During the last decade there has been a surge of interest in developing mid-infrared (mid-IR) fiber-based supercontinuum (SC) sources. Such broadband light sources take advantage of extreme spectral broadening of high-intensity laser pulses in infrared optical fibers usually made of soft glasses, such as chalcogenides that offer the widest transmission window and the highest nonlinearity. Beyond their spatial coherence and high brightness, mid-IR fiber SC sources are nowadays operating over some wavelength ranges of thermal sources with superior performances for spectroscopic applications. However, intrinsic limitations of current fibers or even integrated waveguides now appear to impose the long-wavelength edge of mid-IR SC sources around 13-15 μm. The current research has to focus now on extending the wavelength coverage over the entire mid-IR molecular fingerprint region (often defined as from 2 to 20 μm).
We here overcome this limitation by the engineered nonlinear transformation of femtosecond pulses over the full transmission window of a step-index chalcogenide fiber. In contrast to previous works, we reach the long-wavelength transparency edge of Se-rich glass family near 18 μm, and without including arsenic and antimony compounds considered as toxic elements and pollutants. Our end-to-end control of both materials chemistry and nonlinear fiber optics, including glass synthesis and purification, fiber design and drawing, as well as engineering of SC generation, has allowed us to optimize each of these crucial steps in order to demonstrate coherent mid-IR SC generation spanning from 2 to 18 μm.
Optical fibers mid-infrared (mid-IR) supercontinuum (SC) generation for sources covering the 1–20 μm range are of great interest for many applications in optics, spectroscopy, sensing for environmental monitoring or medical diagnosis and treatment. We present here our work regarding two low phonon energy glasses families, leading to highly nonlinear optical fibers for SC generation: tellurites and seleno-telluride glasses. Tellurite fibers are suitable for working in the 1-5 μm range, when seleno-telluride ones are intended to the 2-16 μm range. For tellurites, we focus on the definition of glass pairs suitable for the drawing of step index fibers with a controlled chromatic dispersion for a femto-second (fs) pumping around 2 μm. In the case of chalcogenide glasses, we focus on the Ge-Se-Te ternary system, which offers the advantage of allowing the drawing of step index or micro-structured fibers avoiding the usage of toxic arsenic. Depending on the fiber geometry the management of the chromatic dispersion is quite different. Suspended core fibers allow to shift deeply the unique zero dispersion wavelength (ZDW) towards short wavelengths for fs pumping around 2- 3 μm. For step index fibers, it is possible to design waveguides with no, one or two ZDW. Various pumping schemes are available between 3 and 9 μm, with a fs tunable source. As a result, SC generation experiments in these different fibers allows to reach wide spanning spectra, between 1 and more than 5 μm for tellurite fibers, and between 2 and more than 14 μm in the case of chalcogenides ones.
The development and the emergence of fully integrated all-fiber optical systems is very interesting from a technical point of view in photonics. Indeed, the development of mutimaterials fibers combining both optical waveguide properties and simultaneous in-fiber electrical excitation could provide plenty of innovative signal-processing, sensing or imaging functionalities. Here, we report the engineering of a new glass/metal composite fiber. For the glass, we have chosen tellurite glasses for their excellent thermo-viscous abilities (low Tg) and linear/nonlinear optical properties. This low Tg allows to have a larger panel of potential metals to be co-drawn with. The synthesis is firstly realized by build-in-casting at room atmosphere which allows to get a large-core. Then, the rod-in-tube technique and the insertion of metallic wires allow to get a step-index fiber with a small-core (7μm) and two continuous metallic electrodes running along the fiber axis (Øelectrodes = 30μm). Thus, we obtain a tellurite-based core-clad dual-electrode composite fiber made by direct, homothetic preform-to-fiber thermal co-drawing. The rheological and optical properties of the selected glasses allow both to regulate the metallic melting flow and to manage the refractive index core/clad waveguide profile. We will discuss the engineering of these multimaterials optical fibers and their characterization: thermal and viscosity properties, linear optical properties (loss), electrical properties with a continuity of the electrodes over meters of fiber.
