A Laser Frequency Comb System for Absolute Calibration of the VTT Echelle Spectrograph

• Published in: Solar physics Vol. 280; no. 2; pp. 663 - 670
• Main Authors: Doerr, H.-P., Steinmetz, T., Holzwarth, R., Kentischer, T., Schmidt, W.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.10.2012; Springer Nature B.V
• Subjects: Advances in European Solar Physics; Astrophysics and Astroparticles; Atmospheric Sciences; Calibration; Lasers; Measuring instruments; Physics; Physics and Astronomy; Recording; Solar physics; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Space telescopes; Spectra; Spectroscopy; Spectrum analysis; Telescopes; ASE, Atlantic, Canary Is; ASE, Atlantic, Canary Is., Tenerife; Germany; Echelle Spectrograph; Limb Effect; Frequency Comb; Free Spectral Range; Photonic Crystal Fiber
• ISSN: 0038-0938; 1573-093X
• DOI: 10.1007/s11207-012-9960-5

A wavelength calibration system based on a laser frequency comb (LFC) was developed in a co-operation between the Kiepenheuer-Institut für Sonnenphysik, Freiburg, Germany and the Max-Planck-Institut für Quantenoptik, Garching, Germany for permanent installation at the German Vacuum Tower Telescope (VTT) on Tenerife, Canary Islands. The system was installed successfully in October 2011. By simultaneously recording the spectra from the Sun and the LFC, for each exposure a calibration curve can be derived from the known frequencies of the comb modes that is suitable for absolute calibration at the meters per second level. We briefly summarize some topics in solar physics that benefit from absolute spectroscopy and point out the advantages of LFC compared to traditional calibration techniques. We also sketch the basic setup of the VTT calibration system and its integration with the existing echelle spectrograph.