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In this work, mode-locked thulium-doped fiber lasers operating in the 2 µm wavelength region were demonstrated using tantalum aluminum carbide (Ta2AlC)-based saturable absorbers (SAs) utilizing the evanescent wave interaction. The Ta2AlC MAX Phase was prepared by dissolving the Ta2AlC powder in isopropyl alcohol and then deposited onto three different evanescent field-based devices, which were the tapered fiber, side-polished fiber, and arc-shaped fiber. Flame-brushing and wheel-polishing techniques were used to fabricate the tapered and arc-shaped fibers, respectively, while the side-polished fiber was purchased commercially. All three SA devices generated stable mode-locked pulses at center wavelengths of 1937, 1931, and 1929 nm for the tapered, side-polished, and arc-shaped fibers. The frequency of the mode-locked pulses was 10.73 MHz for the tapered fiber, 9.58 MHz for the side-polished fiber, and 10.16 MHz for the arc-shaped fiber. The measured pulse widths were 1.678, 1.734, and 1.817 ps for each of the three SA devices. The long-term stability of the mode-locked lasers was tested for each configuration over a 2-h duration. The lasers also showed little to no fluctuations in the center wavelengths and the peak optical intensities, demonstrating a reliable, ultrafast laser system.

No abstract

A simple mirrorless plastic optical fiber displacement sensor was used to determine the concentration of paracetamol (PCM) in an aqueous solution. Paracetamol concentrations between 5 and 45 ppm were tested by the proposed sensor. With a mirror, the substantial sensitivity observed by an output power changed against displacement of 0.0403 mW/μm for the front slope and 0.023 mW/μm for the back slope with linearities of more than 99%. On the other hand, nonmirror reflector showed a sensitivity of 0.0006 mW/μm for the front slope and 0.0002 mW/μm for the back slope for the case of a red reflector and a sensitivity of 0.0007 mW/μm and 0.0003 mW/μm for the front and the back slope, respectively, for the case of a white reflector. The sensor sensitivity for the red and white coloured papers, which were used as the nonmirror reflectors and the mirror reflector itself against changing PCM concentrations, was 0.0004 mW/ppm, 0.0008 mW/ppm, and 0.02 mW/ppm, respectively. The experimental results indicated that the sensor was not only able to detect and measure the concentration of PCM in aqueous solutions but was also very stable with the additional advantages of a cost-effective and practical design that is highly beneficial for real-world sensing applications.

In this work, mode-locked thulium-doped fiber lasers operating in the 2 µm wavelength region were demonstrated using tantalum aluminum carbide (Ta2AlC)-based saturable absorbers (SAs) utilizing the evanescent wave interaction. The Ta2AlC MAX Phase was prepared by dissolving the Ta2AlC powder in isopropyl alcohol (IPA) and then deposited onto three different evanescent field-based devices, which were the tapered fiber, side-polished fiber (SPF), and D-shaped fiber. Flame-brushing and wheel-polishing techniques were used to fabricate the tapered and D-shaped fibers, respectively, while the side-polished fiber was purchased commercially. All three SA devices generated stable mode-locked pulses at center wavelengths of 1937, 1931, and 1929 nm for the tapered, side-polished, and D-shaped fibers. The frequency of the mode-locked pulses was 10.73 MHz for the tapered fiber, 9.58 MHz for the side-polished fiber, and 10.16 MHz for the D-shaped fiber. The measured pulse widths were 1.678, 1.734, and 1.817 ps for each of the three SA devices. The long-term stability of the mode-locked lasers was tested for each configuration over a 2-hour duration. The lasers also showed little to no fluctuations in the center wavelengths and the peak optical intensities, demonstrating a reliable, ultrafast laser system.