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Infrared gradient refractive index (GRIN) lenses have great application value and potential in multispectral imaging systems. This study reports various chalcogenide axial GRIN glasses prepared using the hot‐pressing diffusion method. It is worth noting that the S4–S60 GRIN sample has a difference in refractive index (RI) Δn of greater than 0.3 and a diffusion depth of about 5 mm, which is the deepest diffusion depth reported in chalcogenide glass to date. In addition, the linear portion in the profile of the GRIN sample has a RI difference of 0.15 and a thickness of 1.2 mm. The effects of the temperature, concentration difference, and diffusion time on the sample diffusion process are discussed. The dispersion properties of the GRIN samples were further calculated, providing a new option for correcting chromatic aberrations in optical systems. In addition, a method for the indirect nondestructive characterization of sample RI using the Raman intensity ratio is proposed, and the reliability of the method is verified by practical experiments, which is convenient for the subsequent measurement of the GRIN profile. [ABSTRACT FROM AUTHOR]

Extinction ratio (ER) is one of the important parameters to characterize the polarization‐maintaining (PM) performance of the fiber. In this paper, we report the preparation and properties of a novel chalcogenide microstructure fiber with a high ER. We fabricate a preform using a peeled‐off extrusion method. The core and cladding material of the fiber are Ge9As23Se68 and Ge10As22Se68. The preform was drawn into a fiber with an average ER of −17.08 dB. The loss of the fiber is less than 2 dB over 5.20–8.55 μm, and the minimum loss of the fiber is 0.57 dB/m at 6.2 μm. Moreover, a flat mid‐infrared supercontinuum spectrum spanning from 1.53 to 12.50 μm is generated by pumping an 18‐cm‐long PM fiber for the first time. [ABSTRACT FROM AUTHOR]

We have prepared an ultra‐large core, high numerical aperture (NA) chalcogenide (ChG) step‐index fiber (SIF) with a mode area of >43 600 μm2 at the wavelength of 5.5 μm by an improved extrusion method. The fiber based on two ChG glasses with similar softening temperature has a core diameter of 339.0 μm and ultra‐thin cladding. The fiber exhibits a minimum loss of 1.75 dB/m at 9.74 μm and an optical loss of <5.0 dB/m from 5.3 to 10.8 μm. Broadband supercontinuum (SC) covering from 1.2 μm to 13.7 μm has been generated in a 17‐cm‐long ultra‐large mode area fiber with large core and high NA. All these show that, the fiber possesses the potential for high‐power infrared laser transmission. [ABSTRACT FROM AUTHOR]

By conventional melt‐quenching techniques, a series of Dy3+‐doped (0.1 to 1.0 wt%) Ga5Ge20Sb15S60 bulk glasses were fabricated and their potential for developing mid‐infrared fiber laser beyond 4 μm were evaluated, in which the optimal Dy3+ doping concentration was found to be 0.3 wt% and the largest laser quality factor value (σe × τmea = 2.62 × 10−23 cm2 s) among all of the Dy3+‐doped chalcogenide glass was obtained. On this basis, through using the chemical purification methods with chlorine gas combined with the dynamic distillation process, the high‐purity GGSS glasses with low O–H and S–H absorptions were successfully fabricated, which was confirmed by the optimized mid‐infrared linear transmittance and improved fluorescent lifetimes of Dy3+: 6H13/2, 6H11/2 levels. Furthermore, for the first time to the best of our knowledge, the Dy3+‐doped, single‐mode, and double‐cladding chalcogenide fibers with the core/cladding ratios of 125:60:11 and 125:66:11.5 were achieved by a multistage rod‐in‐tube fiber drawing process and extrusion methods, respectively. The GeS2‐based fiber exhibits excellent transmission performance at 1.0‐5.0 μm: 3.0 dB/m at 2.9 μm (O–H), 2.4 dB/m at 4.1 μm (S–H). Combining the advantages of high‐purity, high doping concentration and single‐mode double‐cladding structure, the optimized active fiber should be an ideal efficient and low‐threshold medium toward mid‐infrared fiber laser beyond 4 μm. [ABSTRACT FROM AUTHOR]

Cr2+‐doped II‐VI crystals have witnessed an excellent gain media for continuously tunable and femtosecond‐pulsed lasers. Despite this, major challenges persist toward realizing ultrabroad emission bandwidth and efficient Cr2+‐doped fiber due to the valence diversity of Cr, especially in chalcogenide glasses. Here, we propose to prepare Cr2+:ZnSe/As2S3‐xSex composite glasses by Hot Uniaxial Pressing (HUP), a method that sinters uniformly mixed crystal and glass powders into geometrically designed composite chalcogenide glasses. The densification of the composite glasses reached 99.88%, indicating that a few or none pores remain. Our research shows that Cr2+:ZnSe crystals have good performance in chalcogenide glasses, and the composite glasses have the potential to be made into mid‐infrared–doped fibers. It was demonstrated by scanning electron microscopy (SEM) and X‐ray diffraction (XRD) that the composite glasses have a uniform Cr2+:ZnSe distribution and no crystal disintegration. The transmittance of the composite glasses was significantly improved by tailoring the refraction index. The mid‐infrared (MIR) fluorescence and decay of the glasses were measured. The lattice constant was measured, calculated, and discussed to reveal the influence of sintering process on lifetime. [ABSTRACT FROM AUTHOR]

