Chalcogenide Glass Optical Fibers Research Articles

Internal examination of mid-infrared chalcogenide glass optical fiber preforms and fiber using near-infrared imaging [Invited

We report on the internal examination of mid-infrared chalcogenide glasses using near-infrared light to reveal light-scattering defects. The technique is demonstrated on imperfectly made chalcogenide glass rods and fiber. This simple, non-destructive technique enables assessment of the interior of glasses and convenient detection of regions containing defects hidden due to the glass opacity to visible light. This method will reveal the presence of unwanted light-scattering defects including nucleated crystals, dust, striae, and bubbles. Hence, this method will help to optimize both chalcogenide glass chemical formulations, against devitrification, and process design to manufacture glass rods and fiber with minimized light scattering defects.

Thermo-mechanical dynamics of nanoimprinting anti-reflective structures onto small-core mid-IR chalcogenide fibers [Invited

Thermal nanoimprinting is a fast and versatile method for transferring the anti-reflective properties of subwavelength nanostructures onto the surface of highly reflective substrates, such as chalcogenide glass optical fiber end faces. In this paper, the technique is explored experimentally on a range of different types of commercial and custom-drawn optical fibers to evaluate the influence of geometric design, core/cladding material, and thermo-mechanical properties. Up to 32.4% increased transmission and 88.3% total transmission are demonstrated in the 2–4.3 µm band using a mid-infrared (IR) supercontinuum laser.

Diffraction Grating Fabricated on Chalcogenide Glass Fiber End Surfaces With Femtosecond Laser Direct Writing

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.

Fabrication and polishing of chalcogenide glass optical fiber connectors

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.

Toward Mid-Infrared, Subdiffraction, Spectral-Mapping of Human Cells and Tissue: SNIM (Scanning Near-Field Infrared Microscopy) Tip Fabrication

Scanning near-field infrared microscopy (SNIM) potentially enables subdiffraction, broadband mid-infrared (MIR: 3-25-μm wavelength range) spectral-mapping of human cells and tissue for real-time molecular sensing, with prospective use in disease diagnosis. SNIM requires an MIR-transmitting tip of small aperture for photon collection. Here, chalcogenide-glass optical-fibers are reproducibly tapered at one end to form a MIR-transmitting tip for SNIM. A wet-etching method is used to form the tip. The tapering sides of the tip are Al-coated. These Al-coated tapered-tips exhibit near-field power-confinement when acting either as the launch-end or exit-end of the MIR optical fiber. We report first time optimal cleaving of the end of the tapered tip using focused ion beam milling. A flat aperture is produced at the end of the tip, which is orthogonal to the fiber-axis and of controlled diameter. A FIB-cleaved aperture is used to collect MIR spectra of cells mounted on a transflection plate, under illumination of a synchrotron-generated wideband MIR beam.

Low loss Ge-As-Se chalcogenide glass fiber, fabricated using extruded preform, for mid-infrared photonics

Chalcogenide glass fibers have attractive properties (e.g. wide transparent window, high optical non-linearity) and numerous potential applications in the mid-infrared (MIR) region. Low optical loss is desired and important in the development of these fibers. Ge-As-Se glass has a large glass-forming range to provide versatility of choice from continuously varying physical properties. Recently, broadband MIR supercontinuum generation has been achieved in chalcogenide fibers by using Ge-As-Se glass in the core/clad. structure. In the shaping of chalcogenide glass optical fiber preforms, extrusion is a useful technique. This work reports glass properties (viscosity-temperature curve and glass transition) and optical losses of Ge-As-Se fiber fabricated from an extruded preform. A robust cut-back method of fiber loss measurement is developed and the corresponding error calculation discussed. MIR light is propagated through 52 meters of a fiber, which has the lowest loss yet reported for Ge-As-Se fiber of 83 ± 2 dB/km at 6.60 μm wavelength. The fiber baseline loss is 83-90 dB/km across 5.6-6.8 μm, a Se-H impurity absorption band of 1.4 dB/m at 4.5 μm wavelength is superposed and other impurity bands (e.g. O-H, As-O, Ge-O) are ≤ 20 dB/km. Optical losses of fiber fabricated from different positions of the extruded preform are investigated.

