Doped Tellurite Fiber Research Articles

Tm3+-doped tellurite fiber weak signal amplifier at a wavelength of 2.27 µm

The amplification of a weak narrow-spectrum pulsed signal at a wavelength of 2.27 µm in Tm3+-doped tellurite fiber was demonstrated. The double-clad Tm3+-doped TeO2–ZnO–La2O3–Na2O glass fiber was used as an amplifier active medium. The pulsed seed signal was selected from the supercontinuum by the high reflective fiber Bragg grating. The experimental setup allowed us to obtain pure amplification data over 2.2 µm without amplified spontaneous emission and nonlinear effects contribution. The gain coefficient of Tm3+-doped tellurite fiber was estimated as 0.11 m−1.

L-Band Wavelength-Tunable Er3+-Doped Tellurite Fiber Lasers

The spectroscopic properties of Er3+-doped tellurite glasses were investigated and a 1 wt.% Er3+-doped tellurite fiber was fabricated for L-band lasers. Wavelength-tunable fiber lasers in a linear cavity based on Littrow configuration were developed and studied with different gain fiber lengths as well as output coupling ratios. Wavelength tunable range of 38 nm from 1589–1627 nm was achieved in the experiment with a 3-m Er3+-doped tellurite fiber laser pumped at 1570 nm. A maximum output power of 52.4 mW was obtained at 1614 nm. Compared to L-band Er3+-doped silica fiber lasers, the demonstrated Er3+-doped tellurite fiber lasers exhibit much higher optical signal-to-noise ratio (>30 dB), even at the longest operating wavelength of 1627 nm. Our simulation shows that the laser wavelength can be further extended to 1634 nm if the tellurite fiber loss is improved and the fiber cavity is optimized.

Dual-band Tm3+-doped tellurite fiber amplifier and laser at 1.9\u2009\u03bcm and 2.3\u2009\u03bcm

Ultrabroadband amplification and two-color CW lasing simultaneously near 1.9 μm and 2.3 μm in a Tm3+-doped tellurite fiber were demonstrated experimentally, for the first time to the best of our knowledge. A low-loss Tm3+-doped core fiber from TeO2–ZnO–La2O3–Na2O glasses stable against crystallization was produced by a special technique, providing a low concentration of hydroxyl groups. Supercontinuum from a highly GeO2 doped silica fiber pumped by an Er fiber laser system was used as a seed for an amplifier. A maximum gain of 30 dB and 7 dB was measured at 1.9 μm and 2.3 μm, respectively. We report detailed experimental and theoretical studies, which are in a very good agreement, of laser amplification and generation in the manufactured fiber with carefully measured and calculated parameters. A quantitatively verified numerical model was used to predict power scalability at 2.3 μm in schemes with optimized parameters at increased pump power. The presented results show that a high-quality tellurite fiber is a promising candidate for developing lasers in the 2.3 μm atmospheric window which are particularly relevant for applications in gas sensing, eye-safe laser radars, breath analysis, remote sensing and stand-off trace gas detection.

20 μm Nd^3+/Ho^3+-doped tungsten tellurite fiber laser

Tellurite glass has emerged as a promising ~2.0 μm laser material owing to its excellent features of supporting efficient mid-infrared emission and easy fiber-pulling over the commonly investigated glasses. In this paper, we report an efficient ~2.0 μm laser output from a new-type of Nd3+/Ho3+ co-doped tungsten tellurite fiber laser by using an ultra-short length fiber of 5 cm upon a 795 nm laser diode. The tellurite fibers have been fabricated by a suction technique with the core and cladding diameters of 32 and 125 μm, respectively. The propagation loss of the fiber is measured to be 4.44 dB/m at 1310 nm by using the cutback method. The large energy transfer coefficient from Nd3+ to Ho3+ (3.8 × 10−40 cm6·s–1) and high gain coefficient of Ho3+: 5I7 → 5I8 transition (1.2 cm–1) have confirmed the success of using Nd3+ as sensitizer to realize the ~2.0 μm laser emission of Ho3+. The maximum output power of the laser is obtained to be 12 mW at a center wavelength of 2052 nm with a slope efficiency of 11.2%. The laser threshold is as low as 38 mW, which is around one order of magnitude lower than the previously reported Tm3+/Yb3+ doped tellurite fiber lasers with the similar pump scheme and fiber geometry. The results indicate that the Nd3+/Ho3+ co-doped tungsten tellurite glass fiber laser is a promising laser medium candidate for achieving the ultra-compact and efficient ~2.0 μm laser.

