Tellurite Glass Fiber Research Articles

Incorporating Er:YAP Microcrystals Into Tellurite Fiber Using Volumetric Interface Doping

AbstractIn this semi‐quantitative study, laser crystal microparticles which are potentially capable of generating mid‐infrared (MIR) light are incorporated into MIR transmitting optical fibers using a volumetric interface doping technique that combines interface doping with volumetric doping. Using confocal microscopy with a refractive index matching fluid, the Er:YAP microcrystals (MCs) inside the tellurite glass fiber are observed based on the detection of the green upconversion fluorescence emission of Er3+ ions, produced under excitation at 976 nm and localized at the central region within the fiber. The key outcome from this proof‐of‐concept study is that MC particles that are fused with the glass during the fiber drawing process survived heat treatment because the MC particles are exposed for a short time to a glass fluid with high viscosity of ≈105 Pa.s, which prevented the glass from exerting a dissolution effect. The survival of the MCs demonstrated the viability of the doping technique for fabricating fibers with exotic crystal‐glass combinations for applications including good refractive index matching across the pump and lasing bands of rare earth ions. This latter parameter provides significant particle size flexibility whilst minimizing additional loss from scattering especially at MIR wavelengths where the MC diameter‐to‐wavelength ratio becomes smaller.

Experimental insights into increasing laser output at 2.8 µm in Er3+-doped zinc-tellurite fibers.

In this paper, we provide a new experimental insight into the lasing process in the erbium-doped tellurite glass fiber at high diode-pump powers and pumping pulse durations. It is shown that lasing occurs at two wavelengths. Initially, at a fixed wavelength of 2.718 µm corresponding to the luminescence maximum, lasing takes place during the first ∼100 µs from the start of the pump pulse, while the main laser power occurs at the 2.8 µm for the rest of the pump pulse and shifts to longer wavelengths with increasing pump power. At pumping durations essentially exceeding the lifetime of the upper laser level, no self-termination of lasing occurs; on the contrary, the lasing power increases, which indicates the key role of the energy transfer upconversion (ETU) process. We demonstrate for the first time to our knowledge efficient lasing with an average power of 60 mW and a pulsed energy of 1.2 mJ in an erbium-doped zinc-tellurite fiber.

Spectroscopic properties and numerical analysis of novel erbium doped multi-component tellurite glasses

In this paper, Er3+ doped TeO2-ZnF2-BaF2-KF-Ta2O5 tellurite glasses with low hydroxyl content (∼0.03 × 10−19 cm−3) were investigated employing both glass composition and glass melting process optimization. The Raman spectra and physical properties were characterized to analyze the structure of the glasses. Under the pumping of 980 nm LD laser, intense up-conversion fluorescence at 1.5 and 2.7 μm of samples and their lifetimes were detected and analyzed, and the related transition mechanisms with gradient-varying Er3+ doping concentrations were discussed. The maximum absorption and emission cross section at 2.7 μm was calculated to be 6.4 × 10−21 cm2 and 6.8 × 10−21 cm2, correspondingly, which were higher than those of traditional tellurite glasses. Using the calculated and measured spectroscopic parameters of bulk tellurite glass, a dual-wavelength pumping model was established to verify the feasibility of mid-infrared laser output in similar tellurite glass fiber. Experimental results support the assertion that the Er3+ doped tellurite glasses hold promise as a candidate laser gain medium for mid-infrared fiber laser systems.

Singly Ho3+-doped tantalum tellurite glass and optical fiber for 2 μm fiber lasers

Singly Ho3+-doped TeO2–Ta2O5–ZnO (TTZ) glass and optical fiber for 2 μm fiber lasers have been investigated. The glass-forming region of the ternary TTZ glass system is determined to study its glass-forming ability and to select an appropriate glass matrix for doping Ho3+ ions. Upon the excitation of a 1940 nm laser diode (LD), an intense emission at 2.06 μm with a full width at half maximum (FWHM) of 61 nm is observed from the Ho3+-doped TTZ glass. The measured lifetime of the Ho3+: 5I7 level in TTZ glass shows a gradual decrease from 3.5 to 0.98 ms as the dopant concentrations increase from 0.2 to 2 mol%. A large emission cross-section (σeMC ∼ 4.56 × 10−21 cm2) and figure of merit (FOM, ∼ 6.83 × 10−24 cm2·s) are obtained. The Ho3+-doped TTZ glass is further fabricated into an optical fiber with an average transmission loss of 0.12 dB/cm at 1310 nm. The results show that singly Ho3+-doped TTZ glass and optical fiber are promising candidates for efficient 2 μm fiber lasers.

