Efficient Sorting of Orbital Angular Momentum States of Light

Abstract

We present a method to efficiently sort orbital angular momentum (OAM) states of light using two static optical elements. The optical elements perform a Cartesian to log-polar coordinate transformation, converting the helically phased light beam corresponding to OAM states into a beam with a transverse phase gradient. A subsequent lens then focuses each input OAM state to a different lateral position. We demonstrate the concept experimentally by using two spatial light modulators to create the desired optical elements, applying it to the separation of eleven OAM states.

Interface between path and orbital angular momentum entanglement for high-dimensional photonic quantum information

“…LG modes can be used to transmit more classical information [5][6][7][8][9] or realize a higher-dimensional quantum state 11,21,22 . To access the encoded information efficiently a MS was developed 18,19 , which consists of two freeform refractive optical elements that convert the OAM content of an incident light field to lateral positions of the output. The first element maps the azimuthal to the lateral coordinates.…”

“…At the same time, we investigate a flexible way to create higher-dimensional OAM entanglement that does not rely on angular momentum correlation. The essential tool in our experiment is a mode sorter (MS) that was invented 18,19 to convert the OAM content of an incident light beam to lateral positions of the output beam. By using this device in reverse, different spatial positions can be transformed to the cylindrically symmetric LG modes.…”

TIM, a ray-tracing program for METATOY research and its dissemination

“…This is called a geometrical optical transformation, and it can be approximated holographically [7]. Our own interest in geometrical optical transformations stems from the application of a polar-to-Cartesian transformation between two planes to the detection of optical angular momentum [8].…”

“…• and a class representing a surface a light ray enters and then continues, from a corresponding position and with a corresponding direction, from the surface of a different scene object (Teleporting -see section 4; we use this to model geometric optical transformations [8]). …”

Massive individual orbital angular momentum channels for multiplexing enabled by Dammann gratings

“…Another technique developed for OAM detection is known as the beam transformation approach. 25,26 The donut-shaped OAM beam is transformed into a line shaped beam and can be focused onto spots distributed laterally depending on their topological charge. However, limited by the irregular shaped focal spots and small separation angles, this technique requires photodiode arrays to detect the separated OAM states, which is not compatible with the conventional optical communication system using single mode fiber collection.…”