We are developing a DIfferential Absorption Lidar (DIAL) for CO2 remote sensing using coherent detection, based on a pulsed hybrid laser emitter at 2.05 μm. In the 2 μm region, the R30 CO2 absorption line has been identified as one of the most promising for space-borne DIAL instrument to provide precise sounding of the atmospheric boundary layer where CO2 sources and sinks are located. In this paper, we present the Tm-doped all-fiber part of the emitter and we demonstrate its ability to measure the CO2 Volume Mixing Ratio (VMR) in the atmosphere. The lidar setup is presented, including the telescope, the heterodyne detection system and a spectral reference system used to infer the absolute frequency of the laser and the ON-line/OFF-line energy difference. We investigate an Integrated-Path-DIAL measurement on a range of 426 m. Results compare well with an in-situ reference sensor (Picarro probe), and the estimate statistics show good agreement with theoretical error calculations. This lidar demonstrator has been called HELENA (Hybrid Emitter Lidar for ENvironmetal Applications). Once completed, it will feature an hybrid emitter combining a semiconductor laser, a high-power Tm-doped fiber amplifier stage, and a final Ho:YLF crystal single-pass amplification stage. This combination aims at benefitting of the versatility, compactness and alignment easiness of a fiber amplifier on one hand, and of the high-peak power attainable with a solid-state amplifier on the other hand. It could allow overcoming the traditional Brillouin limit met in fiber amplifiers, without sacrificing much in compactness and robustness.
For planetology applications, a SuperCam type laser emitting in the UV region (266 nm or 355 nm) would be of great interest. We investigated Third Harmonic Generation (THG) and Fourth Harmonic Generation (FHG) in LBO crystal and BBO crystal respectively. For potential lunar mission on vehicle smaller than a Curiosity class rover, we designed a laser based on SuperCam heritage focusing on size and mass reduction for a compact LIBS instrument.
We report on recent advances at ONERA on fiber-based laser and lidar systems, in the perspective of future space-borne monitoring of greenhouse gas, especially CO2 and CH4. We first present an advancement status of research activities on high-peak-power single-frequency fiber lasers at 2.05 μm and 1.58 μm for CO2 monitoring, and at 1.64 μm for CH4, as well as perspectives for future amplification and frequency-stabilization of these lasers. The second parts deals with activities led on electro-optic dual comb spectroscopy (EO-DCS), which could be a potential future alternative technique to conventional space-borne IPDA lidars (Integrated Path Differential Absorption). We report on an EO-DCS experiment performed in pulsed regime, using an Er-Yb-doped amplifier delivering up to 92 μJ, 2μs pulses at 10 kHz repetition rate. An absorption line of HCN is sampled simultaneously by a 13-teeth frequency comb, and its transmission is measured with a good agreement with respect to the expectation.
In this paper, we will describe the work carried out within the framework of the evaluation of the reliability of pump combiners under space environment. This work includes the definition of the optical and environmental specifications, the selection of the components and their evaluation. The evaluation of these pump combiner under spatial conditions will show which reference is the most resistant to such conditions but it will also highlight what kind of environment can be destructive.
Based on ChemCam/SuperCam heritage, a laser with improved performances is built on a table top set-up. The optical configuration is implemented into new lasers proposed for next generation of LIBS – Raman instruments.
Over the last decade, frequency comb spectroscopy have led to significant developments in view of the identification of varied species and of the understanding of the structure of matter.
Highly efficient amplification of frequency comb femtosecond oscillators in the high pulse energies regime should allow future applications using this approach to Lidar-type measurements.
We report on the millijoule level design of femtosecond amplifiers near 2 μm wavelength having a great optical efficiency and compactness in order to be carrier in satellites. In addition to space applications, laser systems at 2 μm become more and more popular because they offer elegant solutions to generate ultra-broad band super-continuum in the mid-infrared and for material processing.
Our study helps to compare the optical performance of Tm:YAG, Tm:YAP and Tm:YLF crystals as active media, for designing ultrashort pulse regenerative amplifiers with a high gain and wall-plug efficiencies up to 10%. We will present our approach to ensure the conservation of the initial phase shift between the envelope and the carrier of pulses during amplification.
We primarily discuss an innovative model which proposes a gradual path towards the optimization of any regenerative amplifier using crystalline thulium-based, end-pumped doped rods. This also involves the analysis of sizing criteria based on the assumption of rod-based active media, including the doping content, the length of the rod and the beam size inside.
Lasers with sub-hertz line-width and fractional frequency instability around 1×10-15 for 0.1 s to 10 s averaging time are currently realized by locking onto an ultra-stable Fabry-Perot cavity using the Pound-Drever-Hall method. This powerful method requires tight alignment of free space optical components, precise polarization adjustment and spatial mode matching. To circumvent these issues, we use an all-fiber Michelson interferometer with a long fiber spool as a frequency reference and a heterodyne detection technique with a fibered acousto optical modulator (AOM)1. At low Fourier frequencies, the frequency noise of our system is mainly limited by mechanical vibrations, an issue that has already been explored in the field of optoelectronic oscillators.2,3,4
A new conduction cooled compact laser for Laser Induced Breakdown Spectroscopy (LIBS) on Mars is presented. The laser provides pulses with energy higher than 30mJ at 1μm of wavelength with a good spatial quality. Three development prototypes of this laser have been built and functional and environmental tests have been done. Then, the Qualification and Flight models have been developed and delivered. A spare model is now developed.
