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Showing papers on "Radiation mode published in 2017"


Journal ArticleDOI
TL;DR: An all-fiber mode converter based on long-period fiber gratings written in the few-mode fiber that can be realized via a single LPFG with an efficiency of 99% at the resonance wavelength is investigated.
Abstract: We investigated an all-fiber mode converter based on long-period fiber gratings (LPFGs) written in the few-mode fiber. Mode conversion between the fundamental core mode and different higher-order core modes (LP11, LP21, and LP02 modes) can be realized via a single LPFG with an efficiency of 99% at the resonance wavelength. Moreover, optimized mode conversion between the LP01 and LP21 modes can be realized by cascading two LPFGs with different grating pitches. The maximum conversion efficiency is estimated to be ∼99.5% at 1553 nm. The orbital angular momentum states with different topological charges (±1,±2) are demonstrated experimentally. The all-fiber LPFG mode converters could have promising applications in the mode-division multiplexing optical communications.

89 citations


Journal ArticleDOI
TL;DR: An all-fiber passively mode-locked laser with a figure-8 cavity, which generates pulsed cylindrical vector beam output based on a mode selective coupler (MSC) with high mode purity is proposed and demonstrated.
Abstract: We propose and demonstrate an all-fiber passively mode-locked laser with a figure-8 cavity, which generates pulsed cylindrical vector beam output based on a mode selective coupler (MSC). The MSC made of a two mode fiber and a standard single mode fiber is used as both the intracavity transverse mode converter and mode splitter with a low insertion loss of about 0.65 dB. The slope efficiency of the fiber laser is > 3%. Through adjusting the polarization state in the laser cavity, both radially and azimuthally polarized beams have been obtained with high mode purity which are measured to be > 94%. The laser operates at 1556.3 nm with a spectral bandwidth of 3.2 nm. The mode-locked pulses have duration of 17 ns and a repetition rate of 0.66 MHz.

72 citations


Journal ArticleDOI
TL;DR: Mode coupling from the fundamental vector mode (HE11x) to the cylindrical vector beams (CVBs) and optical vortex beams (OVBs) of a few-mode fiber excited by two acoustic flexural waves with orthogonal perturbations is achieved by using a composite acoustic transducer.
Abstract: Mode coupling from the fundamental vector mode (HE11x) to the cylindrical vector beams (CVBs) and optical vortex beams (OVBs) of a few-mode fiber excited by two acoustic flexural waves with orthogonal perturbations is achieved by using a composite acoustic transducer. The HE11x mode is converted to TM01 and TE01 modes, which have radial and azimuthal polarizations, by using the lowest-order acoustic flexural modes of F11x and F11y, respectively. Furthermore, HE11x mode can also be converted to the ± 1-order OVBs of HE21even±iHE21odd through the combined acoustic modes of F11x±iF11y. This technique provides a useful way of generating CVBs and OVBs in optical fiber with conveniently electrically-controlled mode conversion characteristics.

52 citations


Journal ArticleDOI
TL;DR: In this article, a novel waveguide design of a polarization-maintaining few mode fiber (PM-FMF) supporting ≥10 non-degenerate modes, utilizing a central circular air hole and a circumjacent elliptical-ring core, was proposed.
Abstract: We propose a novel waveguide design of a polarization-maintaining few mode fiber (PM-FMF) supporting ≥10 non-degenerate modes, utilizing a central circular air hole and a circumjacent elliptical-ring core. The structure endows a new degree of freedom to adjust the birefringence of all the guided modes, including the fundamental polarization mode. Numerical simulations demonstrate that, by optimizing the air hole and elliptical-ring core, a PM-FMF supporting 10 distinctive polarization modes has been achieved, and the effective index difference Δneff between the adjacent guided modes could be kept larger than 1.32×10−4 over the whole C+L band. The proposed fiber structure can be flexibly tailored to support an even larger number of modes in PM-FMF (14-mode PM-FMF has been demonstrated as an example), which can be readily applicable to a scalable mode division multiplexing system.

