Rotational Doppler shift upon reflection from a right angle prism

“This Letter reports the observation of a rotational Doppler shift on reflected beams carrying Orbital Angular Momentum (OAM). More precisely, we study the beat frequency of two optical beams carrying OAM with opposite signs, reflected on a right angle prism. We show that the interference of the two beams leads to a daisy-like pattern that rotates at twice the rotating frequency of the prism. The rotational Doppler frequency shift is equal to the OAM topological charge change times the rotational frequency. Possible applications in the positioning and detection of rotation of objects are then discussed._x000D_
This publication was supported by the European Union through the European Research Development Fund (ERDF) and the French Region of Brittany, Ministry of High Education and Research, Rennes Métropole and Conseil Départemental 35, through The CPER project SOPHIE/STIC and Ondes. We wish to acknowledge valuable discussions with Professor K. Mahdjoubi (Université de Rennes 1).”