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This work presents a gas-liquid sensor based on chalcogenide etched-tapered fiber (ETF) functionalized with graphene oxide film. Unlike the preparation of conventional tapered fiber sensors, the core diameter of the optical fiber of this gas-liquid sensor was kept constant, and part of its cladding was removed via the chemical corrosion method that the fiber optic modes were the invariant. The energy distribution of transmission mode in the original fiber and tapered fiber is simulated respectively, and obtained the conclusion that the tapered fiber structure has higher sensing sensitivity. The sensors could detect VOCs such as formaldehyde (HCOH) and butane (C4H10) in the mid-infrared band. Results showed that the ETF sensor had a high detection sensitivity of both HCOH solution (2.6731 a.u./mg·mL−1) and C4H10 gas (0.2773 a.u./vol.%). A layer of graphene oxide (GO) film was coated on the ETF to further improve the sensitivity of the sensor. The GO coated etched-tapered fiber (GO-ETF) sensor’ sensitivity was substantially improved owing to the strong hydrophilicity and biocompatibility of GO which can absorb bioactive molecules. The high detection sensitivity of both solution and gas were 4.5091 a.u./mg·mL−1 and 0.4812 a.u./vol.%, respectively, which were 1.69 and 1.74 times higher than that of the sensor without a coating of GO film. The results further showed that the sensor had a rapid response speed, low detection limit, good repeatability, and stability.

Chalcogenide glass (ChG) optical fibers have excellent transmission performance in the mid-infrared range, and microstructured devices prepared on ChG fibers play an important role in the field of infrared sensing and optical integration. In this study, high-quality chalcogenide optical fibers were prepared, and grating structures were produced on their end surfaces. An easy-to-use FC cable was first prepared and polished to high flatness with the surface roughness of less than 0.08 μm. 1- and 2-D diffraction gratings were then prepared on the end surfaces of the chalcogenide fibers via femtosecond laser line-by-line direct writing technology. The ChG fiber end surface gratings prepared with optimized femtosecond laser parameters exhibited high diffraction efficiency and clear diffraction pattern, indicating that they had excellent optical performance. The performance of the grating was tested by using a laser source with wavelengths covering the visible to the near-infrared regions. This measurement showed that the first-order diffraction efficiency of the grating on the end face could reach close to 50% at 1550 nm.

We have prepared a novel fiber consisting of three different glasses with W-type double-cladding structure and constant core-to-cladding ratio by the extrusion method. An ultra-high numerical aperture (NA ≥ 2.17) indicates that this fiber has a good capability of collecting and confining light in a wide wavelength range. The lowest fiber loss is approximately 1.7 dB/m at 6.1 μm. Supercontinuum spectrum covering 1.6 μm to 10.85 μm at a bandwidth of −30 dB has been demonstrated in a 21 cm long fiber pumped by 5 μm laser. This chalcogenide fiber has high-NA and W-type double-cladding structure, and thus shows great potentials in the field of high power laser delivery, high efficiency imaging and high-capacity signal transmission in the mid-infrared.

We have developed an innovative extrusion with double peeling-off process to fabricate chalcogenide (GhG) preform, with an aim to remove the defects, such as bubbles, oxidation, and particles that always induce large optical losses in ChG glass fibers. As a result, none of the defects is found in the core-cladding interface of the fiber. The loss in a wavelength range of 5.5–8.2 μm is generally lower than 1 dB/m, with a minimum value of 0.2 dB/m at 6.3 μm. Moreover, a flat mid-infrared (MIR) supercontinuum (SC) spectrum spanning from 1.4 μm to 13.7 μm is generated in an 18 cm-long Ge-As-Se ChG fiber, accompanied with a highest spectrum flatten ratio of 72.4%.

We reported on a polarization beam splitter based on a novel chalcogenide dual-core photonic crystal fiber. The glass matrix of the optical fiber is Ge10As22Se68. We used computerized numerical control precision drilling methods to manufacture preforms. Then the preform was drawn into an optical fiber with a regular hole structure. The maximum extinction ratio reached -32.76 dB with a 26.27 mm-long optical fiber. Numerical results show that the shortest working length of the designed polarization beam splitter is 636 µm. In addition, the modeling analysis based on the actual structure shows that the theoretical value is consistent with the measured value.

