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- PublicationAccès libreFrequency-stabilised laser reference system for trace-gas sensing applications from spaceA four-wavelength low-power continuous-wave frequency laser reference system has been realised in the 935.4-nm range for water vapour differential absorption lidar (DIAL) applications. The system is built around laboratory extended-cavity and DFB diode lasers. Three lasers are directly locked to three water vapour absorption lines of different strength, whereas the wavelength of the fourth laser lies out of any absorption line (offline). On-line stabilisation is performed by wavelength modulation spectroscopy technique, while precise offline stabilisation is realised by an offset locking at 18.8 GHz. Offset frequency larger than 320 GHz has also been demonstrated at 1.55 μm, based on an all-fibre optical frequency comb. First steps towards the use of a photonic crystal fibre as ultra compact reference cell with long optical pathlength were realised. The developed techniques for direct and offset-lock laser stabilisation can also be applied to other gases and wavelengths, provided the required optical components are available for the laser wavelength considered.
- PublicationAccès libreDiode laser frequency stabilisation for water vapour differential absorption sensingWe describe a low-power continuous-wave laser system for water-vapour sensing applications in the 935-nm region. The system is based on extended-cavity diode lasers and distributed-feedback lasers and delivers four single-mode frequency-stabilised optical signals. Three lasers are locked to three water-vapour absorption lines of different strengths, whereas the fourth lies outside any absorption line. On-line stabilisation is performed by wavelength-modulation spectroscopy using compact water-vapour reference cells. An offset-locking technique implemented around an electrical filter is applied for the stabilisation of the off-line slave laser to an on-line master laser at a frequency detuning of 18.8 GHz. Stabilities in the order of 15 MHz over one day were observed for the strongest lines, at the detection limit of the measurement instrumentation. The developed techniques and schemes can be applied to other wavelength ranges and molecular species. Differential absorption lidar instrumentation can in particular benefit from such a system when the stabilised lasers serve as injection seeders to pulsed power oscillators.
- PublicationAccès libreMethods and evaluation of frequency aging in distributed-feedback laser diodes for rubidium atomic clocksDistributed-feedback laser diodes emitting at 780nm have been evaluated, with respect to the aging of the injection current required for reaching the rubidium D2 resonance line. Results obtained for lasers operating in air and in vacuum for 9 months are reported. When operated at constant temperature, the laser current required for emission at the wavelength of the desired atomic resonance is found to decrease by 50 to 80 uA per month. The impact of this result on the lifetime and long-term performances of laser-pumped rubidium atomic clocks is discussed. © 2011 Optical Society of America OCIS codes: 140.2020, 350.4800.
- PublicationAccès libreEvaluation of the frequency stability of a VCSEL locked to a micro-fabricated Rubidium vapour cellWe present our evaluation of a compact laser system made of a 795 nm VCSEL locked to the Rubidium absorption line of a micro-fabricated absorption cell. The spectrum of the VCSEL was characterised, including its RIN, FM noise and line-width. We optimised the signal-to-noise ratio and determined the frequency shifts versus the cell temperature and the incident optical power. The frequency stability of the laser (Allan deviation) was measured using a high-resolution wavemeter and an ECDL-based reference. Our results show that a fractional instability of ≥ 10-9 may be reached at any timescale between 1 and 100'000 s. The MEMS cell was realised by dispensing the Rubidium in a glass-Silicon preform which was then, sealed by anodic bonding. The overall thickness of the reference cell is 1.5 mm. No buffer gas was added. The potential applications of this compact and low-consumption system range from optical interferometers to basic laser spectroscopy. It is particularly attractive for mobile and space instruments where stable and accurate wavelength references are needed.
- PublicationAccès libreLaser offset-frequency locking up to 20 GHz using a low-frequency electrical filter techniqueA simple, easy-to-implement, and robust technique is reported to offset lock two semiconductor lasers with a frequency difference easily adjustable up to a couple of tens of gigahertz (10 and 19 GHz experimentally demonstrated). The proposed scheme essentially makes use of low-frequency control electronics and may be implemented with any type of single mode semiconductor laser, without any requirement for the laser linewidth. The technique is shown to be very similar to the wavelength modulation spectroscopy method commonly used for laser stabilization onto molecular absorption lines, as demonstrated by experimental results obtained using 935 nm laser diodes.
- PublicationMétadonnées seulementDevelopment of tuneable, narrow-band, and frequency stabilised laser heads in Observatoire Cantonal de NeuchâtelWe describe our investigations on tuneable, narrowband and frequency stabilised laser heads. The work is motivated by the potentials of highly stable and narrowband laser light sources for a variety of technical and scientific applications and in particular for atomic clocks and high resolution space instruments.