Doped Chalcogenide Glass Fibre Research Articles

5 µm CW Ce3+-doped chalcogenide glass fiber laser with 17% slope efficiency.

Efficient room temperature mid-infrared laser action in a Ce3+-doped chalcogenide fiber was demonstrated. The fiber had a doped selenide glass core in an undoped sulfide glass cladding. The pump source was a CW Fe2+:ZnSe laser emitting at 4.14 µm. The optimized fiber length allowed obtaining up to 7 mW of 5.06 µm output with 17% slope efficiency at room temperature.

Short review and prospective: chalcogenide glass mid-infrared fibre lasers

Rare-earth ion doped, silica glass, optical fibre amplifiers have transformed the world by enabling high speed communications and the Internet. Fibre lasers, based on rare-earth ion doped silica glass optical fibres, achieve high optical powers and are exploited in machining, sensing and medical surgery. However, the chemical structure of silica glass fibres limits the wavelength of laser operation to < 2.5 µm, which excludes the mid-infrared longer wavelength range of 3–50 µm. Rare-earth ion doping of fluoride glasses enables manufacture of fibre lasers up to a limiting 3.92 µm wavelength, but the fluoride glass chemical structure again prevents operation at longer wavelengths. Optical fibre lasers that are constructed from different rare-earth ion doped chalcogenide glass fibres will potentially operate across the 4–10 µm wavelength range, where suitable high-power lasers currently do not exist. We present a short review here of our recent work in achieving first time, continuous wave, mid-infrared fibre lasing beyond 5 μm wavelength in Ce3+-doped selenide chalcogenide fibre. We place this disruptive breakthrough into the wider fibre laser context, and also present the unprecedented advances in new cross-sector applications that will be enabled by mid-infrared fibre lasers in the 4–10 µm wavelength range. To surpass the few mW power output of the Ce3+-doped chalcogenide glass fibre lasing achieved to date, the glass quality of the doped chalcogenide fibres must now be improved, similar to the challenges originally facing the first glass fibre lasers based on silica.

Characteristics of a CW ∼5 μm Ce3+-doped chalcogenide glass fiber laser

Energy, spectral and temporal characteristics of a Ce3+-doped chalcogenide glass fiber laser continuously pumped by a 4.16 μm Fe2+:ZnSe laser were investigated. Milliwatt level output power was obtained. In case of low Q-factor of the resonator the laser operated at λ = 4.62 μm corresponding to the narrow peak in Ce3+ emission spectrum. At higher Q-factor, the lasing wavelength changed to 5.0–5.1 μm corresponding to the plateau in the gain spectrum. In contrast to Tb3+-doped mid-infrared fiber lasers, Ce3+-doped fiber laser had no tendency to non-relaxing spike operation.

Designing a W-type index praseodymium-doped chalcogenide fiber for strongly-efficient MIR Laser beyond 4 μm

This study is to propose an efficient design based on W-type index praseodymium (Pr 3+ )-doped chalcogenide fiber to enhance the emission of mid-infrared (MIR) wavelength beyond 4 μm. The advantage of the proposed design is to enlarge the core diameter to 32 μm under single mode guidance in order to restrict any impacts of nonlinearity and enhance the applied pumping power before the damage threshold. The effective mode field areas are about 979 μm 2 and 812 μm 2 at 4.5μm emitted MIR wavelength and 2.04μm pump wavelength, respectively. In the considered laser layout within this paper, a single pair of Fiber Bragg Gratings FBGs lay is adopted in the overlapping area of the emitting cross-sections parts of Pr 3+ ions in the transitions ( 3 F 2 , 3 H 6 → 3 H 5 and 3 H 5 → 3 H 4 ). This selected laser layout avoids the difficulties in the fabrication of concatenated FBGs in Pr 3+ -doped chalcogenide glass fibers. In addition, the efficiency of the laser can be also enhanced at this laser layout by emitting two photons in MIR wavelengths from one excited ion. The simulation outcomes indicate the possibility to exceed 61% of slope efficiency at 4.5 μm for 1dB/m loss in the fiber.

