Felix Tan

Robust multimaterial chalcogenide fibers produced by a hybrid fiber-fabrication process

Double-crucible cane fabrication of highly purified chalcogenide-glass was combined with multimaterial thermal fiber drawing to produce robust low-loss 0.2 NA chalcogenide fibers. Optical transmission losses were shown to be less than 1.1 dB/m at wavelengths of 1.5, 2.0 and 4.6 μm. Fiber transmission > 97% at the 1.5 μm design wavelength was demonstrated using single-layer anti-reflection coatings that were durable under temperature, humidity and abrasion tests. Tensile-strength tests proved that the mechanical strength of the fiber was improved by a factor of 1000 compared to a jacket-free chalcogenide fiber. Multiwatt power transmission in single mode fiber was demonstrated.

Chalcogenide fibers for improved reliability of active infrared sensing systems (Conference Presentation)

Defense sensing systems must be both productive and robust to accomplish their mission. Active infrared sensing devices consist of many components such as the active medium, mirrors, beam-splitters, modulators, gratings, detectors, etc. Each of these components is subject to damage by the laser beam itself or environmental factors. Misalignment of these components due to vibration and temperatures changes can also reduce performance. The result is a complex and expensive system subject to multiple points of degradation or complete failure. However, beam confinement or “no free-space optics” via fiber transmission and even component assembly within the fiber itself can achieve reliability and low cost for sensing systems with reduced component count and less susceptibility to misalignment. We present measurements of high-power infrared laser beam transmission in chalcogenide fibers. The fiber compositions were As39S61 for the core and As38.5S61:5 for the cladding, resulting in a numerical aperture of 0.2. A polyetherimide jacket provided structural support. Multiwatt CW transmission was demonstrated in near single-mode 12 micron core fiber. Efficient coupling of quantum cascade lasing into anti-reflection coated chalcogenide fiber was also demonstrated. Efficient beam transport without damage to the fiber required careful coupling only into core modes. Beams with M2 ≥ 1.4 and powers higher than 1 W produced damage at the fiber entrance face. This was most likely due to heating of the highly absorptive polymer jacket by power not coupled into core modes. We will discuss current power limitations of chalcogenide fiber and schemes for significantly increasing power handling capabilities.

Mid-infrared performance of single mode chalcogenide fibers

Due to the intrinsic absorption edge in silica near 2.4 μm, more exotic materials are required to transmit laser power in the IR such as fluoride or chalcogenide glasses (ChGs). In particular, ChG fibers offer broad IR transmission with low losses < 1 dB/m. Here, we report on the performance of in-house drawn multi-material chalcogenide fibers at four different infrared wavelengths: 2053 nm, 2520 nm and 4550 nm. Polymer clad ChG fibers were drawn with 12.3 μm and 25 μm core diameters. Testing at 2053 nm was accomplished using a > 15 W, CW Tm:fiber laser. Power handling up to 10.2 W with single mode beam quality has been demonstrated, limited only by the available Tm:fiber output power. Anti-reflective coatings were successfully deposited on the ChG fiber facets, allowing up to 90.6% transmission with 12.2 MW/cm2 intensity on the facet. Single mode guidance at 4550 nm was also demonstrated using a quantum cascade laser (QCL). A custom optical system was constructed to efficiently couple the 0.8 NA QCL radiation into the 0.2 NA ChG fiber, allowing for a maximum of 78% overlap between the QCL radiation and fundamental mode of the fiber. With an AR-coated, 25 μm core diameter fiber, >50 mW transmission was demonstrated with > 87% transmission. Finally, we present results on fiber coupling from a free space Cr:ZnSe resonator at 2520 nm.

Hybridized fabrication of robust low-loss multimaterial chalcogenide fiber for infrared applications

Double-crucible cane fabrication of highly purified chalcogenide-glass was combined with multimaterial thermal fiber drawing to produce robust low-loss 0.2 NA chalcogenide fibers monolithically provided with a polymer jacket and featuring losses <;1 dB/m across the infrared.

Diffusive scattering from single microspheres with well-dispersed dielectric nano-scale inclusions

By fabricating a new class of composite microspheres comprising a random distribution of well-dispersed high-refractive-index dielectric nanoparticles, we confirm that forward and backward multiply scattered fields in the visible are diffusive.

3D Printing Preforms for Fiber Drawing and Structured Functional Particle Production

Using our recently developed in-fiber technique for generating particles, we use 3D printing to generate preforms for fiber drawing. We fabricate particles with optical and magnetic dopants confined to specific compartments in the particle.

Benchtop Production of Polymeric Optical Fibers

Novel devices were designed and fabricated for benchtop production of multimaterial fibers by ram extrusion and thermal drawing. The system was experimentally tested by fabricating a large-core polymeric optical fiber from raw materials.

Scalable Production of Digitally Designed Multifunctional Polymeric Particles by In-Fiber Fluid Instabilities

By exploiting fluid instabilities in multimaterial fibers, we present a fabrication methodology for producing multifunctional particles. Particles are produced with optical and magnetic dopants confined to specific compartments within the particle.