RESUMEN
Bending sensing was realized by constructing a tapered four-core optical fiber (TFCF) sensor. The four-core fiber (FCF) between the fan-in and fan-out couplers was tapered and the diameter became smaller, so that the distance between the four cores arranged in a square became gradually smaller to produce supermodes. The two ends of the TFCF were respectively connected to the fan-in and fan-out couplers so that the individual cores in the FCF could link to the separate single-mode fibers. A broadband light source (superluminescent diodes (SLD)) spanning 1250-1650 nm was injected into any one of the four cores, and the orientation was thus determined. In the tapering process, the remaining three cores gradually approached the excitation core in space to excite several supermodes based on the tri-core structure first, and then transited to the quadruple-core structure. The field distributions of the excited supermodes were asymmetric due to the corner-core excitation scheme, and the interference thus resulted in a higher measurement sensitivity. When the diameter of the TFCF was 7.5 µm and the tapered length was 2.21 mm, the sensitivity of the bending sensor could reach 16.12 nm/m-1.
RESUMEN
We demonstrate high-sensitivity fiber strain sensors based on an elongated abrupt taper. The fiber abrupt taper, with a tapered diameter ranging from 40-60 µm, was made by using a hydrogen microflame to break the waveguide adiabaticity so as to convert the fundamental mode into cladding modes. The abrupt taper was further uniformly tapered by using a normal moving flame with a torch diameter of 7 mm to elongate the tapered region until the tapered diameter was down to 2.5-5 µm. The excited high-order modes were confined to propagate along the cladding and then recombined at the rear edge of the fiber taper to produce interferences with extinction ratios of up to 16 dB. The tapered region was pulled outwardly to change the optical path difference (OPD) between modes to measure the tensile strain with all the interfering wavelengths blue-shifted. The measured best strain sensitivity was 116.21 pm/µÎµ and the coefficient of determination R2 of linear fitting exhibits high linearity. This strain sensor based on elongated abrupt taper is several times higher than that of most of the fiber strain sensors ever reported.
RESUMEN
A weakly-coupled multicore fiber can generate supermodes when the multi-cores are closer to enter the evanescent power coupling region. The high sensitivity strain sensors using tapered four-core fibers (FCFs) were demonstrated. The fan-in and fan-out couplers were used to carry out light coupling between singlemode fibers and the individual core of the FCFs. A broadband lightsource from superlumminescent diodes (SLDs) was launched into one of the four cores arranged in a rectangular configuration. When the FCF was substantially tapered, the asymmetric supermodes were produced to generate interferences through this corner-core excitation scheme. During tapering, the supermodes were excited based on a tri-core structure initially and then transited to a rectangular quadruple-core structure gradually to reach the sensitivity of 185.18 pm/µÔ under a tapered diameter of 3 µm. The asymmetric evanescent wave distribution due to the corner-core excitation scheme is helpful to increase the optical path difference (OPD) between supermodes for improving the strain sensitivity.
RESUMEN
Random lasers have attracted great interests and extensively investigation owing to their promising applications. Here, we explored unambiguously the multi-band up-converted random lasing from NaYF4:Yb,Er nanocrystals (NCs). NaYF4:Yb,Er NCs exhibit high effective up-conversion luminescence when they are excited by continuous wave 980 nm laser. We investigated a planar microcavities approach wherein the NaYF4:Yb,Er NCs showed up-converted lasing behavior. The optical pumping of NaYF4:Yb,Er NCs by 980 nm pulsed laser excitation exhibited multi-band lasing. The NaYF4:Yb,Er NCs showed multi-band lasing emission with a line width of 0.2 nm at 540 nm and 0.4 nm at 660 nm. This research promotes potential application in bioimaging and biomedical fields.
RESUMEN
Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) quantum dots (QDs) are the vanguard due to their unique properties. In this work, WSe2 QDs were fabricated via one step ultrasonic probe sonication. Excitation wavelength dependent photoluminescence (PL) is observed from WSe2 QDs. Room-temperature lasing emission which benefits from 3.7 times enhancement of PL intensity by thermal treatment at ~470 nm was achieved with an excitation threshold value of ~3.5 kW/cm² in a Fabryâ»Perot laser cavity. To the best of our knowledge, this is the first demonstration of lasing emission from TMDCs QDs. This indicates that TMDCs QDs are a superior candidate as a new type of laser gain medium.
RESUMEN
In the present study, a tough tetragonal zirconia polycrystalline (Y-TZP) material was developed for use in high-speed infrared windows and domes. The influence of the preparation procedure and the microstructure on the material's optical properties was evaluated by SEM and FT-IR spectroscopy. It was revealed that a high transmittance up to 77% in the three- to five-micrometer IR region could be obtained when the sample was pre-sintered at 1225 °C and subjected to hot isostatic pressing (HIP) at 1275 °C for two hours. The infrared transmittance and emittance at elevated temperature were also examined. The in-line transmittance remained stable as the temperature increased to 427 °C, with degradation being observed only near the infrared cutoff edge. Additionally, the emittance property of 3Y-TZP ceramic at high temperature was found to be superior to those of sapphire and spinel. Overall, the results indicate that Y-TZP ceramic is a potential candidate for high-speed infrared windows and domes.
RESUMEN
The operation of a mid-infrared laser at 2244 nm in a Cr:ZnS polycrystalline channel waveguide fabricated using direct femtosecond laser writing with a helical movement technique is demonstrated. A maximum power output of 78 mW and an optical-to-optical slope efficiency of 8.6% are achieved. The compact waveguide structure with 2 mm length was obtained through direct femtosecond laser writing, which was moved on a helical trajectory along the laser medium axis and parallel to the writing direction.
RESUMEN
A germanate-tellurite glass (GeO2-TeO2-K2O-Nb2O5-La2O3) with thulium doping has been investigated for application as a laser material around 2.0 µm regions. Under the 808 nm laser diode pumped, intense 1.8 µm emission is obtained. Based on the absorption spectra, radiative properties are predicted using Judd-Ofelt theory. The maximum value of emission cross-section of Tm(3+) around 1.8 µm can reach 1.46 × 10(-20) cm(2), which indicated that the germanate-tellurite glass may provide high gain as a good medium for efficient 1.8 µm laser system.
RESUMEN
2.0 µm emission property of a new germanate-tellurite (GT) glass with Ho³âº/Yb³âº codoping is synthesized and analyzed. Efficient 2.0 µm emission of Ho³âº ions sensitized by Yb³âº ions from the host glass was observed under 980 nm pumping. Based on the measured absorption spectra, the Judd-Ofelt parameters were calculated and discussed. The maximum emission cross section of Ho³âº ions transition is 4.36×10(-21) cm2 around 2.0 µm. The energy transfer efficiency is calculated and fitted the decay signals. The good spectroscopic properties suggest that Ho³âº/Yb³âº-codoped GT glass may become an attractive host for developing solid state lasers operating in the mid-infrared.
