Richardson Helps Kick Off the Year of Glass
#YearofGlass
Richardson Helps Kick Off the Year of Glass
#YearofGlass
Research Terms
Researchers at the University of Central Florida have invented a low loss optical nanocomposite material made of glass and high concentrations of nanocrystals (NCs). Unlike conventional crystal laser media, the new glass ceramic medium can be drawn into fiber, coated onto films, deposited as waveguides or formed as bulk optical elements. The new material has better index-matched and viscosity-tuned attributes than other doped glass/NC-containing materials, enabling high NC loading levels. Though similar materials may exhibit luminescence or random lasing in bulk form, they fail to maintain optical function like the new nanocomposite can when formed into a fiber or planar film. Well-suited for laser sources operating in wavelengths of 2 µm or greater, the material can be used for applications such as molecular spectroscopy, non-invasive medical diagnostics and atmospheric sensing.
The invention comprises an optical nanocomposite material and a process for producing said material, which is made of glass and active NCs (rare earth or transition metals). The material creates a matrix which is index-, dispersion-, and thermo-optically matched, enabling the creation of a glass ceramic with unique optical properties. By further tuning the viscosity of the composite, it can be drawn into fiber form, dissolved into a solution and deposited as a thin film, or used as a bulk optical component.
One example use of the invention blends nanosized crystalline powders (NCs) with multicomponent chalcogenide glass (ChG) to form an optical nanocomposite of glass/NCs with matching optical properties (index, dispersion, dn/dT). Specialized methods ensure homogeneous physical dispersion of NCs within the glass matrix during preparation, while minimizing agglomeration and any mismatch in the coefficient of thermal expansion.
Researchers at the University of Central Florida, the Institute of Condensed Matter Chemistry of Bordeaux, and the University of Bordeaux have invented a technology that surpasses the capabilities of conventional thermal poling techniques by giving optical manufacturers the flexibility and scale needed to fabricate arrays of micro-lenses. For example, in amorphous inorganic material (such as glass), the technology enables three dimensions of spatial control to create a refractive index gradient and up to a length scale of several hundreds of micrometers.
In standard thermal poling techniques, the electric field configuration strongly limits the cations to move in directions parallel to the surface of the treated material. Thus, the refractive index gradient cannot be fully controlled. This limitation also causes abrupt transitions from regions of low index refraction to high index refraction, prohibiting a smoother periodic variation of the refractive index on a larger length scale.
Technical Details
The invention is a device and method for inducing by thermal poling a spatially controlled refractive index gradient inside at least one amorphous inorganic material to be treated. It includes a structured electrode arranged on the surface or in proximity to the surface of the material to be treated and at least one dielectric material. The structured electrode includes at least one conductive zone and at least one non-conductive zone. It is confined between the amorphous inorganic material to be treated and the dielectric material.
In one example application, the amorphous inorganic material to be treated is a chalcogenide glass or an oxide glass of the soda-lime silicate family. The dielectric material is an oxide glass of the soda-lime silicate family. The structured electrode is a thin layer of Indium tin oxide (ITO) deposited on an electrically insulating substrate. It is partially ablated to induce a structure of alternating electrically conductive and electrically insulating zones or a nickel grid. N2 forms the controlled atmosphere. Chalcogenide glasses and oxide glasses of the soda-lime silicate family include a wide range of materials whose optical properties cover a large portion of the electromagnetic spectrum. Also, chalcogenide glasses are transparent in infrared light, allowing applications for which other materials are not suited.
The University of Central Florida invention is a processing technique to coat ZnSe (an IR transparent material) particles with an atomically thin functional film. For fabricating optical components such as optical fibers, a high-temperature melting process is used in which the base matrix and the ZnSe powder are mixed and heated past the melting point of the matrix. This important step results in the formation of a composite (that is, a homogeneous mixture of two or more materials at fixed volume fractions) in which the ZnSe phase is intimately mixed in the glass matrix. The challenge in this melting process is that ZnSe can dissolve in the glass matrix resulting in a loss in IR transparency of the fabricated optical component. This technique prevents the dissolution of ZnSe powder during the high temperature melting process.
Researchers at the University of Central Florida and Lockheed Martin Corporation have developed a technology that enables a single glass-ceramic composition to provide a range of refractive indices and dispersion values. The invention expands the single-point solution in the Abbe diagram enabled by the transformation of a glass-ceramic composition from glass (amorphous phase) to various levels of crystallinity (glass-ceramic). The broad index variations of the IR glass-ceramic materials are tailored through a unique manufacturing process.
The tailored ceramization process—that is, the ability to create different filling fractions of crystals and/or different crystal species inside the base glass matrix—which can be achieved in a furnace, electrically or optically via a laser, is what allows a "continuous" linear, circular or elliptical area on the Abbe diagram. It is also the mechanism for replacing many lens elements with fewer elements for chromatic aberration correction. The innovation widens the number of materials that can be used and paired for IR system design, especially in infrared applications, where the number of commercially available compositions is very limited due to the high manufacturing costs of making and optimizing IR compositions.
