An innovative hollow-core fiber with anti-resonant arches (HC-ARA) is designed and made of chalcogenide glass As2S3. The HC-ARA fiber has a single layer of eight non-touching curved arches, each one being solidly attached at two locations on the outer solid region to prevent any lateral displacement and to preserve the arches’ shape and uniformity during the fabrication process. The thickness and spacing between the arches are selected to minimize the fiber transmission loss <0.1 dB/m for CO2 laser at 10.6 micron. Also the higher order modes of the HC-ARA fiber are more attenuated than the fundamental mode, so the fiber is effectively single mode after only a few meters. The HC-ARA preform is made by extrusion of chalcogenide glass through a die specifically designed to produce the anti-resonant arches. The extruded HC-ARA preform is pulled in a fiber using photonic crystal fiber draw techniques. Recent simulation and experimental results on the HC-ARA fiber are presented to illustrate a novel fiber solution for CO2 laser transmission at 10.6 micron.
High-precision chalcogenide molded freeform micro-lenses were designed and produced to perfectly collimate and circularize mid-infrared Quantum Cascade Lasers (QCLs). The innovative micro-lens has an input surface with freeform contour to simultaneously converge the fast axis and further diverge the slow axis, while the output freeform surface collimates both axes. The 5-mm long freeform lens is such that the collimated output fast- and slow-axis beams are circular. This paper presents recent results on the chalcogenide molded freeform micro-lens prototypes specifically designed to collimate and circularize QCL at 9 micron.
High-purity chalcogenide glasses and fiber draw processes enable the production of state-of-the-art mid-infrared fibers for 1.5 to 10 micron transmission. Multimode and single-mode mid-infrared fibers are produced with low-loss (<0.2 dB/m), high tensile strength (>25 kpsi), and high power laser handling capability (>11.8 MW/cm2). Chalcogenide fibers support the development of cutting-edge devices for mid-infrared medical applications. Connectorized cables transmit laser power to a sample or mid-infrared radiation to a detector. Broadband antireflection microstructures are thermally stamped on the chalcogenide fiber tip to reduce the surface reflection from 17% to <5%. Also custom fiber-optic probe bundles are made with multiple fiber legs (source, sample, signal) for reflection and backscatter spectroscopy measurement. For example, a 7 x 1 fiber probe bundle is presented. Additionally imaging fiber bundle is made to perform remote thermal and spectral imaging. Square preforms are drawn, stacked, squared and fused multiple times to produce a 64 x 64 imaging fiber bundle with fiber pixel size of 34 microns and the numerical aperture of 0.3. The 2- meter long imaging fiber bundle is small (2.2 mm x 2.2 mm), flexible (bend radius >10 mm) and transmits over the spectral range of 1.5 to 6.5 micron.
High-precision chalcogenide molded micro-lenses were produced to collimate mid-infrared Quantum Cascade Lasers (QCLs). Molded cylindrical micro-lens prototypes with aspheric contour (acylindrical), high numerical aperture (NA~0.8) and small focal length (f<2 mm) were fabricated to collimate the QCL fast-axis beam. Another innovative freeform micro-lens has an input acylindrical surface to collimate the fast axis and an orthogonal output acylindrical surface to collimate the slow axis. The thickness of the freeform lens is such that the output fast- and slow-axis beams are circular. This paper presents results on the chalcogenide molded freeform micro-lens designed to collimate and circularize QCL at 4.6 microns.
Innovative mid-infrared imaging fiber bundle has been developed that is flexible, rugged and high fiber-count for use with infrared cameras for thermal imaging applications. High-quality chalcogenide fibers are used to produce coherent fiber bundle that is 2 meters in length, 4000 fibers in a 3mm diameter bundle, minimum bend radius of 10cm, and low attenuation over the spectral range of 1.5-6.5 microns. Individual fiber pixel size is 34 microns and the NA is 0.3. This paper presents the fabrication process and the optical characterization of the mid-infrared imaging fiber bundle.
Ongoing efforts on the purification of chalcogenide glasses and fiber draw processes enable the production of commercial-grade mid-infrared (MIR) fibers for 1.5-10 μm transmission. Results show multimode and single-mode MIR fibers with low-loss (<0.1dB/m) and high tensile strength (>20kpsi). High-power laser transmission has been achieved in single-mode fiber (>5 MW/cm2 CW).
Chalcogenide glass fibers are the best candidates for mid-infrared transmission. Their low optical losses and high-power
damage threshold are enabling numerous applications: laser power delivery, chemical sensing and imaging.
Furthermore, chalcogenide glass fibers are best candidates for demonstrating rare-earth doped fiber lasers and
supercontinuum sources in the mid-infrared. The latest results towards the creation of a 4.5 micron fiber laser and a
broadband (2-5 micron) supercontinuum source are presented.
Great strides have been made in reducing optical losses of chalcogenide glass fibers using improved chemical purification and fiberization techniques. The losses are low enough for practical applications which include laser power delivery for infrared missile protection systems. Fiber cables have been fabricated and successfully used in field demonstrations for missile defense