Higher-order micro-fiber modes for Escherichia coli manipulation using a tapered seven-core fiber

Particle trapping with optical nanofibers: a review [Invited]

Optical trapping has proven to be an efficient method to control particles, including biological cells, single biological macromolecules, colloidal microparticles, and nanoparticles. Multiple types of particles have been successfully trapped, leading to various applications of optical tweezers ranging from biomedical through physics to material sciences. However, precise manipulation of particles with complex composition or of sizes down to nanometer-scales can be difficult with conventional optical tweezers, and an alternative manipulation tool is desirable. Optical nanofibers, that is, fibers with a waist diameter smaller than the propagating wavelength of light, are ideal candidates for optical manipulation due to their large evanescent field that extends beyond the fiber surface. They have the added advantages of being easily connected to a fibered experimental setup, being simple to fabricate, and providing strong electric field confinement and intense magnitude of evanescent fields at the nanofiber's surface. Many different particles have been trapped, rotated, transported, and assembled with such a system. This article reviews particle trapping using optical nanofibers and highlights some challenges and future potentials of this developing topic.

Splicing point tapered fiber Mach-Zehnder interferometer for simultaneous measurement of temperature and salinity in seawater

Combined with non-adiabatic tapering and mode field mismatch between two different fibers, a splicing point tapered fiber Mach-Zehnder interferometer is proposed. Theoretically, two sensing units are carefully designed for dual-parameter sensing, and mode exciting and evolution in fibers are analyzed and shown dynamically. In experiment, transmission spectrum is obtained with two sets of clear interference as designed. After a simple capsulation, simultaneous measurement of seawater temperature and salinity are realized with sensitivities of -994.83pm/°C and 290.47pm/‰, respectively. Additionally, short response time of 33ms and good repeatability are also demonstrated. And effects of encapsulation on avoiding strain and press are verified experimentally. The MZI demonstrated here shows advantages of low cost, easy fabrication, simple construction, compact and robust structure, and dual-parameter sensing with high sensitivity and fast response.

High throughput trapping and arrangement of biological cells using self-assembled optical tweezer

Lately, a fiber-based optical tweezer that traps and arranges the micro/nano-particles is crucial in practical applications, because such a device can trap the biological samples and drive them to the designated position in a microfluidic system or vessel without harming them. Here, we report a new type of fiber optical tweezer, which can trap and arrange erythrocytes. It is prepared by coating graphene on the cross section of a microfiber. Our results demonstrate that thermal-gradient-induced natural convection flow and thermophoresis can trap the erythrocytes under low incident power, and the optical scattering force can arrange them precisely under higher incident power. The proposed optical tweezer has high flexibility, easy fabrication, and high integration with lab-on-a-chip, and shows considerable potential for application in various fields, such as biophysics, biochemistry, and life sciences.