3D-printed Tilt Sensor based on an embedded Two-mode Fiber Interferometer

A 3D-printed tilt fiber sensor using a two-mode fiber interferometer (TMFI) as the sensing mechanism has been demonstrated. The TMFI was constructed by splicing single-mode fibers (SMF28s) at both ends of a two-mode fiber (TMF) to generate a comb-like interference spectrum that is sensitive to bending. A 3D-printed cantilever with a weight attached to one end was used to induce bending as the structure was tilted and by embedding the TMFI onto the 3D printed cantilever, different tilt angles can be measured, as a result of the bending of the fiber. The TMFI exhibited a linear response towards the tilt angles, θ, with a responsivity of 1 × 10-2 nm/deg at negative θ (0 to -90°) and 5 × 10-3 nm/deg at positive θ (0 to 90°), respectively. The sensor was able to detect small angle changes in increments as small as 1° and it performs better than embedded FBG sensors. The tilt sensor proposed has a small form factor and simple design, as well as being cost-effective and light-weight, thus showing significant potential for a variety of civil engineering applications

Passively Q-switched thulium-doped fiber laser with silver-nanoparticle film as the saturable absorber for operation at 2.0 μm

In this work, a compact thulium-doped fiber laser with a Q-switched output is proposed and demonstrated. A thulium-doped fiber is used for the laser, with a peak absorption of 200 dB m-1 at 790 nm and a cutoff wavelength of 1350 nm as the primary gain medium, and a silver-based saturable absorber as the pulse generation mechanism. The pulses obtained from the proposed laser have repetition rates from 38.3 kHz up to 56.2 kHz, with a pulse width as low as 4.2 μs and pulse energy as high as 67.3 nJ at a maximum pump power of 228.8 mW. The generated pulses are highly stable, showing no changes or fluctuations over operation for a period of 60 min, and further validated with signal-to-noise ratios of 57.0 dB and 59.5 dB in the optical and frequency domains respectively. The proposed laser has high potential for eye-safe applications in manufacturing and medicine

Q-switched thulium/holmium fiber laser with gallium selenide

A passively Q-switched thulium/holmium fiber laser with a gallium selenide (GaSe) saturable absorber (SA) is proposed and demonstrated for the first time. The GaSe based SA is prepared by mechanical exfoliation and inserted into the proposed laser cavity to generate Q-switched pulses. Stable Q-switching operation is achieved at 1986.0 nm, with output pulse repetition rates ranging from 22.9 kHz to 32.3 kHz over a pump power range of 112.0 mW to 235.0 mW. The generated Q-switched pulses have a maximum pulse energy of 120.3 nJ and minimum pulse width of 6.9 μs. The proposed thulium/holmium fiber laser with GaSe SA will be able to cater to multiple applications requiring pulsed laser outputs in the 2.0 μm regio

70 nm, broadly tunable passively Q-switched thulium-doped fiber laser with few-layer Mo0.8W0.2S2 saturable absorber

In this work, a thin Mo0.8W0.2S2 film is proposed and fabricated for the use as a saturable absorber (SA) in a thulium-doped fiber laser (TDFL) cavity. The few-layer Mo0.8W0.2S2 nanoparticles are obtained through hydrothermal exfoliation as a thin film and suspended in a polymer host, which is then placed between two fiber ferrules to serve as an SA. The proposed laser is capable of generating outputs with a maximum repetition rate of 65.79 kHz and a minimum pulse width of 1.84 µs at the maximum pump power of 168.92 mW, as well as pulse energies andpeak powers as high as 35.73 nJ and 13.92 mW. The laser also has a broad tuning output from 1927.2 nm to 1996.8 nm, giving a tuning band of about 70 nm. The generated pulses are stable with a signal-tonoise ratio of 50.0 dB. The proposed laser has a high potential for operation near the 2000 nm wavelength region, with multiple bio-medical and sensing applications

Tunable passively Q-switched thulium-doped fiber laser operating at 1.9 μm using arrayed waveguide grating (AWG)

Thulium-doped fiber lasers (TDFLs), operating in the 1.8–2.0 µm wavelength region, have been viewed as an important research topic, due to their potential in various fields of applications. However, the growing need to advance the development of applications in various fields for instance medicine and environment sensor, has led to a deeper and specific study of Q-switched TDFLs with wavelength tunability. In this paper, a stable, tunable Q-switched TDFL operating in a wavelength range near to 1.9 µm by exploiting the use of a multiwall carbon nanotube (MWCNT)-based thin film as a saturable absorber (SA), and the use of an arrayed waveguide grating (AWG) for wavelength tunability, is presented. The tuning range of the Q-switched pulses generated covered a wavelength range that spanned from 1871.6 nm to 1888.8 nm. The repetition rate of the generated Q-switched pulses covers a range of frequency starting from 41.19 kHz to 68.3 kHz with a change in pump power from 242.2 mW until 360.9 mW

Tunable single wavelength erbium-doped fiber ring laser based on in-line Mach-Zehnder strain

A tunable single-wavelength of an erbium-doped fiber ring laser is proposed and demonstrated. The laser integrates a tapered in-line Mach-Zehnder interferometer (IMZI) in its ring loop as an intracavity filter. The light spectrum is adjusted by changing an axial strain of the interferometer in a 60 μm range. As a result, a total tuning range of 6.19 nm that covers the wavelength from 1552.94 nm to 1559.13 nm is observed, and the sensitivity of 103.5 pm/μm is recorded. This high sensitivity lasing behavior is useful for high selectivity and fine tuning for narrow wavelength applications

Novel 3D-printed biaxial tilt sensor based on fiber Bragg grating sensing approach

In this work, a novel 3D-printed biaxial sensor system for tilt measurement, based primarily on the use of four Fiber Bragg Grating (FBG) devices, has been developed and its performance characterized. The tilt sensor system created is of a compact design and relatively small dimensions, making it ideally suited to a variety of industrial applications. In the system developed, the four FBGs used were spliced in a serial formation and attached to four different sides of the sensor structure designed, to allow biaxial measurements to be made. The wavelengths' shift of the FBGs used were monitored as a function of the tilt of the device, using an Optical Spectrum Analyzer (OSA) for this development work. In the sensor, an average FBG-based responsivity of 0.01 nm/° of tilt was measured for each of the different FBGs used. To provide compensation for temperature changes in the system itself, a further FBG-based approach was used (in which they were configured to be insensitive to the effect of the tilt). They were thus calibrated by being exposed to a range of operational temperatures for the system, showing, as a result, a calibration of 0.011 nm/°C. Prior work on the sensor system had proved it to be highly linear in response, over the tilt range of 0° ± 90°. The experimental results obtained from the performance characterization indicate that the small, compact design of this type yields excellent responsivity, compared to other larger and more complex designs discussed in the literature. The sensor system was also relatively easy to fabricate using the 3D-printing method, creating in that way an inexpensive, temperature-compensated tilt monitoring device that had a wide variety of potential industrial applications