A novel image-guided FT-IR sensor using chalcogenide glass optical fibers for the detection of combustion gases

An optical-fiber-based sensor suitable for the detection of combustion gases was designed and experimentally implemented with state-of-the-art sensitivity and capabilities. The system can not only provide imaging capability, but also provide spectral capability of the field of view (FOV) center guided by the imaging. The sensor employs a Fourier transform infrared (FT-IR) spectrometer, coupled with chalcogenide glass optical fiber, and a specially designed infrared optic lens. A special kit provided by Bruker Optics is connected on the spectrometer to focus the infrared beam from the lens at the entry of the fiber. It was tested in situ, in real time, under real-world conditions. Since each gas shows a characteristic optical emission spectrum, it is possible to detect selectively and quantitatively the presence of gases in combustion environment by analyzing mid-IR spectra. Spectral investigation techniques based on spectral shape band intensities and areas are tested to find the most effective tool for monitoring combustion gases. A comparison with experimental data has demonstrated that this sensor is well designed to study gases coming from combustion processes.

Nonlinear switching in a two-concentric-core chalcogenide glass optical fiber for passively mode-locking a fiber laser.

We propose an all-fiber mode-locking device, which operates based on nonlinear switching in a novel two-concentric-core fiber structure. The design is particularly attractive given the ease of fabrication and coupling to other components in a mode-locked fiber laser cavity. The nonlinear switching in this coupler is studied, and the relative power transmission is obtained. The analysis shows that this nonlinear switch is practical for mode-locking fiber lasers and is forgiving to fabrication errors.

Tailoring chromatic dispersion in chalcogenide–tellurite microstructured optical fiber

We report fabrication of a highly nonlinear hybrid microstructured optical fiber composed of chalcogenide glass core and tellurite glass cladding. The flattened chromatic dispersion can be achieved in such an optical fiber with near zero dispersion wavelength at telecommunication wavelengths λ=1.35–1.7μm, which cannot be achieved in chalcogenide glass optical fibers due to their high refractive index, i.e. n>2.1. We demonstrate a hybrid 4-air hole chalcogenide–tellurite optical fiber (Δn=0.25) with flattened chromatic dispersion around λ=1.55μm. In optimized 12-air hole optical fiber composed of the same glasses, the chromatic dispersion values were achieved between −20 and 32ps/nm/km in a broad wavelength range of 1.5–3.8μm providing the fiber with extremely high nonlinear coefficient 86,000km−1W−1. Hybrid chalcogenide/tellurite fibers pumped with the near infrared lasers give good promise for broadband optical amplification, wavelength conversion, and supercontinuum generation in the near- to mid-infrared region.

Bend loss in multimode chalcogenide fiber at infrared wavelengths

The bending loss is a critical parameter for packaging, representing a limiting parameter in the minimization of fiber-based devices. For applications in the mid-infrared spectral band, chalcogenide glass optical fibers are one of the few alternatives for high-power beam delivery. We present experimental results for the bending loss of a sulfide-based multimode chalcogenide fiber for a broad range of infrared wavelengths as well demonstrating >5.8 W power handling for a 6.25-mm radius bend.

Infrared Fiber $N \times 1$ Multimode Combiner

Fiber-based multimode combiners allow for wavelength and power scaling of laser sources while maintaining a common emission aperture and divergence. For applications in the mid-infrared spectral band, chalcogenide glass optical fibers are one of the few alternatives with high-power beam delivery. We demonstrated a 7 × 1 multimode fiber combiner based on a sulfide-based multimode chalcogenide fiber with 76% per-port transmission. Wavelength combining and power scaling in the mid-infrared are demonstrated through the fiber combiner.