Mid‐infrared (MIR) band supercontinuum (SC) light source has highly important application prospects in aerospace, biomedicine, MIR sensing, and pollutant monitoring. As–Se–Te glass has high nonlinear refractive index, wide MIR transmission range and weak crystallization ability. As40Se40Te20 glass fiber is suitable for producing wide MIR–SC spectrum. In this study, purified As40Se40Te20 glass was prepared and unclad and step‐index fibers were drawn. An unclad As40Se40Te20 glass fiber with minimum loss of 1.7 dB/m at 8.8 μm was obtained. By pumping the unclad fiber in the normal dispersion region at 5 μm, we recorded the broadest SC generation spectrum, which covered 1.8–13 μm with a 30 dB spectral flatness, from a fiber with 15 cm length. Besides, As40Se40Te20/As40Se42Te18 step‐index fiber with minimum loss of 5.6 dB/m at 5 μm was drawn from isolation extruded preform. The step‐index fiber was pumped in the normal dispersion region at 5 μm, and the SC spectrum, covering 2.1–11.2 μm with a 40 dB spectral flatness, was recorded from a fiber with 15 cm length. The SC spectrum, which was achieved by pumping the As40Se40Te20 fiber, covered almost all the transparent range of material. [ABSTRACT FROM AUTHOR]

A combined infrared suspended-core fiber (SCF) is fabricated using a stacked glass extrusion method. As2S 3 glass is used as the center core host material, and Ge20As20Se15Te45 glass is used to form supporting bridges and act as the ring host material. In this paper, a continuous and robust extrusion process was used to fabricate the SCFs on stacked chalcogenide glass substrates. Glass flow disruption and shear band formation at the interfaces between the different glasses were avoided while the suspended core was formed directly from the core glass. The near-field optical energy distribution image of the resulting multimaterial SCF shows that light propagates effectively in the core. The losses of the multimaterial SCF were also measured at wavelengths ranging between 2.5 and 7 μm, and the lowest transmission loss was 1.86 dB/m at 4.8 μm. The spectral behavior of the supercontinuum (SC) in the SCF is investigated by varying the pump wavelength and the pump power. A mid-infrared SC spanning a wavelength range from 2.05 to 6.95 μm is generated in a 19-cm-long combined chalcogenide SCF that is pumped at 4.5 μm using an optical parametric amplifier laser system. [ABSTRACT FROM AUTHOR]

In this work, a theoretical study was conducted on temperature sensing in Ge-Sb-Se multimode fibre Bragg grating (MM-FBG). The sensing characteristics of the designed MM-FBGs with different fibre parameters and operating wavelengths were calculated using a coupled model method. The temperature sensitivity of this MM-FBG was found to improve significantly by shifting the operating wavelength from telecom range to mid-infrared (MIR) and utilizing the wide transmission range of Ge-Sb-Se glasses. The temperature sensitivity of the proposed Ge-Sb-Se MM-FBG was calculated to be 0.0758 nm/°C at 1550 nm, which is 7.58 times higher than silica FBGs at 1550 nm, and the temperature sensitivity was calculated to be more than 0.16 nm/°C at 3390 nm, which is 2.2 times higher than that at 1550 nm. In addition, the proposed MM-FBGs provided multi-peak information, and the sensitivity of each peak was calculated to be comparable to the single-mode FBG. The proposed Ge-Sb-Se MM-FBG has great potential for temperature sensing in MIR because of its advantages of simple preparation, high coupling efficiency, multi-peak information and wide working window. [ABSTRACT FROM AUTHOR]

This work exhibits design and characteristic study of highly sensitive temperature sensors of long-period fiber gratings (LPFGs) in Ge–Sb–Se fibers. Temperature characterization of the designed LPFGs with different working modes, operating wavelengths, and surrounding refractive indices (SRI) were studied. Results showed that temperature sensitivity of the proposed Ge–Sb–Se LPFGs reached 0.5787 nm/ at 1.55 μm at the lowest LP02 cladding mode, which is approximately 12 times higher than silica LPFGs and 1.2 times higher than that of As–Se LPFGs. When grating period of the designed Ge–Sb–Se LPFG was selected at its dispersion-turning-point, temperature sensitivity reached a maximum absolute value of 24.715 nm/°C. Influences of operating wavelength and temperature sensitivity of these LPFGs on SRI are extremely weak due to relatively high refractive index of Ge–Sb–Se fiber, indicating that the designed Ge–Sb–Se LPFG temperature sensor possesses extremely strong sensing stability on SRI. [ABSTRACT FROM PUBLISHER]

We have experimentally demonstrated the supercontinuum (SC) generation in the As2Se3–As 2S3 multimaterial chalcogenide glass fiber with ultrahigh-numerical aperture (NA∼1.4). The fiber preform was fabricated via a modified one-step coextrusion method before it was drawn into the small-core fiber. With a 10-μm diameter As2Se3 core and a 246-μm diameter As2S3 cladding, the fiber exhibited a zero-dispersion wavelength near 4.5 μm, and a minimum loss around 5.2 dB/m at 5.8 μm. The generated SC spanning from 1.4 to 8.8 μm was generated in a 20-cm-long fiber pumped by a 4.8 μm laser with a short-pulse width of ∼150 fs. The numerical modeling of midinfrared supercontinuum generation in a fiber with an exceptionally high NA at 3.5 and 4.8 μm was presented as well, which were in agreement with their respective experimental results. [ABSTRACT FROM PUBLISHER]

