Designs Of Beam Shaping Elements And Quantum Structure Adjustment Of Optical Transport Properties

The quantum structure manipulation of optical transmission properties inlow-dimensional periodic and quasiperiodic superlattices has important applicationforeground in the design of optoelectronic devices. Optimization design of opticalelements can effectively improve the beam quality. In this thesis, we focus on thefollow issues: light propagation properties in periodic and quasiperiodic superlatticeswith structural defect, optimization design of diffractive optical elements for beamshaping, long focal depth and wavelength demultiplexing and focusing. Some mainresults achieved in this thesis are summarized as follows:A three-component quasiperiodic superlattice structures composing of both positiveand negative refractive index materials are shown to display resonant transportbehavior and optical band gaps. When the structure is composed of non-dispersiverefractive index material, the number of the resonant transmission peaks increases andthe optical band gap becomes broader with the increasing of the medium generation.The band gap covers all the wavelength except for some singular wavelength pointswhen the structure is composed of negative refractive index materials. Moreover, it isfound that the spectrum shifts to low frequency for oblique incidence. And with theincreasing of the optical thickness, the band gap splits and new perfect transportchannels emerge. For a more realistic dispersive negative refractive index material,the transmission coefficients are characterized by a rich transmission profile withoutsymmetry, more wide band gaps and abundance transmissive channels appear.We investigate the optical transmission properties in finite periodic superlatticemodulated with three-component quasiperiodic defect structure. The results show thatwhen the multilayered defect is composed of frequency-independent refractive indexmaterial, more band gaps appear with the growing of the number of the defect order,and new guided channels emerge. Perfect and more wide band gap can be observedwhen the structural defect is composed of negative refractive index materials.Moreover, the band gap can be adjusted by the incident angle and the spectrum shiftsto high frequency for oblique incidence. For a more realistic frequency-dependentrefractive index, the transmission spectra are characterized by a rich transmissionprofile without symmetry.An improved approach named as weighted YangGu(YG) algorithm for the design of diffractive phase element (DPE) that implement beam shaping in the fractionalFourier transform domain and free space is presented. Modeling designs of the DPEare carried out for several fractional orders and different parameters of the beam foroptimization converting a Gaussian profile and hollow Gaussian profile into a uniformbeam. We found that our algorithm can improve the beam shaping effect, reduce theerror function, and increase light intensity imhomogeneous. For different initial phase,the error function tends to nearly zero points. It can be effective for avoiding thesearch process to local extreme point and decreasing the sensitivity to initial phase.We use an optimization weighted YG algorithm for the design of diffractive Axiconwith long focal depth and high lateral resolution. Modeling designs of the diffractiveAxicons are carried out uniform and Gaussian beam for optimization implementing onlong focal depth. For three different wavelengths incident beam, can realize long focaldepth in the predesignated focal range. After more than once weighted, we found thatour algorithm can increase focal depth, achieve an uniform plateau profile in thedomain of focal depth.We use the optimization algorithm design optical elements for wavelengthseparation and focus. A variety of wavelength can be separated and are able to focus atthe predesignated positions and energy consumption is small. For four differentincident wavelengths, they can also be separated and focus at arbitrary predesignatedpositions after expansion the phase distribution.