Development of broadband supercontinuum sources has been studied since decades for its high application potential in various fields like spectroscopy, medical science and others. First experiments were made with silica but the results shown the need to find new materials for supercontinuum generation in the IR wavelength range. Two types of materials have been found interesting for supercontinuum generation: chalcogenide and tellurite glasses. These materials have a high non-linear refractive index and a good transmission in infrared which provides a high potential for applications. Bulks tellurite glasses transmit until 5µm while bulks chalcogenide glasses transmit until 12-20µm depending on their composition. We report here the synthesis of low-OH step-index tellurite fibers and their linear and non-linear characterization. The synthesis is firstly realized by build-in-casting in a glovebox which allows to get a large-core preform(∅clad/∅core 2) and a large core corresponding fiber(∅core 60µm). Then, the rod-in-tube technique allows, from the jacketing of the stretched initial preform, to get a small-core preform and subsequently a small core fiber (∅core 3.5µm). The minimum of losses of the large-core fiber is below 1dB/m, the IR transmission wavelength exceeds 4 µm on several meters of fibers and reaches more than 5 µm on small samples (several centimeters long). We have developed core-clad composition with a large refractive index difference (∆n=0.132) which provides a high confinement in our step-index fibers. We discuss the supercontinuum generation in these fibers exploiting numerical simulations based on the generalized nonlinear Schrödinger equation and then we present the supercontinuum experimental results obtained between 1 and 5µm. Most of pollutant and greenhouse gases emitted by human activity, including methane, carbon dioxide and nitrous oxide, absorbs in the mid-IR. The spectroscopic experiments realized on the gases through supercontinuum generation between 1 and 5 µm are presented.
We present an overview of the fabrication process and characterization of germanate, germanate-tellurite and tellurite microstructured fibers or step-index fibers with different index contrasts. For microstructured fibers, we exploit the generated SC for methane spectroscopy measurements in the mid-infrared by means of the supercontinuum absorption spectroscopy technique. We demonstrate also an ageing process of microstructured fibers in ambient atmosphere. For stepindex fibers, several compatible core/cladding glasses were explored for fiber manufacturing with a dehydration process, allowing the drawing of low-OH tellurite fibers. We report both numerical and experimental demonstrations supercontinuum (SC) generation in these fibers. Finally we report our latest results in the generation of SC until 5.3 μm in a step-index tellurite fiber.
We report the manufacturing and characterization of Tellurite micro structured fibres (MOFs) with low OH content. The different purification processes used during the fabrication of the TeO2 - ZnO - Na2O glass allowed us to reduce the hydroxyl compounds concentration down to 1ppm mass. A suspended core MOF was drawn from this material and then pumped by nanojoule-level femtosecond pulses at 1.7μm, its zero dispersion wavelength (ZDW), and well above it at 2.5μm. We show the related supercontinuum (SC) generated in the two distinct dispersion regimes of the waveguide. Moreover, the SC spanning was extended in both visible and mid-IR regions (between 600nm up to 3300nm) by the taperisation of the previously tested MOFs.
We report on the generation of a supercontinuum in a chalcogenide microstructured tapered fiber. The
suspended core diameter of the fiber is reduced from 5.5 μm to 0.8 μm in the waist of the tapered region.
The zero dispersion wavelength is below 2 μm in the tapered region. To pump the fiber, we use a modelocked
laser of 4 ps, with a central wavelength of 1960 nm. With only 150 W peak power in the fiber a
supercontinuum is generated from 1300 to 2600 nm taking the supercontinuum wavelength edge at -30 dB
from the continuum.
In this work we report our achievements in the elaboration and optical characterizations of low-losses suspended
core optical fibers elaborated from As2S3 glass. For preforms elaboration, alternatively to other processes like the stack and draw or extrusion, we use a process based on mechanical drilling. The drawing of these drilled
performs into fibers allows reaching a suspended core geometry, in which a 2 μm diameter core is linked to the
fiber clad region by three supporting struts. The different fibers that have been drawn show losses close to
0.9 dB/m at 1.55 μm. The suspended core waveguide geometry has also an efficient influence on the chromatic
dispersion and allows its management. Indeed, the zero dispersion wavelength, which is around 5 μm in the bulk
glass, is calculated to be shifted towards around 2μm in our suspended core fibers. In order to qualify their
nonlinearity we have pumped them at 1.995 μm with the help of a fibered ns source. We have observed a strong
non linear response with evidence of spontaneous Raman scattering and strong spectral broadening.
