Tellurite Fiber Research Articles

Supercontinuum generation in a graded-index multimode tellurite fiber.

We report the generation of a broadband supercontinuum (SC) from 790 to 2900 nm in a tellurite graded-index (GRIN) multimode fiber with a nanostructured core. We study the SC dynamics in different dispersion regimes and observe near-single-mode spatial intensity distribution at high input energy values. Numerical simulations of the (3 + 1)D generalized nonlinear Schrödinger equation are in good agreement with our experiments. Our results open a new avenue for the generation of high-power mid-infrared SC sources in soft-glass fibers.

Fabrication of tellurite fiber via air-exhausting extrusion based on ceramics die

During the preparation of tellurite fiber preforms, defects such as air bubbles and contaminated particles at the core-clad interface can significantly increase fiber loss. In this paper, we have proposed an effective method to solve these defects. Firstly, zirconia (ZrO2) ceramics were used as the die material due to their low contamination and high chemical stability, avoiding the surface reduction of TeO2 glass associated with metal-based die. Furthermore, the die was designed with an air-exhausting channel between the interface of the core and cladding glasses. The results demonstrate that the tellurite glass was well-preserved during the extrusion, and no visible particle defects were found at the core-cladding fiber interface. The fabricated fiber exhibits an optical loss as low as 0.67 dB/m at 1.31 μm, which is approximately 77 % lower than that of fibers prepared using a stainless-steel die. This air-exhausting extrusion based on ceramic die, proves to be an effective method for the fabrication of low loss tellurite fibers for mid-infrared.

Investigation of a twisting-fused side-pump coupler based on tellurite fiber

Fiber side-pump couplers can enhance the output power of fiber laser due to their dependable and efficient operation and impressive power handling capability. We developed a tellurite fiber side-pump coupler by twisting and fusing a tapered pump fiber onto a target fiber. The effect of twisting parameters on coupling efficiency was comprehensively investigated through theoretical simulations and experiments. Experimental results exhibited an impressive coupling efficiency of 76.5% and a root mean square stability of 0.086% and 0.091% before and after one month, respectively, driven by an incident pump power of up to 4.2 W.

Design and fabrication of a tellurite hollow-core anti-resonant fiber for mid-infrared applications

The hollow core anti-resonant fibers (HC-ARFs) based on soft glass are in high demand for 3-6 µm laser delivery. A HC-ARF based on tellurite glass with 6 touching capillaries as cladding was designed and fabricated for the first time, to the best of our knowledge. A relatively low loss of 3.75 dB/m at 4.45 µm was realized in it. The effects of capillary number, core diameter, wall thickness of capillary, and material absorption loss on the loss of the HC-ARF were analyzed by the numerically simulation. The output beam quality was measured and the influence of bending on the fiber loss was discussed. The results of numerical simulation suggested that the theoretical loss of the prepared fiber can be reduced to 0.1 dB/m, indicating that tellurite HC-ARFs have great potential for mid-infrared laser applications.

A Theoretical Investigation of an Ultrawide S-, C- and L-Band-Tunable Random Fiber Laser Based on the Combination of Tellurite Fiber and Erbium-Doped Fiber

In this paper, we present a new scheme to generate ultrawide tunable random fiber lasers (RFLs) covering the S-, C- and L-band by combining the broadband Raman gain in tellurite fibers and the active gain in erbium-doped fibers. A numerical simulation based on the power-balance model is conducted to verify the feasibility of the ultrawide tunable random fiber lasing generation. Pumped by a 1450 nm laser, the tunable random Raman fiber laser in the ranges of 1480–1560 nm and 1590–1640 nm can only be realized with a tellurite fiber. To further fill in the emission gap in the range of 1560–1590 nm, the erbium-doped fiber is incorporated in the cavity, which can provide efficient erbium-doped gain in the C- and L-band. By combining a 100 m long tellurite fiber and an 8 m long erbium-doped fiber, an ultrawide tunable RFL based on hybrid erbium–Raman gain can be realized with a wavelength tuning range (1480 nm–1640 nm) covering the S-, C- and L-band at 3.5 W pump power. Such a widely tunable RFL is of great importance in applications such as optical communication, sensing and imaging.