42 citations


Journal ArticleDOI
TL;DR: A unique concept to implement a higher-order mode pass filter using mode-converters with a simulated extinction ratio greater than 20 dB with an excess loss less than 0.6 dB in the C-Band is proposed.
Abstract: We report a unique concept to implement a high-order mode pass filter using mode converters. Our proposed design method implements a high-order mode pass filter of any order, uses different mode converters available, and applies to a variety of planar lightwave circuit material platforms. We fabricate a broadband fundamental mode filter device using a Mach–Zehnder interferometer and Y-junctions to demonstrate our idea. The performance of the fabricated device is demonstrated experimentally in the wavelength range of 1.530–1.565 μm (C-band). This filter exhibits a simulated extinction ratio of 37 dB with an excess loss of 0.52 dB for the first-order mode transmission.

36 citations


Journal ArticleDOI
TL;DR: In this paper, a robust scheme to achieve optical pulling force using the guiding modes supported in a hollow core double-mode photonic crystal waveguide instead of the structured optical beams in free space investigated earlier is proposed.
Abstract: We propose a robust scheme to achieve optical pulling force using the guiding modes supported in a hollow core double-mode photonic crystal waveguide instead of the structured optical beams in free space investigated earlier. The waveguide under consideration supports both the 0th order mode with a larger forward momentum and the 1st order mode with a smaller forward momentum. When the 1st order mode is launched, the scattering by the object inside the waveguide results in the conversion from the 1st order mode to the 0th order mode, thus creating the optical pulling force according to the conservation of linear momentum. We present the quantitative agreement between the results derived from the mode conversion analysis and those from rigorous simulation using the finite-difference in the time-domain numerical method. Importantly, the optical pulling scheme presented here is robust and broadband with naturally occurred lateral equilibriums and has a long manipulation range. Flexibilities of the current co...

36 citations


Journal ArticleDOI
TL;DR: Spinning the preform during drawing introduces a continuous helical twist, offering a novel means of controlling the modal properties of hollow-core SR-PCF, and Prism-assisted side-coupling is used to measure the losses, refractive indices, and near-field patterns of individual fiber modes in both the straight and twisted cases.
Abstract: A hollow-core single-ring photonic crystal fiber (SR-PCF) consists of a ring of capillaries arranged around a central hollow core Spinning the preform during drawing introduces a continuous helical twist, offering a novel means of controlling the modal properties of hollow-core SR-PCF For example, twisting geometrically increases the effective axial propagation constant of the LP01-like modes of the capillaries, providing a means of optimizing the suppression of HOMs, which occurs when the LP11-like core mode phase-matches to the LP01-like modes of the surrounding capillaries (In a straight fiber, optimum suppression occurs for a capillary-to-core diameter ratio d/D=0682) Twisting also introduces circular birefringence (to be studied in a future Letter) and has a remarkable effect on the transverse intensity profiles of the higher-order core modes, forcing the two-lobed LP11-like mode in the untwisted fiber to become three-fold symmetric in the twisted case These phenomena are explored by means of extensive numerical modeling, an analytical model, and a series of experiments Prism-assisted side-coupling is used to measure the losses, refractive indices, and near-field patterns of individual fiber modes in both the straight and twisted cases

24 citations


Journal ArticleDOI
TL;DR: It is found through experiment and numerical analysis, that an SRS comb in a different mode family with a high quality factor (Q) is excited when the authors pump in a low-Q mode and no transverse mode interaction occurs when they excite in a high- Q mode resulting the generation of a single comb family.
Abstract: Comb generation in different mode families via a stimulated Raman scattering (SRS) process is studied using a silica toroid microcavity. The broad gain bandwidth of SRS in silica allows us to excite longitudinal modes at long wavelengths belonging to mode families that are either the same as or different from the pump mode. We found through experiment and numerical analysis, that an SRS comb in a different mode family with a high quality factor (Q) is excited when we pump in a low-Q mode. No transverse mode interaction occurs when we excite in a high-Q mode resulting the generation of a single comb family. We studied the condition of the transverse mode interaction while varying the mode overlap and Q of the Raman mode. Our experimental results are in good agreement with the analysis and this enables us to control the generation of one- and two-mode combs.