Numerical analysis of 2.7 μm lasing in Er(3+)-doped tellurite fiber lasers.

The laser performance of Er3+-doped tellurite fiber lasers operating at 2.7 μm due to 4I11/2 → 4I13/2 transition has been theoretically studied by using rate equations and propagation equations. The effects of pumping configuration and fiber length on the output power, slope efficiency, threshold, and intracavity pump and laser power distributions have been systematically investigated to optimize the performance of fiber lasers. When the pump power is 20 W, the maximum slope efficiency (27.62%), maximum output power (5.219 W), and minimum threshold (278.90 mW) are predicted with different fiber lengths (0.05–5 m) under three pumping configurations. It is also found that reasonable output power is expected for fiber loss below 2 dB/ m. The numerical modeling on the two- and three-dimensional laser field distributions are further analyzed to reveal the characteristics of this multimode step-index tellurite fiber. Preliminary simulation results show that this Er3+-doped tellurite fiber is an excellent alternative to conventional fluoride fiber for developing efficient 2.7 μm fiber lasers.

Broadband 27 μm amplified spontaneous emission of Er^3+ doped tellurite fibers for mid-infrared laser applications

Er3+ doped tellurite fibers have been fabricated using a convenient suction technique. Different scanning calorimetry (DSC), Electro-probe micro-analyzer (EPMA), Raman, steady and dynamic luminescence spectra were performed to investigate their thermal, structure, and luminescent properties. Broadband 2.7 μm amplified spontaneous emission (ASE) emission with concurrent 1.5 μm and visible up-conversion emissions have been achieved in fibers with various lengths upon the excitation of 980 nm laser diode (LD). A quantitative study of the spectroscopic properties has been further analyzed in detail according to the Jude-Ofelt model, rate equation, and Dexter’s theory to evaluate the competitive relationship among them. The desirable spectroscopic characteristics associated with excellent thermal stability and mechanical properties indicate that the Er3+ doped tellurite fibers are excellent host matrices for 2.7 μm lasing and may provide applications in mid-infrared fiber lasers and amplifiers.

All-Fiber Passively Q-Switched Laser Based on Tm3+-Doped Tellurite Fiber

We report all-fiber passively Q-switched Tm3+-doped tellurite fiber lasers. The composite tellurite fiber is specially designed to improve the mechanical strength. Both carbon nanotubes (CNTs) and semiconductor saturable absorber mirror (SESAM) are inserted separately into the laser cavities as SAs to demonstrate a fiber-integrated setup. In a short, 9-cm tellurite fiber, 1.86- $\mu \text{m}$ -pulsed lasers without self-mode-locking effect are demonstrated by in-band pumping at 1.59 $\mu \text{m}$ . An average power of 84 mW is obtained in CNT-pulsed laser with 860-ns duration, whereas in SESAM-pulsed laser, the average power reaches 21 mW with 516-ns pulsewidth.

Fabrication and upconversion luminescence of Er3+/Yb3+ codoped TeO2–WO3–Na2O–Nb2O5–Al2O3 glass fibers

The tellurite fibers based on glasses with the composition TeO2–WO3–Nb2O5–Na2O–Al2O3–Er2O3–Yb2O3 were fabricated by the rod-in-tube technique using a Heathway drawing tower. The upconversion luminescence of Er3+/Yb3+ codoped tellurite glass fibers under 980nm excitation were investigated. The Er3+/Yb3+co-doped tellurite fibers show an efficient up-conversion process in comparison with the Er3+-doped tellurite fibers. The pump power dependent intensities were discussed, which showed that two photons are involved in the upconversion process.

Effect of Ce 3+, Dy 3+, and Tb 3+ additions on the spectroscopic properties of Er 3+/Yb 3+ codoped tellurite glasses

Serious up-conversion process (UCPE) of Er 3+ in Er 3+/Yb 3+ codoped tellurite glass is one of the big challenges impeding Er 3+ doped tellurite fiber amplifier towards full commercialization, though its gain bandwidth is much wider than Er 3+ doped silica fiber amplifier. For solving or suppressing UCPE, it has been proposed to better introduce a third foreign ion with proper layout of energy level into this system, and thus, modulate energy transfer between them. Three rare earth ions, RE 3+=Ce 3+, Dy 3+, and Tb 3+, are selected in this paper, and it turns out that three of them can efficiently reduce the transition probability of UCPE, and Ce 3+ rather than Dy 3+ and Tb 3+ can at the same time enhance the 1.53 μm emission of Er 3+ originating 4I 13/2→ 4I 15/2. The underlying mechanism will be discussed based on both experimental and theoretical results.

