Study On Bio-inspired Broadband Omnidirectional Antireflection Structures

Antireflection structures can dramatically suppress light reflection and thus enhance light absorption and transmission.The ever growing demand for optical device in area as diverse as photovoltaic,optical display,and optical detection has led research for broadband and omnidirectional antireflection structures.However,commercial antireflection structures fail to meet this expectation,because they can only function in a narrow wavelength band at certain incident angle.Bio-inspired optical nanostructures,which survive million years of revolution can bring enlightenment for the design of state-of-art antireflection structures.This thesis was involved in an in-depth research on the reflection from transparent wing of Cryptotympana atrata Fabricius cicada and blue wing of Morpho menelaus butterfly.Based on that,a ?Tower of Hanoi?-like tapered silicon multilayers structure combining broadband(300nm~1100nm)and omnidirectional antireflection properties over UV-VIS-NIR were put forward.The main contents of this thesis is as below:1.Silicon nanocone structure bio-inspired from wing of cicada was established.Cone height L=500nm and bottom diameter S=150nm proved to be the optimal parameter to achieve average reflection as low as 1% over 300nm-1100 nm.Furthermore,reflection curves,photo-generated current distribution of electromagnetic field,power absorption per volume were calculated to confirm the superior antireflection and light trapping property of silicon nanocone over nanopillar and bare silicon structure in a broad wavelength band.2.The low incident angel dependence of reflection from blue Morpho wing was studied via both optical measurements and simulation.The multilayers on scale ridges were found to be responsible for the low incident dependence,thus contributing to the design of silicon multilayers.The impact of layer thickness L1 and interval thickness L2 on the incident angel dependence was explored with the introduction of antireflection factor ?.The resultant tapered silicon multilayer structure combined the nanoprotuberance structure from cicada wing and multilayer structure from lamellar ridges.What‘s more,both broadband and omnidirectional antireflection properties under random polarization light were successfully inherited with the proper control with L1 and L2.Result presented in this thesis is likely to provide valid reference and innovation for silicon-based broadband omnidirectional antireflection structure.The method applied in this thesis also works for antireflection structure design of other material.