Chalcogenide Fiber Research Articles

Experimental observation of gain in a resonantly pumped Pr3+-doped chalcogenide glass mid-infrared fibre amplifier notwithstanding the signal excited-state absorption

We demonstrate a maximum gain of 4.6 dB at a signal wavelength of 5.28 μm in a 4.1 μm resonantly pumped Pr3+-doped selenide-based chalcogenide glass fibre amplifier of length 109 mm, as well as a new signal excited-stated absorption (ESA) at signal wavelengths around 5.5 μm. This work to the best of our knowledge is the first experimental demonstration of gain at mid-infrared (MIR) wavelengths in a Pr3+-doped chalcogenide fibre amplifier. The signal ESA of the fibre is attributed to the transition 3H6 → (3F4, 3F3) after the pump ESA (3H5 → 3H6) at a pump wavelength of 4.1 μm, which absorbs the MIR signal at wavelengths of 5.37, 5.51 and 5.57 μm, and so spoils the amplifier’s performance at these wavelengths. Thus, this signal ESA should be suppressed in a resonantly pumped Pr3+-doped selenide-based chalcogenide fibre amplifier.

Influence of initial frequency chirp on the supercontinuum generation in As2S3 chalcogenide fiber

Initial frequency chirp has significant influence on spectral evolution when the pulse propagates along the fiber. We report on the numerical results of supercontinuum (SC) generation in As2S3 chalcogenide fiber that positive initial chirp is beneficial for spectral broadening, while the negative chirp does the opposite. Besides, when the initial frequency chirp is lower than 30, the SC bandwidth increases with initial frequency chirp. The maximum SC bandwidth is ~2800 nm, which spans from near infrared (IR) to mid-IR region.

Mid-infrared supercontinuum generation in low-loss single-mode Te-rich chalcogenide fiber

A single-mode Te-rich chalcogenide (ChG) fiber for mid-infrared has been fabricated via an isolated extrusion method. The optical loss of the fiber is 3-4 dB/m in a range of 6.5-10.5 µm. Mid-infrared (MIR) supercontinuum (SC) generations were experimentally investigated in the step-index single-mode fiber with femtosecond laser pulse from an optical parametric amplifier (OPA). By pumping 17 cm-long fiber at 5 µm and 8 µm, the spectra spanning from 1.8 to 15 µm and 2.3 to 14.5 µm, respectively, were observed. The results show that the efficiency of SC generation is highest by pumping at near zero dispersion wavelength in single-mode fiber. It reveals that the superiority of single-mode fiber in SC generation over multimode is the elimination of high-order modes (HOMs) interaction. Besides, a repeat SC experiment was carried out for fiber stability test after half a year.

Modeling and simulation of a mid-IR 43 µm Raman laser in chalcogenide glass fibers

Raman lasers based on mid-infrared (IR) fibers that operate at the 3–5 µm atmospheric transparency windows are attractive sources for many important applications. In this work, a Raman laser operating in the mid-IR range at 4.3 µm based on an As2Se3 fiber pumped by a 3.92 µm fiber laser has been designed and systematically optimized. The influences of pump power, fiber length, and output coupling efficiency on laser performance are investigated. Simulation results show that a fiber length of 0.75–1.3 m and an output coupler reflectivity of 89%–98% could obtain the optimized output power. The maximum output power of 0.269 W was obtained at a pump power of 1.5 W. The simulated result can be used for theoretical guidance and design optimization of practical chalcogenide fiber Raman lasers.

All-optical carbon dioxide remote sensing using rare earth doped chalcogenide fibers

As many fundamental spectroscopic signatures associated to gases of interest are in the 2.5 – 15 µm spectral range (4000–350 cm−1), gases can be detected using efficient infrared (IR) emissions from rare earth (RE) ions embedded into chalcogenide glasses, which are well-known for having low phonon energies. An all-optical IR fiber sensor for in-situ carbon dioxide monitoring was developed. The 4.3 µm mid-IR source probing the gas absorption in this sensor is a Dy3+ doped GaGeSbS fluorescent chalcogenide fiber. Following the 4.3 µm partial absorption by CO2, a wavelength conversion from 4.3 µm to 808 nm is implemented using excited state absorption (ESA) mechanisms in Er3+ doped GaGeSbS bulk glasses or fibers. This wavelength conversion allows the use of silica fibers to transport the 808 nm converted signal. This all-optical sensor with a sensitivity of few hundreds of ppm can be typically deployed over the kilometer range, making this tool suitable for field operations. The photon conversion principle used in this gas sensor could be implemented as a general mean to detect infrared radiations using visible or near-IR detectors instead of mid-infrared detectors.