Te-based glasses are ideal material for life detection and infrared-sensing applications because of their excellent far-infrared properties. In this study, the influence of Ag- and AgI- doped Te-based glasses were discussed. Thermal and optical properties of the prepared glasses were evaluated using X-ray diffraction, differential scanning calorimetry, and Fourier transform infrared spectroscopy. Results show that these glass samples have good amorphous state and thermal stability. However, Ge–Ga–Te–Ag and Ge–Ga–Te–AgI glass systems exhibit completely different in optical properties. With an increase of Ag content, the absorption cut-off edge of Ge–Ga–Te–Ag glass system has a red shift. On the contrary, a blue shift appears in Ge–Ga–Te–AgI glass system with an increase of AgI content. Moreover, the transmittance of Ge–Ga–Te–Ag glass system deteriorates while that of Ge–Ga–Te–AgI glass system ameliorates. All glass samples have wide infrared transmission windows and the far-infrared cut-off wavelengths of these glasses are beyond 25 μm. The main absorption peaks of these glasses are eliminated through a purifying method. [ABSTRACT FROM AUTHOR]

In this study, a novel Te-based glass system was investigated. Some properties of Ge–Ga–Te–NaI chalcogenide glasses such as physical, thermal and optical transmitting were discussed. XRD patterns show this glass system with best amorphous state can dissolve content of NaI as much as 35 at.%. The lowest cut-off wavelength of glass samples is 1645 nm which is the smallest wavelength among the reported Te-based glasses doping with halide. DSC curves indicate that all glass samples have good thermal stabilities (Δ T > 100 °C) and the highest Δ T value corresponding to (Ge 15 Ga 10 Te 75 ) 85 (NaI) 15 glass is 120 °C which is 8 °C greater than that of Ge–Ga–Te host glass. The infrared spectra manifest Ge–Ga–Te–NaI chalcogenide glass system has a wide infrared transmission window between 1.6 μm and 20 μm. Consequently, Ge–Ga–Te–NaI glasses can be a candidate material for far infrared optic imaging and bio-sensing applications. [ABSTRACT FROM AUTHOR]

Chalcogenide glasses of the GeSbSeI ( x = 0, 5, 10, 15, 20 at.%) system were prepared. This study was performed to examine some Ge-Sb-Se-I glass physical and optical properties, the structural evolution of the glass network, and the optical properties of the infrared glass fibers based on our previous studies. The variation process of the glass physical properties, such as transition temperature, glass density, and refractive index, was investigated from the glass of GeSbSe to the GeSbSeI glass series. The structural evolutions of these glasses were examined by Raman spectroscopy. The GeSbSeI composition was selected for the preparation of the IR fiber. The GeSbSeI glass was purified through distillation, and the intensity of the impurity absorption peaks caused by Ge-O, HO, and Se-H was reduced or eliminated in the purified glasses. Then, GeSbSeI chalcogenide glass fiber for mid-infrared transmission was fabricated using high-purity materials. The transmission loss of the GeSbSeI fiber was greatly reduced compared with that of the GeSbSe glass fiber. The lowest losses obtained were 3.5 dB/m at 3.3 μm for GeSbSeI fiber, which was remarkably improved compared with 48 dB/m of the unpurified GeSbSe fiber. [ABSTRACT FROM AUTHOR]

Fibers exhibiting flattened and decreasing dispersion are important in nonlinear applications. Such fibers are difficult to design, particularly in soft glass. In this work, we develop a preliminary design of a highly nonlinear tapered hybrid microstructured optical fiber (TH-MOF) with chalcogenide glass core and tellurite glass microstructure cladding. We then numerically studied its dispersion, loss, and nonlinearity-related optical properties under fundamental mode systematically using the infinitesimal method. The designed TH-MOF exhibits low chromatic dispersion that is similar to a convex function with two zero-dispersion wavelengths and decreases with fiber length from 2 to 5 μm band. The potential use of the TH-MOF in nonlinear applications is demonstrated numerically by a supercontinuum spectrum of 20 dB bandwidth covering 1.96–4.76 μm generated in 2-cm-long TH-MOF using near 3.25-μm fs-laser pump. [ABSTRACT FROM PUBLISHER]

In this study, we examined the function of halogen iodine acting as a glass network modifier in green chalcogenide glasses based on the Ge–S system. We obtained a series of Ge–S–I glasses and determined their glass-forming region. We then recorded the physical, thermal, and optical properties and studied the effect of halogen iodine on Ge–S–I glasses. Results show that these glasses have relatively wide optical transmission window for infrared (IR) applications. The softening temperature of Ge–S–I glasses varies from 210.54 °C to 321.63 °C, this temperature fits well with some kinds of high-temperature polymers, such as PES and PEI, the polymers serve as protective layers with high strength and flexibility, thus simplifying the fabrication processes of IR chalcogenide glass fiber. Finally, we performed a purification process to eliminate impurities and to improve optical spectra. [ABSTRACT FROM AUTHOR]

Chalcogenide glasses are known for their high transparency in the mid-infrared (IR) range, which includes two atmospheric windows that lie from 3 to 5 μm and 8 to 12 μm, respectively. Chalcogenide photonic crystal fibers have numerous potential applications in the field of IR, such as spectroscopy, microscopy, astronomy, biology, and sensing. In this paper, GeSbS chalcogenide glass was fabricated and systematically studied. Chalcogenide glass has high transmission property (>70 %), good thermal stability, and good mechanical stability. The glass transition temperature T is 296 °C, and no exothermic peak was associated with crystallization up to 500 °C, which indicates its suitability for fiber drawing. As a result of its excellent mechanical properties, preforms with a variety of geometrical patterns were fabricated by using mechanical drilling. The near-field intensity distribution image of the drawn fiber shows a strong light propagation confinement. [ABSTRACT FROM AUTHOR]

