Search

In this paper, a carboxymethyl cellulose (CMC)/graphene oxide (GO) composite film-coated humidity sensor was proposed based on thin-core fiber Mach-Zehnder interferometer (TCMZI). A segment of thin-core fiber (TCF) was spliced between two segments of single-mode fiber (SMF), and the TCF cladding was first corroded with hydrofluoric acid and then coated with a layer of CMC/GO film via optical driven deposition method. The relative humidity (RH) sensing characteristics of the sensor were experimentally investigated by observing the wavelength shift of resonant dips in the transmission spectrum, which showed that the CMC/GO composite film-coated TCMZI has good repeatability and stability in the measurement of humidity. A maximum average humidity sensitivity of −75.6 pm/%RH was obtained in the RH range of 35%-80%, nearly 2.048 and 3.237 times higher than that of CMC and GO single film coated ones. To the best of our knowledge, this is the first report on using the CMC/GO composite film for humidity measurement, and its excellent performance is expected to be extended to humidity sensitization of more fiber-optic sensors. The proposed sensor has the advantages of simple structure, easy fabrication, low cost, good stability and high performance, which can be applied to the fields of bio-chemical and medicine.

We demonstrate a plug-in tip sensor with a maximum cross section diameter of only 1 mm for real-time thermal monitoring of a high-density miniature winding coil, which can meet the miniaturization development needs of electromagnetic actuators. Due to the high upconversion luminescence efficiency, tellurite glass with an optimized Er

In this paper, we report a successful fabrication of a highly nonlinear chalcogenide all-solid hybrid microstructured optical fiber with polarization maintaining properties and a mid-infrared SC generation. Up to 4.5 × 10−4 at 10 µm of the fiber birefringence can be realized by employing a single As2Se3 core and two As2S5 rods horizontally aligned in the AsSe2 cladding. The fiber possesses a near-zero and flattened all-normal chromatic dispersion profile over the wavelength range from 5 to 10 µm. The polarization maintaining properties of the fiber is experimentally confirmed and a broadband supercontinuum spectrum from 2 to 10 µm in the mid-infrared window was experimentally demonstrated.

Tm3+ doped fluoroaluminate glass fibers are fabricated by using a rod-in-tube method based on AlF3-BaF2-YF3-MgF2-PbF2 glasses. By using a 1400/1570 nm dual-wavelength upconversion pump technique, lasing at ∼2.3 µm is obtained from a 2.3 m long Tm3+ doped fluoroaluminate glass fiber. The measured maximum unsaturated output power is ∼111 mW for a pump power of 1.5/0.14 W at 1400/1570 nm, and the corresponding slope efficiency is ∼11%. The effect of the gain fiber length on lasing at ∼2.3 µm is also investigated. Our results indicate that Tm3+ doped fluoroaluminate glass fibers are promising gain media for constructing ∼2.3 µm fiber lasers.

We demonstrated broadband S-band (1460–1530 nm) amplification in Tm3+-doped fluorotellurite glass fibers (TDFTFs) by using a 1400/1570 nm dual-wavelength pump technique. TDFTFs based on TeO2-BaF2-Y2O3 (TBY) glass were fabricated by using a rod-in-tube method. For an input signal power of 0 dBm (or 1 mW), a broadband positive net gain ranging from 3+ doping concentration of ∼4000 ppm, as the pump powers of the 1400 nm and 1570 nm lasers were 1.7 W and 0.14 W, respectively. The corresponding bandwidth for a net gain of >20 dB was ∼66 nm (1458–1524 nm), and the measured saturated output power was ∼24.84 dBm at 1490 nm. In addition, numerical simulation was performed by using the parameters of the TDFTFs and the pump lasers, and the noise figure was calculated to be

We successfully fabricate a transversely disordered optical fiber made of AsSe2 and As2S5 glasses for high-resolution mid-infrared image transport. By using the fabricated fiber, we experimentally observe transverse Anderson localization of mid-infrared light at the wavelength of 3 µm. Moreover, we numerically evaluate the localization in the fiber by using a cross-sectional image of the fiber.

In this paper, the self-phase modulation (SPM) effect in a double-cladding single-mode tellurite optical fiber (DC-SMTOF) was exploited for temperature sensing. The DC-SMTOF was fabricated based on a TeO2–ZnO–Li2O–Bi2O3 (TZLB) glass material that has a thermo-optical coefficient as high as –16.4×10−6/°C. The temperature sensing performance was evaluated by detecting the 3-dB bandwidth of the SPM spectra with the variation of temperature at different pump wavelength and different average pump power. The temperature sensitivity was obtained to be –2.971 nm/°C with a resolution of 0.0168°C. Both simulation and experiment confirmed that a longer pump wavelength and higher average pump power will result in a higher temperature sensitivity. To the best of our knowledge, this is the first study concerning SPM-based temperature sensing in a tellurite optical fiber. The proposed temperature sensor has a compact structure, and it can realize temperature sensing of high sensitivity without any fiber modification. This work opens the road toward explorations of a novel temperature sensing technology combined with soft glass fibers and nonlinear phenomenon, and is expected to deepen our understanding in the application of these complex nonlinear phenomena.

