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Accueil > Équipes > OPTique et IMAgeries > Instrumentation et Méthodes > Time-frequency methods

Time-frequency methods

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PIs : H. Guillet de Chatellus, O. Jacquin, O. Hugon, E. Lacot, S. Costrel

This research axis is dedicated to the development of experimental concepts and techniques for the metrology of signals in time and in frequency.

This axis is structured in three different topics :


1 Microwave photonics in frequency shifting loops (FSLs)

This research axis, supervised by Hugues Guillet de Chatellus, is dedicated to new functionalities of FSLs for microwave photonics, i.e. the processing and the generation of RF signals in photonic platforms. FSLs are simple photonic systems, based on a fiber loop, where the light is frequency-shifted at each roundtrip. Since 2013, numerous unique properties of these systems have been demonstrated at LIPhy, including the generation of on-demand repetition rates by temporal Talbot effect, real-time Fourier transformation, or the generation of arbitrary RF chirped waveforms.

sketch of a FSL
left : sketch of a FSL. The fiber loop contains an amplifier (EDFA), a filter (TBPF), and a frequency shifter (AOFS). It is seeded by a CW laser. Middle : example of arbitrary signal produced in a FSL. Right : example of spectrogram (freq. vs time) where the seed laser is phase-modulated by a signal with a sinusoidal frequency modulation.

Different collaborators are, or have been involved in this research project : C. Schnébelin, V. Duran Bosch, N. Kanagaraj (LIPhy), L. Romero Cortés, M. Burla, and J. Azaña (INRS), V. Billault, V. Crozatier (TRT), J. Clement, and C. Fernandez-Pousa (UMH)
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2 Heterodyne detection for aperture synthesis imaging

This novel axis is carried out in the frame of a collaboration of Hugues Guillet de Chatellus with the Institut de Planétologie et d’Astrophysique de Grenoble - IPAG (J.-P. Berger, E. Le Coarer). The aim of the project is to demonstrate the viability of the infrared heterodyne detection technique for aperture synthesis imaging in astronomy in the context of the Planet Formation Imager project. The core of the project is double. First, we will design a heterodyne detection architecture based on the joint use of local oscillator frequency comb lasers, a high-dispersion spectral system and ultra-fast photon-count avalanche photodiodes. Second, we investigate the possibility of analog photonics-based correlation of RF signals.

Picture of VLT
Very Large Telescope Interferometer, in Cerro Paranal (Chile).
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3 Full-field optical vibrometer

A third research axis led by Olivier Jacquin, is the development of a full-field optical vibrometer, to measure repeatable high-frequency nanometric amplitude vibrations in the MHz range. The principle is to freeze the studied vibration in the frequency domain with an off-axis heterodyne interferometer. The reference wave is frequency shifted, to compensate for the Doppler effect caused by vibration. This concept is equivalent to measuring the Fourier transform of the vibration at the shift frequency. A frequency scan allows to measure the vibration spectrum and to determine the vibration by reverse Fourier transform.

Vibrometer
Very Large Telescope Interferometer, in Cerro Paranal (Chile).
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