Capillary Optical Fiber For Particle Manipulation And Sensing Application

Hollow core fiber(HCF)is a powerful carrier in the fields of nonlinear optics,optical fiber sensing and lasers,which is includes hollow photonic bandgap fiber(PBF),photonic crystal fiber(PCF),silica capillary optical fiber(COF)and multi-hole fiber(MHF).Among them,the silica COF,which is similar in diameter to the single-mode fiber(SMF)and consists of tubular cladding and air capillary,has a special hollow core structure.After being fused with other special optical fibers,a series of cascaded sensing devices with simple structure,high sensitivity and fast response speed can be prepared.In recent years,with the progress of optical fiber processing technology,researchers can freely design complex optical fiber shapes with higher precision and optical quality.In this paper,a variety of optical fiber devices are designed and fabricated based on the silica COF,which are applied in the fields of optical fiber tweezers and sensing.The specific research contents are as follows:1.A tapered COF structure is designed,in which the tapered transition region can excite the fundamental mode transmitted in the SMF into the higher-order mode transmitted in the tubular cladding,and the tapered structure can refocus the light near the fiber tip.With 980 nm laser,the yeast cells with a diameter of 4-8mm are rotated and shunted.The rotation speed of the short axis of particles can reach 8.94 rad/s,and the average speed of shunting and transporting the particles is about 10mm/s.The mechanical characteristics of the particles in the process of manipulation are analyzed by finite element method,and the moments at different angles in the process of particle rotation are calculated,and the total optical trapping force in the process of particle shunting is obtained.In addition,the manufacturing method of tapered COF is simple,and the unique tapered structure has a good effect on beam convergence,which has a broad application prospect.2.The preparation scheme of helical COF is put forward,and the mechanism in the helical structure is analyzed.By optimizing the torsional structural parameters,the sensing performance of long-period fiber grating is improved.High-sensitivity parameter measurement of strain and temperature is realized,and the structure is insensitive to refractive index parameters.When the inner diameter ID is 10mm,the twisting number N is 5 and the twisting pitch(?)is 1200mm,the sensitivity of strain and temperature can reach-9.29 pm/meand 17.14 pm/℃,respectively.Benefiting from eliminating the cross influence of temperature and strain parameters,the sensor has potential application value in complex environment.To sum up,COF is used as the carrier platform of a new type of fiber-integrated photonic device,which realizes the optical manipulation of cell capture,rotation and shunt,and also realizes the optical sensing function of strain,temperature and other parameters in this paper.Combined with fiber micromachining technology,photonic integrated devices based on capillary optical fiber have a very potential application prospect in the fields of multifunctional particle optical manipulation,microfluidic,optical sensing,optical imaging and other related cross fields.