JLab Student Seminar 3/22/2017 Gamma-ray vortex beams carrying orbital angular momentum Yoshitaka Taira National Institute of Advanced Industrial Science and Technology (AIST), Japan Visiting scientist: Mississippi State University and Jefferson Lab. In this seminar... I will talk about so called vortex beam, orbital angular momentum beam, twisted beam. Does someone know that? Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 1 Outline Polairzation and wave fronts of light Optical vortex Electric field and Poynting vector Generation, Measurement, Application Electron vortex, X-ray vortex Gamma-ray vortex Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 2 Light Sun LED Synchrotron light Wikipedia YY.. TTaaiirraa,, GGaammmmaa--rraayy vvoorrtteexx bbeeaammss ccaarrrryyiinngg oorrbbiittaall aanngguullaarr mmoommeennttuumm 3 Electromagnetic wave spectrum Frequency (Hz) 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 2 7 8 9 0 1 2 3 4 5 6 7 8 9 0 V Radio, TV Microwaves Infra-red is Ultraviolet X-rays Gamma-rays ib le 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 m c m µ n p 0 m c m 0 µ m 0 n m 0 p m m m m µ m n m p m m m m Wavelength 7 6 5 4 0 0 0 0 0 0 0 0 n n n n m m m m λ λ Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 4 Linear polarization λ z y Incoming electric field ( ) E = e E exp ikz − iωt x 0 x Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 5 Circular polarization λ z y Incoming electric field e + iσe ( ) x y E = E exp ikz − iωt 0 2 Spin angular momentum (SAM) x = σħ (σ = ±1) Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 6 Wave front -position of the same phase- Wave front Electromagnetic wave Phase 0 2π 4π Wave fronts of plane wave Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 7 Outline Polairzation and wave fronts of light Optical vortex Electric field and Poynting vector Generation, Measurement, Application Electron vortex, X-ray vortex Gamma-ray vortex Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 8 Vortex beams -Helical wave front creation- Wave front Phase Forming a helical wave front. ( ) E ∝ exp iφ Carrying orbital angular momentum (OAM) ℓħ Total AM = OAM + SAM = ℓħ + ħ M. Padgett et al., Phys. Today 57 (2004) 35. Y. Taira, Gamma-ray vortex beams carrying orbital angular momentum 9