Robust extruded tungsten tellurite glass fiber with excellent mechanical properties for infrared applications

Robust tungsten tellurite (70TZLW) glass fiber consisting of 70TeO2-16ZnO-4La2O3-10WO3 core and 70TeO2-16ZnO-5.5La2O3-8.5WO3 cladding (in mol.%) was prepared by extrusion method. Due to the adding of La2O3 and WO3, 70TZLW glass exhibits higher glass transition temperature (385–395 °C) and thermal stability (>145 °C) than those of TeO2-ZnO-Na2O glasses, which is beneficial to the drawing of optical fiber. In addition, the mean optical losses of the bare wires drawn by the core and cladding glass preform are about 1.19 dB/m and 1.16 dB/m, while that is about 1.04 dB/m for the fiber drawn from the accordingly extruded preform at the wavelength of 1310 nm. Moreover, the average mechanical bending strength of the fiber reaches to about 570 MPa with a Weibull slope of 67.4. These results show the improvement in work ability and the greater practical potential of the 70TZLW extruded fiber compared to TeO2-ZnO-Na2O fibers for infrared application.

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.

Broadband NIR radiative transitions in Er3+/Tm3+ co-doping tellurite glass material

The radiative property of Er3+/Tm3+ co-doping tellurite glass containing metallic silver nanoparticles (Ag NPs) in near-infrared (NIR) band region was studied under the 808 nm pumping. The tellurite glass was prepared by applying melt-quenching and heat-treated technique, and characterized by measuring differential scanning calorimeter (DSC) curve, transmission electron microscopy (TEM) image, absorption spectrum and fluorescence spectrum. Under the optimized combination of Er3+ and Tm3+ ions, a flat and wide NIR band fluorescence in spectral range of 1350 to 1650 nm with full width at half maximum (FWHM) of 161 nm, originating from Er3+:4I13/2→4I15/2 radiative transition (1.53 µm) and Tm3+:3H4→3F4 radiative transition (1.47 µm), was observed in the studied tellurite glass. The fluorescence intensity was increased by about 91% when the Ag NPs with size of ∼17.4 nm was embedded into the doping glass. A similar wide optical amplification spectrum was also observed through the theoretical simulation of stimulated radiative transition of tellurite glass fiber co-doped with Er3+/Tm3+ ions, indicating the potential of Er3+/Tm3+ co-doping tellurite glass applied for broadband fiber amplifiers and tunable lasers. Additionally, the DSC curve revealed the excellent thermal stability of glass host with transition temperature of 381°C and the difference between crystallization onset temperature and transition temperature of 141°C. Some important spectral parameters like radiative transition probability and fluorescence branching ratio among different levels were determined according to Judd-Ofelt theory to better understand the observed broadband and flat NIR luminescence phenomenon.

Towards Quantum Noise Squeezing for 2-Micron Light with Tellurite and Chalcogenide Fibers with Large Kerr Nonlinearity

Squeezed light—nonclassical multiphoton states with fluctuations in one of the quadrature field components below the vacuum level—has found applications in quantum light spectroscopy, quantum telecommunications, quantum computing, precision quantum metrology, detecting gravitational waves, and biological measurements. At present, quantum noise squeezing with optical fiber systems operating in the range near 1.5 μm has been mastered relatively well, but there are no fiber sources of nonclassical squeezed light beyond this range. Silica fibers are not suitable for strong noise suppression for 2 µm continuous-wave (CW) light since their losses dramatically deteriorate the squeezed state of required lengths longer than 100 m. We propose the generation multiphoton states of 2-micron 10-W class CW light with squeezed quantum fluctuations stronger than −15 dB in chalcogenide and tellurite soft glass fibers with large Kerr nonlinearities. Using a realistic theoretical model, we numerically study squeezing for 2-micron light in step-index soft glass fibers by taking into account Kerr nonlinearity, distributed losses, and inelastic light scattering processes. Quantum noise squeezing stronger than −20 dB is numerically attained for a customized As2Se3 fibers with realistic parameters for the optimal fiber lengths shorter than 1 m. For commercial As2S3 and customized tellurite glass fibers, the expected squeezing in the −20–−15 dB range can be reached for fiber lengths of the order of 1 m.