Preparation of high purity Sm3+-doped Ga-Ge-As-Se glass and low-loss fiber

The high-purity 700 ppmw Sm3+-doped Ga2.2Ge26.5As14.6Se56.7 glass is prepared and investigated. The glass has an extra-low content of impurities, a wide transmission range (0.9–16 μm), a high glass transition temperature (330 °C), and high stability against crystallization. The low content of limiting impurities is the result of the multistage procedure for the purification of individual components, the basic glass-forming melt, as well as the chemical transport reactions technique. The Sm3+-doped Ga-Ge-As-Se glass shows photoluminescence in the spectral regions 1.2–1.3 μm, 1.4–1.6 μm, 1.75–2 μm, 2.2–3 μm, and 3.5–4.2 μm. In a complex system of samarium levels, the longest-lived energy transition is established to be the one at 3.7 μm with a lifetime of 60 μs From the high-purity Sm3+-doped Ga-Ge-As-Se glass, the single-index fiber with minimum optical loss of 0.5 dB/m at 5.7 μm and without impurity bands in spectrum is fabricated. It is the best result concerning the glass purity and optical loss among Sm3+-doped chalcogenide glass fibers.

Core-clad terbium doped chalcogenide glass fiber with laser action at 5.38 μm

The core-clad Tb3+-doped Ga-Ge-As-Se/Ge-As-S chalcogenide glass fiber is fabricated and tested in laser experiment. To prepare the high-purity terbium doped Ga-Ge-As-Se core glass, the special multi-stage purification technique is developed. The 1050 ppmw Tb3+-doped core Ga3.2Ge24.9As15.3Se56.6 glass is characterized by an extra-low content of limiting hydrogen impurity, high stability against crystallization and strong broadband photoluminescence in the middle infrared range. The doped chalcogenide fiber has a total diameter of 400 μm, a core diameter of 18 μm, and minimum optical losses of 3 ± 0.3 dB/m at a wavelength of 7.1 μm. Using a Tm3+ 1.98 μm fiber laser as a pump source, the threshold of 5.38 μm lasing with spike structure was reached in chalcogenide fiber for the first time.

Large Mode Area Pr3+-Doped Chalcogenide PCF Design for High Efficiency Mid-IR Laser

We propose a novel design of a photonic crystal fiber made of praseodymium (Pr3+)-doped chalcogenide glass with single mode operation beyond 4 $\mu \text{m}$ . Our design has an enlarged Pr3+-doped core diameter of 60 $\mu \text{m}$ . The field area of the emitted fundamental mode is about 3160 $\mu \text{m}^{2}$ at 4.5 $\mu \text{m}$ and 2050 $\mu \text{m}^{2}$ at a pump wavelength of 2.04 $\mu \text{m}$ . This large mode field area not only reduces the nonlinear effects but also increases the possible pump power before the damage threshold. The selected laser layout avoids fabrication difficulties associated with cascaded fiber Bragg gratings in Pr3+-doped chalcogenide glass fibers. The proposed design also increases the laser efficiency by using the overlap of the emission cross sections of Pr3+ in the transitions (3F2, 3H6 $\to$ 3H5 and 3H5 $\to$ 3H4) to enable both transitions to simultaneously produce a single coherent mid-infrared wavelength. The simulation results reveal that more than 64% of slope efficiency could be achieved at 4.5 $\mu \text{m}$ for a fiber loss of 1 dB/m.

Numerical and experimental investigation of mid-infrared laser action in resonantly pumped Pr3+ doped chalcogenide fibre

Numerical modelling of a Pr3+-doped chalcogenide glass fibre laser is presented in this paper. The spectroscopic parameters are extracted from in-house prepared Pr3+ doped selenide-chalcogenide glass samples and used in the modelling. In this contribution, particular attention is paid to a novel resonant pumping scheme. The modelled laser performance is tested as a function of pump wavelength, fibre length, signal wavelength, fibre background loss and output coupler reflectivity. The modelling results show that the proposed resonant pumping scheme, which might be achieved in practice using a high power QCL pump, allows for a significant reduction in the laser threshold and an increase in the laser efficiency. A slope efficiency of 54% is calculated when the fibre losses are brought down to 1 dB/m.

Mid-infrared photoluminescence in small-core fiber of praseodymium-ion doped selenide-based chalcogenide glass

Rare earth (RE)-ion doped chalcogenide glasses are attractive for mid-infrared (MIR) fiber lasers for operation >4 μm. Our prior modeling suggests that praseodymium (Pr) is a suitable RE-ion dopant for realizing a selenide-based, chalcogenide-glass, step index fiber (SIF) MIR fiber laser operating at 4-5 μm wavelength. Fabrication of RE-ion doped chalcogenide glass fiber, especially with a small core, is a demanding process because crystallization must be avoided during the heat treatments required to effect shaping. Here, a 500 ppmw (parts per million parts, by weight) Pr3+-doped Ge-As-Ga-Se glass SIF with a 10 μm or 15 μm diameter core is reported; the cladding glass is Ge-As-Ga-Se-S. The multistage process to produce the fiber is outlined. Thermal and optical properties of the core/clad. glass pair, and the crystalline/amorphous nature and optical behavior of the small core fiber are reported. MIR photoluminescence and lifetime of a RE-ion doped chalcogenide glass small core fiber are reported for the first time.

