Modified chalcogenide glasses for optical device applications

This thesis focuses on two different, but complementary, aspects of the modification ofgallium lanthanum sulphide (GLS) glasses. Firstly the addition of transition metal ionsas dopants is examined and their potential for use as active optical materials is explored.It is also argued that the spectroscopic analysis of transition metal ions is a useful toolfor evaluating the local environment of their host. Secondly femtosecond (fs) lasermodification of GLS is investigated as a method for waveguide formation.Vanadium doped GLS displays three absorption bands at 580, 730 and 1155 nmidentified by photoluminescence excitation measurements. Broad photoluminescence,with a full width half maximum of ~500 nm, is observed peaking at 1500 nm whenexciting at 514, 808 and 1064 nm. The fluorescence lifetime and quantum efficiency at300 K were measured to be 33.4 μs and 4% respectively. Analysis of the emissiondecay, at various vanadium concentrations, indicated a preferentially filled, highefficiency, oxide site that gives rise to characteristic long lifetimes and a low efficiencysulphide site that gives rise to characteristic short lifetimes. X-ray photoelectronspectroscopy measurements indicated the presence of vanadium in a broad range ofoxidation states from V+ to V5+. Tanabe-Sugano analysis indicates that the opticallyactive ion is V2+ in octahedral coordination and the crystal field strength (Dq/B) was1.84. Titanium and nickel doped GLS display a single absorption band at 590 and 690nm, and emission lifetimes of 97 and 70 μs respectively. Bismuth doped GLS displaystwo absorption bands at 665 and 850 nm and lifetime components of 7 and 47 μs. Basedon comparisons to other work the optically active ions are proposed to be Ti3+, Ni+ andBi+, all of these displayed emission peaking at ~900 nm.Through optical characterisation of fs laser written waveguides in GLS, a formationmechanism has been proposed. Tunnelling has been identified as the dominantnonlinear absorption mechanism in the formation of the waveguides. Single modeguidance at 633 nm has been demonstrated. The writing parameters for the minimumpropagation loss of 1.47 dB/cm are 0.36 μJ pulse energy and 50 μm/s scanning speed.The observation of spectral broadening in these waveguides indicates that they mayhave applications for nonlinear optical devices. Fs laser written wav

Arquitecturas basadas en micro- y nanohilos de Ga₂O₃ con aplicaciones en fotónica

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física de Materiales, leída el 23-10-2020Transparent Conductive Oxides (TCOs) are materials which combine a very low absorption in the visible range of the electromagnetic spectrum with a moderate electrical conductivity. Among them, gallium oxide ( -Ga2O3) is one of the widest band gap semiconductors (almost 5 eV). Lately, this material is experiencing an exponential increase in its research interest, mainly due to two reasons: the better performance and lower cost of some high power electronic devices of Ga2O3 compared to the semiconductor giants SiC and AlN and the recent development of high quantum efficiency Ga2O3 deep-ultraviolet (deep-UV) photodetectors...Los óxidos conductores transparentes (TCOs, por sus siglas en inglés) son materiales que combinan una baja absorción en el rango visible del espectro electromagnético con una conductividad eléctrica moderada. Perteneciente a la familia de los TCOs, el óxido de galio ( -Ga2O3) tiene uno de los mayores band gaps de todos los semiconductores (casi 5 eV). Últimamente, el interés científico sobre este material está aumentando exponencialmente por dos principales motivos: el desarrollo de dispositivos de Ga2O3 de alta potencia con mejores capacidades y menor coste que los semiconductores comerciales de este sector (SiC y AlN) y el desarrollo de fotodetectores ultravioleta con gran eficiencia cuánticaFac. de Ciencias FísicasTRUEunpu

