Atomic clocks based on Coherent Population Trapping (CPT) in cesium  or other sensors based on CPT require the development of specific low noise laser sources at resonant wavelengths. For instance, the double lambda scheme for CPT probed by lin ⊥ lin laser beams, which has been shown to create Raman–Ramsey fringes with a larger contrast than the usual simple lambda scheme in , requires the availability of two cross-linearly polarized frequencies at 852 nm with a low beat note phase noise and a low intensity noise. One way to generate these two frequencies with low amplitude and phase noises is to build a dual-frequency VECSEL (Vertical External Cavity Surface Emitting Laser) . In this talk we will present our efforts to understand the physical origin of the laser amplitude and phase noises , and the developments that we have made to reduce these noises to the levels necessary to achieve a relative clock stability of 10-13 at 1 s integration time.
The generation of optically carried radio frequency (RF) is an important issue in the area of microwave photonics (MWP), which has gained tremendous developments and has a bright future . Dual-frequency vertical-external-cavity surface-emitting laser (DF-VECSEL) , sustaining two cross-polarized laser in a same optical cavity, is an attractive solution to generate such an optically carried RF signal. With class-A dynamics, DF-VECSEL can exhibit a low intensity noise and be free of relaxation oscillation (RO), due to the fact that the lifetime of the photons inside the external cavity can be longer than the lifetime of the semiconductor gain media carriers. Additionally, DF-VECSEL is also interesting for atomic clocks. Indeed, coherent population trapping (CPT) atomic clock  is promising to realize miniaturized atomic clocks, but requires a trade-off between performance and size. Recently, a report gives out a solution using two pulses and a double lambda atomic system to obtain high contrast Ramsey fringes . It is expected that the trade-off can be improved by the combination of DF-VESCEL and the double lambda atomic system configuration of CPT atomic clocks . One key parameter of the DF-VECSEL for such applications is its noise. We report in this paper our efforts to understand the origin of the amplitude and phase noises of the laser and to reduce these noises by optimizing the laser cavity design and the pumping architecture.
1. J. Capmany, José and D. Novak. Nature Photonics 1, 319 (2007).
2. G. Baili, L. Morvan, M. Alouini, D. Dolfi, F. Bretenaker, I. Sagnes, and A. Garnache. Opt Lett. 34, 3421 (2009).
3. J. Vanier, Appl. Phys. B 81, 421 (2005).
4. T. Zanon et al., Phys. Rev. Lett. 94, 193002 (2005).
5. P. Dumont et al. J. Lightwave Technol. 32, 3817 (2014.
Quantum technologies have been identified as breakthrough technologies with a potential high impact on future navigation, sensing and communication systems since the end of the 90’s. In this paper we will review how these technologies can contribute to electromagnetic spectrum dominance through the use of SHB (spectral hole burning) based spectral holography and of NV (nitrogen vacancy) centers in diamond. Quantum technologies, combined with integration techniques, will also improve the performances of navigation systems thanks to ultra-precise compacts atomic clocks, accelerometers and gyros.
Through the European Defence Agency, the Joint Investment Programme on CBRN protection funded the project AMURFOCAL to address detection at stand-off distances with amplified quantum cascade laser technology in the longwave infrared spectral range, where chemical agents have specific absorptions features.
An instrument was developed based on infrared backscattering spectroscopy. We realized a pulsed laser system with a fast tunability from 8 to 10 μm using an external-cavity quantum cascade laser (EC-QCL) and optical parametric amplification (OPA). The EC-QCL is tunable from 8 to 10 μm and delivers output peak powers up to 500 mW. The peak power is amplified with high gain in an orientation-patterned gallium arsenide (OP-GaAs) nonlinear crystal. We developed a pulsed fiber laser acousto-optically tunable from 1880 to 1980 nm with output peak powers up to 7 kW as pump source to realize an efficient quasi-phase matched OPA without any mechanical or thermal action onto the nonlinear crystal. Mixing the EC-QCL and the pump beams within the OP-GaAs crystal and tuning the pump wavelength enables parametric amplification of the EC-QCL from 8 to 10 μm leading to up to 120 W peak power. The output is transmitted to a target at a distance of 10 – 20 m. A receiver based on a broadband infrared detector comprises a few detector elements. A 3D data cube is registered by wavelength tuning the laser emission while recording a synchronized signal received from the target. The presentation will describe the AMURFOCAL instrument, its functional units and its principles of operation.