We propose a method of merging the minimum deviation and the interferometric method to determine the refractive index dispersions of glasses in a wide range of the mid-infrared region with high accuracy. By the proposed method, the refractive index dispersions of telluride glasses, included in chalcogenide glasses, are successfully determined in the wavelength range from 3 to around 20 μm. The accuracy of the refractive index by the proposed method is no more than 1 × 10−3.

A fiber-based beam shaper to adjust the distribution of spatial modes in a few-mode fiber (FMF) is theoretically and experimentally investigated in this work. A compact and robust device, composed with a single mode fiber-graded index multimode fiber-few mode fiber (SMF-GIMF-FMF), is fabricated by simply fusion splicing of the fibers. Switchable spatial modes and multi-wavelength comb are obtained by the combination of the beam shaper and the few-mode fiber Bragg grating (FM-FBG). This combination acts as a filter to select the wavelength and spatial mode in the laser. A spatial mode switchable fiber laser with high mode purity is extended among LP01, LP11 and cylindrical vector beam (CVB) by adjusting the pressure applied on the beam shaper. Five-discrete wavelengths and their free combination wavelength comb are emitted with a slope efficiency higher than 10%. The fiber laser can be used in the spatial- and wavelength-division multiplexing (SWDM) fiber communication networks requiring particular structure light field.

We demonstrate broadband mid-infrared cascaded stimulated Raman scattering (SRS) and flat supercontinuum (SC) generation in a chalcogenide optical fiber made from A s 2 S 5 glass. By using a 2 µm nanosecond laser as the pump source, mid-infrared cascaded SRS up to six orders ranging from 2149 to 3425 nm was experimentally observed, and this all-fiber Raman laser operating at 3.43 µm was realized for the first time to our knowledge. By introducing a 2 µm femtosecond laser as the excited source, the broadband flat mid-infrared SC with the spectral range of ∼ 10 d B (from ∼ 1030 to 3441 nm) was observed. Our results verify that the A s 2 S 5 optical fibers possess promising applications for tunable mid-infrared Raman fiber lasers and SC light sources pumped by 2 µm pulsed lasers.

Soft glass optical fibers, especially highly nonlinear optical fibers, have expanded their application fields. We have been engaged in soft glass optical fibers, such fluoride, tellurite and chalcogenide glass, for optical signal processing, lightwave generation and waveguide applications. Furthermore, we have challenged the research on novel waveguides, for example, transverse Anderson localization of mid-infrared light using transversely disordered optical fiber. Here we report our achievements on SC generation and novel waveguides research using the soft glass highly nonlinear optical fibers.

We demonstrate the generation of broadband dispersive waves (DWs) and solitons in an 80-cm tellurite microstructured optical fiber (TMOF) designed and fabricated with 78TeO2-5ZnO-12LiCO3-5Bi2O3 (TZLB) glass. A 1810-nm femtosecond laser is used as the pump source with an average pump power ranging from 33 mW to 175 mW, where the tunable frequency range is 211.1 THz, which corresponds to the tunable wavelength range of 1742.9 nm. At 175 mW, the trapped multiple DWs are located at 923.8 nm, 1039.2 nm, 1121.6 nm, and 1204.6 nm and the multiple solitons are located at 2666.7 nm, 2426.1 nm, 2165.9 nm, 1952.7 nm, and 1842.1 nm. The experimentally obtained maximum DW conversion efficiency is 14%, and the maximum soliton conversion efficiency is 43%. The experimental and theoretical results of pulse evolution in the TMOF agree very well. To the best of our knowledge, this is the first time that nine peaks of frequency conversions have been realized simultaneously in non-silicon fibers. The exceptionally high nonlinearity and broadband-tunable characteristics of the proposed TMOF are promising components for the development of compact and highly efficient tunable mid-infrared fiber lasers, wavelength converters, and time-frequency metrology.

