Annular Core Fiber Research Articles

All-Fiber Hollow Bessel-Like Beam for Large-Size Particle Trap

A 32 μm large-size microparticle is trapped by an all-fiber hollow Bessel-like beam. In order to realize the proposed high-order Bessel-like beam, we fabricate the optical fiber probe by splicing an annular core fiber with a step-index multimode fiber. We grind the fiber tip into a truncated cone shape to converge the hollow Bessel-like beam to obtain a large focal area. Simulation and experimental results show that the trapping field introduced by the Bessel-like beam provides a relatively strong optical force and has the capability of 3-D capture of a large particle (whose diameter is 32 μm). These highly integrated fiber tweezers provide hollow Bessel-like beams with strong optical force and large trapping area, which can be promisingly applied in biomedical and integrated optical research.

Optical trapping and manipulation of Hexogen particles

The microscopic explosion of energetic materials has been a hotspot in the research of energetic materials properties. Observing and analyzing the micro-feature of micro/nano-particles in energetic materials has become inevitable. The use of optical methods to manipulate and research various microscopic particles is a great mature technology Optical tweezers can trap, shift micro/nano-particles such as biological cells, standard particles, and absorptive particles. Therefore, using optical tweezers to study the micro-feature of energetic materials is a feasible method. In this paper, we propose and demonstrate the three-dimensional optical trapping and manipulation of irregular hexogen (RDX) particles in a liquid environment using the annular core fiber tweezers. A converging light field with a large-angle focus is obtained by assembling a high-refractive-index glass microsphere on the facet of annular core fiber. The proposed optical fiber tweezers have the advantages of large trapping stiffness, low cost, simple manufacturing. The optical trapping of RDX is beneficial to the research of RDX and has potential in the research of RDX micro-explosion.

Transmission enhanced SPR nano-microscope.

We propose a transmission enhanced surface plasmon resonance nano-microscope. The nano-microscope is prepared at the cone-frustum-shaped annular-core fiber (ACF) end by mechanical polishing at the end of the ACF, and the gold film deposition on this end surface through magnetron sputtering technology obtains an excited surface plasmon resonance (SPR) that can direct to the center along the radial direction of the fiber. The cone-frustum-shaped ACF end surface is taken as a stage, and with the advantage of the SPR resonance enhancement effect, the ordinary microscope can realize nano-imaging. The imaging experiment results of 300nm polystyrene nano-spheres show that this auxiliary microscopic imaging technology can break through the diffraction limit and can eliminate the smear image caused by the surface plasmon wave (SPW) illumination in a single direction.

Laser-induced rotary micromotor with high energy conversion efficiency

Light is a precious resource that nature has given to human beings. Converting green, recyclable light energy into the mechanical energy of a micromotor is undoubtedly an exciting challenge. However, the performance of current light-induced micromotor devices is unsatisfactory, as the light-to-work conversion efficiency is only 10 − 15 – 10 − 12 . In this paper, we propose and demonstrate a laser-induced rotary micromotor operated by Δ α -type photopheresis in pure liquid glycerol, whose energy conversion ratio reaches as high as 10 − 9 , which is 3–6 orders of magnitude higher than that of previous light-induced micromotor devices. In addition, we operate the micromotor neither with a light field carrying angular momentum nor with a rotor with a special rotating symmetrical shape. We just employ an annular-core fiber to configure a conical-shaped light field and select a piece of graphite sheet (with an irregular shape) as the micro-rotor. The Δ α -type photophoretic force introduced by the conical-shaped light field drives the rotation of the graphite sheet. We achieve a rotation rate up to 818.2 r/min, which can be controlled by tuning the incident laser power. This optical rotary micromotor is available for twisting macromolecules or generating vortex and shear force in a medium at the nanoscale.

Circular Airy Beam Shaping by Annular Arrayed-Core Fiber

We propose and theoretically demonstrate a beam shaping method using a novel all-fiber device composed of a single mode fiber, a tapered annular-core fiber, and an annular arrayed-core fiber. By using the proposed device, a circular Airy beam with outward acceleration can be generated using a Gaussian beam shaping and the autodefocusing Airy beam can be converted into an autofocusing Airy beam through a cone-frustum shaped fiber end. The properties of wave propagation in fiber and surrounding media are studied by using coupled-mode theory and angular spectrum method. The calculated results show that the output beam from the proposed device has a circular Airy-like pattern, which experiences autodefocusing (or autofocusing) during propagation, and forms a Bessel-like beam after the focal point. The tolerances of the beam generation device are discussed and we show that the focused output beam from the cone-frustum shaped fiber end can be used for multi-point trap to form an optical trap array.