We present the fabrication of tellurite TeO2-ZnO-Na2O (TZN) microstructured optical fibers (MOFs) with a suspended
core and the characterization of their optical properties. The fibers are designed to develop an infrared supercontinuum
generation using a sub-nJ femtosecond pulsed laser at 1.56μm. By pumping a 20 cm long fiber we generate a
supercontinuum (SC) spanning over 800 nm in the 1-2 μm wavelength range. For a MOF with a core size of 2.2 μm the
zero dispersion wavelength (ZDW) is at 1.45 μm. The effective area of TZN MOF is 3.5 μm2 and the nonlinear coefficient is calculated to be 437 W-1km-1.
The development of chalcogenide glasses fibers for application in the infrared wavelength region between 1 and 10
μm is a big opportunity. More particularly, the possibility to generate efficient non linear effects above 2 μm is a real
challenge. We present in this work the elaboration and optical characterizations of suspended core microstructured
optical fibers elaborated from the As2S3 chalcogenide glass. As an alternative to the stack and draw process a
mechanical machining has been used to the elaboration of the preforms. The drawing of these preforms into fibers
allows reaching a suspended core geometry, in which a 2.5 μm diameter core is linked to the fiber clad region by
three supporting struts. The zero dispersion wavelength is thus shifted towards 2 μm. At 1.55 μm our fibers exhibit a
dispersion around -250 ps/nm/km. Their background level of losses is below 0,5 dB/m. By pumping them at 1.55 μm
with a ps source, we observe self phase modulation as well as Raman generation. Finally a strong spectral
enlargement is obtained with an average output power of - 5 dbm.
Chalcogenide glasses are known for their large transparency in the mid infrared and their high refractive index (>2).
They present also a high non linear refractive index (n2), 100 to 1000 times larger than for silica. An original way to
obtain single-mode fibers is to design photonic crystal fibers (PCFs). Until now, chalcogenide PCFs are realized using
the stack and draw process. However this technique induces defects, like bubbles, at the capillaries interfaces, causing
significant scattering losses. Until now, the best transmission obtained was 3dB/m at 1.55μm. The poor PCF
transmission reduces significantly their application potential. So, we present a new efficient method to realize low-loss
chalcogenide PCFs. This original method by molding permits to reduce the optical losses down to 1dB/m at 1.55μm and
less than 0.5dB/m between 3 and 5μm for an As-Se PCF. Furthermore, this molding method can be used for different
compositions. Single mode fibers were realized. Moreover, very small core fibers were realized with this method,
obtaining a non linear coefficient of 15 000W-1km-1 with an As-Se PCF. We also observed self phase modulation at
1.55μm on a fiber with a 2.3μm2 mode area.
In recent years, infrared light sources have attracted great attention for their application in remote sensing, sensors, optical communication, medical and military technology, and so on. Innovative erbium-doped microstructured optical fiber ring lasers (EDFRLs) have been proposed in order to increase the performance of the conventional fiber lasers, enabling a number of advantages such as smaller size, higher power, better beam quality. In a previous work, the authors proposed a design of a Fabry Perot laser made of a novel erbium-doped
Ga5Ge20Sb10S65 chalcogenide glass, operating in the Mid-IR wavelength range. This work reports the design of a ring laser, made of the same glass, operating at the signal wavelength λs = 4600 nm and at the pump wavelength λp = 806 nm. The design and optimization has been performed in order to improve the laser performance. The numerical computer code, implemented ad-hoc to investigate the fiber ring laser, takes into account the rate equations of the 5-level erbium ion system, the pump and signal power propagation, the energy transfer of the
up-conversion and cross-relaxation phenomena, the cavity losses and the coupling losses. The measured amplified spontaneous emission ASE power spectrum has been accurately sampled in 150 wavelength slots from λ1=4200 nm to λ2=4800 nm, to obtain more realistic simulations.