Formation of Non-Classical Multiphoton States of Light with Squeezed Quantum Fluctuations in Bismuth-Modified Tellurite Glass Fibers

Formation of Non-Classical Multiphoton States of Light with Squeezed Quantum Fluctuations in Bismuth-Modified Tellurite Glass Fibers

Mid-IR Rare Earth Doped Tellurite Glass and Optical Fiber

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Quantum noise squeezing of CW light in tellurite glass fibres

Light with suppressed quantum fluctuations is desirable for a lot of applications. There are several approaches to suppress a noise including Kerr squeezing in optical fibres. Silica fibres are commonly used for this purpose. Here we propose to use highly nonlinear tellurite glass fibres for Kerr squeezing of CW laser field and demonstrate by simulations in the framework of the stochastic generalized nonlinear Schrödinger equation the possibility of –20 dB noise suppression. In simulations, Raman terms and losses are switched on and switched off to find their contributions to the limits of squeezing. The analytical estimates without loss and with lumped loss are also given.

Design and Dispersion Control of Microstructured Multicore Tellurite Glass Fibers with In-Phase and Out-of-Phase Supermodes

High nonlinearity and transparency in the 1–5 μm spectral range make tellurite glass fibers highly interesting for the development of nonlinear optical devices. For nonlinear optical fibers, group velocity dispersion that can be controlled by microstructuring is also of great importance. In this work, we present a comprehensive numerical analysis of dispersion and nonlinear properties of microstructured two-, four-, six-, and eight-core tellurite glass fibers for in-phase and out-of-phase supermodes and compare them with the results for one-core fibers in the near- and mid-infrared ranges. Out-of-phase supermodes in tellurite multicore fibers are studied for the first time, to the best of our knowledge. The dispersion curves for in-phase and out-of-phase supermodes are shifted from the dispersion curve for one-core fiber in opposite directions; the effect is stronger for large coupling between the fields in individual cores. The zero dispersion wavelengths of in-phase and out-of-phase supermodes shift to opposite sides with respect to the zero-dispersion wavelength of a one-core fiber. For out-of-phase supermodes, the dispersion can be anomalous even at 1.55 μm, corresponding to the operating wavelength of Er-doped fiber lasers.

A 200 mW, 2.3 µm Tm3+-doped tellurite glass fiber laser

In this paper we present for the first time the 2.3 µm thulium doped tellurite glass fiber laser with practically significant output parameters. The 200 mW average and 400 mW peak output powers at 2.3 µm were obtained using a 30 cm long fiber pumped by a 794 nm fiber coupled commercial laser diode.

Fabrication of a hybrid-cladding tellurite glass fiber doped with Tm3+ and Ho3+

To improve the mechanical properties of tellurite glass fiber, a hybrid-cladding optical fiber with Tm3+/Ho3+ co-doped TeO2-WO3-La2O3 glass core, tellurite glass inner cladding and phosphate glass outer cladding was proposed and fabricated by rod in tube and twice drawing method in this work. The spectroscopic characteristics of the core glass were systematically investigated too, the results showed that the maximum emission cross section was about 7.91 × 10−21 cm2, the longest fluorescence lifetime at 2030 nm was 2.47 ms, the value of σem × τrad was 19.53 × 10−21 cm2ms, and the maximum gain coefficient was about 2.02 cm−1 when 1.2 mol% Tm3+ and 0.6 mol% Ho3+ were co-doped in tellurite glass. The hybrid-cladding tellurite glass fiber fabrication process was presented in detail. A single-mode glass fiber with hybrid-cladding was fabricated and NA1 of the core is 0.116, and NA2 of the inner cladding is 1.249 and is beneficial for pump light collection. The core diameter of which is 6.8 μm, and the fiber loss is 20.16 dB/m. The fabricated hybrid cladding glass fibers can be easily cut without obvious defect.