Abstract: In order to develop novel far infrared window material, a series of Ge–Ga–Te–ZnI2 chalcohalide glasses were prepared by traditional melt-quenching method and their glass-forming region was determined also. Here, some measurements including X-ray diffraction (XRD), differential thermal analysis (DTA), UV–Vis–NIR absorption spectrum, and infrared optical transmission spectra were carried out. The allowed indirect transition optical band gap was calculated according to the classical Tauc equation. The results show that with the addition of ZnI2, the glass-forming ability and thermal stability are improved gradually. With the contents of ZnI2 increased from 5 to 20at.%, continued blue-shifting occurs in the cutting-off absorption edge of short-wavelength and the values of indirect optical band gaps were observed with ranges from 0.596 to 0.626eV in these glasses. These GeTe4.3–GaTe3–ZnI2 glasses show wide optical transmission and the infrared cut-off wavelengths are larger than 25μm, which implies that the Ge–Ga–Te–ZnI2 chalcogenide glasses possess the potential of far-IR optical window applications. [Copyright &y& Elsevier]

Highlights: [•] The glass-forming region of Te-based glasses was enlarged after Ga and CuI adding. [•] With the help of Ga and CuI, all these glasses have relatively high Tg values (>175°C). [•] Studied glass samples all have wide IR transmission window from 1.8 to 20μm. [ABSTRACT FROM AUTHOR]

Compared with the traditional fluoride fibers and tellurite fibers that can work in the near-infrared region, suspended-core fibers based on chalcogenide glasses have wider transmitting regions and higher nonlinear coefficients, thus the mid-infrared supercontinuum generations can be achieved easily. Rather than adopting the traditional fabrication technique of hole-drilling and air filling, we adopted a totally novel extrusion technique to fabricate As2S3 suspended-core fibers with four holes, and its mid-infrared supercontinuum generation was investigated systematically by integrating theoretical simulation and empirical results. The generalized nonlinear SchrÖdinger equation was used to simulate the supercontinuum generation in the As2S3 suspended-core fibers. The simulated supercontinuum generation in the As2S3 suspended-core fibers with different pump wavelengths (2-5 µm), increasing powers (0.3-4 kW), and various fiber lengths (1-50 cm) was obtained by a simulative software, MATLAB. The experimental results of supercontinuum generation via femtosecond optical parametric amplification (OPA) were recorded by changing fiber lengths (5-25 cm), pump wavelengths (2.9-5 µm), and pump powers (10-200 kW). The simulated consulting spectra are consistent with the experimental results of supercontinuum generation only if the fiber loss is sufficiently low. [ABSTRACT FROM AUTHOR]

Chalcogenide glass is fragile and devitrifiable to be fabricated into micro-structured optical fibers (MOFs). In this article, MOFs which have jacket tubes with inner hexagon are designed and fabricated. The optical properties, such as effective refractive index, electric field intensity, effective mode area, nonlinear coefficient and chromatic dispersion of the fundamental mode are simulated by using full-vectorial finite element method (FVFEM). The effects of structural parameters variation on these optical characteristics of the proposed MOFs are investigated. Furthermore, the As 2 S 3 glass capillaries and jacket tubes are made by extrusion. The MOF with three layers of capillaries is fabricated by the “Stack & Draw” technique. The lowest attenuation of 6.34 dB/m of the MOF is measured at the wavelength of 4.61 μm using the cut-back method. [ABSTRACT FROM AUTHOR]

A highly sensitive mid-infrared evanescent wave sensor based on side-polished (SPF) chalcogenide fiber (ChG) was proposed in this work. The optimum optical fiber parameters were determined via numerical simulation by detecting the leakage intensity of evanescent waves from the optical fiber of different polish depths. The SPF remarkably enhanced the evanescent wave sensing while maintaining fiber loss and strength. Graphene oxide (GO) was coated on the fiber to enhance the sensitivity of SPF sensor for butane (C 4 H 10). GO has a great specific surface area and abundant oxygen-containing functional groups, which enlarges the contact area of GO with gas molecules and enables to adsorb gas. Results show that the GO-SPF sensor can be three and five times more sensitive than the original fiber optic sensor and SPF sensor for butane gas detection, and has a fast response time and good repeatability. [ABSTRACT FROM AUTHOR]

Chalcogenide glasses (ChGs) excellent optical materials in the infrared range. ChG lens has important applications in the environmental detection and biochemical imaging field. In this paper, microlens arrays (MLA) with good optical quality were prepared by wet-etching assisted femtosecond laser direct writing technology and 2300 microlenses were prepared in the range of 1 mm2. By controlling the power of laser direct writing and the time of chemical etching, microlenses with diameters ranging from 15 to 70 μm could be prepared. An uniform dense stacked MLA with a small volume in the wavelength range of 0.6–12 μm was achieved. The fabricated MLA has a broad application scenario in cutting-edge mid-infrared fields, due to their tiny size, light weight, high integration, and excellent optical quality. [ABSTRACT FROM AUTHOR]

A Co2+:ZnS-doped chalcogenide glass with broadband mid-infrared emission was prepared by using a hot uniaxial pressing process. The refractive index difference (Δn) between matrix glass (As 2 S 5) and crystal (Co2+:ZnS) was controlled to be 0.0042 in the emission spectral range of Co2+ to minimize the scattering effect. An ultrabroadband mid-infrared emission of 2–4 μm was observed at room temperature in the samples after excitation by using a commercially available laser diode of 1550 nm. The significant changes in the lifetime and fluorescence intensity of Co2+:ZnS-doped chalcogenide glass were measured in the temperature range of 90–290 K. A resolution of approximately 0.18 K was observed when used as a temperature detector. Furthermore, a gas-sensing device was built by using the strong and broad emissions of the sample, and the detection sensitivity of butane reached 56 ppm. These results show that this glass-ceramics can be used as optical sensing of gas and temperature. [ABSTRACT FROM AUTHOR]