This laser will be mounted on the ChemCam Instrument of the NASA mission MSL 2009. ChemCam Instrument is developed in collaboration between France (CESR and CNES) and USA (LANL). The goal of this Instrument is to study the chemical composition of Martian rocks. A laser source (subject of this presentation) emits a pulse which is focused by a telescope. It creates a luminous plasma on the rock; the light of this plasma is then analysed by three spectrometers to obtain information on the composition of the rock.
The laser source is developed by the French company Thales Laser, with a technical support from CNES and CESR. This development is funded by CNES. The laser is compact, designed to work in burst mode. It doesn't require any active cooling.
A new conduction cooled compact laser for laser induced spectroscopy on the Mars Science Laboratory (MSL) to be launched in 2009 is presented. An oscillator combined to amplifiers generates 30mJ at 1μm with a good spatial quality. Development prototype of this laser has been built and characterized. Environmental testing of this prototype is also reported.
ChemCam is a LIBS Instrument mounted on the MSL 2011 NASA mission. The laser transmitter of this Instrument has been developed by the French society Thales Optronique (former Thales Laser) with a strong technical support from CNES. The paper will first rapidly present the performance of this laser and will then describe the postChemCam developments realized on and around this laser for new planetology programs.
T. Lévèque, B. Faure, F. Esnault, O. Grosjean, C. Delaroche, D. Massonnet, C. Escande, Ph. Gasc, A. Ratsimandresy, S. Béraud, F. Buffe, P. Torresi, Ph. Larivière, V. Bernard, T. Bomer, S. Thomin, C. Salomon, M. Abgrall, D. Rovera, I. Moric, Ph. Laurent
PHARAO (Projet d'Horloge Atomique par Refroidissement d'Atomes en Orbite), which has been developed by CNES, is the first primary frequency standard specially designed for operation in space. PHARAO is the main instrument of the ESA mission ACES (Atomic Clock Ensemble in Space). ACES payload will be installed on-board the International Space Station (ISS) to perform fundamental physics experiments. All the sub-systems of the Flight Model (FM) have now passed the qualification process and the whole FM of the cold cesium clock, PHARAO, is being assembled and will undergo extensive tests. The expected performances in space are frequency accuracy less than 3.10-16 (with a final goal at 10-16) and frequency stability of 10-13 τ-1/2. In this paper, we focus on the laser source performances and the main results on the cold atom manipulation.
A new conduction cooled compact laser for SuperCam LIBS-RAMAN instrument aboard Mars 2020 Rover is presented. An oscillator generates 30mJ at 1µm with a good spatial quality. A Second Harmonic Generator (SHG) at the oscillator output generates 15 mJ at 532 nm. A RTP electro-optical switch, between the oscillator and SHG, allows the operation mode selection (LIBS or RAMAN). Qualification model of this laser has been built and characterised. Environmental testing of this model is also reported.
Distributed feedback (DFB) diode lasers are convenient, small footprint and robust single mode laser sources. DFB lasers have an emission linewidth in the MHz to several MHz range, which may be too large for some applications, such as cold atom physics, optical clocks, laser ranging, lidar or gas sensing... Control of the diode forward current allows for the control the frequency of the emitted laser beam.
A new conduction cooled compact laser for Laser Induced Breakdown Spectroscopy (LIBS) on Mars is presented. The
laser provides pulses with energy higher than 30mJ at 1μm of wavelength with a good spatial quality (M2 between 1 and
3 according to the temperature). The performance of the laser is within the specifications on a large temperature range
(-20°C/+20°C). This laser will be mounted on the ChemCam Instrument of the NASA mission MSL 2009 (finally
reported to 2011). The goal of this instrument is to study the chemical composition of Martian rocks. A laser source
(subject of this presentation) emits a pulse. It creates a luminous plasma on the rock, which is then analyzed by three
spectrometers. The laser source was developed by the French company Thales Laser, under funding and with technical
support from CNES. The laser is compact and does not require any active cooling. More recently, the laser was studied
by the LATMOS (Laboratoire Atmosphères, Milieux, Observations Spatiales, former Service d'Aéronomie). The goal of
this study was to make spectral measurements on the laser to evaluate its capacity to be used as a luminous source for
Lidar applications, and in particular for a Doppler Lidar measuring the wind speed. As the laser is very well adapted to
the harsh Martian environments, one of the possible applications would be wind speed measurements on Mars. The first
results obtained by the LATMOS are good and do not show any impossibilities for this target application.
Microlenses arrays are commonly used in CMOS images sensors to focus the incident light onto the photosensitive area of the pixel. These microlenses are fabricated using a thermal reflow method. Currently, due to the fast evolution of CMOS Imager technology, the understanding of the mechanisms involved in microlens formation becomes essential to better control what occurs during the process. We have seen in a previous study that the complexity of the reflow method comes from the competition between two phenomena occurring during the melt bake step: on one hand the surface tension tends to push the resist patterns into a spherical shape, on the other hand the resist crosslinking reaction drastically increases the resist viscosity hindering the microlens formation. In this paper the influence of resist crosslinking, resist volume and resist/substrate interface on the final shape of the microlens has been investigated. It appears that the contact angle between microlens and substrate varies depending on substrate wettability but is the same whatever the resist volume for a given substrate/resist combination. The microlens shape depends also significantly on bake temperature and crosslinking kinetics. In fact the right tuning of process conditions seems to be the key parameter in the control of the final microlens shape because it enables to adjust the kinetics of each mechanism and thus favour the microlens formation with regards to resist crosslinking.
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