An all fiber apparatus for microparticles selective manipulation based on a variable ratio coupler and a microfiber

• An all fiber apparatus to manipulate micro-particles is proposed based on a variable ratio coupler.
• The direction of transportation is controllable.
• Manipulation of single particle, two particles and three particles is acquired.
• Manipulation of three particles one by one is acquired.

We propose an all fiber apparatus based on a variable ratio coupler which can transport microparticles controllably and trap particles one by one along a microfiber. By connecting two output ports of a variable ratio coupler with two end pigtails of a microfiber and launching a 980 nm laser into the variable ratio coupler, particles in suspension were trapped to the waist of microfiber due to a gradient force and then transported along the microfiber due to a total scattering force generated by two counter-propagating beams. The direction of transportation was controlled by altering the coupling ratio of the variable ratio coupler. When the intensities of two output ports were equivalent, trapped particles stayed at fixed positions. With time going, another particle around the micro fiber was trapped onto the microfiber. There were three particles trapped in total in our experiment. This technique combines with the function of conventional tweezers and optical conveyor.