Colloquia & Guest Speakers

Spin and Orbital Angular Momentum Interactions of Light

Prof. Siddharth Ramachandran, Boston University

Thursday, February 27, 2020
4 p.m.

Bausch and Lomb 109

Siddharth Ramachandran
Siddharth Ramachandran


Light can carry both orbital angular momentum (OAM) and spin angular momentum (SAM), related to wavefront rotation and polarization, respectively. The ability to exploit these degrees of freedom in so-called optical vortices has spawned applications across the fields of opto-mechanics, sensing, telecommunications and manufacturing. In free space or bulk-optic media, SAM are OAM represent independent quantum numbers. However, from atomic and molecular systems, we also know that the presence of a confinement potential yields a spin-orbit interaction Hamiltonian that hybridises these states. Photonic analogues of such spin-orbit interactions are now accessible in optical fibers, since an optical waveguide is essentially a confining “potential” for light. In this talk, we will show how generation, stable propagation and nonlinear interactions of light beams containing phase or polarization singularities are both altered by, and, from a device perspective, benefit from engineering spin-orbit interactions of light via optical waveguide design.


Dr Siddharth Ramachandran obtained his PhD in Electrical Engineering from the University of Illinois, Urbana-Champaign, in 1998. Thereafter, he joined Bell Labs as a Member of Technical Staff and subsequently continued with its spin-off, OFS Labs. After a decade in industry, Dr. Ramachandran moved back to academics in 2010, and is now a Professor in the Depts. of Electrical Engineering and Physics, and the Division of Materials Science, at Boston University. Prof. Ramachandran’s research focuses on the optical physics of guided waves. For his contributions, he was named a Distinguished Member of Technical Staff at OFS (2003), a fellow of OSA (2010), IEEE (2019 and SPIE (2019), an IEEE Distinguished Lecturer (2013-2015), a Distinguished Visiting Fellow of the UK Royal Society of Engineering (2016), and a Vannevar Bush Faculty Fellow (2019). He serves the optics community in several capacities, including, currently, as a topical editor for Optica.

Location: Bausch and Lomb 109

Refreshments will be served.