Development of low‐loss lead‐germanate glass for mid‐infrared fiber optics: II. preform extrusion and fiber fabrication

Abstract

Fiber optics based on soft glasses have shown their great advantages over silica and silicate-based glasses for generation and transmission of mid-infrared (mid-IR) light, especially in the spectral range of 2.5-5.0 µm, 1 enabling their applications ranging from materials processing, laser medical surgery 2-4 and biomedical diagnostics, 5 to defense, for example, for directional infrared countermeasures, light detection, and ranging (LIDAR) for atmospheric and chemical sensing and monitoring. 6 The rapid progress in emerging novel mid-IR fiber lasers and mid-IR supercontinuum (SC) light sources, eg, the room

Development of low‐loss lead‐germanate glass for mid‐infrared fiber optics: I. glass preparation optimization

“…However, annealing of these glasses at temperatures above T g , where the viscosity is in the typical range for extrusion (10 8 dPa•s) and fiber drawing (10 6 dPa•s), revealed differences between the use of dry O 2 and dry air (20% O 2 + 80% N 2 ). The samples melted in dry O 2 without or with small portion of ultra‐dry N 2 (ie without and with GBP) did not show any color change, whereas the samples melted in dry air became amber colored and the samples melted in dry N 2 became even black, as described in detail in part II of this study 35 . The annealing of the glasses melted in N 2 ‐rich atmosphere facilitated reduction in ionic Pb to metallic Pb and subsequent growth into Pb nanoparticles.…”

“…35 For the sample N18-A2-O4 with high NaCl content, the formation of localized regions with reduced amount of nonbridging oxygens around Pb 2+ ions as a consequence of the reaction of Cl − ions in the melt with Pb 2+ facilitated localized formation of metallic Pb as described in detail in part II of this study. 35 Since high background loss in the mid-IR is detrimental for mid-IR transmission, it is important to achieve both low OH loss and low background loss. This requires lead-germanate glass fabrication using dry O 2 atmosphere complemented with ultra-dry N 2 via GBP and chloride dehydration agent.…”

“…However, the use of PbCl 2 dehydration agent together with NaNO 3 in the batch as well as the use of high amount of 18 mol% NaCl cause high mid-IR loss due to a large amount of scattering points inside the glass, which are attributed to metallic Pb microparticles as described in part II of this study. 35 Therefore, 10 mol% NaCl is found to provide the appropriate balance between low evaporation weight losses, high glass thermal stability, high dehydration efficiency, and absence of scattering defects in the glass.…”

“…The samples melted in dry O 2 without or with small portion of ultra-dry N 2 (ie without and with GBP) did not show any color change, whereas the samples melted in dry air became amber colored and the samples melted in dry N 2 became even black, as described in detail in part II of this study. 35 The annealing of the glasses melted in N 2 -rich atmosphere facilitated reduction in ionic Pb to metallic Pb and subsequent growth into Pb nanoparticles. This caused the amber or black color due to redshift of the UV edge because of intense LSPR absorption of the Pb nanoparticles.…”

Phonon Sideband Analysis and Near-Infrared Emission in Heavy Metal Oxide Glasses

“…Lead germanate glasses containing Ag nanoparticles are recommended in photonics and catalysis [ 9 ]. Low-loss lead germanate-based glasses are useful for mid-infrared fiber optics [ 10 , 11 ]. They are also interesting from the structural point of view.…”