A fast-response mid-infrared gas sensor based on a chalcogenide suspended-core fiber with microchannels fabricated by a tightly focused femtosecond laser pulse was demonstrated. Chalcogenide four-hole suspended-core fiber was fabricated by extrusion and exhibited the lowest transmission loss of 1 dB/m at 4.7 μm. The 50-μm-diameter solid core in the suspended-core fiber was protected by an outside solid jacket to avoid other environmental factors, such as dust and liquid pollution and touch damage. To increase gas filling rate, we introduced microchannels on the side of the suspended-core fiber by femtosecond laser writing to allow gases to enter into the fiber and fully interact with the core. The distribution, shape, and size of the channels could be controlled by laser writing technology. The engineered technique showed the advantage of increased minor loss in the suspended-core fiber. Methane gas sensing utilizing evanescent wave in the core was carried out in the prepared suspended-core fiber with several hundred microchannels. The methane sensitivity was 100 ppm, and the response time was estimated to be less than 20 s.

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.

A combined infrared suspended-core fiber (SCF) is fabricated using a stacked glass extrusion method. As2S3 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.

We experimentally demonstrate the mid-infrared supercontinuum generation in a chalcogenide step-index fiber consisting of an As 2 Se 3 core and an As 2 Se 2 S cladding. The fiber with the core diameter of 21 μ m was fabricated through the rod-in-tube technique and fiber-drawing process. The effect of pump wavelength, fiber length, and pump power on the spectral bandwidth and output power of the supercontinuum spectra generated from the fiber pumped by the ultrashort pulses of ∼ 150 fs with a repetition rate of 1000 Hz was systematically investigated. When pumping a 12-cm-long fiber at a wavelength of 6 . 5 μ m with 14 mW pump laser power, a broadband supercontinuum spanning from 2 . 0 μ m to 12 . 7 μ m with an output power of 300 μ W was obtained.

We report a broadband supercontinuum generation in a chalcogenide fiber taper with an ultra-high numerical aperture. The chalcogenide step-index fiber consisting of As2Se3 core and As2S3 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.

We have prepared a three-hole AsS suspended-core fiber (SCF) with an As2S3 core and a Ge15Sb10Se75 cladding via a robust technique combining the traditional rod-in-tube process with the preform extrusion method. The as-fabricated chalcogenide SCF has a core diameter as small as $2.33~\mu \text{m}$ . The lowest fiber loss is 0.62 dB/m at $2.71~\mu \text{m}$ and the nonlinear Kerr coefficient is up to 4251.96 $\text{W}^{-1}\cdot \text {km}^{-1}$ at $1.55~\mu \text{m}$ . The simulation of the dispersion distribution in the fiber indicates that there are two zero-dispersion wavelengths (ZDW) at $2.57~\mu \text{m}$ and $6.35~\mu \text{m}$ , respectively, and the ZDW can be further turned into a shorter wavelength if the core size of the fiber is reduced via the in situ tapering process. This makes the fiber much easier to be pumped by cheap and commercial lasers available. Finally, a broad supercontinuum spectrum covering $1.5-9.5~\mu \text{m}$ is obtained in the SCF pumped by an optical parametric amplifier laser system at $3~\mu \text{m}$ .

The fabrication and characterization of IR chalcogenide polarization-maintaining (PM) step-index optical fibers with elliptical-core and 1-in-line-core have been reported for the first time. An improved isolated co-extrusion method was used to fabricate these core-shaped PM fibers. The elliptical core had a horizontal radius of a = 3.66 μm, vertical radius of b = 1.83 μm and the 1-in-line core of a = 4.83 μm, b = 1.42 μm, respectively. Single-mode PM beam spots were observed for the elliptical-core and 1-in-line-core fibers in the near-field energy distributions. The highest values of birefringence of the elliptical-core and 1-in-line-core fibers are 2.09 × 10 −4 at 2.7 μm and 3.272 × 10 −4 at 2.8 μm, respectively. The extinction ratios of −3.7 dB and −2 dB were achieved in fibers of 0.5 m long with elliptical-core and 1-in-line-core, respectively.