Within the framework of the first European Defence Agency (EDA) call for protection against chemical, biological, radiological and nuclear threats (CBRN Protection) we established a project on active multispectral reflection fingerprinting of persistent chemical agents (AMURFOCAL). A first paper on the project AMURFOCAL has been issued last year on the SPIE conference in Warsaw, Poland. This follow up paper will be accompanied by an additional paper that deals specifically with the aspect of the 100 W-level peak power laser system tunable in the LWIR. In order to close a capability gap and to achieve detection at stand-off distances our consortium built a high peak power pulsed laser system with fast tunability from 8 to 10 μm using an external-cavity quantum cascade laser and optical parametric amplification. This system had to be tested against different substances on various surfaces with different angles of inclination to evaluate the ability for an active stand-off technology with an eye-safe laser system to detect small amounts of hazardous substances and residues. The scattered light from the background surface interferes with the signal originating from the persistent chemicals. To account for this additional difficulty new software based on neutral networks was developed for evaluation. The paper describes the basic setup of the instrument and the experiments as well as some first results for this technology.
We report on the development of a prototype solidstate ring laser gyro based on a diode-pumped neodymium-doped yttrium aluminum garnet crystal as the gain medium. We describe in this paper how we circumvent mode competition between the counter-propagating modes using a feedback loop acting on the differential losses. We then show how the non-linear frequency response can be significantly improved by vibrating the gain medium along the laser axis, leading to a behavior similar as a typical Helium-Neon ring laser gyro. We finally discuss the undergoing improvements for achieving high inertial performance with this device, with significant potential benefits in terms of cost and robustness as compared to other highperformance gyro technologies.
Remote detection of toxic chemicals of very low vapour pressure deposited on surfaces in form of liquid films, droplets or powder is a capability that is needed to protect operators and equipment in chemical warfare scenarios and in industrial environments. Infrared spectroscopy is a suitable means to support this requirement. Available instruments based on passive emission spectroscopy have difficulties in discriminating the infrared emission spectrum of the surface background from that of the contamination. Separation of background and contamination is eased by illuminating the surface with a spectrally tune-able light source and by analyzing the reflectivity spectrum.
The project AMURFOCAL (Active Multispectral Reflection Fingerprinting of Persistent Chemical Agents) has the research topic of stand-off detection and identification of chemical warfare agents (CWAs) with amplified quantum cascade laser technology in the long-wave infrared spectral range. The project was conducted under the Joint Investment Programme (JIP) on CBRN protection funded through the European Defence Agency (EDA).
The AMURFOCAL instrument comprises a spectrally narrow tune-able light source with a broadband infrared detector and chemometric data analysis software. The light source combines an external cavity quantum cascade laser (EC-QCL) with an optical parametric amplifier (OPA) to boost the peak output power of a short laser pulse tune-able over the infrared fingerprint region. The laser beam is focused onto a target at a distance between 10 and 20 m. A 3D data cube is registered by tuning the wavelength of the laser emission while recording the received signal scattered off the target using a multi-element infrared detector. A particular chemical is identified through the extraction of its characteristic spectral fingerprint out of the measured data.
The paper describes the AMURFOCAL instrument, its functional units, and its principles of operation.
We report our progress towards a high performance solid-state ring laser gyro using a diode-pumped Nd-YAG crystal as the gain medium. We then discuss the possibility of including in this device a highly dispersive medium, which could serve for testing the recent proposal by Shariar and coworkers of a fast-light ring laser gyro. This discussion is supported in particular by the recent results obtained at Laboratoire Aimé Cotton with electromagnetically induced transparency in metastable helium
Among quasi-phase matching (QPM) materials, PPLN suffers from a limited transparency, strongly limiting both the
output power and the beam quality above 4 μm. We are developing a new QPM technology based on Orientation-
Patterned Gallium Arsenide (OP-GaAs) crystals, transparent up to 16 μm and showing excellent nonlinear and thermal
properties and very low losses (<0.02 cm-1).
We demonstrated with such samples a high-repetition rate tunable OPO attractively pumped by a remote Thulium fiber
laser and integrated in a 25×30×6 cm transportable head. A 3 W level output in the 3-5 μm range was obtained with a
53% efficiency and an unprecedented beam quality (M2=1.4), making this module most suited to study directed infrared