Correlation between native As2Se3 preform purity and glass optical fiber mechanical strength

Based on their mid-infrared transparency and tailorable thermo-mechanical properties, chalcogenide glass optical fibers have found numerous technological useful applications in the fields of optic and sensing. However they tend to suffer from mechanical limitations as compared to more conventional oxide-glass fibers, which impede their further integration into components where high strength is required. Reported here are findings on the mechanical properties of fibers based on the glass As2Se3, with a focus on unraveling how extrinsic impurities embedded in the native preform impact the maximum stress that the resulting fibers can endure. Preforms were prepared and subjected to four levels of purification (standard moisture removal, surface oxide volatilization, and synthesis over AlCl3 getter, followed by distillation) and subsequently drawn into fibers. To effectively decouple the real effect of impurity content on fibers strength from other peripheral parameters, such as manufacturing, handling or aging, each purification protocol was duplicated on one bare fiber and one fiber drawn with a protective coating. Weibull statistics on the strength of As2Se3 fibers were determined in both tension and bending. We demonstrate that coated and uncoated fibers follow a similar trend with purification. Specifically, oxide volatilization treatment increases the fibers resistance to failure, while the addition of AlCl3 getter in the melt without subsequent distillation degrades it. If further distillation is carried out the fibers strength improves only slightly as compared to oxide volatilization treatment alone. These results provide both insights into the interplay between chemical, optical, and mechanical properties as well as practical steps benefiting the continued utility of these glass optical fibers.

Comparison between chalcogenide glass single index and microstructured exposed-core fibers for chemical sensing

Chemical bonds of most of the molecules vibrate at a frequency corresponding to the near or mid infrared field. It is thus of a great interest to develop sensitive and portable devices for the detection of specific chemicals and biomolecules for various applications in health, environment, security and so on. A microstructured exposed-core (MEC) fiber has been elaborated for the first time. This design consists of a chalcogenide glass optical fiber with a suspended micron-scale core that is partially exposed to the external environment. This configuration has been chosen to elaborate, using the molding method, a chalcogenide fiber for chemical species detection. The sensitivity of this fiber to detect molecules such as acetone and propan-2-ol has been compared with those of single index fibers. Although evanescent wave absorption is inversely proportional to the fiber diameter, the results show that an exposed-core fiber is more sensitive than a single index fiber having a twice smaller diameter.

Direct laser writing of relief diffraction gratings into a bulk chalcogenide glass

We inscribed relief diffraction gratings with periods of 6, 14, and 24 μm into the surface of Ge15Ga3Sb12S70 bulk glass by the material’s ablation using a femtosecond λ=800  nm Ti:sapphire pulsed laser. The laser writing was done with sample implemented on a computer-controlled stage employing surface-to-beam alignment, laser power, and raster pattern control. Pulse energies of 1.5, 3.0, and 4.5 μJ were focused on spot diameter of 1.5 μm, resulting in channel widths, measured on the surface, of around 4, 5, and 6 μm and depths up to 1.7 μm. The first-order diffraction efficiency of the fabricated gratings was up to 10% at λ=650  nm. We have also fabricated a “composite” grating combining the three relief diffraction gratings inscribed in the same position, but with a mutual tilt. The composite grating provides complex multidirectional diffraction of the light in accordance with geometrical arrangement and grating period of all the gratings inscribed. We propose practical applications of femtosecond pulsed-laser surface patterning, for example, surface-relief diffraction microgratings integrated at the ends of multimode mid-IR chalcogenide optical waveguides or on the surfaces of bare core chalcogenide glass optical fibers used for chemical sensing.

Recent advances in preparation of high-purity glasses based on arsenic chalcogenides for fiber optics

The processes of production of high-purity glasses based on arsenic chalcogenides and optical fibers with low optical losses in the middle IR have been analyzed. Physical–chemical, technological and methodological factors determining the degree of purity of glasses and the level of optical losses in optical fibers are considered. Dominant factors, rational actions and approaches optimizing the manifestation of these factors in glasses formed by arsenic chalcogenides are discussed. Vitreous As 2S 3 is produced with the content of hydroxyl groups not more than 1 ppb wt, of hydrogen in the form of SH-groups — 75 ppb mol, of silicon — 0.2 ppm wt. From this glass a multi-mode optical fiber was manufactured with optical losses of 12 and 14 dB/km at 3.0 and 4.8 μm, respectively, which is the best result published in literature for chalcogenide glass optical fibers.