In this letter, we demonstrate efficient cascaded Raman amplification in fluorotellurite fibers pumped by a 1550 nm nanosecond laser. All-solid fluorotellurite fibers with a core diameter of ∼ 5 µm are fabricated by using a rod-in-tube method. By using a continuous wave (CW) 1765 nm fiber laser as the signal source for first-order Raman amplification, the amplified 1765 nm laser with an average output power of ∼ 190.9 mW and a pulse width of ∼ 3.42 ns is obtained from a 3 m long fluorotellurite fiber for an average pump power of ∼ 519.35 mW and an input signal power of ∼ 1.05 mW, corresponding to a net gain of ∼ 22.6 dB and an optical-to-optical conversion efficiency of 36.76%. Furthermore, a CW 2049.2 nm fiber laser combined with the above 1765 nm laser are used as the signal sources for second-order cascaded Raman amplification. As the power of the 1765 nm and 2049.2 nm lasers are set as 1.05 and 1.00 mW, respectively, the amplified 2049.2 nm laser with an average output power of ∼ 135.35 mW and a pulse width of ∼ 3.36 ns is obtained from the fluorotellurite fiber for an average pump power of ∼ 558.37 mW, corresponding to a net gain of ∼ 21.3 dB and an optical-to-optical conversion efficiency of 24.24%. As the length of the fluorotellurite fiber is increased to 10 m, third-order cascaded Raman amplification is observed by using a 2442.6 nm signal generated by four-wave mixing and the above 1765/2049.2 nm lasers as the signal sources, causing the generation of the amplified 2442.6 nm laser with an average output power of ∼ 18.84 mW. Our results show that fluorotellurite fibers are promising gain media for constructing cascaded Raman fiber amplifiers with a wide range of wavelengths.

In this Letter, we demonstrate a third-order cascaded Raman shift in an all-solid fluorotellurite fiber pumped by a 1550 nm nanosecond laser. The fluorotellurite glass with a composition of TeO2–BaF2–Y2O3 (TBY) has a usable Raman shift of ∼785 cm−1 and a Raman gain coefficient of ∼1.65 × 10−12 m/W at 1550 nm, which is approximately 25.4 times larger than that of silica glass. By using a 5.38 m fluorotellurite fiber as the Raman gain medium and a 1550 nm nanosecond laser as the pump light, a third-order cascaded Raman shift is obtained via spontaneous cascaded Raman amplification in the fluorotellurite fiber, causing the generation of the first-, second-, and third-order Stokes emissions that peak at 1765, 2049, and 2438 nm, respectively. For an average pump power of ∼491.5 mW, the output power of the generated first-, second-, and third-order Stokes light is approximately 14.1, 67.4, and 31.6 mW, respectively. The corresponding conversion efficiency is approximately 2.87%, 13.70%, and 6.43%, respectively. Our results show that fluorotellurite fibers are promising Raman gain media for constructing cascaded Raman fiber lasers with a wide range of wavelengths.

We demonstrate dispersive wave generation at 4 µm in a dispersion-engineered fluorotellurite fiber pumped by a 1.98 µm femtosecond fiber laser. All-solid fluorotellurite fibers with a core diameter of ∼2.6 µm are fabricated by using a rod-in-tube method. The fluorotellurite fibers have two zero-dispersion wavelengths (ZDWs). The first ZDW is 1.328 µm and the second one is 3.551 µm. As the pump laser is launched into the fluorotellurite fiber, firstly, tunable mid-infrared Raman solitons are generated through higher order soliton compression, soliton fission and soliton self-frequency shift. Then, red-shifted dispersive wave at 4 µm is generated as those Raman solitons meet the second ZDW (∼3.551 µm) and soliton self-frequency shift cancellation occurs. Our results show that dispersion-engineered fluorotellurite fibers are promising nonlinear media for constructing all-fiber 4 µm light sources

Aiming at maintaining the chromatic dispersion properties and fiber optical parametric amplification (FOPA) performance when fiber core fluctuation occurs, we propose a buffer step-index optical fiber. The AsSe2 chalcogenide glass is employed as the core material due to its high nonlinearity and broad transmission spectrum. The calculated results in this study show that the chromatic dispersion variation due to the change of core diameter can be greatly suppressed and a continuous and very broad FOPA signal gain spectrum can be obtained and maintained by carefully controlling the core, buffer and cladding properties such as refractive index and diameters. The calculated results in this study showed that by using the proposed 3-cm-long fiber pumped at 5.02 µm, a broad signal gain bandwidth from 3 to 14 µm at about 15 dB is attainable although the fiber core diameter Dc drastically fluctuated from 2 to 5 µm and the buffer diameter Db varies from 8.9 to 9.3 µm. Moreover, when Dc varies in smaller range from 3 to 4 µm, the FOPA signal gain spectra calculated at different fixed values of Db in the range from 8.9 to 9.3 µm are highly maintained. When Db is kept at 9.0 µm and Dc varies from 3 to 4 µm, the calculated FOPA signal gain spectra at different pump wavelengths from 4.98 to 5.02 µm are also nearly identical in the wavelength range from 3 up to 13 µm.