Recently, different substances designated for local anesthesia or as substances harmful to health have had a boom in their illegal use to perpetrate crimes associated with adulterated beverages. These substances are colorless and odorless liquids, almost imperceptible to the taste. A sensing system based on a double-aperture common-path interferometer for rapid detection of different types of adulteration (methanol and ethanol) added in different types of alcoholic beverages (brandy and rum) is proposed. The method for determining the adulteration degree is based on measurement of variations on the interference free spectral range from a one-shot interferogram.
We demonstrate generation of passive Q-switched laser pulses of a linear cavity Er-Yb double-clad fiber laser based on the use of a fiber ball lens coated with a thin film of titanium oxynitride (TiOxNy). The fiber ball lens is inserted within the laser cavity in a reflection configuration, alongside a reflecting mirror. Dual-wavelength and tunable single operations of the laser is obtained with the ball lens acting as an interference filter. At the same time, the ball lens coated with TiOxNy, deposited by DC reactive magnetron sputtering, allows saturable absorption suitable for generation of passive Q-switched laser pulses. Single wavelength laser generation tuned in a range of ~4.5 nm and simultaneous dual wavelength generation with separation of 5.1 nm are obtained at the 1.55 µm wavelength region. Pasive Q-switched pulses with maximum repetition rate of 124 kHz, minimum duration of 3.6 µs and peak power of 360 mW are achieved. The maximum pulse energy estimated is of 1.3 µJ.
We present an optical sensor for solute concentration in solutions by using aluminum-doped zinc oxide (AZO) coatings on silica single-mode/coreless/single-mode and single-mode/multimode/single-mode fiber structures. The fiber sensor is based on the detection of the second lossy-mode resonance (LMR) order of the AZO coated fiber structures which covers the near-infrared C and L wavelength bands. AZO thin films with Zn:Al atomic concentration proportions of 92%:8% were deposited on the fiber structures by radio frequency magnetron sputtering technique. Wavelength displacement of the second order LMR notch as a function of concentration variation on isopropyl-alcohol/glycerin liquid mixtures where measured by a simple optical transmission setup, detected in the 1.55 μm wavelength range. In glycerin concentration percentages (c%) variations from 5% to 30%, maximum sensitivity of 1.42 nm/c% was obtained for coreless-fiber-based structures.
We report an experimental study erbium-doped fiber laser for gas pressure detection in the L-band wavelength region by laser intracavity absorption spectroscopy. By using a high-birefringence fiber optical loop mirror as spectral filter within the ring cavity laser, the wavelength of the generated laser line is finely selected and tuned in a range of ~10 nm in order to select the wavelength where the gas absorption line is exhibited. Experimental results for detection of CO2 pressure with absorption at 1573.2 nm are shown and discussed. The proposed fiber laser sensor exhibits reliability and stability for gas detection with absorption in the L-band such as CO2, CO, and H2S.
We report an in-fiber structure based on the use of a multimode fiber segment and a double cladding fiber segment, and its application as spectral filter in an erbium-doped fiber laser for selection and tuning of the laser line wavelength. The output transmission of the proposed device exhibit spectrum modulation of the input signal with free spectral range of ~21 nm and maximum visibility enhanced to more than ~20 dB. The output spectrum of the in-fiber filter is wavelength displaced by bending application which allows a wavelength tuning of the generated laser line in a range of ~12 nm. The use of the proposed in-fiber structure is demonstrated as a reliable, simple, and low-cost wavelength filter for tunable fiber lasers design and optical instrumentation applications.
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