24 citations


Journal ArticleDOI
TL;DR: The dynamics of the output beam from a kilowatt-level all-fiber amplifier based on the low-numerical-aperture (<0.04) step-index (SI) fiber before and after the onset of the MI, including the temporal dynamics and mode evolution is investigated for the first time.
Abstract: The study on mode instability (MI) in the large-mode-area fiber is generating great interest regarding the high-power applications of fiber lasers. To the best of our knowledge, we have investigated for the first time the dynamics of the output beam from a kilowatt-level all-fiber amplifier based on the low-numerical-aperture (<0.04) step-index (SI) fiber before and after the onset of the MI, including the temporal dynamics and mode evolution. The temporal power fluctuations indicate three evolution stages apart from the onset threshold of the MI, defined as stable, transition, and chaotic regions. In addition, the mode decomposition technique is utilized to accurately observe and investigate the mode evolution and relevant modal content corresponding to the transition and chaotic regions in the SI fiber laser for the first time. According to the mode decomposition results, the reduction of the extracted power can be explained by the high bending loss of the high-order mode excited in the MI process. Finally, the difference of MI dynamics between the fiber lasers based on the SI fiber and rod-type photonic crystal fiber is discussed.

23 citations


Journal ArticleDOI
TL;DR: In this article, a finite element method is used to analyze the performance of a microstructured optical fiber-based surface plasmon resonance sensors aimed for biomedical applications, such as the detection of blood carried species.
Abstract: A finite element method is used to analyze the performance of a microstructured optical fiber-based surface plasmon resonance sensors aimed for biomedical applications, such as the detection of blood carried species. Birefringence obtained by removing of a row of holes in a two-ring hexagonal lattice of holes in a gold covered silica fiber leads to a relatively high sensitivity of the fiber optical response to a refractive index of the analyte surrounding the fiber. This fiber structure supports two types (I and II) of resonant modes. In these modes, there is an opposite variation of some sensing parameters with the increase of the refractive index of the analyte between 1.36 and 1.39. Thus, for a smaller value (1.36) of the refractive index of the analyte n a, the resonance spectral width δλ 0.5 is large for the core mode I and small for the core mode II but for a larger value (1.39) of n a, δλ 0.5 is small for the core mode I and large for the core mode II. Also, for n a = 1.36, the amplitude sensitivity S A is small for the core mode I and large for the core mode II but for n a = 1.39, S A is large for the core mode I and small for the core mode II. By adjusting the radius of the gold layer, the proposed sensor shows high spectral sensitivity S λ and narrow δλ 0.5 at the same resonance wavelength and n a (1.39) where the figure of merit (FOM) is very large in comparison with the most recently published values.

21 citations


Journal ArticleDOI
TL;DR: This work has demonstrated a versatile mode matching method for Fabry-Pérot Cavities that employs an assembly of a graded-index and large core multimode fiber directly spliced to a single mode fiber, making this approach highly versatile and integrable.
Abstract: In fiber based Fabry-Perot Cavities (FFPCs), limited spatial mode matching between the cavity mode and input/output modes has been the main hindrance for many applications. We have demonstrated a versatile mode matching method for FFPCs. Our novel design employs an assembly of a graded-index and large core multimode fiber directly spliced to a single mode fiber. This all-fiber assembly transforms the propagating mode of the single mode fiber to match with the mode of a FFPC. As a result, we have measured a mode matching of 90% for a cavity length of ~400 μm. This is a significant improvement compared to conventional FFPCs coupled with just a single mode fiber, especially at long cavity lengths. Adjusting the parameters of the assembly, the fundamental cavity mode can be matched with the mode of almost any single mode fiber, making this approach highly versatile and integrable.

Journal ArticleDOI
TL;DR: In this paper, a heterogeneous 12-core 4-LP-mode fiber having two different types of cores and trench-assisted graded-index profiles was designed. And the numerical analyses based on the coupled-mode equation show that the inter-core crosstalk levels of the proposed fiber are lower than $-$ 55 dB/km, regardless of modes, as long as the fiber is not bent tightly with a bending radius of $\times$ 10 $-$ 3 $\mu {\rm m}$ $-$ 2 and 42.2, respectively.
Abstract: We design a heterogeneous 12-core 4-LP-mode fiber having two different types of cores and trench-assisted graded-index profiles. For the optimum design of the index profiles of these two heterogeneous cores, we first investigate the impacts of various geometric parameters on the effective refractive index of each LP mode, maximum differential modal delay (DMD), and bending losses of the guiding and higher order modes. We then design a heterogeneous 12-core 4-LP mode fiber having a cladding diameter of 242 $\mu {\rm m}$ . The numerical analyses based on the coupled-mode equation show that the inter-core crosstalk levels of the proposed fiber are lower than $-$ 55 dB/km, regardless of modes, as long as the fiber is not bent tightly with a bending radius of $\times$ 10 $-$ 3 $\mu {\rm m}$ $-$ 2 and 42.2, respectively.