Optimization of Very Short Multi-Pump Discrete Raman Amplifiers based on Tellurite Fibers

Optimization of Very Short Multi-Pump Discrete Raman Amplifiers based on Tellurite Fibers

Mid-infrared supercontinuum generation by tellurite oval-core optical fiber

For generating polarization-maintained mid-infrared supercontinuum light, we have simulated, and fabricated tellurite oval-core optical fiber. Polarization-maintained supercontinuum light from 1660 to 2570 nm has been generated from the fabricated tellurite oval-core optical fiber.

Coherent mid-infrared supercontinuum generation in tellurite all-solid microstructured optical fibers with anomalous and normal dispersion property

Tellurite all-solid hybrid microstructured optical fibers (ASHMOFs) can be used to generate supercontinua with broad bandwidths in both anomalous and normal dispersion regimes. In the anomalous dispersion regime, a supercontinuum spectrum from 1.1 to 6.7 μm can be generated with a pump power of 10 kW and a pump wavelength of 3.5 μm. In the normal dispersion regime, a supercontinuum spectrum from 2.0 to 4.4 μm can be generated with the same pump power and wavelength. The simulations of supercontinuum generation in ASHMOFs show promising results for applications such as broadband infrared spectroscopy and enviromental monitoring. The all-solid nature of these fibers also makes them more robust and easier to handle than conventional soft-glass fibers.

Broadband Amplification in the 2.6–2.9 μm Wavelength Range in High-Purity Er3+-Doped Zinc-Tellurite Fibers Pumped by Diode Lasers

In recent years, great progress has been made in the technology of high-purity and ultra-dry tellurite glasses, which has enabled the creation of high-purity single-mode tellurite fibers doped with rare-earth ions. This technology has made it possible to demonstrate laser generation in the range of about 2.7 μm in erbium-doped tungsten tellurite fibers. In this paper, we present an experimental study of broadband amplification in erbium-doped zinc-tellurite fibers. Zinc-tellurite glasses containing modifying components, such as Na2O, La2O3, Bi2O3, or rare-earth metal oxides, are known to have noticeably lower phonon energy than heavy metal-tellurite systems, namely, tungsten tellurite glasses, which leads to better lasing output. The on-off gain of 30- and 60-cm long zinc-tellurite fibers has been measured in a wide range of diode pump powers. It has been shown for the first time that the amplification band is essentially extended, with pump power reaching over 250 nm (2600–2850 nm) at a peak power of about 40 W for a 30-cm long fiber.

Transmissive fluorescent temperature sensor based on Er3+/Yb3+/Mo6+ tri-doped tellurite fiber for real-time thermal monitoring of motors using the FIR technique.

In this paper, we fabricate a transmissive fluorescent temperature sensor (TFTS) that based on Er3+/Yb3+/Mo6+ tri-doped tellurite fiber, which has the advantages of compactness and simplicity, corrosion resistance, high stability and anti-electromagnetic interference. The doping of Mo6+ ions will enhance the up-conversion (UC) fluorescence emission efficiency of Er3+ ions, thus improving the signal-to-noise ratio of TFTS. Using the fluorescence intensity ratio (FIR) technique, the real-time thermal monitoring performance of TFTS is evaluated experimentally. Apart from good stability, its maximum relative sensitivity is 0.01068 K-1 at 274 K in the measured temperature range. In addition, it is successfully used to monitor the temperature variation of the stator core and stator winding of the motor in actual operation. The results show that the maximum error between the FIR-demodulated temperature and the reference temperature is less than 1.2 K, which fully confirms the effectiveness of the TFTS for temperature monitoring. Finally, the FIR-based TFTS in this work is expected to provide a new solution for accurate and real-time thermal monitoring of motors and the like.

Numerical Study of Efficient Tm-Doped Zinc-Tellurite Fiber Lasers at 2300 nm

Fiber laser sources operating near 2300 nm in the atmospheric transparency window are interesting for different applications, such as remote sensing, lidars, and others. The use of Tm-doped fiber lasers based on tellurite fibers is highly promising. We propose and theoretically study a highly efficient diode-pumped Tm-doped zinc-tellurite fiber laser operating at two cascade radiative transitions at 1960 nm and 2300 nm, with additional energy transfer between these laser waves due to the Raman interaction. We demonstrate numerically that a dramatic increase in the slope efficiency up to 57% for the laser wave at 2300 nm, exceeding the Stokes limit by 22% relative to the pump at 793 nm, can be obtained with optimized parameters thanks to Raman energy transfer from the laser wave at 1960 nm to the wave at 2300 nm.

