Enhanced Interferometric Identification of Spectra in Habitable Extrasolar Planets

Abstract

An Earth-like extrasolar planet emits light that is many orders of magnitude fainter than that of the parent star. We propose a method of identifying bio-signature spectral lines in light of known extrasolar planets based on Fourier spectroscopy in the infrared, using an off-center part of a Fourier interferogram only. This results in superior sensitivity to narrower molecular-type spectral bands, which are expected in the planet spectrum but are absent in the parent star. We support this idea by numerical simulations that include photon and thermal noise, and show it to be feasible at a luminosity ratio of 10-6 for a Sun-like parent star in the infrared. We also carried out a laboratory experiment to illustrate the method. The results suggest that this method should be applicable to real planet searches.

White light Sagnac interferometer—a common (path) tale of light

“…The Sagnac interferometer is a common-path interferometer first devised for the purpose of measuring rotations via the Sagnac effect [14 -16]. The Sagnac effect is implemented in a vast number of fields of research [17][18][19], with one very intriguing suggestion as the next-generation detector for recently observed gravitational waves [20,21]. However, it is mostly implemented in current optical gyroscopes (fiber ring lasers) that exploit this effect for navigation purposes and geodesic measurements [22,23].…”

Sagnac effect in an off-center rotating ring frame of reference

“…The path difference is linearly proportional to the rotation frequency of the system. This famous effect is manifested in various current research fields including atom interferometry [3][4][5], astronomy [6], general relativity effects such as Lense-Thirring precession [7,8] and presently even is being explored as a possible advanced detection method for gravitational waves [9,10].…”

Optical fiber interferometer array for scanless Fourier-transform spectroscopy

“…Fourier-transform (FT) spectrometry [1] is an elegant and practical realization of the principle of Fourier decomposition of waves, with a plethora of applications ranging from the study of atomic and molecular electronic structures [2] to the search for biosignature spectral lines in extrasolar planets [3]. In an FT spectrometer, the intensity variation of the output beam is measured while scanning an interferometer delay line whose longest optical path determines the spectral resolution of the device, with the latest developments [4] reaching a resolution limit of 0.0005 cm −1 as a result of an optical delay of 11.7 m. Resolutions up to 100 kHz have also been demonstrated with frequency comb FT spectrometers [5].…”