In the context of the global warming, it is now primordial to have a better understood of the greenhouse gases cycles, especially CO2, and to characterize these cycles. The use of a spaceborne Lidar could answer this need. The principle of such a Lidar is to compare the backscattered light coming from Earth at two different but closed wavelengths, one being absorbed by the CO2, the other not. The differential absorption enables to calculate the concentration of CO2 along the light path between the satellite and Earth (IPDA technique: Integrated-Path Differential Absorption).
In the frame of the building of a future space Lidar program, some actions are led by different space agencies (NASA, ESA, JAXA, CNES) for the development of new laser sources emitting in the near Infrared region (1.5µm- 2µm). A pulsed, singlemode, powerful, compact, transportable, efficient, robust, laser source is necessary. All-fibered laser sources present most of these proprieties, but the energy per pulse is limited by non-linear effects inside the fiber. Solid-state lasers can them reach higher energies per pulse but present other drawbacks (complexity, sensitivity to space environments,…)
The use of a hybrid (fibered/solid-state) laser source would enable to cumulate the advantages of both technologies and to obtain a performant and reliable solution. ONERA has recently developed a new and powerful fibered laser source emitting at 2 µm, a well suited wavelength for space detection of CO2. At this wavelength, LMD recently demonstrated a strong potential of amplification in Holmium doped crystals.
The proposal then consists in the development of a hybrid laser source at 2 µm, constituted of a fibered laser and a Holmium solid-state amplifier, inside a Lidar instrument, and then to realize measurements of CO2 concentration in direct or coherent detection. More precisely, the work will consist in (1) taking in hand and characterize the fibered laser, (2) realizing CO2 Lidar measurements with this sole fibered laser, (3) adding an amplification stage using Holmium crystals, and (4) making new lidar measurements after amplification.
The use of a fibered technology for the laser will enable to monitor the temporal and spectral characteristics of the emitted pulses, offering additional degrees of freedom for the lidar conception and for the optimization of the instrument performances.
The student will mainly work in the ONERA Palaiseau facilities, with measurement stages inside the LMD lab (in Palaiseau too). He or she will be totally integrated inside these two Lidar research teams.
Master or Optics Engineer, Physics, Laser
To apply, we invite you to contact the PhD/research supervisor and fill, with him/her, the co-financing part of the online application form (Reply to the offer) by March 31st, 2018.