which may reduce many experimental works. In the current study, AA1100 alloy was set as the reference material, and the effects of each material parameter on the U-R relationship were investigated by carrying out the deformation and sensitivity analysis of the FEA simulation results. The results show that the bending radius increases with the decrease of elastic modulus (E), density (ρ), and strain-hardening exponent (n) and the increase of strength coefficient (K) and initial yield stress (σs), where σs has the greatest influence on the U-R relationship. Moreover, the U-R relationship prediction method for arbitrary power hardening Al alloy circular tube was presented based on the sensitivity analysis of the reference material. Finally, the bending tests of the AA6061-T6 tubes were carried out to prove the accuracy of the U-R relationship prediction method. The bending results show that the experimental U-R relationship of the AA6061-T6 tube was consistent with the predicted value, and the prediction method had good applicability to power hardening Al alloy circular tube.

Journal ArticleDOI
TL;DR: In this paper, a plasmonic arc is fabricated with materials, mainly silicones, carefully selected with the aim to be used as mechanically flexible single-mode optical interconnections.
Abstract: We present the design, fabrication and characterization of long-range surface plasmon polariton waveguide arrays with materials, mainly silicones, carefully selected with the aim to be used as mechanically flexible single-mode optical interconnections, the so-called “plasmonic arc” working at 1.55µm. The fabricated plasmonic arcs show a TM/TE polarization ratio of ~25 dB. By using the cut-back method, the straight propagation loss at 1.55µm is estimated to 0.5-1 dB/mm and coupling loss to ~1-2 dB/facet after dicing. In the free-standing S-curved configuration, the bending loss of single cladding plasmonic arc is 2.2-2.8 dB/90° at bending radius 2.5 mm. For double cladding plasmonic arcs, it is decreased to 0.7-1.7 dB/90° for the same radius. The coupling loss with single-mode glass PCB waveguides is estimated to be 1.7 dB/interface in the best condition.

Journal ArticleDOI
TL;DR: In this paper, a 1.6 mm diameter symmetric tape round (STAR) wire made with six 2.5 mm wide symmetric tapes reached an engineering current density (J e) of 454 A mm−2 at 4.2 K in a background field of 15 T at a bend radius of 15 mm.
Abstract: Round REBCO (RE = rare earth) wires of 1.6–1.85 mm diameter have been fabricated using ultrathin REBCO tapes where the superconductor film is positioned near the geometric center. Such symmetric tape round (STAR) wires exhibit excellent tolerance to bend strain with a critical current retention of more than 97% when bent to a radius of 15 mm. A 1.6 mm diameter REBCO STAR wire made with six 2.5 mm wide symmetric tapes reached an engineering current density (J e) of 454 A mm−2 at 4.2 K in a background field of 15 T at a bend radius of 15 mm. Such superior performance at a small bend radius can enable fabrication of future accelerator magnets, operating at magnetic fields above 20 T.

Journal ArticleDOI
TL;DR: In this article, numerical simulation, analytical approach, and forming experiments were conducted to assess the multi-point cylindrical bend-forming process of bi-directional trapezoidal sandwich panel.
Abstract: Bend-forming is an efficient and economical method to manufacture curved sandwich panels, and the major concerns for fabricating precise products are forming characteristics and springback prediction. In this paper, numerical simulation, analytical approach, and forming experiments were conducted to assess the multi-point cylindrical bend-forming process of bi-directional trapezoidal sandwich panel. Analysis was performed on the deformation characteristics, regularity, and forming defects of sandwich panel in the early stage. And afterwards, equivalent elastic constants of the core layer were deduced by the semi-analytic approach combined with finite element method (FEM). On this basis, a theoretical model was established to calculate bending moments and predict springback within formable range. The results indicate that the stress of face sheet in the welded area was obviously lower than that in the suspended area. The core cell was primarily deformed by changing the angle between the inclined plane and the platform, and the deformation of the cell layer mainly occurred in the transition surface area. The dimple and straight plane effect are the most common forming defects during the bending process. The main factors that affect the forming defects are face sheet thickness and bending radius. The springback amount of the sandwich panel approximates the equivalent thickness plate. Thus, it is easy to control the forming precision for small springback, and the springback ratio increases with the increase of bending curvature radius. The springback in theoretical model and experiment has an error of less than 1.0 mm, verifying the accuracy of the theoretical prediction model.