Journal ArticleDOI
Xiaobei Zhang1, Haiyang Shao1, Yong Yang1, Haiyang Pan1, Fufei Pang1, Tingyun Wang1 
TL;DR: In this paper, a simple structure for the refractive index sensing by splicing a segment of capillary with two segments of single-mode fibers (SMFs) is demonstrated, where two mode coupling regions can be formed with tapered air-cavities on both sides of the capillary.
Abstract: We demonstrate a simple structure for the refractive index sensing by splicing a segment of capillary with two segments of single-mode fibers (SMFs). By selecting appropriate splicing parameters, two mode coupling regions can be formed with tapered air-cavities on both sides of the capillary. This simple structure allows us the light propagation in the capillary with a ring mode distribution, while the high-order mode distributed in the capillary will be affected by the surrounding environment. With the inner diameter of the capillary increases, there is an enhancement of interaction between ring modes and the surrounding environment. Therefore, we can realize a tailored sensitivity based on the inner capillary diameter. Maximum refractive index sensitivities of 789, 1196, and 1684 nm/RIU can be obtained in the refractive index range from 1.3360 to 1.4365 when the inner diameter is 5, 15, and 25 μm, respectively. The distinguishing feature of such a capillary-based fiber sensor is that it can be used for the refractometry with a tailored high sensitivity through choosing the inner capillary diameter.

Journal ArticleDOI
TL;DR: Detailed in situ distributed temperature measurements inside a high power fiber amplifier show that photodarkening has a negligible impact on the thermal load and, therefore, on the TMI threshold in this fiber.
Abstract: We report on detailed in situ distributed temperature measurements inside a high power fiber amplifier. The deducted thermal load and the transversal mode instability (TMI) threshold of a commercial large mode area fiber with 25 μm core and 400 μm cladding were measured at various seed wavelengths. By matching these results with detailed simulations we show that photodarkening has a negligible impact on the thermal load and, therefore, on the TMI threshold in this fiber.

Journal ArticleDOI
TL;DR: In this article, a fiber laser for on-demand modes in the 1550-nm band was provided to prescribe the pure and high-quality emission of a higher-order transverse laser mode, based on a simple construction with one spatial light modulator (SLM) and a single-mode erbium-doped fiber (SM-EDF).
Abstract: Transverse mode characteristics of a laser are related to a variety of interesting applications An on-demand mode solid laser in the 1064 nm band was proposed previously In this paper, we provide a fiber laser for on-demand modes in the 1550 nm band to prescribe the pure and high-quality emission of a higher-order transverse laser mode, based on a simple construction with one spatial light modulator (SLM) and a single-mode erbium-doped fiber (SM-EDF) The SLM is designated to generate the desired higher-order mode and separate the higher-order mode and the fundamental mode The fundamental mode oscillates in the fiber ring laser, and therefore the SM-EDF can be pumped with a single-mode 980 nm laser, no matter what higher-order mode is prescribed In this proof-of-principle experiment, high-quality higher-order modes are observed from LP01 to LP105 Stable emission and real-time switching between modes can be easily realized by altering the phase on the SLM In addition, the propagation of the LP01, LP11, LP21, and LP02 modes from the fiber laser is also demonstrated in a four-mode few-mode fiber

Journal ArticleDOI
TL;DR: In this article, the authors proposed a method to generate stable orbital angular momentum (OAM) mode by superposing multiple LP11 modes with micro-phase difference distributed along fiber propagation.
Abstract: We propose a new method to generate orbital angular momentum (OAM) mode by superposing multiple LP11 modes with microphase difference distributed along fiber propagation. This way, OAM mode can be generated by superposing a series of LP11 mode with phase difference much less than π /2, which is necessary for schemes using two degenerated LP11 mode superposition but is difficult to generate and hard to keep stable. We demonstrate this principle experimentally by utilizing few-mode fiber long period grating (FMF-LPG), in which a series of LP11 modes with microphase difference distribution can be generated by twisting FMF-LPG. This scheme provides a potential all-fiber, compact, and low-attenuation scheme to generate stable OAM modes.