Exploiting dispersion of higher-order-modes using M-type fiber for application in mid-infrared supercontinuum generation

M-type fibers have the exceptional property that the higher-order LP0n modes are core-confined and easily excited, while the LP01 and other modes are confined to a high-index ring surrounding the core, so they are not easily excited. This has profound consequences for mid-infrared supercontinuum sources, where the high zero-dispersion wavelength of chalcogenide and ZBLAN fibers means that exotic pump sources have so far been necessary. We show here that in chalcogenide and ZBLAN M-type fibers the lower ZDW of the core-confined higher-order LP02 mode can be in the range of 2 to 3 µm (around 1.55 µm), while the fiber still has a large core diameter and thus supports high average power. This will allow established pump laser technology to be used in future high-power mid-infrared supercontinuum sources.

Design and analysis of long-period fiber gratings in tapered multimode chalcogenide glass fiber for temperature measurement

A highly sensitive temperature sensor based on long-period fiber gratings (LPFGs) in tapered multimode chalcogenide fiber was designed. The transmission characteristics of these LPFGs and their temperature sensitivities of different cladding modes with variations in the waist diameters and surrounding refractive indices (SRIs) were theoretically studied. Simulation results showed that the temperature sensitivity of LPFGs could be effectively increased by reducing the waist diameter. The temperature sensitivity of the proposed LPFGs with a 75 μm waist diameter at the lowest LP02 cladding mode was calculated to be 1.89 nm/°C at 1.55 μm. When the grating period of the designed LPFG is selected at its dispersion-turning point, the temperature sensitivity can achieve a maximum absolute value of 15.2 nm/°C at 1.55 μm, which is approximately 120 times higher than that of tapered silica LPFGs. The influences of variations in SRIs on resonant wavelength and temperature sensitivity of these LPFGs were very weak due to the relatively large cladding refractive index of As–Se fiber, which indicated that this sensor showed a high stability against changes in SRIs. Therefore, this designed sensor can be used in complex environments where high-precision temperature measurement is required.

Simulation of Multilayered Heterojunction-Based Chalcogenide Fiber SPR Sensor With Ultrahigh Figure of Merit in Near Infrared

The dynamic nature of radiation damping in plasmonic structures can have immense potential in relation to significant improvement in plasmonic sensor performance. In this paper, we have explored the careful tuning of dynamic radiation damping in Si-Ag-graphene-Al2O3 heterojunction-based fiber optic plasmonic sensor structure. Low-refractive index rare-earth doped chalcogenide glass is considered as fiber material in near infrared spectral region. The simultaneous tuning of Ag and Al2O3 layer thicknesses with wavelength in appropriate broad ranges is investigated to enhance the sensor’s performance as much as possible. As another interesting step, the presence/absence of graphene layer on sensor’s performance is also examined. The results indicate that significantly large figure of merit (FOM) of magnitude 19212.67 RIU $^{-1}$ at $\lambda = 969$ nm for 5.2-nm-thick Al2O3 layer, and 36.6-nm-thick Ag layer is achievable from the proposed sensor with graphene. The above FOM is substantially larger than the existing (reported) plasmonic sensors claiming large FOM values. The findings of this paper can be crucial for developing surface plasmon reasonance biosensors with highly enhanced performance.

Mid-infrared two-octave spanning supercontinuum generation in a Ge–Se–Te glass suspended core fiber

We report on both the fabrication and the application of a Ge–Se–Te glass-based suspended core fiber for mid-infrared supercontinuum generation. A two-octave spanning mid-infrared light source (from 3.25 to 13 µm) is experimentally demonstrated by pumping the chalcogenide fiber with sub-100 fs pulses at 8.6 µm. Numerical simulations of nonlinear pulse propagation as well as fiber properties are also provided and support experimental measurements.

Optical fibers based on special pure Ge20Se80 and Ge26As17Se25Te32 glasses for FEWS

For middle infrared fiber-optic evanescent wave spectroscopy, the single-index Ge20Se80 and Ge26As17Se25Te32 glass fibers are fabricated by a crucible method. The background optical loss in the Ge20Se80 fiber is 1.5 dB/m in the 5–7.8 μm spectral range (minimum is 0.9 dB/m at 7.1 μm), and that in the Ge26As17Se25Te32 fiber is 1 dB/m in the range of 5.5–8.5 μm (minimum is 0.65 dB/m at 6.6 μm). On the basis of these chalcogenide glass fibers, the middle infrared sensors with the different geometry of sensitive zone (straight, U-shaped form, one loop, two loops) are manufactured. By the example of diesel fuel, it is shown that when passing from the straight section of the sensitive zone to the double loop, the integrated intensity of the absorption bands increases by an order of magnitude. The method of regression analysis was applied to plot a calibration dependence for the additive concentration in diesel fuel in the range of 0.1–1 vol% using a U-shaped fiber sensor. The possibility of using the luminescent Pr(3+)-doped chalcogenide fiber as the source of mid-IR radiation for recording the absorption spectra of substances absorbing in the spectral range 4–5 μm is demonstrated.

