Due to its high toxicity, monitoring of hydrogen sulfide (H2S) concentration is essential in many industrial sites (such as natural gas extraction sites, petroleum refineries, geothermal power plants, or waste water treatment facilities), which require sub-parts-per-million sensitivities. We report on a quantum cascade laser-based spectroscopic system for detection of H2S in the midinfrared at ∼7.2 μm. We present a sensor design utilizing Herriott multipass cell and a wavelength modulation spectroscopy to achieve a detection limit of 140 parts per billion for 1-s integration time.
In this work we analyze two aspects of our research towards a laser-based setup for open-path hydrogen sulfide detection. We demonstrate a compact and portable electronic part of the sensing system that can be constructed solely with commercially available, off-the-shelf components. Comparison with the setup that uses benchtop lock-in amplifier for signal demodulation is presented. We also discuss challenges in spectral modelling of H2S transitions in the near-IR spectral region using the data available in HITRAN base. We show that in order to perform correct spectral simulations (for both direct absorption spectroscopy and wavelength modulation spectroscopy) appropriate corrections to the data available in the database have to be applied.
In this work we present a laser-based system for standoff/remote, sensitive detection of gases based on a tunable diode laser source and Wavelength Modulation Spectroscopy method (WMS). System performance was experimentally characterized. The constructed device has proven its capacity of efficient detection of methane in air at the single ppm levels and distances from 10 to 50 m (distance to a scattering object). The minimum detection limit of the system was estimated at the level of 10 ppm-m for the standoff arrangement and the measurement path of approximately 20 m (round trip). Potential application of the device to hydrogen sulfide detection and current limitations in this area are discussed.
In this paper we demonstrate a preliminary work done on employing antimony telluride (Sb2Te3) topological insulator as a saturable absorber for Yb-doped fiber lasers. The material was deposited onto a side-polished fiber by means of a pulsed magnetron sputtering technique. Fabricated absorber was implemented in an all-normal dispersion cavity and allowed for self-starting dissipative soliton generation. The laser emitted stable pulse train at a repetition rate of 17.07 MHz with 4.25 nm broad output spectrum centered around 1039.4 nm. Average output power amounted to 0.54 mW with 32 pJ pulse energy.
In this work, we would like to demonstrate our results on performing (6+1)x1 tapered fiber bundle combiners using a trielectrode fiber splicing system. In our combiners we have used 9/80 μm (core/clad) diameter fibers as single-mode signal input ports. Using this fiber, instead of a conventional 9/125 μm single-mode fiber allowed us to reduce the taper ratio and therefore significantly increase the signal transmission. We have also performed power combiner which is based on the LMA fibers: input signal fiber 20/125μm and passive double clad fiber 25/300 μm at the output.
A new design of an erbium-ytterbium doped fiber amplifier is demonstrated. The amplifier contains a wavelength-tuned
loop resonator for the 1 μm signal. The amplified spontaneous emission (ASE) from Yb ions is used to stimulate a laser
emission at several wavelengths from the 1 μm band in the 1550 nm amplifier. The wavelength of this lasing is selected
by introducing a spectral filter. The results show, that the efficiency of the amplifier at nominal 1550 nm wavelength can
be increased by introducing a feedback loop with 1040 nm and 1050 nm filters. This loop also protects the Er-Yb
amplifier from parasitic lasing and allows output power scaling without risk of self-pulsing at 1 μm.