Theoretical And Technical Research On Fabricating Micro Fiber F-P (Fabry-Perot) Sensor With Femtosecond Laser Pulses

An intense femtosecond laser pulse can provide an electric field strength which exceeds the electric field force of valance electrons that holds the electrons to their ionic cores. Compared with picosecond, nanosecond laser pulse, in the process of femtosecond laser micromachining object,a femtosecond laser pulse shows excellent advantages such as little or no thermal affected zone, the break of optical diffraction limit and space-selection. Based on those virtues, femtosecond laser pulse which creat a new laser processing technology field,can be used any material micromachining with important value. The past most of the work focused on internal of transparent materials changing and applicating,such as refractive index changing,phase changing, fluorescent or phosphorescent producing et al.But on the surface of the micro-processing is rarely reported.This paper sums up the femtosecond laser etching the surface of the insulator in the physical mechanism, describing the micro-lens and the production of micro FP fiber cavity.In theory,femtosecond laser acting the glass surface which is not conductive and eliminating the material by Coulomb explosion or the phase explosion is summarized, the former process is ionization through the process of multi-photon absorption of the laser energy, the result of strongly ionization is all electronic overflow, with the rest of the positive charge Ion, because of the Coulomb repulsion between the charges and plasma Mission launched a damage pit; blasting phase is due to the high concentration of electronics - hole caused lattice changed for the plasma gas or liquid, this process is no more than the 1 ps.The two processes consumes most of laser energy while heat transmission time in the order of picoseconds, so this form has no thermal effect.In experiment,this thesis ranges over ultrashort laser pulse fabricating production of microprocessing and non-intrinsic-FP-line fiber optic sensors, discussed the femtosecond laser processing of the surface finish problems ,FP cavity of the parallel issues, how to improve the signal to noise ratio and other issues, through Controlling of laser pulse energy and improving processing methods, over 20 dB fringe visibility of F-P interferometric sensor has been realized. This technical means overcomes the production and performance deficiencies of the traditional fiber Fabry Perot sensors, it solves the strain of high-temperature accurate measurement problems.In addition, femtosecond laser operates object surface,first nonlinear absorption, the final materials will be eliminated with phase and Coulomb blasting.Our research shows that the shape of elimination is the same as the pulse spatial shape.Using the principle, the concave microlens arrays are fabricated on optical glasses with femtosecond laser, and hydrofluoric acid etching controlls the surface roughness of optical MLA.The production technology has the advantage of the surface shape of micro-lens controlled by the space shape of laser pluse.