Absorbing particle 3D trap based on annular core fiber tweezers

We proposed and demonstrated a new method to trap and manipulate a strongly absorbing particle by harnessing strong Δα-type photophoretic forces in pure liquid glycerol with a focused annular beam, which was introduced by an annular core fiber optical tweezers. We performed the focused annular light field by integrating a high refractive index silica microsphere on the annular core fiber end facet. The silica microsphere, which acted as a lens, focused laser beam for trapping. We tested and calculated Δα-type photophoretic forces tendency by using the fluorescence dye method, and the simulated results were in agreement with the experimental results. The proposed optical fiber tweezers were small in size, large in capture range, simple to manipulate, and inexpensive in cost. It provided a new approach for absorbing particles trapping. Tailoring the trapping and manipulation of absorbing particles in liquid environments will open avenues for studying the special, yet-unexplored characteristics of absorbing particles.

HACF-based optical tweezers available for living cells manipulating and sterile transporting

We propose and demonstrate a single fiber optical tweezers based on a hollow annular-core fiber (HACF), which is available for living cells manipulating and sterile transporting due to the hollow structure, there exists a fluidic channel in the fiber, which is naturally a microfluidic passageway in the fluidic environment, both the optical trapping forces (OTF) and the liquid viscous resistances (LVR) play the important roles. We perform the particles manipulating and transporting by adjusting and controlling the net forces of OTF and LVR. We employ the fiber grinding–polishing technology to fabricate the HACF probe, producing the OTFs. We employ the micropump to perform the positive or negative pressure in the hollow hole of the HACF, changing the liquid velocity and direction, adjusting the LVRs. It is ideally suited for rare cells manipulating and sterile transporting. The implantation of the hollow hole and annular waveguide in a HACF provides the availability for particles manipulating and transporting, constitutes a new development for single fiber optical trapping and makes possible of more practical applications in particles manipulating and transporting fields.

Single-mode annular chirally-coupled core fibers for fiber lasers

Chirally-coupled core (CCC) fiber can transmit single fundamental mode and effectively suppresses higher-order mode (HOM) propagation, thus improve the beam quality. However, the manufacture of CCC fiber is complicated due to its small side core. To decrease the manufacture difficulty in China, a novel fiber structure is presented, defined as annular chirally-coupled core (ACCC) fiber, replacing the small side core by a larger side annulus. In this paper, we designed the fiber parameters of this new structure, and demonstrated that the new structure has a similar property of single mode with traditional CCC fiber. Helical coordinate system was introduced into the finite element method (FEM) to analyze the mode field in the fiber, and the beam propagation method (BPM) was employed to analyze the influence of the fiber parameters on the mode loss. Based on the result above, the fiber structure was optimized for efficient single-mode transmission, in which the core diameter is 35 μm with beam quality M2 value of 1.04 and an optical to optical conversion efficiency of 84%. In this fiber, fundamental mode propagates in an acceptable loss, while the HOMs decay rapidly.

Single fiber optical trapping of a liquid droplet and its application in microresonator

We propose and demonstrate an optical trapping of a liquid droplet and its application based on an annular core microstructured optical fiber. We grind and polish the annular core fiber tip to be a special frustum cone shape to make sure the optical force large enough to trap the liquid droplet non-intrusively. The axial and transverse optical trapping forces are simulated. In addition, we investigate the whispering gallery modes resonance characteristic of the trapped liquid droplet as the example of applications. The whispering gallery modes spectrum is sensitive to the size of the micro liquid droplet. Due to the simple construction and flexible manipulation, the fiber-based optical trapping technology for micro liquid droplets trapping, manipulating, and controlling has great application penitential in many fields, such as physics, biology, and interdisciplinary studies.

Perfect vortex beam: Fourier transformation of a Bessel beam.

We derive a mathematical description of a perfect vortex beam as the Fourier transformation of a Bessel beam. Building on this development, we experimentally generate Bessel-Gauss beams of different orders and Fourier transform them to form perfect vortex beams. By controlling the radial wave vector of a Bessel-Gauss beam, we can control the ring radius of the generated beam. Our theoretical predictions match with the experimental results and also provide an explanation for previous published works. We find the perfect vortex resembles that of an orbital angular momentum (OAM) mode supported in annular profiled waveguides. Our prefect vortex beam generation method can be used to excite OAM modes in an annular core fiber.