Highlights: [•] A minimum losses of 0.037dB/mm at 12μm are obtained in the Te-chalcogenide glass. [•] The absorption band of impurity Ga–O at 15–20μm was eliminated perfectly. [•] A cut-off based method to measure the bulk glass loss was proved effectively. [Copyright &y& Elsevier]

Abstract: Structural changes of metals (Zn, Sb, In, Ga) and metal halides (AgI, ZnI2, CdI2, PbI2, BiI3) modified GeTe4 glasses were investigated with the aid of Raman spectroscopy. The Raman spectra of these glasses in the frequency region between 100cm−1 and 300cm−1 display four main bands at about 124, 140, 159 and 275cm−1 which are contributed by Ge–Te, Te–Te, Te–Te and Ge–Ge vibration modes. The intensity of 159cm−1 and 275cm−1 bands vary with the addition of different glass modifiers. While the relative intensity of the 124cm−1 and 140cm−1 bands are insensitive to composition changes. Glass modifiers like Zn, In and Sb act as glass network unstabilizer which will disorganize the glass network by opening up the chain structures of Ge–Te and Te–Te. In the case of Ga and metal halides, Ga can open up Ge–(Te–Te)4/2 tetrahedra and form Ga–(Te–Te)3/2 triangle. Iodine can form covalent bonds with tellurium and decrease the tendency of microcrystal formation. Thus both Ga and iodine ultimately act as glass network stabilizer. [Copyright &y& Elsevier]

Abstract High quality large-core As Se 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. Highlights • A peeled-off extrusion technique was presented for chalcogenide glass fiber. • This step-index As-Se fiber shows a low optical loss in midinfrared with a minimum value of 0.6 dB/m at 8.3 μm. • A flatness supercontinuum spectrum covering 1.5-13.3 μm can be obtained in this As-Se fiber pumped with a femtosecond laser. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we described the fabrication and polishing characteristics of the end-faces of highly stable physical contact type chalcogenide optical fiber connectors. The effects of downforce pressure, polishing duration, and polishing fluid on the polishing process with abrasive grit size of 0.02 μm were investigated, and the final polishing parameters were determined. The surface roughness Ra was approximately 20 nm in the fiber area, and the average fiber roughness of the core region (10 μm × 10 μm) was about 3 nm, which were measured by the profilometry and atomic force microscope. Finally, the optical performance was analyzed in terms of the insertion loss of 1 dB and return loss of -18 dB. [ABSTRACT FROM AUTHOR]

• The –OH absorption coefficients were drastically reduced from 0.21 cm−1 (0.09 ppm) to 0.023 cm−1 (0.01 ppm). And the 4I 11/2 lifetime was significantly improved from 2.3 ms to 4.8 ms. • A perfect S-DCF was designed and fabricated via a novel extrusion-stacking method for the first time. • Emission spectra of single cladding fiber, circle double cladding fiber (C-DCF) and S-DCF at 1600–1640 nm and 2500–2900 nm wavelength were compared, and all the results certificate the excellence of S-DCF in pump-absorption efficiency. High-purity chalcogenide glasses and optimal fiber structure design are essential to enhance fluorescence lifetime and pump absorption efficiency in a chalcogenide-based fiber laser. Here, Er3+-doped As 2 S 3 glasses, with a low –OH concentration of only 0.023 cm−1 (0.01 ppm), were prepared by the novel purification method, and the 4I 11/2 level lifetime of purified glasses was increased successfully from 2.3 ms in unpurified glass to 4.8 ms in the purified glass. Furthermore, a special chalcogenide preform with square inner double cladding (S-DCF) was designed and fabricated via a novel extrusion-stacking method for the first time. Compared with circle inner double cladding fiber and single cladding fiber, the pump absorption efficiency is increased by 2–5 times, which fits well with the simulation result by the three-dimensional ray tracing method. All the results mentioned above demonstrated that the elimination of –OH and the optimized structure of S-DCF can improve the luminescence efficiency apparently and promote the development of mid-infrared fiber laser based on Er3+-doped chalcogenide glass. [ABSTRACT FROM AUTHOR]

We report a broadband supercontinuum generation in a chalcogenide fiber taper with an ultra-high numerical aperture. The chalcogenide step-index fiber consisting of As 2 Se 3 core and As 2 S 3 cladding was fabricated by using the isolated stacked extrusion method. The fiber taper with a core diameter of 1.75 μm was prepared by employing a homemade tapering setup. By pumping the fiber taper with a femtosecond laser pulses at 3.3 μm, a broadband supercontinuum generation spanning from 1.9 to 5.7 μm was achieved. [ABSTRACT FROM AUTHOR]

We have investigated the optimization parameters for polishing end-surface of chalcogenide glass fiber connector in the paper. Six SiC abrasive particles of different sizes were used to polish the fiber in order of size from large to small. We analyzed the effects of polishing parameters such as particle sizes, grinding speeds and polishing durations on the quality of the fiber end surface and determined the optimized polishing parameters. We found that, high-quality fiber end surface can be achieved using only three different SiC abrasives. The surface roughness of the final ChG fiber end surface is about 48 nm without any scratches, spots and cracks. Such polishing processes could reduce the average insertion loss of the connector to about 3.4 dB. [ABSTRACT FROM AUTHOR]

