Novel acousto-optical tunable filter (AOTF) based spectropolarimeter for the characterization of auroral emission

J. Vanhamel, Emmanuel Dekemper, Sophie Berkenbosch, Roland Clairquin

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Auroras can be observed at the north and south pole of the Earth. At these locations, the Earth magnetic field enters the atmosphere, causing ionization of the atmospheric constituents. Due to this phenomenon, different optical wavelengths are emitted from these constituents, causing the typical spectacular displays. Several optical wavelengths are representative for the auroral emission. The purpose of the described instrument is to measure the degree of linear polarization of the northern lights, in order to detect and confirm previous observations in which only a low level of polarization was seen. The instrument is capable of resolving the polarization measured at any wavelength in the visible region, using two optical chains, each containing an acousto-optical tunable filter (AOTF). The latter is responsible for the selection of the desired optical wavelength and projects the two polarized beams onto an optical detection system. The driving of the AOTF, using a radio-frequency (RF) signal, is a key-element in establishing trustworthy results. The design of this double RF chain, consisting of a generator, an amplifier, and the necessary circumjacent electronics, is described in the study. In addition , the optical setup of the instrument, together with the detection system is explained. The instrument will be used in the harsh environment of the pole regions, so it must be able to withstand these weather conditions. Hence, a thermal compensation system is necessary and is also described.
Original languageEnglish
Pages (from-to)245-257
Number of pages13
JournalInstrumentation Science & Technology
Volume49
Issue number3
DOIs
Publication statusPublished - 2020
Externally publishedYes

Keywords

  • Acousto-optical tunable filter (AOTF)
  • aurora
  • radio frequency (RF)
  • spectroscopy

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