Patent
06 Feb 2017
TL;DR: In this paper, the authors present a mode mixing optical fiber that includes a core having a refractive index profile; and a cladding disposed about the core, which supports at least two (eg, at least five) guided modes at the wavelength.
Abstract: The present disclosure relates more to mode mixing optical fibers useful, for example in providing optical fiber laser outputs having a desired beam product parameter and beam profile In one aspect, the disclosure provides a mode mixing optical fiber that includes a core having a refractive index profile; and a cladding disposed about the core The core of the mode mixing optical fiber supports at least two (eg, at least five) guided modes at the wavelength The mode mixing optical fiber is configured to substantially distribute optical radiation having the wavelength propagating therein (eg, input at its input end or generated or amplified within the core) among a plurality of the guided modes (eg, to distribute a substantial fraction of the optical radiation having the wavelength propagating therein from its lower-order guided modes to its higher-order guided modes)

Journal ArticleDOI
Heng-He Tang1, Bin Huang1, Tie-Jun Huang1, Yunhua Tan1, Pu-Kun Liu1 
TL;DR: In this paper, an ultracompact design method based on the inner-embedded subwavelength metallic gratings is provided, which relies on modulating the phase velocities of spoof surface plasmon polaritons (SSPPs) supported on the gratings to generate π phase difference.
Abstract: In this paper, waveguide mode conversions in a parallel plate waveguide, rectangular waveguide, and circular waveguide are all demonstrated at terahertz frequencies. Different from the traditional ways to realize mode conversions, an ultracompact design method based on the inner-embedded subwavelength metallic gratings is provided. The principle of the method relies on modulating the phase velocities of spoof surface plasmon polaritons (SSPPs) supported on the gratings to generate π phase difference. Owing to the gradient matching the phase velocities of the waveguide modes and SSPPs, the efficiencies of the mode conversions are considerable. The output mode purities of the both demonstrations are very good. Besides, waveguide bend is also achieved by this method. The work in this paper hopes to establish a universal technique for compact waveguide mode control, especially in the terahertz frequency range.

Patent
Chubing Peng1
07 Sep 2017
TL;DR: In this article, a read/write head with a bend waveguide coupled to a mode converter at an interface is described, and a near-field transducer is offset from the facet of the input coupler in a cross-track direction.
Abstract: A read/write head has an input coupler that receives light at a fundamental mode from an energy source. A mode converter of the read/write head converts light from the fundamental mode to a higher-order mode. The read/write head has a bent waveguide coupled to the mode converter at an interface. The bent waveguide includes a curve with a taper. The taper nullifies the fundamental mode generated in the curve and recovers the higher-order mode at an output of the bent waveguide. A near-field transducer that receives the output of the bent waveguide is offset from the facet of the input coupler in a cross-track direction.

Journal ArticleDOI
TL;DR: A junction structure in which light in the waveguide is first coupled to a high-group-velocity radiation mode at an expanded core and subsequently converted to the slow-light mode in a tapered core of the PCW supports the practical use of PCWs.
Abstract: Silica-clad silicon photonic crystal waveguides (PCWs) are promising components for various applications because of their simple fabrication and generation of slow light. However, an optical loss higher than 4 dB occurs when they are simply coupled to input/output silicon wire waveguides. To reduce the optical loss, we proposed a junction structure in which light in the waveguide is first coupled to a high-group-velocity radiation mode at an expanded core and subsequently converted to the slow-light mode in a tapered core of the PCW. The coupling loss at a junction is calculated to be 0.28 dB at its minimum and less than 0.5 dB for the wavelength range of 12 nm. We measured a coupling loss of 0.46 dB for the device fabricated by the silicon photonics process. This low-loss junction well supports the practical use of PCWs.