Theoretical Modeling of a $\sim {2}~\mu{\rm m}~{\rm Tm}^{3+}$-Doped Tellurite Fiber Laser: The Influence of Cross Relaxation

A rate equation approach is used to model an experimentally realized ~ 2 mum Tm3+-doped tellurite fiber laser utilizing an in-band pumping scheme (3H6 rarr 3F4) . Excellent agreement between the theoretically predicted and experimentally measured slope efficiency is obtained. It is shown that in order to achieve agreement between the predicted and measured thresholds it is important to include cross-relaxation mechanisms with the 3H4 level, even with the in-band pumping scheme. By fitting the results of the model with level lifetime measurements and the threshold pump powers we have extracted the cross-relaxation parameters of Tm-doped tellurite glass.

Efficient ~2 μm Tm^3+-doped tellurite fiber laser

Laser emission in the range of 1.88-1.99 micrim from a Tm3+ -doped tellurite fiber is demonstrated when pumped with a diode-pumped Er3+/Yb3+-doped silica fiber laser operating at 1.57-1.61 microm. This pump source excites the Tm3+ ions directly into the F43 upper laser level and yields an output power of 280 mW with a slope efficiency of 76% in a 99%-12% laser cavity arrangement and a 32 cm long fiber. This result is very close to the Stokes efficiency limit of approximately 80%. This is, to the authors' knowledge, the first demonstration of high efficiency lasing in a tellurite fiber at wavelengths longer than 1.56 microm.

∼2 μm Tm3+/Yb3+-doped tellurite fibre laser

We present, for the first time, laser emission in the range 1.910–1.994 μm in Tm3+/Yb3+-doped tellurite fibre when pumped using an Yb3+-doped double-clad silica fibre laser operating at 1.088 μm. With this pump scheme there was strong pump excited state absorption (ESA) which caused upconversion emission at 800 nm and 480 nm due to the Tm3+: 3H4 → 3H6 and Tm3+: 1G4 → 3H6 transitions, respectively. This strong ESA limited the maximum slope efficiency to 10% with respect to absorbed pump power, and the maximum output power to 67 mW. This is however the highest output power which has been achieved in a tellurite fibre laser so far. The lowest observed threshold was 114 mW for a 22 cm long fibre and a 90% reflective output coupler. Further power scaling was limited due to thermal damage at the pump end of the fibre. The optimum fibre length for this arrangement was around 16 cm but lasing was achieved in lengths ranging from <9 to 30 cm. Tellurite glass offers significant advantages over silicate and fluoride glasses which make it a very promising material for compact, medium power, near and mid-IR fibre lasers for range-finding, medical and atmospheric monitoring and sensing applications.

Spectroscopic characterization of signal gain and pump ESA in short-lengths of RE-doped tellurite fibers

We report the results of emission and amplification in Tm3+- and Er3+-fibers for signal gain in the 1460–1600nm region, which covers a large part of S-, C- and L-bands of silica fiber optical communication networks. The paper explains the mechanism for alleviating the pump-excited absorption in Er3+-doped and Tm3+-doped tellurite fibers for maximizing the pump inversion efficiency at 980nm using the co-dopants and via the structural modification of TeO2 glass by incorporating a high phonon energy oxide namely, B2O3. The spectroscopic data and gain bandwidth of Er-doped fibers are reported in the C- and L-bands. To date the measured maximum relative gain in short fibers of 5–10cm in length in C- and L-bands are: 30dB and 15dB, respectively. By comparison the internal gain in a 20cm long Tm/Yb ion co-doped fiber pumped with a 980nm source was 7dB.

Infrared emission and energy transfer in Tm^3+, Tm^3+-Ho^3+ and Tm^3+-Yb^3+-doped tellurite fibre

The infrared emission spectra and decay lifetimes of Tm(3+)-doped and Tm(3+)-Ho(3+), Tm(3+)-Yb(3+) co-doped tellurite fibres were measured using 808 nm and 978 nm diode laser pump sources in the range 1.35 mum to 2.2 mum. The spectra were compared with varying fibre lengths and core diameters. Tm(3+)-doped fibre shows strong emission at ~1.8 mum and when co-doped with Ho(3+), energy transfer results in strong Ho(3+) fluorescence at ~2.0 mum. These fibres show promise for compact mid-IR fibre laser sources.