Glass-ceramics embedded Te and α-GeTe particles were fabricated from (GeTe 4 ) 85 (AgI) 15 chalcohalide glass using an appropriate heat-treatment at fairly low temperatures ranging from 160 to 190 °C for different times. The crystallization behavior and physical properties of the obtained samples were studied in detail. The glass transition temperature of crystallized samples increases with the elongation of crystallization times. And the results of mechanical properties show that, compared with the base glass, the crystallized samples present improved thermal shock resistance and fracture toughness, and meanwhile still remain its good IR transmittance. This study could provide an initial observation of crystallization in telluride glasses, and be of good guidance to fabricate novel telluride glass-ceramics that operating in far-IR spectral region ranging from 2.5 μm to 25 μm. [ABSTRACT FROM AUTHOR]

Chalcogenide suspended core fibers are considered as an excellent candidates for several applications in near-and-mid IR applications because of their characteristics of higher linearity and nonlinearity. In this paper, the influence of the fiber structure and host glass on dispersion and nonlinear properties, including the core size and the width of the bridge, especially the shape of the fiber core were analyzed with the finite element method in detail. And then, the optimized structure of SCFs made of As 2 S 3 , Ge 20 Sb 5 Se 75 , As 2 Se 3 , Ge 15 As 15 Se 17 Te 5 , which stand for the typical samples of S-based, Se-based and Te-based chalcogenide glasses, have been adopted to get suitable dispersion properties and highest nonlinear optical properties in all kinds of glasses. [ABSTRACT FROM AUTHOR]

• The RCF with excellent efficiency on optical mode controlling and dispersion tuning. • The first order vortex light OAM 0,1 can be stably transmitted in the RCF. • The lowest loss of the RCF is 0.28 dB/m at 8.1 μm. • SC spectra form 1 to 14.4 µm in this RCF via pumping it near its ZDW around 4.5 µm. The efficiency of mode controlling and dispersion tunning in chalcogenide glass fiber is vital to improve the transmission capacity and spectral spanning efficiency in the mid-infrared. A solid-state ring-core fiber (RCF) is designed for mode controlling and dispersion tuning. The simulation results show that LP 01 -mode is well confined in the high-index cladding-ring, and the confinement loss (CL) analysis of other modes is performed as well. RCF can be regarded as an LP 02 -mode fiber in the center, which is different from LP 01 -mode in the step-index fiber when the wavelength is larger than 5.6 μm. Moreover, OAM 0,1 can be stably transmitted in the ring, since LP 01 -mode and OAM 0,1 have identical ring-shaped profiles. For LP 02 in the core, the zero-dispersion wavelength (ZDW) can be blue-shifted to 4.4 µm from 6.7 µm. For the first time, we have successfully fabricated a novel mid-infrared RCF based on Ge 9 As 22 Se 69 -Ge 9 As 22.5 Se 68.5 -Ge 10 As 22 Se 68 glasses. The lowest loss is 0.28 dB/m at 8.1 μm. The supercontinuum (SC) spectra can be effective broadening (1–14.4 µm) in this RCF via pumping the ZDW around 4.5 µm. In all, this RCF has great advantages in effective mode controlling and dispersion tuning, and has great potentials in developing broad SC and vortex mode controlling. [ABSTRACT FROM AUTHOR]

A number of Ge 17 Ga 4 Sb 10 S 69− x Se x ( x = 0, 15, 30, 45, 60, and 69) chalcogenide glasses have been synthesized by a melt-quenching method to investigate the effect of the Se content on thermo-mechanical and optical properties of these glasses. While it was found that the glass transition temperature ( T g ) decreases from 261 to 174 °C with increasing Se contents, crystallization temperature ( T c ) peak only be observed in glasses with Se content of x = 45. It was evident from the measurements of structural and physical properties that changes of the glass network bring an apparent impact on the glass properties. Also, the substitution of Se for S in Ge–Ga–Sb glasses can significantly improve the thermal stability against crystallization and broaden the infrared transmission region. [ABSTRACT FROM AUTHOR]

A mechanical drilling method for the preparation of photonic crystal fibers (PCFs) is presented in this paper. Several PCFs were fabricated with Ge 20 Sb 15 S 65 chalcogenide glasses, which have high transparency in the mid-infrared (IR) range. The mechanical drilling method has been identified as a powerful tool to prepare fibers with a variety of structures and to increase the transmission of the obtained fibers. For a three-ring PCF, the near-field intensity distribution and the transmission loss were measured. It was found that most of the optical energy is contained in the core of the PCF. The profile of the near-field intensity image shows that the prepared PCF can work with a large mode area, which is important in high-power laser propagation and fiber amplifiers. [ABSTRACT FROM AUTHOR]

We report broadband supercontinuum (SC) spectra generated from low-loss single-mode fibers (SMF) based on novel Ge–As–S–Se (GASS) chalcogenide (ChGs) glasses. The step-index fibers (SIF) possess an ultra-low background loss of 0.27 dB/m at wavelength of 2.5 ∼ 7. 5 μ m were fabricated by an optimized peeled-off extrusion method. SC generation was studied by pumping the fiber with 15 cm and 100 cm at same condition (5 μ m, ∼ 150 fs, 1 kHz, 25 mW), respectively. Output SC covering 1.46 ∼ 9. 32 μ m was obtained in this 15-cm fiber, while a relatively wide output SC spanning from 1.68 to 8. 28 μ m was observed in 100-cm fiber. Due to simulated numerical model does not account for higher-order modes at shorter wavelengths, cladding modes, polarization effects etc. Experimental SC spectral profile in the short and long S/Se fibers is slightly different with the simulation analysis. To the best of our knowledge, this is the first report on the performance of GASS fiber. • The fiber with an ultra-low background loss of 0.27 dB/m in 2.5 ∼ 7. 5 μ m. • SC spectrum covering 1.46–9.32 μ m was obtained in a 15 cm fiber, 1.68–8.28 μ m for 100 cm. • This fiber was better than As 2 S 3 fiber in operating window and higher damage than As 2 Se 3. [ABSTRACT FROM AUTHOR]