Journal ArticleDOI
01 Jan 2017
TL;DR: In this paper, the influence of the linear mode coupling caused by the fiber bending on the nonlinear distortions in a mode-division multiplexed system was analyzed analytically.
Abstract: This paper is focused on the influence of the linear mode coupling caused by the fiber bending on the nonlinear distortions in a mode-division multiplexed system. The system under test utilizes the fundamental Gaussian mode and the conjugated first-order vortex modes propagating in the step-index fiber at the same wavelength. For such kind of system, the nonlinear impairments are caused mainly by the cross-phase and self-phase modulations. Propagation of the modal composition is described by the system of generalized coupled nonlinear Schrodinger equations, which serves as a basis of our simulations. Considering the nonlinear operator analytically, we show that it reaches its maximum value due to the power transfer between mode channels caused by the linear mode coupling. Simulation results for equal initial powers in NRZ-coded mode channels demonstrate that nonlinear signal impairments increase significantly for all mode channels in the case of strong linear mode coupling. In the case of weak linear coupling, the increase of nonlinear impairments was also observed, but this effect was appreciably weaker. Moreover, simulations show that the effect described above is stronger for the first-order modes than for the fundamental mode.

Patent
Akira Oka1
02 Mar 2017
TL;DR: In this article, the effective refractive index of a TM0 polarized wave guided through a first core (11a) when existing alone and the execution this article of a TE 0 polarized wave (11b) when operating in a second core (12b) are continuous as a function of distance from a starting point of a parallel traveling section (I).
Abstract: According to the present invention, the effective refractive index of a TM0 polarized wave guided through a first core (11a) when existing alone and the execution refractive index of a TE0 polarized wave guided through a second core (11b) when existing alone are continuous as a function of distance from a starting point of a parallel traveling section (I), a magnitude relation between the effective refractive index of the odd mode of the TE0 polarized wave guided through the parallel traveling section (I) and the effective refractive index of the even mode of the TM0 polarized wave guided through the parallel traveling section (I) is reversed at the starting point and the ending point of the parallel traveling section (I), and the refractive index distribution in an interactive section (i) is vertically asymmetric.

Proceedings ArticleDOI
01 Jun 2017
TL;DR: In this article, the authors investigated mode conversion along a longitudinally uniform mode-selective transmission line (MSTL) and demonstrated physical evidence of the mode conversion through examining the field distributions of the MSTL.
Abstract: This work investigates mode conversion along a longitudinally uniform mode-selective transmission line (MSTL) and demonstrates physical evidence of the mode conversion. Mode conversion of the fundamental mode is observed through examining the field distributions of the MSTL. Characteristic mode conversion frequency is defined based on the distribution properties of the longitudinal magnetic field component and the intrinsic physical implications. The accuracy and effectiveness of this definition are verified numerically and experimentally. The result indicates that a quasi-TEM fundamental mode and a quasi-TE10 fundamental mode dominate in the MSTL below and above this frequency, respectively. This mode conversion could have specific applications in the design of microwave, millimeter-wave, and THz wideband and multi-band components and systems.

Journal ArticleDOI
TL;DR: In this article, the radiation modes for external radiating cylinders which account for both axial and circumferential dependence are presented using cylindrical basis functions which are a more natural match to the geometry than past developments, which have been based on spherical harmonics.

Journal ArticleDOI
TL;DR: In this article, a theory describing excitation of transmitted and reflected modes in each domain is developed and direct numerical simulation of described structures using Comsol multiphysics code and show that the results obtained by these approaches for millimeter-sized dielectric waveguide coincide with less than percent accuracy.
Abstract: We analyze radiation produced by a single TM mode incident on the open end of a cylindrical waveguide with uniform dielectric filling. This open-ended waveguide is placed inside concentric vacuum waveguide with a larger radius. Rigorous theory describing excitation of transmitted and reflected modes in each domain is developed. We also perform direct numerical simulation of described structures using Comsol Multiphysics code and show that the results obtained by these approaches for millimeter-sized dielectric waveguide coincide with less-than-percent accuracy. The analytical approach is more efficient for calculation of mode structure at high frequencies (up to Terahertz) and high permittivity. We also consider the situation where generated radiation is extracted into free space through the open end of the outer waveguide. We calculate radiation patterns in the far-field zone using both our algorithm and direct simulations and show that these results are in very good agreement too.