We experimentally demonstrate the 2-8 μm high-power supercontinuum generation and theoretically propose a statistical method for precise estimation of the multi-pulse spectral evolution in the ZBLAN and As2S3 fiber cascaded all-fiber structured nonlinear system. In the experiment, with the aid of the ultra-low loss fusion splice technology, high-efficiency fiber butt-coupling technology and precise thermal management technology, we obtained a record-breaking supercontinuum source with a spectrum spanning from 2 μm to 8 μm at a power of 730 mW. Considering the strong pulse splitting and soliton fission effects in fibers, to precisely estimate the multi-pulse spectral evolution in this system, we, for the first time, built a multi-pulse pump model with the Pearson product-moment correlation coefficient method based multi-pulse selection mechanism. In combination with the existing approaches and some new programmatic work, finally, we verified that the simulation results are in good agreement with the experimental one.

Two kinds of single-mode (SMF) step-index(SIF) chalcogenide fibers based on S-rich and S-poor As-S-Se glass have been fabricated successfully by an isolated extrusion method. We experimentally explored the effects of S and Se weights on the IR light transmission in the infrared area of the waveguide medium. By exploring the infrared transmission. It is found that the As-S-Se system has a transmission varied range between full S-based (As2S3) and full Se-based (As2Se3) glasses. The results show that with the addition of selenium, the red-shift is observed in both the short-wavelength absorption edge and long-wave cut-off wavelength. This phenomenon can be sourced from the varying of optical band gaps and phonon energies. Simultaneously, single-mode fibers was employed to evaluate the attenuation and supercontinuum(SC). We found that S-rich fiber shows a lower optical loss of 0.67–1.5 dB/m in 4.1–5.9 μm region, with a minimum value of 0.67 dB/m at 4.6 μm than that of S-poor fiber does. Yet, the SC results of S-poor fiber shows a flatter and broader spectrum region than that of S-rich fiber does.

We have prepared GexGa8S92-x glasses with x=20, 26.67 and 36, and investigated the photoinduced effects under illumination at sub-bandgap wavelength with different power densities. It was found that, Ge20 and Ge36 undergo photodarkening (PD) and photobleaching (PB), respectively, and the change of transmission ratio with and without illumination increases with increasing illumination power density as well as prolonging illumination time. On the other hand, Ge26.67 is almost optical stable in any cases. This potentially offers a chance to reduce additional optical loss induced by PD and achieve net optical gain in the erbium doped chalcogenide planar waveguide amplifier using chemically stoichiometric Ge26.67 glass.

We have prepared GexSe10Te90-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 n0 decreases but optical bandgap energy Eg increases with decreasing Te contents in the glasses. We also analysed the evolution of n2 and β as a function of Ge content, both the evolution of n2 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 n2 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 Ge17.5Se10Te72.5. 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.

The ZBLAN glass with high content of Er3+ was prepared and studied. The glass has a wide infrared transmittance range of 2.5–8.0 µm, which means a lower maximum phonon energy. By testing and analyzing the fluorescence spectrum and lifetime curves under different penetration depths, the intrinsic emission spectrum and lifetime of the sample are obtained without the influence of sub-absorption. Under 980 nm excitation, the maximum emission cross section and the lifetime of 2.7 µm are 6.10 × 10−21 cm2 and 6.49 ms, indicating that high-concentration doping has a larger laser quality factor. According to the rate equation and transmission equation, cascaded and non-cascaded fiber laser models are established to conduct research on 2.7 µm fiber lasers. The slope efficiency can reach 40.38% at a pump wavelength of 980 nm and a fiber background loss of 0.1 dB/m. The high emission cross section, long fluorescence lifetime and high slope efficiency output make ZBLAN glass heavily doped with Er3+ an ideal host material for mid-infrared lasers.

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...

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.

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.

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 As2S3, Ge20Sb5Se75, As2Se3, Ge15As15Se17Te5, 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.