The influence of extrusion on the properties of chalcogenide glasses and fibers was investigated systematically via measuring and analyzing their structural and physical properties of Ge 10 As 22 Se 68 and As 2 S 3. The experimental results showed that the extrusion processing has an insignificant effect on the glass network, crystallization, and compositions, but does have an influence on the glass transmission rate, refractive index and density. Meanwhile, the fiber loss after extrusion processing was greatly improved with 57.65% or 71.43%, corresponding to Ge 10 As 22 Se 68 or As 2 S 3 fiber, respectively. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Tm3+-doped chalcogenide glass exhibited a strong emission peak around 3.8μm. [•] An approximate model for the Tm3+-doped PCF amplifier was developed. [•] The amplifying characteristics of the designed PCF amplifier were worked out. [•] The designed PCF amplifier exhibits a large signal gain around 3.8μm. [ABSTRACT FROM AUTHOR]

• High quality Ge-As-S glass and low loss fibers were prepared. • FZP working in visible and near infrared bands was fabricated on Ge-As-S glasses surface by laser direct writing. • With a well-designed FZP on the fiber end face, ChG fiber can achieve excellent self-focusing effect without the collimating and focusing lens. Chalcogenide glass (ChG) has excellent optical properties in the mid-infrared range. The micro-optical fiber devices made of ChG play a strong part in various infrared sensing and detection fields. In this work, Fresnel zone plate (FZP) was fabricated on the Ge-As-S ChG surface and the end face of ChG fiber through femtosecond laser direct writing. FZP with high optical quality was obtained by optimizing the laser writing parameters. Clear focusing pattern can be observed in the visible and infrared bands with the prepared FZP. The full width at half maximum (FWHM) of laser beam with wavelength of 1550 nm is recorded to be 10.39 μm at the focus of FZP, and the numerical aperture (NA) is 0.122. With a well-designed FZP on the fiber end face, the ChG fiber can achieve a self-focusing effect without the collimating and focusing lens. The FWHM of the 1550 nm laser beam at the focus is measured to be 7.46 μm, and NA is 0.162. The combination of FZP and ChG fiber can make the structure of the optical fiber more compact and has potential application value in enhancing the interaction between light and material in the infrared band. [ABSTRACT FROM AUTHOR]

Abstract: A systematic series of (Ge20Se15Te65)1− x –(SnI2) x (x =0, 0.05, 0.1, 0.15) chalcogenide glasses have been prepared. The amorphous nature can be confirmed by XRD and SEM. With the SnI2 content increasing, the indirect optical band gaps are decreased from 0.662 to 0.622eV according to Tauc laws. The introduction of SnI2 makes the glasses much easier to prepare and more stable against crystallization, making them drawable as optical fibers. The highest ΔT (130°C) value for (Ge20Se15Te65)0.9–(SnI2)0.1 glass composition can be obtained. A slight red-shifting of the long-wavelength cutting-off edge from 18.4 to 19.4μm was shown and it seems that SnI2 in these glasses offers the improvement in the far-infrared properties. [Copyright &y& Elsevier]

We have prepared Ge x Se 10 Te 90-x glasses with a composition of x from 17.5 to 26.25 and measured their properties using various diagnosis tools. It was found that, all the glasses have a transmittance more than 40% at a wavelength range from 2 to 15 μm, and linear refractive index n 0 decreases but optical bandgap energy E g increases with decreasing Te contents in the glasses. We also analysed the evolution of n 2 and β as a function of Ge content, both the evolution of n 2 and β are close to the prediction by Sheik-Bahae et al. for optical nonlinearity of semiconductors. In all cases, the nonlinear optical refractive index n 2 measured at 3.0 μm is larger than that at 2.5 μm due to the two-photon resonance effect, and a maximum nonlinear index is 2.46 × 10−13 cm2/W at composition of Ge 17.5 Se 10 Te 72.5. Such larger nonlinearity around 10−13 cm2/W observed in the present paper is one order of the magnitude larger than that in S- and Se-based chalcogenide glasses, demonstrating potentials of Te-based glasses for the applications as mid- and far-infrared nonlinear optical devices. • Glasses show a good transmittance more than 40% from 2 to 15 um. • n 0 decreases but E g increases with increasing Ge (and thus decreasing Te) contents. • A maximum nonlinear index is 2.46 × 10−13 cm2/W at composition of Ge 17.5 Se 10 Te 72.5. [ABSTRACT FROM AUTHOR]

• Arsenic-free low-loss fiber was fabricated by a process of peeled-off extrusion. • The fiber exhibits a minimum optical loss of 0.87 dB/m at 5.1 μm. • The broadest spectrum from 1.56 to 7.59 μm at −30 dB was achieved successfully. A low-loss and Arsenic-free sulfur-based chalcogenide fiber(Ge-Sb-S) was fabricated by a novel process of peeled-off extrusion. The fiber has an optical loss of <2 dB/m in a range from 5 to 6 μm with a minimum loss of 0.87 dB/m at 5.1 μm. A mid-infrared (MIR) supercontinuum (SC) spectrum covering 1.56–7.59 μm was generated from a 22-cm long fiber pumped with a femtosecond laser at 4 μm (−150 fs, 1 kHz). Simultaneously, we demonstrated that the optical fiber has a transmission efficiency of 53% at 4 μm, which is the key significance for applications such as IR night vision, bio-photonics, military defense and environmentally friendly industry. [ABSTRACT FROM AUTHOR]