Among the measures to reduce CO2 emissions, capture and geological storage holds out promise for the future in the
fight against climate change. The aim of this project is to develop a remote optical sensor working in the mid-infrared
range which will be able to detect and monitor carbon dioxide gas. Thus, chalcogenide glasses, transmitting light in the
1-6 μm range, are matchless materials. The first of our optical device is based on the use of two GeSe4 chalcogenide
optical fibers, connected to an FTIR spectrometer and where CO2 gas can flow freely through a 4 mm-spacing between
fibers. Such sensor system is fully reversible and the sensitivity threshold is about 0.5 vol.%. Fiber Evanescent Wave
Spectroscopy technology was also studied using a microstructured chalcogenide fiber and first tests led at 4.2 μm have
provided very promising results. Finally, in order to explore the potentiality of integrated optical structures for microsensor,
sulphide or selenide Ge25Sb10S(Se)65 rib waveguide were deposited on Si/SiO2 wafer substrates, using pulsed
laser deposition and RF magnetron sputtering deposition methods. The final aim of this study is to develop a rib
waveguide adapted for middle-IR including an Y-splitter with a reference beam and sensor beam targeting an accurate
CO2 detection.
In this work, we review recent progress on the realization of chalcogenides Photonic Crystal Fibers (PCFs). We present
the fabrication of chalcogenide PCFs with a solid core for three different glass compositions containing a variety of
chalcogens. We show that the Stack and Draw technique currently used for silica PCFs can be problematic in the case of
chalcogenides glasses. We present correct PCF design enables a significant improvement of final fiber losses. We
obtained a lowest attenuation of 3 dB/m at 1.55 μm, of 4.5 dB/m at 3.39 μm and 6 dB/m at 9.3 μm. We also present
experimental demonstration of self phase modulation spectral broadening around 1,55 μm. Moreover, we investigate the
Brillouin and Raman scattering properties of a GeSbS PCF.
Chalcogenide glasses present several original properties when being compared to the reference silica glass. They are
very non linear, hundred to thousand times more non linear than the standard silica, they are very transparent in the
infrared, until 10 μm to 20 μm depending on their composition, and they can be drawn into optical fibers. Thus, the case
of chalcogenide photonic crystal fibers (PCF) is of particular interest. Indeed, the effective modal area is adjustable in
PCF thanks to geometrical parameters. Then chalcogenide microstructured fibers with small mode area could lead to
huge non linear photonic devices in the infrared by the combination of the intrinsic non linearity of these glasses with
the non linearity induced by the PCF. Chalcogenide photonic crystal fibers offer therefore a great potential for
applications in the fields of Raman amplification or Raman lasers and supercontinuum generation in the mid infrared
until at least 5 μm. The possibility to design PCF exhibiting a working range in the mid infrared and more specifically
in the 1-6 μm wavelength range opens also perspectives in the optical detection of chemical or biochemical species.
This contribution presents the advances in the elaboration of such chalcogenide photonic crystal fibers.
Mid-infrared (IR) lasers are of interest for a variety of applications including environmental sensing, LIDAR and
military counter measures. However, this wavelength range lacks powerful, coherent, robust and compact sources. A
solution can lie in chalcogenide glasses as host materials for rare earth ions. With an extended infrared transparency, low
phonon energy limiting the non radiative multiphonon relaxation rates and suitable rare earth solubility, sulfide glasses
based on Ge-Ga-Sb-S system make available radiative transitions in the mid-IR range. The glasses with nominal
composition of Ge20Ga5Sb10S65 doped with Er3+ (500 to 10000 ppm) were prepared by means of conventional melting
and quenching method. The Er3+, widely studied in glass fibers for near-IR amplification, was initially selected for the
transition 4I9/2 to 4I11/2 emitting at around 4.5 &mgr;m in order to demonstrate the ability of this sulfide composition for midinfrared
fiber lasers application. In these objectives, absorption and emission spectra have been recorded and the
radiative decay lifetime of excited levels (4I9/2, 4I11/2 and 4I13/2) has been determined. These last experimental results were
compared with those obtained by Judd-Ofelt model from absorption cross-sections of all observable transitions.
Therefore, the 4I9/2 radiative quantum efficiency was estimated at 67 %. The emission cross-section was 2.6x10-21 cm2 at
4.6 &mgr;m obtained by Fütchbauer-Ladenburg theory. The product of measured lifetime and emission cross-section for 4I9/2
-> 4I11/2 transition is about 1.87x10-24 cm2.s is comparable with that for GaLaS glasses. The fiber drawing of the Er3+
doped Ge20Ga5Sb10S65 glasses and measurements of optical losses in mid-IR are currently in progress and first results
were presented.