A series of Pr3+-doped selenide glasses was prepared by a melt-quenching method. The Pr3+ doped fibre optic preform was fabricated using extrusion and was successfully drawn into a low optical loss, step-index fibre. Intense mid-infrared (2.8–5.5 μm) fluorescence spectra were achieved at different concentrations of Pr3+ doped selenide glass with a pump of 2.0 μm. A comparison of the emission spectra of bulk glass and the fibres is presented under 2.0 μm wavelength excitation. The strongest emission was achieved due to the dispersion effect of Ga by forming bonds of Pr3+–Se–Ga. Based on the measured absorption spectra, the Judd–Ofelt parameters were calculated, discussed and compared with other host glasses. Given these properties, this system has the potential to be a good gain material for further development to realize both fibre lasers and amplified spontaneous emission fibre sources in the mid-infrared region.

A novel low-loss selenium-based chalcohalide fiber, with a low zero-dispersion wavelength, was prepared by an innovative preparation process. The composition optimized fiber has a wide transmission range of up to 11.5 μm, a lowest fundamental mode zero-dispersion wavelength of 4.03 μm, and a minimum optical loss of 1.12 dB/m at 6.4 μm, which provides a possibility to replace As2S3 and As2Se3 in a cascade of ZrF4−BaF2−LaF3−AlF3−NaF(ZBLAN)−As2S3−As2Se3 fiber in the practical all-fiberized supercontinuum (SC) source. Meanwhile, the broadest SC spectrum, ∼1.2 to 15.2 μm, was achieved by pumping a 12-cm-long fiber with a femtosecond laser at a deep anomalous-dispersion region. Furthermore, simulations are adopted to interpret the results as well as to demonstrate spectral evolution along the fiber. To the best of our knowledge, this is the broadest SC spectrum reported in any selenium-based chalcogenide fiber.

We demonstrated an ultrabroadband supercontinuum (SC) generation with high coherence property in all-normal-dispersion (ANDi) Te-based chalcogenide tapered fiber. The fibers made of Ge20As20Se15Te45 core and Ge20As20Se20Te40 cladding glasses were fabricated via isolated stacked extrusion. The waist diameter and length can be accurately controlled by a homemade tapering platform. When the core diameter of the waist was ≤14 μm, the fiber showed an ANDi characteristic in the wavelength range of 1.7-14 μm. A coherent SC generation covered 1.7-12.7 μm was generated in a 7-cm-long tapered fiber, pumped at 5.5 μm. To the best of our knowledge, this is the first SC experimental demonstration in Te-based step-index tapered fiber and the broadest SC generation in chalcogenide tapered fiber when pumped in the normal dispersion regime so far.

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

All-optical switching in long-period fiber grating (LPFG) with Ge–As–Se chalcogenide fibers was proposed. The switching performances at different resonant wavelengths and cladding modes were systematically investigated using coupled-mode theory. By utilizing the ultra-high nonlinearity of chalcogenide glass, the switching power threshold of the proposed LPFG switching at 1.55 μm was 105 MW/cm2 with power coupling for the low-order LP09 cladding mode, which was approximately 200 times lower than that of silica LPFG. Furthermore, the temperature stability of the proposed LPFG switching was examined. The optical switching instability due to the laser thermal effect can be well suppressed by optimizing the cladding radius and grating period. Considering the balance between temperature sensitivity and switching power threshold, an all-optical switch with temperature sensitivity of 51 pm/°C was finally realized by selecting the LP051 mode with a cladding radius of 39 μm.

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

A large mode-area (LMA) chalcogenide multicore fiber (MCF) with 13 hexagonally arranged cores has been designed and fabricated for mid-infrared (MIR) high power laser delivery. The dependence of mode distributions, bending loss and dispersion characteristics on the fiber structure parameters has been investigated by the method of finite element analysis at a wavelength range from 3 to 5 μm. An ultra-large fundamental mode (FM) effective area of ∼8000 μm2 as well as a low normal dispersion down to -46 ps/nm/km at 3 μm are theoretically obtained, which is of great benefit to high power MIR laser delivery. The fiber possesses a calculated low bending loss less than 0.075 dB/m as the bending radius is larger than 0.4 m. Finally, a well-structured 13-core fiber consisting of Ge9As23Se68 and Ge10As22Se68 glasses is fabricated via the continuous two-stage extrusion method, and this fiber shows a low optical loss of 0.28 dB/m at 6.6 µm, which is the lowest fiber loss for a micro-structured chalcogenide fiber obtained via extrusion, to the best of our knowledge.

