Rapid manufacturing of high purity fused silica glass micro-optics using a filament-based glass 3D printer has been demonstrated. A multilayer 5 x 5 microlens array was printed and subsequently characterized, showing fully dense lenses with uniform focal lengths and good imaging performance. A surface roughness on the order of R-a = 0.12 nm was achieved. Printing time for each lens was <10 s. Creating arrays with multifocal imaging capabilities was possible by individually varying the number of printed layers and radius for each lens, effectively changing the lens height and curvature. Glass 3D printing is shown in this study to be a versatile approach for fabricating silica micro-optics suitable for rapid prototyping or manufacturing.

We report the development of a specialty optical fiber preform fabrication system based on carbon monoxide (CO) laser heating. The laser heating is accomplished via a single-beam optical arrangement integrated into a rotating glass lathe. The CO laser output power and its beam quality are affected by absorption of the laser radiation by water vapor present in the surrounding air. This is addressed by construction of an enclosed and fully motorized system to enable preform processing in a dry air environment. The performance of the system is evaluated, and the ability to maintain a desired preform processing temperature is demonstrated. Relevant aspects of preform manufacturing, such as glass cutting, splicing, tapering, and overcladding, are described in detail. The process of using these aspects to fabricate optical fiber preforms made of highly dissimilar materials and of various core-to-cladding ratios is discussed. Specialty fibers drawn from these preforms exhibit low-loss and show good optical performance.

This thesis describes the development of a new prototyping technique for specialty optical fibers and covers all the fabrication steps from preform to fiber. The technique allows to produce fibers of a custom core structure and material composition, mainly focusing on semiconductor core fibers. By combining the optoelectronic properties of semiconductors with the advantages of the glass optical fiber platform, such fibers become a promising candidate in applications that require a wider infrared transmission window or stronger non-linear response. In contrast to traditional optical fibers, semiconductor core fibers are not standard off-the-shelf components. They exist as research samples, typically short in length, limited in core size, and exhibit a high loss due to the challenging and expensive fabrication process. 

The proposed preform fabrication method utilizes a carbon monoxide laser as a heat source. Employing this laser ensures extremely effective heat transfer to the preform with low surface silica vaporization, a minimal thermal gradient across the preform cross-section, and short exposure time of the preform to high temperatures. This allows to reduce the manufacturing time of the preforms and improve their optical properties. 

The aim of this thesis work was to design and build a system to fabricate fiber preforms made of semiconductors or other crystalline core materials. The work was primarily focused on preforms with silicon cores, but germanium and sapphire cores were also demonstrated. The ability to achieve preform tapering was a vital part of the preform fabrication. The process was developed using silicon as a test core material due to its abundance and widespread applications. As a typical representative of hybrid core materials, the properties of silicon imposed some common challenges that had to be addressed during the preform fabrication process. This includes a drastic difference in thermal expansion and thermal conductivity of the core compared to the cladding. Combined with a rod-in-tube approach, this system was used throughout the project to create silicon core fiber preforms in a wide range of core-to-cladding ratios, covering the core sizes from 17 μm up to 1 mm for preforms of 6 mm in diameter. The silicon core fibers produced from these preforms showed record minimal loss values of 0.1 dB/cm.

Additionally, glass additive manufacturing was applied for the first time in combination with the laser-based preform manufacturing technique to prototype specialty optical fibers of custom core composition and structure. In particular, the Laser Powder Deposition method was used to prototype fiber preforms with alumina, titania, and erbium-aluminum doped cores in concentrations not achievable by standard techniques. The drawn fibers showed losses as low as 3.2 dB/m, which is the best result achieved for glass fibers produced using 3D printing. Furthermore, multicore fiber preforms made of multi-component glass using a filament-based glass 3D printer have been demonstrated, showing the potential of using additive manufacturing for specialty fiber fabrication.

These silicon core and glass-doped preforms were pulled into hundreds of meter-long fibers of a standard 125 μm diameter and a core size in the range of 1 to 20 μm. This was achieved in a specially designed lab-sized fiber draw tower. To further utilize the benefits provided by the laser heating, the tower was also retrofitted with a carbon monoxide laser-based furnace. This allowed a very flexible operation of the tower, suitable for on-demand fiber prototyping of different types and experimental compositions.

We utilized a powder-based, 3D printing technique for prototyping optical fibers. Co-doped silica rods were printed using sub-micron powders with various compositions. The rods were sleeved and drawn into fibers. Ti/Al/Er-co-doped fibers are demonstrated.

We utilized a powder-based, 3D printing technique for prototyping optical fibers. Co-doped silica rods were printed using sub-micron powders with various compositions. The rods were sleeved and drawn into fibers. Ti/Al/Er-co-doped fibers are demonstrated.

We utilized a powder-based, 3D printing technique for prototyping optical fibers. Co-doped silica rods were printed using sub-micron powders with various compositions. The rods were sleeved and drawn into fibers. Ti/Al/Er-co-doped fibers are demonstrated. 

Optical fibre consisting of a pure silicon core in silica cladding combines the advantageous properties of silicon waveguides with the convenience of optical fibre. However, the optical quality of these fibres is highly dependent on the crystalline structure and the purity of the silicon. The fabrication of these fibres requires engineering of the thermal gradients during the drawing process to ensure optimal crystallisation of the silicon. Here, we investigated the effects of draw speed and analyse the induced stresses at multiple stages in the fabrication process. The thermal exposure of the silicon while in contact with a silica cladding was found to increase the optical losses. This was attributed to the diffusion of impurities from the silica cladding into the silicon core.

We demonstrate a method for rapid prototyping of optical fibers. Silica-based glass rods were 3D printed using laser powder deposition. Different doping of the 3D printed rods is evaluated, including alumina, titania, and erbium-doped glass. The rods were subsequently used as the core material in preforms with optical fibers drawn using a laser-based draw tower. A transmission loss of 3.2 dB/m was found for a fiber with 1 wt% titania doped core and pure silica cladding. Using this fabrication method, prototyping from powder to optical fiber could be achieved within a few hours.

Silicon core optical fibres have been fabricated using an experimental draw tower based on a CO laser furnace. Fabricated fibres have achieved a submicron core size and shown a record low loss of 0.1 dBcm. Frontiers in Optics / Laser Science

Rapid manufacturing of silica glass microlens arrays is demonstrated using a novel glass 3D printing technology. A 5×5 array was printed and subsequent characterization showed dense microlenses with uniform focal lengths and good imaging performance. Frontiers in Optics / Laser Science