Research Note

Detecting photons with orbital angular momentum in extended astronomical objects: application to solar observations

¹ Laboratorio de Instrumentación Espacial (LINES)Instituto Nacional de Técnica Aeroespacial (INTA), Ctra. Ajalvir km 4, Torrejón de Ardoz, 28850 Madrid, Spain
e-mail: uribepnr@gmail.com; alvareza@inta.es
² THEMIS, CNRS UPS 853, C/ vía Láctea s\n, La Laguna, 38205 Tenerife, Spain
e-mail: arturo@themis.iac.es; bgelly@themis.iac.es; claude.lemen@gmail.com
³ Instituto de Astrofisica de Canarias, C/ vía Láctea s\n, La Laguna, 38205 Tenerife, Spain
e-mail: aasensio@iac.es; rms.iac@gmail.com
⁴ Departamento de Astrofisica, Univ. de La Laguna, La Laguna, 38205 Tenerife, Spain

Received: 22 April 2010
Accepted: 17 October 2010

Abstract

Context. The orbital angular momentum (OAM) of the photon is a property of light from astronomical objects that has not yet been measured. We propose a method of measuring the OAM spectrum of light from an extended natural source, the Sun. Relating the OAM spectrum of different solar areas to its structures could lead to a novel remote sensing technique.

Aims. We present a method for measuring the OAM spectrum of solar photons.

Methods. The THEMIS^⋆ telescope is being used with a novel phase-diversity technique. A spatial light modulator is placed on one pupil image, and an ad-hoc optical setup allows the measurement of two simultaneous phase-diverse images in the same CCD, with equal optical paths.

Results. Preliminary results show that very good seeing is mandatory for this kind of observation. The method works in the laboratory, and good seeing conditions in the 2010 campaign are being awaited.