Laser Sources Based on Rare-Earth Ion Doped Tellurite Glass Fibers and Microspheres

In recent years, huge progress has been made in the development of rare-earth ion doped tellurite glass laser sources, ranging from watt- and multiwatt-level fiber lasers to nanowatt level microsphere lasers. Significant success has been achieved in extending the spectral range of tellurite fiber lasers generating at wavelengths beyond 2 μm as well as in theoretical understanding. This review is aimed at discussing the state of the art of neodymium-, erbium-, thulium-, and holmium-doped tellurite glass fiber and microsphere lasers.

An Experimental and Theoretical Investigation of a 2 μm Wavelength Low-Threshold Microsphere Laser

We present our results on an experimental and theoretical investigation into a glass microsphere laser emitting at 2 μm wavelength. First, we fabricated Ho3+-doped tellurite glass fiber and measured the absorption and emission spectra, and the fluorescence lifetime. Using this fiber, a tellurite glass microsphere with a Q-factor of 2 × 106 was also prepared, and a single-mode laser output with a low threshold of 342 μW was observed using a 1150 nm laser as the pump source. The dynamic characteristics of the microsphere laser were studied theoretically by considering rare-earth ion spectroscopy, the rate equation of the rare-earth energy level, and the light-matter interactions in the microsphere. This work can be used to study laser emissions with low thresholds in rare-earth doped compound glass microresonators for a wide range of applications, such as gas sensing, integrated photonics, and medical surgery.

Solid-core bismuth–tellurite glass fiber with low propagation loss and high nonlinearity

We have fabricated a single-mode bismuth-doped tellurite solid-core glass fiber using a multi-stage fiber fabrication method. Owing to the optimization of the glass composition and rod-in-tube fiber drawing technology, this fiber features a small mode area of 24.63 μm2 and low propagation loss of 0.9 dB/m at 1550 nm. By using the continuous-wave self-phase modulation method, the effective nonlinear parameter γ of this bismuth-doped tellurite glass fiber is estimated to be 417 W−1 km−1 at 1550 nm, which is the highest to date among all known solid-core tellurite glass fibers. Thus, we have developed an unprecedented high nonlinearity and low loss tellurite glass fiber. © 2019 Elsevier B.V. All rights reserved.

Possibilities of laser amplification and measurement of the field structure of ultrashort pulses in the range of 2.7 – 3μm in tellurite glass fibres doped with erbium ions

The amplification of ultrashort signals in the range 2.7 – 3 μm in active tellurite glass fibres with high Kerr nonlinearity and high concentration of erbium ions in the core is theoretically investigated under diode pumping at a wavelength of 0.975 μm. The possibility of producing pulses with the energy ∼10 nJ and the duration smaller than 100 fs with ∼20 dB gain is shown. Moreover, using a specially developed iterative computer algorithm, the possibility of determining the intensity and phase of the generated pulses by measuring their fundamental spectra and two additional spectra obtained by means of nonlinear-optical conversion in short pieces of these optical fibres is demonstrated. Optical fibre samples are made of high-purity TeO2 – ZnO – La2O3 – Na2O glasses with 1021 cm−3 concentration of erbium ions in the core and a low content of hydroxyl groups that causes small losses in the spectral range under consideration. The group velocity dispersions, effective mode fields, nonlinear coefficients and field overlap integrals of the LP01 fundamental modes with a doped core for optical fibres with different core diameters are calculated, and the emission and absorption cross sections are calculated basing on the experimental luminescence spectrum. The optimal parameters of the amplifier are determined by numerically modelling the dynamics of ultrashort pulses using the measured and calculated characteristics.

2.3 µm laser action in Tm3+-doped tellurite glass fiber

A 2.3 µm laser action, as well as a cascade 2.3 µm and a 1.9 µm lasing in a diode-pumped tellurite glass fiber, is demonstrated for the first time.