Chalcogenide glass fibers with a rectangular core for polarized mid-infrared supercontinuum generation

A step-index chalcogenide fiber with a rectangular core and a circular cladding was fabricated through an approach that combines an extrusion technique and a multiple-stage rod-in-tube method. This fiber has a Ge12As24Se64 glass core with a size of ~2.8 μm × 5.9 μm, and a Ge10As24S66 glass cladding with a diameter of ~220 μm, and shows a relatively large birefringence. When ~10 cm long fiber was pumped at 4.0 μm with 330 fs pulses, ~2.2–9.5 μm supercontinuum with a flatness of 20 dB and a polarization extinction ratio of ~10 dB was generated.

Monolithic all-fiber mid-infrared supercontinuum source based on a step-index two-mode As2S3 fiber**Project supported by the National Natural Science Foundation of China (Grant Nos. 61435009, 61235008, and 61405254).

We demonstrate efficient supercontinuum generation extending into mid-infrared spectral range by pumping a two-mode As2S3 fiber in the normal dispersion regime. The As2S3 fiber is fusion spliced to the pigtail of a near-infrared supercontinuum pump source with ultra-low splicing loss of 0.125 dB, which enables a monolithic all-fiber mid-infrared supercontinuum source. By two-mode excitation and mixed-mode cascaded stimulated Raman scattering, a supercontinuum spanning from to is obtained. Over 70% of the supercontinuum power is converted to wavelengths beyond m. This is the first experimental report with respect to the multimode mid-infrared supercontinuum generation in a step-index two-mode chalcogenide fiber.

Broadband high-power mid-IR supercontinuum generation in tapered chalcogenide step-index optical fiber

We report a design, analysis, and numerical modeling of a tapered chalcogenide step-index fiber for broadband high-power mid-infrared supercontinuum extending from the 1.5–14.5 µm molecular ‘fingerprint region’. The reported tapered chalcogenide fiber structure is able to generate a broadband supercontinuum spectrum with output average power of 82 mW (27.7 mW for the wavelengths >5 µm) when it is pumped with 200 fs laser pulses with a repetition rate of 76 MHz and average power of 200 mW at 3.5 µm. Such a bright and broadband mid-infrared supercontinuum light source covering both the 3–5 µm and 8–13 µm atmospheric windows and most of the molecular fingerprint spectral region has practical applications in various fields, including mid-infrared spectroscopy, imaging, and biomedical diagnostics.

A novel chalcohalide fiber with high nonlinearity and low material zero‐dispersion via extrusion

AbstractHigh nonlinear fibers with low zero‐dispersion wavelength (ZDW), high laser power tolerance and large band‐gap are urgent for all‐optical‐band supercontinuum (SC) generations. Widely used chalcogenide fibers usually have a large ZDW and low laser power tolerance, and thus are not ideal for such purpose. Here, an ultra‐low material ZDW chalcohalide (ChH) glass fiber with high nonlinearity as well as high laser power tolerance has been fabricated successfully via a novel peeling‐off‐extrusion method. The step‐index fiber has double‐cladding structure, the inner cladding is GeGaSe‐CsI glass and the outer one is GeSbS jacket. The core glass has an ultra‐low material ZDW of 3.5 μm and large absorption edge of 2.0 eV. The nonlinear refractive index is 6.67 × 10−18 m2/W @1.55 μm. Broadband SC generation covering 1.05‐13.0 μm is demonstrated in this novel ChH fiber. Such glass fiber with high nonlinearity, wide transparent range, low ZDW and high laser damage threshold is promising for the applications in the mid‐infrared.

Potential use of nonlinearity-induced virtual gain on parabolic pulse formation in highly nonlinear tapered fiber system

The objective of this work is to investigate the effect of nonlinearity-induced virtual gain in parabolic pulse (PP) formation by dispersion varying fibers and utilizing this gain over that of dispersion. As chalcogenides show high values of nonlinear coefficient, a dispersion decreasing fiber, named as nonlinearly tapered chalcogenide fiber (NLTCF), is designed here by optimizing different combinations of chalcogenide materials and core radius profiles such that efficient PP can be generated at considerably shorter optimum lengths with respect to the corresponding constant dispersion fiber. With suitable manoeuvring of the nonlinearity-induced virtual gain, a fiber combination consisting of a dispersion increasing fiber and the NLTCF shows enough efficiency to reduce the optimum length significantly. Although the virtual gain due to dispersion dominates over that due to nonlinearity in silica fibers, the situation is completely reversed in the case of specially designed highly nonlinear fibers. When compared to silica-based fibers, these types of fibers perform remarkably better in PP formation at shorter values of optimum fiber length with a higher amount percentage reduction of length making the higher order dispersive terms ineffective as well.

