In this experiment, a passively mode-locked erbium-doped fiber laser was successfully realized by utilizing chromium aluminum carbide (Cr2AlC) MAX phase as a saturable absorber (SA). The Cr2AlC MAX phase was fabricated by casting method with polyvinyl alcohol to compose a thin film. By a 203-m cavity length, a stable mode-locked laser operating at 1559 nm was achieved at the threshold pump power of 121.69 mW with a pulse width of 4.45 ps and pulse rate of 1 MHz. The pulse energy was 0.91 nJ and output power was 0.91 mW at a maximum pump power of 167 mW. As the cavity length was shortened to 103 m, we observed that pulse width, pulse energy, and output power decreased to 2.5 ps, 1.60 nJ, and 3.02 mW, respectively, while the repetition rate increased to 1.88 MHz at a maximum pump power of 167 mW. To the best of our knowledge, this is the first time utilizing Cr2AlC MAX phase SA to produce the pulse laser in the 1.5-μm region.
A Single-mode multimode single-mode (SMS) fiber structure coated with MWCNTs is proposed and demonstrated for the detection of magnesium ion. The SMS fiber has a length of 30 mm multimode fiber and was fabricated by connecting two optical fiber single-mode and multimode fiber. As the magnesium concentration increases from 0% to 5%, the output power of the SMS fiber structure decreases linearly with sensitivity and resolution of 3.0261 dBm/% and 0.0379 % respectively, for the SMS fiber structure coating with MWCNTs. MWCNTs as magnesium ion sensors will change the refractive index of fiber as the magnesium ion concentration changes due to the optical properties of adsorption. Hence, the SMS fiber structure coating with MWCNTs is more sensitive than the one without coating for magnesium concentration detection.
A highly stable mode-lock fiber laser with a thin film coating of graphene oxide (GO) nanoparticles on a D-shaped fiber is proposed and demonstrated. The GO-coated D-shaped fiber, which serves as the cavity’s saturable absorber (SA), is fabricated by drop-casting GO nanoparticles on the smooth and consistently polished area of the D-shaped fiber made using a disk-polishing machine. Mode-locking is induced through the interaction of the evanescent field from the D-shaped fiber and GO nanoparticle layer. The cavity has a length of 12.5 m with a fundamental frequency of 16.5 MHz and operates in the anomalous dispersion regime. Stable soliton mode-locking is obtained above a pump power of 76.6 mW, with a central lasing wavelength of 1555.7 nm and well-defined Kelly’s sidebands. The generated pulses have a repetition rate of 16.5 MHz and pulse duration of 1.18 ps over a pump power range of 76.6 to 280.5 mW, with only minor fluctuations observed. A signal-to-noise ratio of 58.3 dB is computed, indicating a highly stable output. The proposed SA fabrication technique provides a simple, cost-effective, and consistent method of generating mode-locked pulses in fiber lasers.
A simple sensor is proposed and demonstrated using a silica tapered fiber for sensing different concentration of potassium in de-ionized water. The tapered fiber is fabricated using a flame brushing technique to achieve a waist
diameter and length of 10 μm and 80 mm, respectively. For a concentration change from 0 to 50 %, the ouput signal of the sensor decreases exponentially from -10.04 dBm to -11.11 dBm with linearity of more than 92%. The increment of potassium concentration increases the refractive index of the solution, which in turn reduces the index difference
between core and cladding of the tapered fiber and thus allows more light to be leaked out from the fiber. This new
potassium monitoring system provides numerous advantages such as simplicity of design and low cost of production.
In this paper, a novel optical approach is proposed and demonstrated for the non-contact measurement for the thickness
of silica thick films. This approach is based on the principal of an optical based displacement sensor. The calibration
curve for the measurement of the thickness of an unknown sample is obtained using four sample with known thicknesses
of 6.90, 10.23, 19.69 and 25.47 μm respectively. As compared to a prism coupler, which is assumed to provide the most
precise measurement of thick film thicknesses, the proposed system has an error of approximately 8%. The proposed
method is able to provide a simple, low cost and time saving approach in measuring thick films thicknesses during
fabrication.
The purpose of this study is to investigate the potential of intensity modulated fiber optic displacement sensor scanning system for the imaging of dental cavity. Here, we discuss our preliminary results in the imaging of cavities on various teeth surfaces, as well as measurement of the diameter of the cavities which are represented by drilled holes on the teeth surfaces. Based on the analysis of displacement measurement, the sensitivities and linear range for the molar, canine, hybrid composite resin, and acrylic surfaces are obtained at 0.09667 mV/mm and 0.45 mm; 0.775 mV/mm and 0.4 mm; 0.5109 mV/mm and 0.5 mm; and 0.25 mV/mm and 0.5 mm, respectively, with a good linearity of more than 99%. The results also show a clear distinction between the cavity and surrounding tooth region. The stability, simplicity of design, and low cost of fabrication make it suitable for restorative dentistry.
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