Journal ArticleDOI
TL;DR: In this article, the amplitude modulation caused by the variation in the radius of a concave micro-mirror crafted into the end of an SMF optical fiber is investigated, which can be used in a wide range of applications.
Abstract: This article presents a fibre-optic sensor that measures temperature and pressure. Its operating principle is based on the amplitude modulation caused by the variation in the radius of a concave micro-mirror crafted into the end of an SMF optical fibre. In fact, a micro-cavity engraved into the end of the fibre by selective chemical etching is filled with a PDMS (Polydimethylsiloxane)-type polymer. Due to surface tension, the polymer micro-drop takes on a hemispheric shape characterised by a certain radius. After polymerisation in an oven at 100 °C for one hour, the hemispheric micro-drop is coated with a thin layer of gold using the vacuum evaporation technique. Typically, concave micro-mirrors can be obtained with bend radii of between 10μm and 30μm. Under the action of a temperature gradient or a variation in pressure, the thickness of the PDMS changes and causes a variation in the bend radius of the micro-mirror. As a result, the light intensity guided by the optical fibre and reflected by the micro-mirror is modulated by the variation in its bend radius. In this configuration, the sensor has a thermo-sensitivity of – 0.08dB/°C with a resolution of 0.13 °C in a range of between 20 °C and 100 °C. It also has a pressure sensitivity of 0.11dB/bar between 10 and 20 bars. The measurements are taken by a reflectometer (OTDR). In addition, the experimental results have been validated by theoretical modelling. This sensor is relatively simple to make and can be used in a wide range of applications, in particular biomedical and industrial ones.

Journal ArticleDOI
TL;DR: In this paper, a bend-loss free, high-resolution, fiber-optic distributed sensor was proposed by using a new sensing fiber namely Ge-doped-core photonic crystal fiber (PCF) in optical frequency domain reflectometer (OFDR).
Abstract: We propose a bend-loss free, high-resolution, fiber-optic distributed sensor by using a new sensing fiber namely Ge-doped-core photonic crystal fiber (PCF) in optical frequency domain reflectometer (OFDR). PCF is fabricated with high concentration of Ge-doping in the small core leading to large refractive index difference between core and air-silica cladding. We achieved negligible macrobending loss in our Ge-doped-core PCF for a bend radius of curvature down to 1 mm in experiment and the results are validated by numerical simulation. By using OFDR, with a bend radius of 1 mm, the strain and temperature sensitivities in Ge-doped-core PCF are measured to be 0.138 GHz/ $\mu \varepsilon $ and 1.46 GHz/°C, respectively, with 5 cm spatial resolution.


Proceedings ArticleDOI
01 May 2018
TL;DR: In this article, a new test protocol has been developed for replicating the stresses of daily motion for flexible substrates and the effect of cyclic mechanical bending, exposure to human body temperature has been studied and analyzed using Flex-PCBs.
Abstract: Flexible electronics in wearable applications may be subjected to flexing, bending, stretching in addition to exposure to temperature and humidity. Presently, there is a general lack of test protocols for the reliability assessment and survivability assurance of the flexible substrates. Flexing and bending in operation may be accrued under stresses of daily motion. Flexible substrates often use serpentine patterns to accommodate high stretch in the neighborhood of 25-100 percent. Flexible copper traces subjected to cyclic mechanical bending result in stretching of the outside layers and simultaneously compressing the inner layers. Cyclic bending may also result in formation of wrinkles on the flexible substrate causing delamination. Meaningful accelerated test protocols and acceleration transforms relating test-performance to operational reliability are needed. In this paper, a new test protocol has been developed for replicating the stresses of daily motion for flexible substrates. The conventional-fabricated flexible circuits have been studied. Test coupons have been designed to include the common trace geometries encountered in flexible electronics applications. The effect of cyclic mechanical bending, exposure to human body temperature has been studied and analyzed using Flex-PCBs. Flex-PCBs have been subjected to cyclic bending and the failure modes were analyzed as a function of bend radius, bend angle and number of cycles to failure. Extremely tight bend radius and bend angle larger than 90° have been studied. Further, in order to monitor the resistance of copper traces and develop life prediction model, Data Acquisition unit has been used. This prognostic health monitoring technique captures the increase in resistance of copper traces with the growth in fatigue due to cyclic mechanical bending. The study addresses the need for life prediction models of flexible copper traces on flexible polyimide substrate.

Journal ArticleDOI
TL;DR: In this article, a series of experiments and a finite element analysis was carried out in order to investigate an optimum condition of a mandrel for preventing defects in a rotary draw bending of a copper tube with thin wall.

Journal ArticleDOI
TL;DR: Simulation results show this novel PCF can achieve LMA and have effective single-mode operation when the bending orientation angle ranges in ±110° and has potential application in high-power fiber lasers.
Abstract: In this paper, an asymmetric large-mode-area photonic crystal fiber (LMA-PCF) with low bending loss at a smaller bending radius is designed. The finite-element method with a perfectly matched layer boundary is used to analyze the performance of the PCF. To achieve LMA-PCF with low bending loss, the air holes with double lattice constants and different sizes at the core are designed. Numerical results show that this structure can achieve low bending loss and LMA with a smaller bending radius at the wavelength of 1.55 μm. The effective mode area of the fundamental mode is larger than 1000 μm2 when the bending radius is ≥10 cm. The bending loss of the fundamental mode is just 0.0113 dB/m, and the difference between the fundamental and high-order modes of the bending loss is larger than 103 when the bending radius is 10 cm. Simulation results show this novel PCF can achieve LMA and have effective single-mode operation when the bending orientation angle ranges in ±110°. This novel photonic crystal has potential application in high-power fiber lasers.

Journal ArticleDOI
TL;DR: In this article, a hollow-core anti-resonant fiber with a large mode area and good single mode performance is proposed for high power delivery in mid-infrared region.