Enhancement in pump inversion efficiency at 980 nm in Er3+, Er3+/Eu3++ and Er3+/Ce3+doped tellurite glass fibers

Amplification properties have been compared in Er(3+), Er(3+)/Eu(3+) and Er(3+)/Ce(3+) doped tellurite glass fibers using a 980 nm pumping scheme. The pump efficiency has been compared in the 3 types of fibers. Er(3+) ion upconversion in bulk glasses and fibers in visible range has been measured and the Er(3+) ion IR fluorescence intensity and lifetimes have been recorded to understand the amplification characteristics. Codoping with Ce3+ is more efficient in Er(3+) doped tellurite fibre.

Fabrication and amplified spontaneous emission spectrum of Er 3+-doped tellurite glass fiber with D-shape cladding

Tellurite glass is proposed as a host for broadband erbium-doped fiber amplifiers because of their excellent optical and chemical properties. A single-mode Er 3+-doped tellurite glass fiber with D-shape cladding was fabricated in this work. The characterization of amplified spontaneous emission (ASE) from this newly fabricated Er 3+-doped tellurite fibers are exhibited. When pumped at 980 nm, a very broad erbium ASE nearly 150 nm around 1.53 μm is observed. The changes in ASE with regard to fiber lengths and pumping power were measured and discussed. The output of 2 mW from Er 3+-doped tellurite fiber ASE source was obtained under the pump power of 660 mW. The broad 1.53 μm emission of Er 3+ in tellurite glass fiber can be used as host material for potential broadband optical amplifier and tunable fiber lasers.

Characterization of broadband amplified spontaneous emission of erbium-doped tellurite fiber with D-shape cladding

In this presentation, we report the results of spectral characteristics of amplified spontaneous emission (ASE) from a newly Er3 +-doped tellurite fiber with D-shape cladding. When pumped at 980 nm, an erbium ASE source that has nearly a flatten FWHM bandwidth of 100 nm is obtained in the D-shape cladding erbium-doped tellurite fiber with 30–60 cm length. The changes in ASE with regard to pumping power and fiber lengths were measured. Output power up to 2.0 mW is obtained with a total pump power of 660 mW.

Characterization of Amplified Spontaneous Emission fromEr3+-Doped Tellurite Fibre

We present the characterization of amplified spontaneous emission(ASE) from newly fabricated Er3+-doped tellurite fibres.When pumped at 980 nm, a very broad erbium ASE in the range1450–1650 nm is observed. The changes of ASE with regard to fibrelengths and pumping power were measured. The output of 2 mW from anEr3+-doped tellurite fibre ASE source is obtained with thepump power of 540 mW.

Intrinsic defects and glass stability in Er3+ doped TeO2 glasses and the implications for Er3+-doped tellurite fiber amplifiers

The Er3+-doped tellurite fiber amplifier is of great interest for telecommunications, although noise hinders its performance. We report on intrinsic photoluminescence in tellurite glasses and propose that it is due to intrinsic defects, such Te–Te bonds and bi-co-ordinated Te. The defects are due to oxygen vacancies, which are created during glass melting; up to 0.5 wt% volatilization loss from the melt is observed, which corresponds to up to 2.5 at.% loss with respect to total at.% oxygen. In other words, for every 100 oxygen atoms in the melt 2.5 are missing. We show that doping with Er3+ of up to 2 at.% with respect to total at.% oxygen increases the host glass stability, i.e. diminishes the first crystallization peak above the glass transition temperature, Tg, and increases by 80 °C the gap between Tg and the first crystallization peak temperature. This increase should aid drawing of the Er3+-doped tellurite. Further doping up to 4 at.% of Er3+ results in a poor glass prone to crystallization. We argue that Er3+-dopants are efficiently incorporated near to the intrinsic defects of the tellurite glass structure. This may modify spectroscopic properties of the Er3+ ion, such as spontaneous emission resulting in the unfortunate noise found for the Er3+-doped tellurite fiber amplifier.

1.5 Tbit/s (75×20 Gbit/s) DWDM transmission using Er 3+ -doped tellurite fibre amplifiers with 63 nm continuous signal band

63 nm continuous signal band of a 1.5 Tbit/s (75×20 Gbit/s) dense wavelength division multiplexed transmission over 200 km was demonstrated by applying Er3+-doped tellurite fibre amplifiers.