High-Fidelity Optical Parametric Amplification Of Ince-Gaussian Beams

As an eigen solution in elliptic coordinate system,Ince-Gaussian(IG)beam is a transition mode between Laguerre-Gaussian(LG)beam and Hermite-Gaussian(HG)beam.It has the characteristics of non-diffraction,propagation invariance and full-domain spatial mode,and has great potential in optical communication,particle control and quantum key distribution.In practical applications,in order to realize long-distance transmission and nonlinear interaction,IG beam needs to be amplified to obtain high power IG beam,so as to expand its application range.However,relevant researches are mainly focused on the amplification and nonlinear transformation of orbital angular momentum beams with angular structure,and there are few reports on the study of spatial modes such as IG beam.In particular,the high-fidelity and mode-independent amplification of global spatial modes is still an urgent problem to be solved in the field of nonlinear optical field.In order to solve the problem,the thesis proposes a scheme of IG beam optical parametric amplification(OPA),which uses flattop-beam to realize the high-fidelity and mode-independent amplification of IG beam.The nonlinear transformation of LG spectrum in IG beam space under gaussian and flattop-beam pumping is studied theoretically,and the physical mechanism of mode distortion under Gaussian pumping is revealed and verified experimentally.Based on the theoretical models of LG,IG and HG beam,the conversion relationship between IG beam and LG and HG beam is constructed.The nonlinear coupled wave equation and small signal model are derived from Maxwell equation.On this basis,Gaussian beam is used as pump beam,and the waist relation of different pump as well as signal beam and propagation evolution of output signal beam under different gain conditions are studied theoretically.Through theoretical analysis of LG spectra of IG beam,it is revealed that radial degeneracy is the main cause of mode distortion.Therefore,a scheme for optical parametric amplification using a flattop-beam as pump is proposed.The results show that the proposed scheme can solve the amplification mode distortion caused by the uneven spatial distribution of Gaussian pump.In terms of experiment,the influence of different beam waist ratios on OPA output signal spot under Gaussian pumping condition was studied firstly,and the distortion mechanism of IG beam after amplification was verified.Then,a perfect flattop-beam is generated as the pump beam by using spatial light modulator complex amplitude holography.Flattop pump can effectively solve the problem of mode distortion and realize the high-fidelity amplification of IG beam.The inner product of the matrix between the intensity distributions of corresponding IG beam greater than 98%.Finally,the amplifying energy and corresponding gain of IG signal under different light energy are measured to achieve the mode-independent OPA.The proposed scheme can be extended to the amplification of other arbitrary structure light field modes,which provides a reference for the nonlinear foundation and application of generalized high-order global spatial mode.