Microstructured optical fibers as new optical objects have been developed in the recent past years, firstly from silica
glass and then from other oxide glasses such as tellurite or different heavy cations oxide glasses. However very few
results have been reported concerning non-oxide glasses and more particularly chalcogenide glasses. In a photonic
crystal fiber the arrangement of air holes along the transverse section of the fiber around a solid glassy core leads to
unique optical properties, such as for example broadband single-mode guidance, adjustable dispersion, nonlinear
properties. Since the effective modal area is adjustable thanks to geometrical parameters, chalcogenide microstructured
fibers with small mode area are of interest for nonlinear components because of the intrinsic non linearity of
chalcogenide glasses, several order of magnitude above these of the reference silica glass (100 to 1000 times the non
linearity of silica glass). On the other hand, chalcogenide holey fibers with large mode area are of interest for infrared
power transmission, in a wavelength range out of reach of silica fibers, and more particularly in the 3-5 μm atmospheric
window. The aim of this paper is to present more specifically the recent results that have been achieved in the
elaboration, light guidance and characterization of photonic crystal fibers from the sulfide Ge20Ga5Sb10S65 glass, which
presents a large transparency window from 600 nm to 11 μm.
Second harmonic generation was obtained with an interesting efficiency in thermally poled sulfide glass. The best results obtained to date for chalcogenide glasses were on a Ge-Sb-S system thanks to an adapted treatment of thermal poling. The poling parameters like temperature (100-310 °C), applied voltage (2.5-4 kV)and duration (5-60min) were explored. A large NL second-order susceptibility χ(2) of about 10 ± 0.5 pm/V was measured. The nonlinear susceptibility profile as a function of the depth under the anode for Ge25Sb10S65 poled glass was determined using the analyze of remained second harmonic signal during the NaOH etching treatment. In parallel, a study of the concentration variation of elements being able to be involved in the formation of a charge space was achieved by using the secondary ion mass spectroscopy.
Infrared chalcogenide glasses are studied with respect to their non linear optical properties. These glasses are sulfur or selenide glasses synthesized in the binary or ternary systems of the Ge-As-S-Se family and are transparent from the end of the visible region to wavelengths above 10 μm depending on the composition. The non linear optical characteristics are firstly determined through a spatially resolved Mach Zender interferometer with the help of a Nd-YAG laser at 1064 nm. Non linearities three order of magnitude above the non linearity of silica glass are achieved. Then, the non linear imaging technique has been used to characterize the glasses at the telecommunication wavelength of 1.55μm. This one shot technique has allow us to obtain values for the non linear refractive index n2 as high as 14 10-18 m2/W. The non linear absorption at 1.55 μm has also been evaluated and is below 1 cm/GW for all the glasses. These third order non linear optical properties make these glasses suitable candidates for integrated ultra fast all optical devices. On the basis of the GeSe4 vitreous composition, an optical fiber, single mode at 1.55 μm, is achieved.
We present an improved method to measure the third order nonlinearity of materials. The principle is based on a pump/probe experiment using a Mach-Zehnder interferometer coupled to a CCD camera. Experiments are performed with fluoride glasses (PZG) and chalcogenide glasses. A comparison with the nonlinear coefficients obtained with the Z-scan technique is done and has led us to improve the detailed analysis of the Z-scan technique.
A new glass in the fluoroarsenate family was fabricated and doped with Er3+ ions. The compositions made are (Na4As2O7)40 (BaF2)30 (YF3)x with xequals 0, 0.1, 0.5, 1, 3, and 5. The optical properties of Er3+ ions were established in terms of absorption and emission spectra, Judd-Ofelt calculations, and lifetime measurements in the visible and infrared domains. Because of the presence of arsenic, these glasses show lower phonon energies than their fluorophosphate counterparts. As a result, the green emission from the 4S3/2 level of Er3+ can be observed. At concentration of 0.1 mol $ ErF3, the experimental lifetime for 4S3/2 is well accounted for by thermalization processes and the occurrence of multiphonon relaxations. For the 4I11/2 and 4I13/2 levels, the lifetime is maximum for 1% erbium concentration, due to the occurrence of signal self-absorption. Excellent agreement is obtained between the radiative and experimental lifetimes of the 4I13/2 level, which validates the application of the Judd-Ofelt theory.
Tm3+ are new candidates for optical amplifiers in the 1.5micrometers region, the S band. For the moment, Tm3+-doped Fibers Amplifiers (TDFA) h ave been studied in fluoride matrices because of the lowest phonon energy of this glasses compared to the silica ones. We proposed to evaluate the spectroscopic potential of this ion in sulfide GeGaSSb glasses where the phonon energy is around 350cm-1. Absorption and emission cross sections were measured. Lifetime measurements were carried out. Results were compared with the Judd-Ofelt calculations.