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 As2Se3-Ge7As23S70-Ge10As23Se67 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.

International audience; 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.

We conducted a numerical study of mid-infrared (MIR) supercontinuum (SC) generation with femtosecond pulses in Ge 23 Sb 12 S 65 chalcogenide photonic crystal fiber (PCF). This PCF has multilayer air holes in the cladding region, which renders its flexibility for controlling the dispersion and confinement loss of the fiber. The broad and flat dispersion profiles and the low confinement loss of the designed PCF combined with the wide MIR transparent window of Ge 23 Sb 12 S 65 chalcogenide glass largely contributed to the broadband MIR SC generation. Owing to the ultra-high nonlinearity of the designed Ge 23 Sb 12 S 65 PCF, an ultra-broadband SC ranging from 1.9 μm to 9.3 μm was obtained in a 15 cm fiber by applying a very low pump power of 165 W at 3.3 μm wavelength.

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.

Third-order nonlinear optical properties of Ge10AsxTe90-x chalcogenide glasses were investigated utilizing the Z-scan method at the mid-infrared wavelengths of 2.5 and 3.0 µm. The compositional dependence of the third-order nonlinearity was analyzed, and their correlation with the refractive index and the optical bandgap was discussed. The results show that nonlinear refractive index n2 can be significantly enhanced by the addition of tellurium, and larger n2 values are observed at 3.0 µm rather than 2.5 µm due to the two-photon resonance effect, and the maximum of n2 is 4.96 × 10−13 cm2/W at the composition of Ge10As20Te70. In addition, the experimental results are in good agreement with the semi-empirical Miller’s rule whilst the variation of dispersive n2 values are in relatively good coincidence with the theoretical model by Sheik-Bahae et.al. for direct bandgap semiconductors.

A novel robust tri-cladding stepped fiber structure has been proposed for the dispersion tuning, and a systematic simulation has been given for the fibers with different sizes of claddings and cores. The results show that double zero-dispersion wavelength (ZDW) points can be obtained, and the first ZDW is shorter at 3.3 µm and the second ZDW at 9.9 µm. Based on the simulation of the structural optimization, we have prepared a well-structured tri-cladding fiber with a minimum loss of 1.55 dB/m at 6.77 µm by a novel continuous two-stage extrusion method. Moreover, a flattened supercontinuum extending from 1.3 to 12.9 µm pumping at anomalous dispersion wavelength of 5 µm between the two ZDWs can be achieved, which fits well with the simulated results. After all, the optimized fiber consisting of As2Se3, Ge10As22Se68, As2S3 exhibits excellent properties that demonstrate the potential for a simple way to prepare high quality fiber with a tri-cladding structure.

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.

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 (λvis) 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.

We report an ultrabroadband supercontinuum (SC) generation with high coherence property in all-normal-dispersion (ANDi) Te-based chalcogenide all-solid microstructured optical fiber (AS-MOF). The fiber was fabricated using a rod-in-tube method that presents four A s 2 S 3 glass rods selected as low refractive index material ( n = 2.4 ) embedded in a G e 20 A s 20 S e 20 T e 40 glass matrix ( n = 3.1 ). The highly symmetrical four-hole MOF preform was fabricated through the computerized numerical control precision mechanical drilling method. By engineering the structure of the fiber, we determined an ANDi characteristic in the range of 2–13.5 µm when the core diameter of the fiber was ≤ 10 µ m . Under pumping at 5 µm, a highly coherent SC generation in the range of 2–13.2 µm was generated in a 16-cm-long AS-MOF with core diameter of 9.8 µm.

A chemically stoichiometric chalcogenide (ChG) glass fiber with ultra-high germanium-containing has been realized for the first time. Here, an isolated extrusion (ISE) with a peeled-off method was carried out for the fiber fabrication with glasses of core Ge33As12.5Se54.5 and cladding Ge33As12Se55. The fiber exhibits an optical loss of

Chalcogenide glasses have the advantages of a wide transparency window (over 20 μm) and high optical nonlinearity (up to a thousand times greater than that of silica glasses), making them good candidates for mid-infrared supercontinuum generation. In this review, we describe both the history and recent developments in mid-infrared supercontinuum generation from chalcogenide fibers according to three kinds of fiber structures: step-index, microstructured and tapered fibers. We also review the coherence properties of mid-infrared supercontinuum generation and all-fiber supercontinuum sources based on chalcogenide fibers.

