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.
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.
Over the last few years, there has been an increasing demand for medium-grade gyroscopes to fill the gap (in terms of cost and performance) between MEMS and current optical devices. There has also been a longstanding quest for a compact high-grade gyroscope to reduce the size of current inertial navigation units and make them available for most carriers (extending their time of GPS-free autonomous navigation). In this paper, we will describe two approaches we are following towards these goals, with support from the European Space Agency: the solid-state ring laser gyroscope and the resonant hollow-core fiber optic gyroscope.
We present a simple analysis of the design of a passive miniature resonant optical gyroscope. By combining the requirements on the angular random walk and the bias stability, we end up with simple expressions of the minimum diameter of the ring waveguide cavity and the maximum power that should be used to probe it. Using state-of-the-art performances of photonic integrated circuit and whispering gallery mode technologies in terms of propagation losses and mode size, we show that tactical grade gyroscope performances can be achieved with a diameter of a few cm provided the detrimental influence of the Kerr effect is mitigated using, for instance, an active control of the unbalance in the intensities. We further extend the analysis to medium performance gyroscope and give some hints on the efforts to be made to potentially demonstrate a miniature resonant optical gyroscope with this level of performance.
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
This contribution deals with Carbon Nanotubes Field Effect transistors (CNTFETs) based gas sensors fabricated using a
new dynamic spray based technique for SWCNTs deposition. This technique is compatible with large surfaces, flexible
substrates and allows to fabricate high performances transistors exploiting the percolation effect of the SWCNTs
networks achieved with extremely reproducible characteristics. Recently, we have been able to achieve extremely
selective measurement of NO<sub>2</sub> , NH<sub>3</sub> and DMMP using four CNTFETS fabricated using different metals as electrodes
(Pt, Au, Ti, Pd), exploiting the specific interaction between gas and metal/SWCNT junction. In this way we have identify
a sort of electronic fingerprinting of the gas. The time response is evaluated at less than 30sec and the sensitivity can
reach 20ppb for NO<sub>2</sub>, 100ppb for NH<sub>3</sub> and 1ppm for DMMP (Di-Methyl-Methyl-Phosphonate).
To enhance discrimination of UV-laser-induced-fluorescence based bio-aerosol-detection-system, a UV-laser is described that allows multiple wavelength excitation of bio-aerosols and both fluorescence spectral and time-decay analysis. The latter requiring sub-ns pulse duration, a two-stage-amplifier boosts a 20-µJ-1064-nm-500-ps-actively-Q-Switch microchip-oscillator output energy up to 2.5 mJ. After frequency doubling and beam splitting, 20-µJ-293-and-337-nm pulses are generated by two different periodically-poled-KTP (parametric generation) and BBO (frequency doubling) crystal arrangements. In order to get distinct fluorescence signals for each wavelength, the beams are then time-delayed with two optical fibers of different lengths and launched into a chamber for bio-aerosol excitation connected to a fast detection system.
Laser Induced Fluorescence (LIF) could permit fast early warning systems either for point or stand-off detection if a reliable classification of warfare biological agents versus biological or non-biological fluorescing background can be achieved. In order to improve LIF discrimination capability, a new system is described in which the fluorescence pattern is enriched by the use of multiple wavelength delayed excitation while usual spectral fluorescence analysis is extended to time domain to use both aspects as criteria for classification. General considerations and guidelines for the system design are given as well as results showing good discrimination between background and simulants.
Fluorescence induced by ultraviolet laser light has shown a strong potential to help detect and identify hazardous bioaerosols. After several demonstrations limited to standard 266 nm or 355 nm sources, recent developments emphasized the advantages of tunable excitation or time-resolved experiments to increase discrimination capabilities. Taking advantage of the recent availability of frequency converting crystals with unprecedented efficiency, we present a three-stage laser design suited to the generation of 500 picoseconds pulses of several microjoules ruggedly tunable from 290 to 350 nm.
For DPSSL applications at low duty cycle (typically 150 microsecond(s) /20 Hz), we have developed a new concept of `High Brightness' stacked arrays, which leads to power density of 10 kW/cm<SUP>2</SUP>, and to 40 kW/cm<SUP>2</SUP> when directly coupled to a lens-duct. The high intensity is made possible thanks to a new proprietary stacking technology that permits a stacking pitch of only 100 micrometers : the principle is to directly stack the arrays without any heat spreaders other than the arrays themselves. When compared to standard commercial QCW stacked arrays, the benefits of using these high brightness laser diodes pumping sources are the following: (1) an important cost reduction related to a drastic simplification in the assembling process, and (2) an improved pumping efficiency associated with an improved brightness (approximately 1 factor 4), consequence of a reduced pitch between linear bar arrays. High-efficiency, frequency-quadrupled, end-pumped 8 mJ, 12-ns-long UV pulses 0.266 micrometers Nd:YAG laser has been developed using these high brightness pump sources. This air-cooled laser is an attractive alterative to the more conventional millijoules-range UV source. A compact high energy 300 mJ Q-switched diode-pumped laser has been developed. Laser performances and integration level demonstration contribute to a preliminary laser design for future airborne laser applications.
A high-brightness component is used to longitudinally pump Nd:YAG and Nd:YVO<SUB>4</SUB> crystals. The light is focused by a simple, compact and efficient nonimaging concentrator. A 50% at 1.064 micrometer and a 25% at 0.532 micrometer optical-optical efficiencies were demonstrated with a near TEM<SUB>00</SUB> beam.
A new simple, compact, and efficient optical device is presented which allows any commercially available laser diode arrays or stacks to longitudinally pump laser materials. A Nd:YVO<SUB>4</SUB> laser was built and an optical-optical efficiency as high as 50% was demonstrated with a diffraction limited output beam.
The CNES (Centre National d'Etudes Spatiales, French space agency) established the laser system characteristics for Mars-Earth spatial communications using the Pulse Position Modulation technique. Today, diode-pumped solid-state lasers are under intense research and development. Indeed, in comparison with flash-lamp pumped laser, they offer significant advantages in terms of efficiency, compactness, lifetime and high beam quality. We have demonstrated that gain-switch operation is preferable to Q-switching technique to control and to obtain a good pulse width and amplitude reproducibility. The pulse width requirement and the laser-diode pumping scheme lead to a preferred configuration based on a microchip laser oscillator coupled to an amplifier. Best results were performed with a Nd:YVO<SUB>4</SUB> microchip longitudinally-pumped by fiber-coupled laser-diode bar. Diffraction limited beam, 15 ns pulse width and 100 kHz repetition rate were achieved. The output beam was actually also single frequency and linearly polarized. A transversally-diode-pumped 7-pass amplifier is also demonstrated.
The CNES (Centre National d'Etudes Spatiales) established the laser system characteristics for Mars-Earth spatial communications using the Pulse Position Modulation (PPM) technique. Today, diode-pumped solid-state lasers are under intense research and development. Indeed, in comparison with flash-lamp pumped laser, they offer significant advantages in terms of efficiency, compactness, lifetime and high beam quality. We have demonstrated that gain- switch operation is preferable to Q-switching technique to control and to obtain a good pulse width and amplitude reproducibility. The pulse width requirement and the laser-diode pumping scheme lead to a preferred configuration based on a microchip laser oscillator coupled to an amplifier. Experiments were performed with several microchips of Nd:YAG and Nd:YVO<SUB>4</SUB> crystals pumped by fiber-coupled laser-diode. The design of the transversally-pumped amplifier is based on a modified multipass 1:1 confocally reimaging longitudinally-pumped amplifier proposed by Plaessmann et al.