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Query: UMLS:C0002986 (Fabry)
 5,646 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Continuous, broad, and single-mode wavelength tuning of thermoelectrically cooled short-pulse quantum-cascade lasers is demonstrated with a combination of coarse grating tuning and fine phase tuning of the gain element. This approach overcomes the problem of a poor facet antireflection coating of the gain chip by shifting a Fabry-Perot longitudinal mode to coincide with the desired grating-selected wavelength. The 9-microm laser was tested with NH3 gas absorption and showed fine frequency tuning at a rate of 31 MHz/step and a time-averaged linewidth of 500-750 MHz. The total tuning range was 9.08-9.36 microm and was limited only by the intrinsic gain of the device.
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PMID:Broadband, continuous, and fine-tune properties of external-cavity thermoelectric-stabilized mid-infrared quantum-cascade lasers. 1295 34

A porous graphene-coated optical fiber Fabry-Perot interferometer (G-FPI) and Fe3O4-graphene nanocomposite coated Fabry-Perot interferometer (FG-FPI) have been investigated and compared for the detection of ammonia gas at room temperature. The sensor probes were subjected to ammonia concentrations varying from 1.5 ppm to 150 ppm. An increased sensitivity was observed for FG-FPI (36 pm ppm-1) when compared with that of G-FPI (25 pm ppm-1). The observed sensor detection limits for FG-FPI and G-FPI were around 7 and 10 ppb, respectively. The sensing mechanism was based on the change in refractive index/dielectric constant of the material; which changed the conductivity of coated material in presence of NH3. It was observed that the modified refractive index induced a wavelength shift in the FPI. The highly porous structure of graphene and the uniform dispersion of Fe3O4 nanoparticles into this framework effectively facilitated the target gas diffusion and hence improved the sensing performance. The sensing was correlated to the oxygen vacancies on the Fe3O4 surfaces and the depletion region manipulations with the ammonia interactions along with Schottky-type electron conductivity via the conducting graphene assembled porous carbon framework. The mathematical evaluation of the phenomenon also justified the excellent repeatability and reversibility of this sensitive, room temperature sensor.
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PMID:Fe3O4-decorated graphene assembled porous carbon nanocomposite for ammonia sensing: study using an optical fiber Fabry-Perot interferometer. 2956 Sep 94