The Generation And Propagation Of The Airy-like Beam

Compared with the traditional non-diffractive beams,Airy beam not only maintains the diffraction-free and self-healing properties,but also enjoys its special self-bending property.Because of the peculiar propagation characteristics,Airy beam can find its application in many fields,such as optical manipulations,vacuum electron acceleration,surface plasmon polarization,optical tweezers,and so on.In the past few years,the researches of Airy beam focused on three parts: generation,propagation and application,where many breakthroughs have been obtained.With the progress of Airy beam,a series of Airy-like beams emerge and receive many attentions recently.Airy-like beams have more advantages than the traditional Airy beam in some fields.For example,the autofocusing property of circular Airy beam with high-pass filtering is enhanced strongly,while the focal position,focal trajectory and focal spot size do not change.And the main lobe of Super Airy beam has smaller size and stronger energy.In order to improve some properties of Airy beam,we systemly investigate the generation and propagation characteristics of Airy-like beams in this thesis.Details are as follows:(1)Inspired by modified circular Airy beam with high-pass filter in Fourier space,we impose two kinds of filters(low-pass filter and band-pass filter)to modify the spectrum of the circular Airy beam.The propagation characteristics of these modified circular Airy beams are investigated in details.The results show that the focal spot will be stretched and form an “optical needle”,if the spectrum of circular Airy beam modified by a low-pass filtering or the band-pass filtering.More interestingly,we can control the length,the width and the energy gradient of these “optical needles” by changing the parameters of the filters.(2)The propagation characteristic of a circular Airy beam in uniaxial crystals is investigated in details.We found that the beam loses its boundary cylindrical symmetry during propagation because of the medium anisotropy,although it propagates along the optical axis.The effect of anisotropy on the propagating beam becomes increasingly evident with the increase in propagation distance.Another main influential factor on the propagation characteristics is the ratio of the extraordinary refractive index to the ordinary refractive index(0/en n).The more the value of 0/en n deviates from 1,the worse the intensity distribution symmetry of the beam will become.In addition,the polarization state becomes notably complicated,and it possesses vortex of topological charge 2 during propagation.(3)Because the traditional device of generating Super Airy beam is very expensive and needs large horizontal space,we propose a laser emitting a super Airy beam directly.The 1% neodymium-doped yttrium aluminum garnet rod is pumped by a laser diode,and the diffraction grating,modulated to impose the phase of Super Airy beams,is used as output mirror of the laser.The numerical results show that the threshold power of the laser is 1.4W,and the output power will rise up to 678 mW with 2W pump power.