Theoretical study of population inversion in active doped MIR chalcogenide glass fibre lasers (invited).

We study the mechanism of the population inversion in mid-infrared fibre lasers based on a chalcogenide glass host doped with active lanthanide ions. Three lanthanide dopant ions are considered: terbium, dysprosium and praseodymium. We predict the relevant trivalent ion level populations and gain. The simulation parameters were obtained by fabricating and optically characterising a series of trivalent ion doped chalcogenide glass samples. We also provide simple analytical expressions that aid the design of the cascade lasing process.

Numerical investigation of mid-infrared emission from Pr $$^{3+}$$ 3 + doped GeAsGaSe fibre

The experimentally obtained luminescence characteristics of a praseodymium (Pr\(^{3+})\) doped chalcogenide glass fiber are studied numerically using a rate equation approach. The numerical model includes both the radiative and non-radiative transition paths whilst it neglects the up-conversion processes. Photoluminescence spectra at mid-infrared wavelengths ranging from 3.5 to 6 \({\upmu }\)m were obtained by using two pump wavelengths: 1.55 and 1.94 \({\upmu }\)m. A good agreement between the experiment and theory is obtained for the photoluminescence decay profiles.

Theoretical studies on mid-infrared amplification in Ho3+-doped chalcogenide glass fibers

This paper investigated the MIR emission of Ho3+-doped Ge20Ga5Sb10S65 chalcogenide glasses upon excitation of 900nm laser diode. The spontaneous emission probability, absorption cross-section, and emission cross-section were calculated using the Judd-Ofelt theory and the Fuchbauer–Ladenburg equation. Theoretical studies of the Ho3+-doped chalcogenide glass fiber amplifier operating in the MIR wavelength range, specifically around the 2.86μm wavelength, were performed based on the rate and light propagation equations. The results indicate that the chalcogenide glass fiber presented a larger signal MIR gain and wider MIR gain spectrum. The maximum signal gain was 36dB and the gain width was 20dB.

Modelling of a simple Dy3+ doped chalcogenide glass fibre laser for mid-infrared light generation

A simple Dy3+-doped chalcogenide glass fibre laser design for mid-infrared light generation is studied using a one dimensional rate equation model. The fibre laser design employs the concept of cascade lasing. The results obtained demonstrate that efficient cascade lasing may be achieved in practice without the need for fibre grating fabrication, as a sufficient level of feedback for laser action is provided by Fresnel light reflection at chalcogenide glass fibre–air interfaces. Further enhancement of the laser efficiency can be achieved by terminating one of the fibre ends with a mirror. A numerical analysis of the effect of the Dy3+ doping concentration and fibre loss on the laser operation shows that with 5 W of pump power, at 1.71 μm wavelength, output powers above 100 mW at ∼ 4.5 μm wavelength can be achieved with Dy3+ ion concentrations as low as 3 × 1019 cm−3, when fibre loss is of the order 1dB/m.

Mid-wave IR and long-wave IR laser potential of rare-earth doped chalcogenide glass fiber

The mid-wave IR and long-wave IR laser potential of rare-earth ions in chalcogenide glass fiber is reviewed. Spectroscopic data for the mid-wave and long-wave IR transitions for Pr/sup 3+/, Dy/sup 3+/, and Tb/sup 3+/ in chalcogenide glass is presented and used as a basis for discussion of laser potential in these glasses.

Proposal for an Er/sup 3+/-doped chalcogenide glass fiber upconversion laser operating at 980 nm and pumped at 1480 nm

We propose a novel fiber upconversion laser operating at 980 mn and pumped at 1480 nm, which will allow remote optical pumping of erbium-doped optical amplifiers. From the measured spectroscopy, we show Er/sup 3+/-doped gallium lanthanum sulphide glass to be a potential host for such a 1480-nm/980-nm upconversion laser. The small-signal gain is analyzed numerically and the lasing possibilities are discussed.

Rare-earth doped chalcogenide glass fibre laser

We report on the first laser action in a rare-earth doped chalcogenide glass fibre. Laser action at 1080nm was obtained in a 22mm long gallium lanthanum sulphide glass fibre with a neodymium doped core, fabricated by the rod-in-tube technique. The laser was pumped continuous wave with a Ti:sapphire laser at 815nm and showed a self-pulsing behaviour.