Franco GORI,¹ Vittorio BAGINI,¹ Massimo SANTARSIERO,¹ Fabrizio FREZZA,² Giuseppe SCHETTINI² and Giuseppe Schirripa SPAGNOLO³

¹Dipartimento di Fisica, UniversitEgLa Sapienza,h Piazzale A. Moro 5, 00185 Roma, Italy, ²Dipartimento di Ingegneria Elettronica, UniversitEgLa Sapienza,h Via Eudossiana 18, 00184 Roma, Italy, ³Dipartimento di Energetica, UniversitEdell'Aquila, Localita' Monteluco di Roio, 67040 Roio Poggio, L'Aquila, Italy

(Accepted September 9, 1994)

We present coherent and partially coherent beams that exhibit transverse pattern expansion and rotation upon free propagation. Coherent twisting beams may be generated by a suitable superposition of Laguerre-Gauss modes, while a model for partially coherent twisting beams is given by a continuous incoherent superposition of lowest order modes.

Key words : laser modes, propagation, interference, coherence, invariance