Solid Microstructured Chalcogenide Glass Optical Fibers for the Near- and Mid-Infrared Spectral Regions

This paper demonstrates a new and flexible route to microstructuring of chalcogenide glass fiber for operation in the near- to mid-infrared, presenting an alternative to air-glass microstructuring. For the first time, a one-layer, solid microstructured optical fiber is successfully drawn from As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">40</sub> Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sub> and Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">23.4</sub> Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">66.6</sub> (atomic %) chalcogenide glasses. Light guiding is demonstrated in the center core of this fiber at 1.55-mum wavelength.

Monitoring of pollutant in waste water by infrared spectroscopy using chalcogenide glass optical fibers

Infrared optical fibers based on chalcogenide glass are used as sensor for the determination of volatile organic pollutants in groundwater. The system work following the fiber evanescent wave spectroscopy principle, so-called fiber evanescent wave spectroscopy (FEWS). It was tested in situ, in real time, under real-world conditions. The measurement set-up consisted of a FTIR spectrometer (BRUKER V22), coupled with the fiber (about 2 m), and a cooled mercury–cadmium–telluride detector. A special kit provided by Bruker was connected on the spectrometer to focus the infrared beam from the black body at the entry of the fiber. Some preliminary pilot scale tests, led in an artificial aquifer, show that the fiber permits access to the absorption line positions in a wide range from 4000 to 800 cm −1 . Moreover, it is shown that the original design of the fiber enables detection of weak concentrations of pollutants down to 1 ppm of C 2 Cl 4 . Then the experiments in “real-world” conditions are carried out after having applied a proper protection on the fibers. A comparison with the chemical analysis data shows that the optical fibers enable to follow the evolution of pollutant rates in water versus time. Finally, this work is promising in view of installing some permanent checking devices into wells to control the rate of pollutants in groundwater of landfill.

Monitoring of pollutant in waste water by infrared spectroscopy using chalcogenide glass optical fibers

Infrared optical fibers based on chalcogenide glass are used as sensor for the determination of volatile organic pollutants in groundwater. The system work following the fiber evanescent wave spectroscopy principle, so-called fiber evanescent wave spectroscopy (FEWS). It was tested in situ, in real time, under real-world conditions. The measurement set-up consisted of a FTIR spectrometer (BRUKER V22), coupled with the fiber (about 2m), and a cooled mercury–cadmium–telluride detector. A special kit provided by Bruker was connected on the spectrometer to focus the infrared beam from the black body at the entry of the fiber. Some preliminary pilot scale tests, led in an artificial aquifer, show that the fiber permits access to the absorption line positions in a wide range from 4000 to 800cm−1. Moreover, it is shown that the original design of the fiber enables detection of weak concentrations of pollutants down to 1ppm of C2Cl4. Then the experiments in “real-world” conditions are carried out after having applied a proper protection on the fibers. A comparison with the chemical analysis data shows that the optical fibers enable to follow the evolution of pollutant rates in water versus time. Finally, this work is promising in view of installing some permanent checking devices into wells to control the rate of pollutants in groundwater of landfill.

Scanning near field infrared microscopy using chalcogenide fiber tips

Chalcogenide glass optical fibers were fabricated into functional apertured probes for near field scanning infrared microscopy. Probe fiber tips were chemically etched and aluminum coated for the purpose of simultaneously collecting near field shear force and optical signals. Surface topography and infrared optical reflectivity data were obtained using the tips in a scanning near field microscope while illuminating an integrated microcircuit with the output from a free electron laser operating at a λ of 4.7 μm. Approximately 25 nm topographical and 100 nm optical lateral resolution were observed.

Active and passive chalcogenide glass optical fibers for IR applications: a review

Chalcogenide glass fibers based on sulfide, selenide, telluride and their rare earth doped compositions are being actively investigated worldwide. Great strides have been made in reducing optical losses using improved chemical purification techniques, but further improvements are needed in both purification and fiberization technology to attain the theoretical optical losses. Despite these problems, current single mode and multimode chalcogenide glass fibers are enabling numerous applications. Some of these applications include laser power delivery, chemical sensing, imaging, scanning near field microscopy/spectroscopy, fiber IR sources/lasers, amplifiers and optical switches. The authors assert that the research and development of chalcogenide glasses will grow in the foreseeable future, especially with respect to improvements in the optical quality of the fibers and the performance of the fibers in existing and future applications.