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 SchrOdinger 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.

This study theoretically investigated a feasible modal phase-matching second-harmonic generation (SHG) in chalcogenide photonic crystal fiber. SHG is a technique that enables the acquisition of the mid-infrared resource at 5.3 µm with the use of a 10.6 µm commercial laser. The phase-matching condition between two low-order modes can be realized simply by modifying the air hole size and lattice pitch in the designed photonic crystal fiber. Numerical results showed that the confinement loss of the second-harmonic wave was 4.15×10−4 dB/m at 5.3 µm, and the effective phase-matched fiber length reached as long as 6.382 m.

A tangencypoint method (TPM) is presented to derive the thickness and optical constants of chalcogenide thin films from their transmission spectra. It solves the problem of the abnormal value of thickness in the strong absorption region obtained by Swanepoel method. The accuracy of the thickness and refractive index is better than 0.5% by using this method. Moreover, comparing with Swanepoel method by using the same simulation and experimental data from the transmission spectrum, the accuracy of the thickness and refractive index obtained by the TPM is higher in the strong absorption region. Finally the dispersion and absorption coefficient of the chalcogenide films are obtained based on the experimental data of the transmission spectrum by using the TPM.

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, Ge20Sb15S65 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 g 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.

The Er3+/Tm3+ codoped WO3 modified tellurite glasses with molar composition of (75−x)TeO2–20ZnO–5Na2O–xWO3–0.2 wt%Er2O3–0.8 wt%Tm2O3 (x=0,4,8,12 mol%) were prepared to realize the blue upconversion emission. The absorption spectra, visible upconversion spectra and 1.53 µm band fluorescence spectra of glass samples were measured, together with the quantitative calculations of relevant spectroscopic parameters of Tm3+ and energy transfer micro-parameters between Er3+ and Tm3+ ions, to evaluate the effects of WO3 oxide on the spectroscopic properties of Er3+–Tm3+ ions. It was found that the introduction of WO3 oxide can further improve the blue upconversion emission of Tm3+ through an enhanced phonon-assisted energy transfer process. Meanwhile, with the increase of WO3 amount, the thermal stability of glass hosts, characterized by the difference between the glass crystallization onset temperature and the transition temperature which obtained from the measured differential scanning calorimeter (DSC) curves, increased and no obvious crystallization peak was detected when the WO3 amount increased to 12 mol%. Furthermore, the glass structure was briefly analyzed with the obtained Judd–Ofelt intensity parameters, the measured Raman spectra and X-ray diffraction (XRD) curves. The present results demonstrate the feasibility of realizing strong blue upconversion emission by introducing WO3 oxide with high phonon energy into the Er3+/Tm3+ codoped tellurite glass and also indicate its potential application as a glass host applied for the blue upconversion lasers.

In this study, we investigated femtosecond laser-induced damage on the end face of an As2S3 chalcogenide (ChG) glass fiber by repeatedly inducing 1 kHz ultrashort pulses with 150 fs duration at 800 nm wavelength in comparison with the bulk As2S3 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 As2S3 fibers calculated using the linear regression method was 32.15 mJ/cm2, whereas that of As2S3 bulk glass was approximately 24.32 mJ/cm2. The femtosecond laser-induced damage on the As2S3 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.

A novel tellurium chalcogenide (ChG) multicore fiber has been fabricated via extrusion for the first time. The fiber has seven cores in a hexagonal structure, with one center core surrounded by six other ones. The loss of the fiber is less than 3.5 dB/m in a range of 5-11 µm, and the minimum optical loss is 0.38 dB/m at 6 µm. When light is coupled to each core, the maximum transmission power is up to 1.1 W at 10.6 µm. Supercontinuum spectrum covering 2-12 µm at a bandwidth of -30 dB has been demonstrated. This tellurium ChG multicore fiber shows great potential in the field of high-power laser propagation and wide supercontinuum generation in the mid-infrared.

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.