Research On Mode Multiplexing Single Fiber Optical Tweezers With Its Application

Optical tweezers is a microscopic particles manipulation tools based on optical trapping effect,which was proposed in 1986 by Ashkin and his colleagues in the Bell Laboratories.Thanks to the non invasive manipulation(non-contact)produced by the optical tweezers when we manipulate micro/nano particles,it will not produce contacting damages on the living cells or micro particles itself.Besides that,the living cells have good transmission property in the infrared waveband,which makes the optical tweezers technology having a decent performance in the biology and medicine fields.Optical tweezers technology is not only in terms of micro particles operation and control,it also can monitor state of the trapped micro particle,even can be a sensor by using its own characteristics.With the continuous innovation and development of the optical tweezers technology,it will not be limited to the functional of operation,but with a broader field.This paper makes a ordinary single tapered fiber optical tweezers having multiple functions by using the mode division multiplexing technology and the wave division multiplexing technology.This technique aims at upgrading the original single fiber optical tweezers,which can easily achieve by adding some equipment in the original optical tweezers system.We realize multi functions of single fiber optical tweezers system by increasing not too much cost and gain more attention in the future of application and promotion.Besides that,the mode division multiplexing technology and the wave division multiplexing technology can also be widely applied in other fields.The trapping ability of the tapered single fiber optical tweezers has been studied.We analyze the trapping ability in detail by using the FDTD algorithm,including the effects of the refractive index and the size of the micro particles and the light source wavelength.We also obtained special micro particle torque model by combining of the calculation of the output light field,optical trapping force and the light-induced torque.By using the 1310 nm single mode fiber,we fabricate multimode fiber coupler.We research the LP11 mode,which is used in the mode division multiplexing technology,including how to excite the LP11 mode;how to choose and control the power ratio of the LP01 and LP11 mode in the fiber;and how to control the output light field of the LP11 mode.Here,for the first time,we propose and demonstrate the coupling of two different mode beams from different light sources into one same fiber.We realize the further various forms control of one or multi micro particles,including the deflection and rotation by using the two light fields with independent control of the light field.In this paper,we only employ the LP01 and LP11 mode,however in the future research,two or more relatively independent light fields can be used,which are realized by integrating any mode or splitting ratio higher order mode light fields.Therefore it is similar to integrate multi independent single fiber optical tweezers in a single fiber optical tweezers,which makes it can achieve more complex and delicate manipulation.A WDM system has been built and established,which couple multiple wavelengths into a same optical fiber probe for trapping.We calibrate optical trapping force of different wavelength,and find that 1480 nm light source can not trap the micro particle.The absorption rates of the aqueous solution with different wavelength are different,and in the vicinity of 1500 nm wavelength has a larger absorption peak.When use the 1480 nm wavelength single fiber optical tweezers,there generates an obvious temperature field in the vicinity of the optical fiber probe tip.We build a simulation model to calculate the temperature gradient field and velocity field on the base of the detailed analysis of the natural flow field.Different from the other wavelength,1480 nm optical tweezers has unique functions,such as launching,sweeping,aggregating functions.Two micro particle launching system has been built by using the mode division multiplexing technology and wavelength division multiplexing technology.We may measure some physical parameters by using this launching system.We obtain the launched micro particle moving information by using the F-P interference principle,and obtaining the viscosity coefficient of the liquid by using the micro particle moving information,and finally obtaining the temperature information by using the viscosity coefficient of liquid.