The Study On The Interaction Between Chiral Molecules And Orbital Angular Momentum Induced By Plasmon

It is well known that some molecules possess optical activity, which they are very sensitive to the right- and left-handed circularly-polarized photons. Circular dichroism(CD) spectroscopy is one of the central methods to probe chiral nature of molecules through describing the difference in absorption of right- and left-handed circularly-polarized photons. This means that optical activity of molecules is intrinsically linked to the spin angular momentum(SAM) of the photons.More recently, it was recognized that photons can additionally carry orbital angular momentum(OAM). Does this additional degree of freedom play a role in CD? Considering such a problem, the interaction of OAM light with atoms and molecules has been studied in a number of works, with controversial outcomes: Some predict that such an interaction should be observable within the electric dipole approximation, and some do not find such effects.Motivated by the above problems, in this thesis we study the interaction between the OAM and the chiral molecule-nanoparticle nanocomposites, and explore plasmon-induced interaction between chiral molecules and orbital angular momentum of light. Thus, two experimental schemes have been proposed and performed. One is by measuring the difference in CD for positive and negative OAM beams. Another is by measuring the difference in absorption of positive and negative OAM beams. Unfortunately, the interaction signal between the OAM and the chiral molecule- nanoparticle nanocomposites has not been found. This is in contrast to our theoretical calculation. the theoretical calculations have been analyzed. The origin of the conflict has been clarified. The direction of the next step to observe such a phenomenon has been pointed.