A temperature sensor based on Er3+/Yb3+ co-doped tellurite fiber for real-time thermal monitoring of transformers

In this paper, a temperature sensor based on fluorescence intensity ratio (FIR) technique is prepared by the dual curing method. The pumping threshold is only 0.1 mW for the application of real-time thermal monitoring on small transformers. This not only greatly reduces the thermal effects accumulated by laser irradiation but also contributes to the integration and portability of the light source. Based on the FIR, the temperature information could be demodulated through tracking the fluorescence spectral changes. The basic temperature sensing characteristics of this sensor were evaluated, which showed that the maximum stability deviation and reproducibility error were within ±1.1 K and ±0.8 K, respectively. Notably, it has a maximum measurement error of only 0.61 K when applied to the temperature monitoring of transformers. And a fast time response of 2.1 s was exhibited in the cyclic exhalation experiment. This proposed sensor is suitable for mass production due to its resistance to electromagnetic interference, low pumping power, fast time response, excellent stability and reproducibility.

Numerical analysis of optical confinement insilica and tellurite multicore fibers fornear-infrared image transportation.

We analyzed light confinement in circular step-index cores of tellurite and silica fibers through numerical calculations and also examined crosstalk between the fundamental modes of cores in multicore fibers. Our analysis showed that tellurite fibers have a pixel density about 2.2 times higher and a brightness about 1.4 times brighter than silica fibers. As a result, tellurite multicore image fibers have the potential to provide improved resolution and brightness for near-infrared image transportation compared with silica fibers.

Mid-infrared refractive index sensor with high sensitivity and wide detection range based on multimode interference in tellurite optical fibers

In this paper, a section of tellurite no-core optical fiber (NCF) is compactly sandwiched between two segments of tellurite single-mode optical fibers (SMF) to form multimode interference (MMI) sensor for refractive index (RI) measurement. Theoretical investigation reveals that the sensitivity of this MMI-based RI sensor can be enhanced by reducing the diameter of the NCF. As the NCF diameter is lowered to 20 µm, the sensor presents good RI sensing performance in the mid-infrared range of 2–5 µm and the sensitivity rises with the increase of the wavelength. At 4–5 µm and within the detectable RI range of 1.36–1.63, the maximum sensitivity is 3069.1 nm/RIU. The proposed sensor combines the material superiority of tellurite glass and the structural advantage of the SMF-NCF-SMF sensing unit, exhibiting high sensitivity and wide detection range in terms of RI sensing. It provides a new method for detecting the concentration of toxic organic compounds with high RI.

Fabrication of a tellurite-fiber-based side-pump coupler based on the tapered-fused method.

In this study, (1 + 1) × 1 side-pump couplers made of tellurite fibers were fabricated and investigated. The whole optical design of the coupler was established on the basis of ray tracing models and validated by experimental results. By optimizing the preparation conditions and structural parameters, the tested component achieved a coupling efficiency of 67.52% and an insertion loss of 0.52 dB. To the best of our knowledge, this is the first time a tellurite-fiber-based side-pump coupler was developed. The fused coupler presented will simplify many mid-infrared fiber lasers or amplifier architectures.

Luminescence enhanced temperature sensor based on the up-conversion emission in Er3+/Yb3+/Mo6+ tri-doped tellurite fiber