Journal ArticleDOI
TL;DR: In this paper, a transverse mode converter based on a binary micro relief implemented directly on the endface of a few-mode fiber was numerically investigated and the results of numerical simulation demonstrated the converter to form LP-11 and LP-21 modes with high efficiency, providing a more than 92 % mode purity.
Abstract: A transverse mode converter based on a binary micro relief implemented directly on the endface of a few-mode fiber was numerically investigat ed. The results of numerical simulation demonstrated the converter to form LP-11 and LP-21 modes with high efficiency, providing a more-than 92 % mode purity. Transformations of modes excited by a fiber microbending were also numerically investigated. The excited beams were sh own to save their mode purity even in a strong bending as the arising parasitical modes wer e mostly unguided by the fiber. The resulting beam power and mode content were also demonstrated o depend on the beam and bending mutual orientation for beams with strong rotational symmet ry.

Journal ArticleDOI
16 May 2017-Sensors
TL;DR: A PVDF-based radiation mode (C-mode) approach concept is introduced to determine the sound power radiation from the output signals of PVDF films of the vibrating structure and is a hybrid of vibration measurement and numerical calculation of C-modes.
Abstract: The theory for calculation and/or measurement of sound power based on the classical velocity-based radiation mode (V-mode) approach is well established for planar structures However, the current V-mode theory is limited in scope in that it can only be applied to conventional motion sensors (ie, accelerometers) In this study, in order to estimate the sound power of vibrating beam and plate structure by using polyvinylidene fluoride (PVDF) films as sensors, a PVDF-based radiation mode (C-mode) approach concept is introduced to determine the sound power radiation from the output signals of PVDF films of the vibrating structure The proposed method is a hybrid of vibration measurement and numerical calculation of C-modes The proposed C-mode approach has the following advantages: (1) compared to conventional motion sensors, the PVDF films are lightweight, flexible, and low-cost; (2) there is no need for special measuring environments, since the proposed method does not require the measurement of sound fields; (3) In low frequency range (typically with dimensionless frequency kl < 4), the radiation efficiencies of the C-modes fall off very rapidly with increasing mode order, furthermore, the shapes of the C-modes remain almost unchanged, which means that the computation load can be significantly reduced due to the fact only the first few dominant C-modes are involved in the low frequency range Numerical simulations and experimental investigations were carried out to verify the accuracy and efficiency of the proposed method

Journal ArticleDOI
TL;DR: In this paper, a hybrid plasmonic waveguide is proposed, and its propagation properties are investigated using the finite-element method, where a V-shaped silver nanowire is embedded in a low-index dielectric cladding above a semiconductor substrate, which can confine light in the subwavelength region with a long propagation length.
Abstract: A new kind of hybrid plasmonic waveguide is proposed, and its propagation properties are investigated using the finite-element method. This waveguide consists of a V-shaped silver nanowire embedded in a low-index dielectric cladding above a semiconductor substrate, which can confine light in the subwavelength region with a long propagation length. The field distribution, the mode effective index, the propagation length, and the normalized mode area of the hybrid mode supported by the waveguide are investigated at the wavelength of 1550 nm, which are dependent on the geometric parameters.

Journal ArticleDOI
Yu Liu1, Yuean Mi1, Bofeng Zhu1, Haisu Li1, Wei Jian1, Guobin Ren1, Shuisheng Jian1 
TL;DR: In this paper, the authors present a theoretical study on the mode coupling between core modes and cladding modes of the tilted long period fiber grating (TLPFG) in dual-mode fiber.

Proceedings ArticleDOI
01 Mar 2017
TL;DR: In this article, a novel TM01 to TE11 mode converter with aligned ports, wide bandwidth and high conversion efficiency is proposed with a circular waveguide partitioned into two semicircular sections with different path length.
Abstract: A novel TM01 to TE11 mode converter with aligned ports, wide bandwidth and high conversion efficiency is proposed Mode conversion is performed with a circular waveguide partitioned into two semicircular sections with different path length Lower semicircular section has a cosine profile to provide a path difference of Ag/2 for the mode conversion Mode converter was designed and simulated at 3GHz operating frequency Electric field calculation shows that the mode converter can handle upto 3 GW high power microwave signal The mode converter was fabricated and the mode conversion was verified experimentally, by measuring farfield radiation pattern of the output mode The proposed mode converter has a symmetric structure and has the advantage of aligned ports and wide bandwidth