Highly Focused Conical Optical Field for Pico-Newton Scale Force Sensing

We propose to use a highly focused conical optical field generated by cone-frustum-shaped annular core fiber (ACF) tip for Pico-Newton scale force sensing. And we theoretically calculate the wave propagation in the ACF tip and its surrounding medium based on angular spectrum representation. The propagation properties and focusing effect of the highly focused conical optical field are also discussed and demonstrated experimentally. The ACF tip provides very strong focusing effect for the guided mode in the ACF. We show that there are stable three-dimensional trap-points for Rayleigh particles in the main lobe and every ring of the focused field with Bessel-like profile. And the transverse trapping forces are much greater (almost 30 times) than their corresponding longitudinal radiation forces so that a particle trapped by highly focused conical beam is only sensitive for disturbing force in longitudinal direction. Force sensitivities in longitudinal direction and the detection range are also discussed.

Hybrid structured fiber-optic Fabry-Perot interferometer for simultaneous measurement of strain and temperature.

We fabricate and experimentally demonstrate a hybrid structured Fabry-Perot interferometer (FPI) embedded in the middle of a fiber line for simultaneous measurement of axial strain and temperature. The FPI is composed of a silica-cavity cascaded to a spheroidal air-cavity, both of which are formed in a hollow annular core fiber (HACF). The fabrication process of the FPI includes only a fusion splice between a single-mode fiber and a HACF and several electrical arc discharges at the HACF near the splice point. Experimental results show that the strain and temperature sensitivities of the air-cavity can be 5.2 pm/με and 1.3 pm/C°, respectively, and those of the silica-cavity can be 1.1 pm/με and 13 pm/C°, respectively. The different sensitivities of silica-cavity and air-cavity to strain and temperature enable us to implement simultaneous sensing in strain and temperature.

Simultaneous Measurement of Temperature and Curvature Based on Hollow Annular Core Fiber

We propose a simultaneous temperature and curvature sensor based on a hollow annular core fiber (HACF) Mach-Zehnder interferometer (MZI). The MZI is fabricated by inserting a short section of HACF between two short pieces of multimode fibers, and interference occurs between the light beams transmitting along the air hole and annular core of the HACF. Curvature and temperature can be measured through fringe visibility variation and wavelength shift of the interference spectrum, respectively. The experimental results show that the temperature sensitivity is 30 pm/°C in the range of 30°C-100°C, and the maximum visibility variation is 32.4 dB from 0.555 to 5.405 m-1. In addition, the device is insensitive to external refractive index.

Free-space propagation of guided optical vortices excited in an annular core fiber

The analytical expression for the propagation of guided optical vortices through free space is derived and used to study the dynamic evolution of guided optical vortices after passing through the free space, and the dependence of guided optical vortices on the control parameters where the effect of propagation distance is stressed. It is shown that the motion, pair creation and annihilation of guided optical vortices may take place. In particular, the creation and annihilation of a pair of guided optical vortices do not take place by varying fiber length.

应用耦合模理论研究光在圆对称双包层光纤中的传输

For better understanding the light propagation in a double clad fiber(DCF),the perfect circular double clad fiber is numerically investigated by using the coupled mode method with translating the DCF into a single mode fiber(SMF)and an annular core fiber(ACF).The coupling coefficients between the LP01 mode of the SMF and the guided modes of the ACF are calculated.The results show that the LP0n modes of the ACF have greater coupling coefficients than the other guided modes,and for the LP0n modes the coupling coefficient of the high-order mode is larger than that of the low-order mode.The field distribution in the DCF core calculated by the coupled mode equations shows a quasi-periodic distribution along the DCF.The average period of the field distribution increases with the increasing of wavelength for different DCF parameters and the average normalized power of the field distribution is closely related to the chosen parameters of the DCF.

A Novel Approach to Fiber-Optic Tweezers: Numerical Analysis of the Trapping Efficiency

We present a novel all-fiber optical tweezer (OT) for biological applications. The tweezer is based on a new approach relying on total internal reflection in an annular core fiber or into a fiber bundle. The proposed device, whose trapping efficacy has been recently demonstrated experimentally, is extremely promising, also because optical manipulation and analysis functions can be easily added to the tweezer basic structure, leading to the realization of a powerful biotool. In this paper, a detailed numerical analysis of the structure properties and of its efficiency is carried out in the Mie regime. Moreover, by defining a new parameter to evaluate the trapping efficiency, we perform a comparison between the proposed tweezer structure and a standard OT based on a strongly focused Gaussian beam.

Comments on “On the analysis of a weakly guiding doubly clad dielectric optical fiber with an annular core”

AbstractA discussion of the dispersion relation of the modes guided by an annular core fiber is done in order to prove that the fundamental mode has a zero cutoff. It also gives the inequalities satisfied by the cutoff frequencies of the first lower modes. A relation is established between the propagation constants of two modes with the same radial order but different azimuthal orders. It allows us to precisely set the conditions for these constants to be almost similar. Numerical results are shown to confirm these assertions. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 249–254, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11029