Chalcogenide glasses in the [Ge-Se-S-As] system have been synthesized and studied with respect to their nonlinear optical properties from third and second order. Z-scan and Mach Zehnder interferometry measurements of the nonlinear refractive index (n2) and nonlinear absorption ((beta) ) have been performed at 1064 nm. Some z-scan measurements have been also realized at 1430 nm. The results have been correlated to the structures of the glasses and the figure of merit has been calculated with the purpose of a potential utilization of these glasses in the realization of ultra- fast all-optical switches. Nonlinearities as high as 850 times the nonlinearity of silica glass have been obtained and some glasses exhibit at 1430 nm nonlinear optical characteristics suitable for telecommunication applications. The all-optical poling of a chalcohalogenide glass has been realized with a Q-switch mode-locked Nd:YAG laser at 1064 nm emitting 45 ps pulses at a repetition rate of 10 Hz with frequency doubling at 532 nm. A nonlinear coefficient deff equals 2.8 10-17 m/V similar to that of the reference glass Schott SF 57 has been obtained. The thermal poling of a chalcogenide glass also has been realized and a transient second order nonlinear susceptibility (chi) (2) has been observed.
New alkaline free phosphate glass compositions are presented. Phosphate glass with a temperature coefficient of refractive index close to zero and a good chemical durability can be achieve. These new glass compositions are very promising for high quality optical fibers with a constant mode profile, and erbium doped fiber amplifiers with a high gain per unit length.
TeX glass fibers with monoindex structure are routinely achieved with a minimum attenuation, less than 1dB/m, in the 8-12 micrometers strategic window. Their exceptional properties in the IR allow to investigate many potential applications such as laser power delivery, temperature sensing as well as remote chemical monitoring. Chalcohalide fibers having optical losses of 0.5dB/m between 7 and 9 micrometers have been obtained by the preform drawing technique. These optical fibers are generally protected with an appropriate coating, thermal and/or UV plastic. Such materials show clearly improved mechanical properties and a high flexibility suitable for industrial manipulations. A high sensitivity of TeX glass fibers for chemical analysis by remote evanescent wave spectroscopy has been demonstrated. The detection efficiency has been studied as a function of various parameters especially the fibers' diameter. TeX glass fibers with a tapered shape have allowed to detect very low concentrations of less than 1 percent vol. in ethanol.
New rare-earth-rich fluoroarsenate glasses are synthesized in the M2O, As2O5, BaF2, YF3 system, with M equals Na or K. The glass-forming region is remarkably large in the Na4As2O7, BaF2, YF3 system. Stable compositions with rare-earth fluoride concentration as high as 40 mol% can be synthesized. Thermal and optical properties are given for these new glasses. The behavior of neodymium ions in this new host is investigated in terms of Judd-Ofelt calculations, emission and excitation spectroscopy, and lifetime measurements as a function of temperature and concentration.
Optical properties of rare-earth ions in glasses based on barium, indium, gallium, zinc, yttrium/lutetium, and thorium fluorides are presented. Multiphonon relaxations are determined and are found to be significantly lower than in ZBLAN fluoride glasses. Also, spectroscopic properties of the 1.3?m emission of neodymium (III) and praseodymium (III) ions in fluoride glasses are studied. Excited state
absorption from the 4F3/2 emitting level of neodymium (III) as well as radiative and non-radiative properties of the 1G4 level of praseodymium (III) are compared in Ba-In-Ga and ZBLAN glasses.
The thermal and optical properties of a new series of fluoride glasses suitable for active fiber applications are presented. The glasses are based on barium, indium, gallium and zinc fluorides, and in the presence of LuF3 and PbF2 they exhibit a critical cooling rate of 16 degree(s)C min-1. The lowest fiber attenuation is found to be 0.5 dB m-1 at 2.7 micrometers . Compared to fluorozirconate glasses, their infrared transparency is shifted nearly 1 micrometers toward longer wavelengths. By means of Judd-Ofelt calculations and lifetime measurements on Er3+ doped samples, the multiphonon emission rate for this hose is investigated and compared to fluorozirconates.
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