Mid-infrared supercontinuum in well-structured As[sbnd]Se fibers based on peeled-extrusion

High quality large-core AsSe chalcogenide fiber was fabricated via a novel extrusion method to peel off the out-layer of the core glass, and thus all the defects, such as deformations, interface bubbles between the core and cladding can be eliminated effectively. The raw materials were purified by the dynamic distilling and the glasses were prepared by the melt-quenching method. The preform was prepared by an improved isolated stacked homemade extrusion (ISE) machine. The fibers coated with polymer protection were drawn out with a core diameter of ∼240 μm. The core/cladding ratio of the fiber were kept approximately 1:2, and the optical loss was generally lower than 1.5 dB/m in a wavelength range of 5.6–9.7 μm, with a minimum value of 0.6 dB/m at 8.3 μm. The calculated fiber numerical aperture was approximately 0.55. Supercontinuum (SC) generation experiments of fiber at different wavelengths and pump powers were performed. A flattened SC spectrum can be obtained in this large-core fiber with femtosecond pumping.

Mid-infrared flattened supercontinuum generation in all-normal dispersion tellurium chalcogenide fiber.

We have prepared a well-structured tellurium chalcogenide (ChG) fiber with a specialized double cladding structure by an improved extrusion method, and experimentally demonstrated an ultra-flat mid-infrared (MIR) supercontinuum (SC) generation in such a fiber. The step-index fiber had an optical loss of <1 dB/m in a range from 7.4 to 9.7 μm with a minimum loss of 0.69 dB/m at 7.87 μm. Simulation showed that an all-normal dispersion profile can be realized in this double cladding tellurium fiber. An ultra-flat MIR SC spectrum (~3.2-12.1μm at -10 dB, ~2-14 μm at -30 dB) was generated from a 22-cm long fiber pumped with a femtosecond laser at 5 μm (~150 fs, 1 kHz). Then the degree of coherence was calculated out based on a simulation, showing that a high coherent MIR SC (from 2.9 to 13.1 μm) can be generated in this double-cladding tellurium fiber.

Experimental and numerical investigation of mid-infrared laser in Pr3+-doped chalcogenide fiber**Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 61605095), the Natural Science Foundation of Zhejiang Province, China (Grant No. LY19F050004), the Natural Science Foundation of Ningbo City (Grant No. 2015A610038), the Open Fund of the Guangdong Engineering Technology Research and Development

We report on a chalcogenide glass fiber doped with Pr3+ that can be used for commercialized 1.5- and 2- laser excitations by emitting broadband – fluorescence, which is extruded into a preform and then drawn into a step-index fiber. The spectroscopic properties of the fiber and glass are reported, and the mid-infrared fiber lasers are also numerically investigated. Cascade lasing is employed to increase the inversion population of the upper laser level. The particle swarm approach is applied to optimize the fiber laser parameters. The output power can reach 1.28 W at 4.89- wavelength, with a pump power of 5 W, excitation wavelength at , Pr3+ ion concentration at 4.22 ×1025 ions/m3, fiber length at 0.94 m, and fiber background loss at 3 dB/m.

Использование высших мод халькогенидных световодов для оптимизации метода эванесцентной спектроскопии среднего ИК-диапазона

Based on a theoretical approach, new for evanescent wave spectroscopy, it has been shown that the dispersion properties of higher modes of a multimode chalcogenide fiber partially immersed in an absorbing medium can be used to create fiber devices that combine the functions of a supercontinuum generator and a sensing element of a spectroscopic sensor of the mid-IR range. The propagation of radiation in higher modes will allow one to control the position of the group velocity dispersion zero and to obtain a supercontinuum pumped in the near IR range. In the sensing element, the use of higher-order evanescent modes will allow for greater sensitivity and broaden the dynamic range of the sensor.

Chalcogenide Fabry–Perot Fiber Tunable Filter

We demonstrate the first mid-infrared compatible all-fiber Fabry–Perot filter. It consists of chalcogenide fibers terminated with high-reflective coatings made of germanium and calcium fluoride. In addition to the transmission compatibility with mid-infrared wavelength, the filter has both tunability and free spectral range >350 nm as well as a finesse of 27. To demonstrate the application of the filter, a thulium-doped fiber laser is built and shows continuous tunability from 1.835 to 1.920 $\mu \text{m}$ .