Study Of Novel Specialty Optical Fiber

Until 1970s,optical fiber show very impressive historic and future growth potential in optical communication.With the continuous development of science and technology,specialty optical fibers have arisen to solve some problems which are hard to tackle using conventional optical fibers.Now more and more searchers focus on specialty optical fibers.To integrate optical devices in optical fiber,we propose three kinds of specialty optical fibers to modulate input optical light and output special optical field.The primary contents of this thesis are:1.Airy optical fiber.There are two kinds of Airy optical fiber.The first one has two orthogonal array-core embedded in cladding.Each core only supports a single mode.And both the horizontal and vertical array-core distribution in cross section is satisfied or approximately satisfied Airy function.And the second one has several coaxial annular cores which also has Airy distribution along radial direction.The coupled-mode theory and beam propagation method have been applied for analyzing wave propagation along these two Airy fibers.The simulated results showed that the output beams from Airy fibers have abilities to remain quasi-nondiffraction,transverse accelerating and self-healing during propagation.Because a slight variation(10nm)in incident wavelength can lead to obvious change in transverse acceleration of output beams from Airy fibers,the rainbow effect is introduced to explain this phenomenon.Based on this,the output beams from Airy fibers can be modulated by optical wavelength.2.Bessel optical fiber.There are two methods to generate a Bessel beam.One is formed by ring beam focused by lens,and the other one is generated by focused Gaussian beam with an axicon.Based on these two methods,we propose several Bessel beam generator using specialty optical fibers and fiber lens.We also propose a highly focused conical optical filed generated by cone-frustum-shaped annular core fiber tip for Pico-Newton scale force sensing.The tip provides a very strong focusing effect so that there are stable three dimensional trap-points for particles in the focused field with Bessel-like profile.And we also use a novel integrated fiber-based device fabricated by cone-frustum-shaped annular-core fiber end to achieve two functions:particle trapping and launching.Such two functions integrated in one annular-core fiber end and we call it "optical gun".We have successfully used this device to trap and launch an 8.6 ?m polystyrene microsphere in fluid flow environment.And the maximum of launching speed can reaches nearly 1 cm/s/W with a running range of dozens of micrometer.The simulated results also show that the launching velocity in air is nearly ten times greater than in fluid,whose maximum is over 10 cm/s/W.3.Vortex optical fiber.There are two kinds of vortex optical fiber with a circular core and an annular core,respectively.They have single-helix chiral refractive index distribution when the transverse refractive index profile is linear along one direction(such as x-axis)in core region.And they also have double-helix chiral refractive index distribution when the transverse refractive index profile is saddle or parabolic.The coupled-mode perturbation theory has been applied for analyzing wave propagation along these vortex beam fibers.And the calculation results show that vortex beams with topological charge 1 and 2 can be generated by single-helix chiral and double-helix chiral vortex beam fiber,respectively.However,the length of different vortex beam fiber to form a vortex beam depends on coupling coefficients between fundamental mode and vortex modes.For example,one can get the vortex beam from a single-helix(or double-helix)chiral vortex beam fiber with a circular core which has length from a few millimeters to dozens of millimeters.However,it's difficult to generate a vortex beam from a single-helix chiral vortex beam fiber with an annular core when its length is longer than ten millimeters.But you can choose any specific length double-helix chiral vortex beam fiber with an annular core to generate a vortex beam with topological charge 2.In this dissertation,we study three kinds of special beam generator using specialty optical fibers.These all-fiber devices have many unique features,such as small size,easy handling,stable and strong anti-jamming capabilities.Therefore,it has a great scientific significance to investigate these specialty optical fibers to implement all-optical switching and all-optical signal processing in a fiber.