The authors report the detection of nitrous oxide gas using intracavity fiber laser absorption spectroscopy. A gas cell based on a hollow-core photonic crystal fiber was constructed and used inside a fiber ring laser cavity as an intracavity gas cell. The fiber laser in the 1.55 μm band was developed using a polarization-maintaining erbium-doped fiber as the gain medium. The wavelength of the laser was selected by a fiber Bragg grating (FBG), and it matches one of the absorption lines of the gas under investigation. The laser wavelength contained multilongitudinal modes, which increases the sensitivity of the detection system. N2O gas has overtones of the fundamental absorption bands and rovibrational transitions in the 1.55 μm band. The system was operated at room temperature and was capable of detecting nitrous oxide gas at sub-ppmv concentration level.

The authors demonstrate a fibre laser system for detection of the greenhouse gas, nitrous oxide (N2O), at sub-ppmv concentration levels. The fibre laser is stabilized by a saturable absorber. The sensitivity is enhanced by multiple circulations of ASE light under threshold conditions, and multi-longitudinal mode oscillation of the laser. An intra-cavity Herriott cell of effective path length 30 m was used to detect the P (12) rotational line of N2O at ~1522.20 nm.Index Terms-Laser spectroscopy, intracavity spectroscopy, fibre laser, fibre sensors, gas sensor

We report a novel CW tunable high-power single-longitudinal-mode fiber laser with a linewidth of ∼9 MHz. A tunable fiber Bragg grating provided wavelength selection over a 10 nm range. An all-fiber Fabry-Perot filter was used to increase the longitudinal mode spacing of the laser cavity. An unpumped polarization-maintaining erbium-doped fiber was used inside the cavity to eliminate mode hopping and increase stability. A maximum output power of 300 mW was produced while maintaining single-longitudinalmode operation.

We report on a single-longitudinal-mode singlewavelength fiber laser and its applications for measuring localized temperature variation. The laser was developed using a fiber Bragg grating. The laser wavelength was single-longitudinal-mode with optical signal-to-noise ratio (OSNR) of more than 40 dB. The temperature sensitivity of the system was 11.08 pm/ C. To demonstrate the promising application of the laser sensor developed, we used the sensor to monitor the localized temperature of TiO 2 nanotubes during the photochemical process, and superparamagnetic iron oxides nanoparticles when exposed to low frequency magnetic field. The output of the laser was monitored using a scanning Fabry-Perot spectrum analyzer of resolution 6.7 MHz and an optical spectrum analyzer of resolution 3.75 GHz.

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