In this study, the green up-conversion (UC) fluorescence emission in Er3+/Yb3+/Mo6+ tri-doped tellurite glasses (TeO2–ZnO–Li2CO3–Bi2O3, TZLB) was explored for temperature sensing. The doping of Mo6+ ions allowed enhanced luminescence at moderate power pumping, avoiding the introduction of undesired laser-induced thermal effects while improving the spectral signal-to-noise ratio. The luminescence characteristics were investigated in detail at different doping molar ratio of Mo6+ ions, and the strongest was observed at 8 mol%. Drawing on tri-doped TZLB glass with the strongest UC emission intensity, a tri-doped TZLB fiber was fabricated and coupled with two multimode fibers (MMFs) via Ultraviolet (UV) adhesive, forming the temperature sensor. The sensor was further encapsulated by a silica tube sealed with Ultraviolet adhesive, overcoming the poor mechanical property of tellurite fiber. The temperature information could be demodulated based on the fluorescence intensity ratio technique. The temperature sensing performance of the tri-doped TZLB sensor was investigated as temperature varied from 258 to 420 K and its repeatability was experimentally verified. The Er3+/Yb3+/Mo6+ tri-doped TZLB has an application prospect in the field of lighting, and the so-based temperature sensor is expected to be applied to thermal detection in the fields of medical diagnostics, environmental monitoring, and optical thermometers, etc.

Highly Nonlinear Multimode Tellurite Fibers: From Glass Synthesis to Practical Applications in Multiphoton Imaging

Herein, a tellurite multimode optical fiber with a rectangular step‐index core to combine easy coupling of the pump power with the exceptionally cubic nonlinearity of such type of glass is developed. An alkali‐free composition (TeO2–ZnO–La2O3) is prepared to produce a preform with the use of both the stack‐and‐draw and the direct‐bonding methods. The linear and nonlinear optical responses of the fiber are characterized and are then used to generate a homogeneous supercontinuum (SC) in the near‐infrared domain. The spectral broadening, which is obtained in this work in a short fiber sample, is used for imaging mouse kidney cells, labeled with three different fluorochromes, by means of two‐photon absorption (2PA) and three‐photon absorption (3PA). Despite the multimode nature of the output beam, clear images of tubules, actin, and nucleus are collected with a spatial resolution down to 1.2 μm. Although image acquisition at better resolution has already been reported in the literature using relatively long spans of graded‐index silica multimode fibers, here, the combination of high third‐order susceptibility of the glass and the large Raman gain in short segments of tellurite fiber is exploited to obtain nonlinear imaging with adequate spatial resolution.

Mid-Infrared Frequency Modulation Spectroscopy of NO Detection in a Hollow-Core Antiresonant Fiber

Mid-infrared frequency modulation spectroscopy (FMS) in a tellurite hollow-core antiresonant fiber (HC-ARF) is investigated for gas detection. The spectroscopic system is demonstrated for nitric oxide (NO) detection by exploiting its strong absorption line at 1900.08 cm−1 with a quantum cascade laser (QCL). By modulating the injection current of the QCL at 250 MHz and measuring NO in a 35 cm long HC-ARF, we achieve a noise equivalent concentration of 67 ppb at an averaging time of 0.1 s. Compared to direct absorption spectroscopy with a low-pass filter for etalon noise reduction, the FMS technique shows an improvement factor of 22. The detection limit of FMS can be further improved to 6 ppb at a longer averaging time of 100 s, corresponding to a noise equivalent absorption coefficient of 1.0 × 10−7 cm−1.

Broadband gain performance in the mid-IR using supercontinuum: 2.7 µm gain in high-purity Er3+doped tungsten tellurite glass fibers.

This paper presents an experimental study of broadband mid-IR amplification that is carried out, for the first time, to the best of our knowledge, in an erbium-doped tungsten tellurite fiber. A simple, robust supercontinuum source based on a tapered germanate fiber is developed as a seed input in the region of 1.5-3µm. We show that gain by a factor of 5 on one pass can be achieved in the 2.7µm range by pumping a low-cost, high-efficiency diode laser at 976nm using high-purity tellurite glass fibers.

Lasing at 2.72 µm in an Er3+-doped high-purity tungsten-tellurite glass fiber laser.

This Letter reports the experimental realization, for the first time to our knowledge, of lasing in an erbium-doped tellurite fiber at 2.72 µm. The key to the successful implementation was the use of advanced technology for obtaining ultra-dry preforms of tellurite glasses, as well as the creation of single-mode Er3+-doped tungsten-tellurite fibers with an almost imperceptible absorption band of hydroxyl groups, with a maximum of ∼3 µm. The linewidth of the output spectrum was as narrow as 1 nm. Our experiments also confirm the possibility of pumping the Er-doped tellurite fiber with a low-cost high efficiency diode laser at 976 nm.