Journal ArticleDOI
TL;DR: In this paper, the influence of stresses/strains on critical current degradation in REBCO high-temperature superconducting (HTS) tapes wound onto a round cable were investigated.
Abstract: The influences of stresses/strains on critical current, I c in REBCO high-temperature superconducting (HTS) tapes wound onto a round cable were investigated. In the first step, the HTS tapes were helically wound on copper tubes with various diameters in the range of 2.95-8 mm. Considerably better results were achieved in case the superconducting layer was positioned during the winding at the inner side of the helix. The cables with tape wound on the tube with a diameter of 6.35 mm were subjected to bending tests with various bending radii in range from 21 to 60.5 mm. The I c degradation as a function of both the tube diameter and bending radius has been assessed from a current- voltage curve, from which the critical current was determined. The I, degradation in all samples was confirmed by microstructural investigation of an HTS layer by scanning electron microscopy.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a broadband polarization beam splitter on the silicon-on-insulator platform using the concept of multimode interference, where the angle between the input waveguide and the multimode interferometer was optimized in order to extract the images corresponding to the fundamental transverse electric (TE) and transverse magnetic (TM) polarizations from a single, compact MMI.
Abstract: We propose and experimentally demonstrate a broadband polarization beam splitter on the silicon-on-insulator platform using the concept of multimode interference. The angle between the input waveguide and the multimode interferometer (MMI) was optimized in order to extract the images corresponding to the fundamental transverse electric (TE) and transverse magnetic (TM) polarizations from a single, compact MMI. By changing the direction of propagation, the input angle enabled the addition of a parallelepiped to facilitate exclusively TM collection above the MMI, therefore eliminating the need to cascade successive MMIs. The MMI was tapered to improve coupling at the ports. The design allowed for a compact geometry with a length of 67.5 μm and width of 4 μm, while maintaining a feature size comparable to the waveguide width. The design was experimentally characterized over 72 parameter variations, including input angle, output TM and TE port positions, and bend radius of the output TE waveguide. The performance was consistent over the 100 nm wavelength range of 1500–1600 nm, with an average insertion loss of 2 dB. The device maintained an extinction ratio of at least 13.96 and 11.45 dB in the C-band for the TE and TM polarizations, respectively.

Journal ArticleDOI
TL;DR: In this paper, a femtosecond laser direct writing of 3D waveguides in fused silica was proposed to suppress the bend loss by sandwiching the waveguide between a pair of walls formed by internal modification of glass.
Abstract: We provide a solution toward compact and low-loss three dimensional (3D) photonic circuits by femtosecond laser direct writing of 3D waveguides in fused silica. We suppress the bend loss by sandwiching the waveguide between a pair of walls formed by internal modification of glass. Our method allows to reduce the bend loss of a curved waveguide with a bending radius of 15 mm by more than one order of magnitude.

Journal ArticleDOI
01 Jan 2018
TL;DR: In this paper, the authors focused on the minimum bending radii of 2196-T8511 and 2099-T83 Al-Li alloy extrusions and derived a safe lower limit for the bending radius which can serve as a guideline for tool and product design.
Abstract: In this investigation, the attention is focused on the minimum bending radii of 2196-T8511 and 2099-T83 Al-Li alloy extrusions. To predict the failure of Al-Li alloys, sheet and extrusion stretch bending tests are developed, carried out and simulated using finite element model. The theoretical minimum bending radius is introduced to derive a safe lower limit for the bending radius which can serve as a guideline for tool and product design. Stretch bending tests of Al-Li alloys are performed using the three-point bending test and displacement-controlled stretch bending test at room temperature. The finite element model incorporates three-dimensional solid elements and ductile damage modeling. The experimental results show that Al-Li alloy extrusions in stretch bending show three types of failures, occurring at the unbent region near the entrance of the jaws, at the region below the exit of the die and within the region in contact with the die, respectively. Comparison between predicted values and experimen...

Journal ArticleDOI
TL;DR: In this paper, an analysis of the bend die for different bending radii is presented, based on the distributions of contact normal stresses determined in finite element simulations, a method to simplify the tools' geometries was developed.

Journal ArticleDOI
TL;DR: In this paper, a low-loss U-bend waveguide for realization of GaAs-based gain elements employed in hybrid photonic integration is presented, where the input and output ports of the gain waveguide are placed on the same facet and thus alleviates the geometrical constrains in hybrid integration.
Abstract: We report a low loss U-bend waveguide for realization of GaAs-based gain elements employed in hybrid photonic integration. This architecture allows us to position the input and output ports of the gain waveguide on the same facet and thus alleviates the geometrical constrains in hybrid integration, i.e., the need for precise alignment with silicon photonic waveguides on both ends of the III–V chip. As an exemplary demonstration, we report the loss and gain characteristics of GaInNAs/GaAs U-bend waveguides operating at 1.3 μm. In particular, we demonstrate a bending loss as low as 1.1 dB for an 83 μm bending radius. Efficient laser diode operation is also demonstrated.