Chalcogenide glass fiber usually possesses a single zero-dispersion wavelength (ZDW) that is more than 5 µm. Here, a novel W-typed double cladding chalcogenide glass fiber was designed and fabricated with optimized dispersion properties based on As 2 Se 3 -Ge 7 As 23 S 70 -Ge 10 As 23 Se 67 glasses. The results show that there are two ZDWs locating at near-infrared 2.95 µm and far-infrared 11.77 µm, and the dispersion less than 8 ps/km/nm at this range. Based on numerical simulation and viscosity analysis, a novel W-typed double-cladding fiber is fabricated via extrusion method, and the lowest loss of 1.15 dB/m is obtained at 5.68 µm. The optimized structure and dispersion distribution of the fiber ensure the excellent supercontinuum generation. When pumping at 3 µm near the first ZDW, a bandwidth supercontinuum (SC) spanning from 1 to 10.9 µm can be obtained. By pumping at 5 µm, a broad bandwidth of SC output from 1.3 to 13 µm can be obtained. This kind of low ZDW fiber has great potential for the generation of supercontinuum in the future. [ABSTRACT FROM AUTHOR]

It is well known that, the incorporation of halide will improve the optical properties of chalcogenide glasses with a broad transparent range. Here, we investigated the optical properties and structure of Ge-As-Se-I glasses in order to disclose the role of halogen iodine in the formation of chalcogenide glassy network. It was found that, refractive index, zero dispersion wavelength and glass transition temperature Tg decrease with increasing iodine contents, while the cut-off edge (λ vis) in the shorter wavelength blue-shifts apparently, and the whole transmission range is expanded widely. The glasses show good chemical stability against moisture. The zero dispersion wavelength of the glasses can be decreased to 4.32 μm by iodine-doping. The evolution of Raman spectra of the glasses indicates that, there is no obvious peak of iodine in Ge-As-Se-I glasses and the dominated glassy network are still the (Ge Se) heteropolar bonds. Unlabelled Image • These novel glass samples possess wide IR transparent window of 0.75-18 μm. • The ZWD of the glass can be decreased to 4.32μm while the refractive index is as low as 2.162 @1.7μm. • The strong absorption peaks of Ge O bond(12.5μm) and H 2 O(6.31μm) are all eliminated after effective purification. [ABSTRACT FROM AUTHOR]

• A dual-clad step-index chalcogenide fiber based on tellurium glasses was proposed and investigated detailedly for midinfrared coherent supercontinuum generation. • The structure of the fiber with a W-type refractive-index profile was numerically studied and optimized for all-normal dispersion profile. • Due to the large material zero dispersion wavelength, an all-normal dispersion tellurium chalcogenide fiber was realized via the waveguide chromatic engineering. • The optimized fiber was fabricated via extrusion and employed for coherent supercontinuum generation. • The result shows that a high coherent supercontinuum covering 3.5–10.5 μm can be generated in this fiber with 5 μm femtosecond laser pumping. • This is the first numerical investigation on the dispersion engineering of tellurium chalcogenide dual-clad step-index fiber. Considerable investigations have been carried out for chromatic dispersion tailoring of chalcogenide glass fiber with various structures and different material compositions. Here we proposed a tellurium-based chalcogenide glass fiber with a dual-clad structure in a W-type refractive-index profile. The structure of the fiber based on Ge-As-Se-Te glasses was numerically analyzed in detail. The simulation results indicate that an all normal dispersion profile can be realized in this tellurium glass fiber with an optimized dual-cladding structure. Then the optimized tellurium chalcogenide fiber with an all-normal dispersion profile was fabricated by multi-extrusion method. Pumping with a 5 μm ultra-short pulsed laser (150 fs, 1 kHz), abroadband supercontinuum (SC) covering 1.5–11 μm can be generated in the 19 cm-long fiber. The coherence of SC was also investigated by numerical simulation. The result shows that a high coherent SC covering 3.5–10.5 μm can be generated in this all-normal dispersion fiber. In conclusion, all-normal dispersion profile can be realized easily in this tellurium-based glass fiber due to their large materials ZDWs. [ABSTRACT FROM AUTHOR]

• Morphologies of damage craters were inequable with an increasing laser fluence. • Damage threshold on surface of As 2 S 3 fiber is slightly larger that of As 2 S 3 glass. • Morphologies of damage craters on surface of As 2 S 3 fiber and glass were similar. • Compared with damage in MIR region, damage threshold decreased under 800 nm laser. In this study, we investigated femtosecond laser-induced damage on the end face of an As 2 S 3 chalcogenide (ChG) glass fiber by repeatedly inducing 1 kHz ultrashort pulses with 150 fs duration at 800 nm wavelength in comparison with the bulk As 2 S 3 glass. The damage size, geometries, and morphology changes under different laser powers were measured and analyzed with optical, and scanning electron microscopes (SEM). The laser-induced damage threshold on the end face of three As 2 S 3 fibers calculated using the linear regression method was 32.15 mJ/cm2, whereas that of As 2 S 3 bulk glass was approximately 24.32 mJ/cm2. The femtosecond laser-induced damage on the As 2 S 3 bulk glass at 800 nm wavelength was also compared with that in the mid-infrared (MIR) region, which indicates a decrease in the damage threshold and an aggravation in the morphologies of damage craters under an irradiation of 800 nm femtosecond pulsed laser. To the best of our knowledge, this study is the first to investigate the interaction of femtosecond laser with the end face of ChG glass fiber. This work provides scientific guidance for the fabrication of novel photonic devices based on ChG glass fibers. [ABSTRACT FROM AUTHOR]