Rare-earth ion doped chalcogenide waveguide amplifiers

Chalcogenide glass waveguide devices have received a great deal of attention worldwide in the last few years on account of their excellent properties and potential applications in mid-infrared (MIR) sensing and all-optical signal processing. Waveguide propagation losses, however, currently limit the potential for low power nonlinear optical processing, and the lack of suitable on chip integrated MIR sources is one of the major barriers to integrated optics based MIR sensing. One approach to overcome the losses is to employ rare-earth ion doped waveguides in which the optical gain can compensate the loss, in such a way that the conversion efficiency of nonlinear effects is increased significantly. For infrared applications, the long wavelengths potentially attainable from rare-earth ion transitions in chalcogenide hosts are unique amongst glass hosts. New rare-earth ion doped chalcogenide sources in the MIR range could benefit molecular sensing, medical laser surgery, defence etc. Despite these promising applications, until now, no one has succeeded in fabricating rare-earth ion doped chalcogenide amplifiers or lasers in planar devices. This work develops high quality erbium ion doped chalcogenide waveguides for amplifier and laser applications. Erbium ion doped As2S3 films were fabricated using co-thermal evaporation. Planar waveguides with 0.35 dB/cm propagation loss were patterned using photolithography and plasma etching on an erbium ion doped As2S3 film with an optimised erbium ion concentration of 0.45x1020 ions/cm3. The first demonstration of internal gain in an erbium ion doped As2S3 planar waveguide was performed using these waveguides. With different film deposition approaches, promising results on intrinsic lifetime of the Er3+ 4I13/2 state were achieved in both ErCl3 doped As2S3 films (2.6 ms) and radio frenquency sputtered Er3+:As2S3 films (2.1 ms), however, no waveguide was fabricated on these films due to film quality issues and photopumped water absorption issues. The low rare-earth ion solubility of As2S3 is considered the main factor limiting its performance as a host. Gallium-containing chalcogenide glasses are known to have good rare-earth ion solubility. Therefore, a new glass host material, the Ge-Ga-Se system, was investigated. Emission properties of the bulk glasses were studied as a function of erbium ion doping. A region between approximately 0.5 and 0.8 at% of Er3+ ion was shown to provide sufficient doping, good photoluminescence and adequate lifetime to envisage practical planar waveguide amplifier devices. Ridge waveguides based on high quality erbium ion doped Ge-Ga-Se films were patterned. Significant signal enhancement at 1540 nm was observed and 50 % erbium ion population inversion was obtained, in waveguides with Er3+ concentration of 1.5x1020 ion/cm3. To the Author's knowledge, this is the highest level of inversion ever demonstrated for erbium ions in a chalcogenide glass host and is an important step towards future devices operating at 1550 nm and on the MIR transitions of erbium ions in chalcogenide glass hosts. Photoinduced absorption loss caused by upconversion products in the waveguides is the remaining hurdle to achieving net gain. Further research is needed to find suitable compositions that possess high rare-earth ion solubility whilst avoiding the detrimental photoinduced losses

Design, processing and characterization of glass fibers and coatings for healthcare industries

In this PhD, several bioactive phosphate glasses doped with erbium ions (Er3+) were synthesized and characterized in order to develop new bioactive fiber sensors for medical diagnostics and therapeutics in healthcare applications. Firstly, Er3+-doped phosphate glasses within the glass system P2O5-SrO-Na2O were fabricated using the melt-quenching technique. The glasses were prepared with different compositions and analyzed to understand the impact of the addition of Al2O3, TiO2 or ZnO on the thermal, structural and luminescence properties of the glasses. The results showed that with the addition of Al2O3 and TiO2 the phosphate network became more connected, whereas the addition of ZnO did not modify the optical, thermal and structural properties but it led to an enhanced fluorescence emission as compared to the other glasses. Secondly, glass-ceramics (GCs) were processed by heat-treating the glasses to induce in-situ crystal growth. The effect of the crystallization on the properties of phosphate glasses containing Al2O3, TiO2 or ZnO was investigated. The structural, optical, and spectroscopic characterization allowed assessing the occurrence and properties of the Er3+-doped crystals in the glasses. Different crystal phases were obtained depending on the glass composition but Sr(PO3)2 was identified in all the glasses. Moreover, the surface crystallization of the GCs was increased along with the duration of the heat treatment. However, the site of the Er3+ ions was not strongly affected by the heat treatment except for the reference GC, where an increase of the luminescence properties was observed after the heat treatment probably due to the incorporation of Er3+ ions into the crystals. Thirdly, particles-containing glasses were prepared using the direct doping method. A series of different Er3+-doped Al2O3, TiO2, ZnO and ZrO2 nano- and microparticles were synthesized using soft chemistry and then were added to phosphate-based glass batches prior to and after the melting. The survival and dispersion of the particles were optimized in order to increase the luminescence properties of the glasses. As evidenced by the morphological and compositional analyses, the Er3+ ions diffused from the particles to the glass matrix and no improvement of the spectroscopic properties was observed. A large amount of Er3+-doped particles were dissolved into the glasses probably due to the high temperatures achieved during the melting. As an alternative, glasses with different composition and lower melting temperatures were tested. The last part of the project was the production and characterization of a multimode optical fiber made from phosphate-based glasses. The core composition was 0.25 Er2O3 – 97.25 (0.5 P2O5 – 0.4 SrO – 0.1 Na2O) – 2.5 ZnO, while the cladding composition was 98.25 (0.5 P2O5 – 0.4 SrO – 0.1 Na2O) – 1.75 ZnO. The cladding component was processed using the rotational casting technique, and the preform was successfully drawn into an optical fiber. This novel optical fiber was found to be able to allow in-line monitoring of the fiber dissolution in H3PO4 and in simulated body fluid (SBF) solution. Bioactivity of the fiber was also assessed by the formation of a hydroxylapatite layer at the surface of the fiber after 4 weeks of immersion in SBF solution at room temperature. In this thesis, a bioactive fiber sensor able to monitor its optical properties and in vitro reactivity was reported. This research activity demonstrates as a proof of principle the idea of tracking the bio-response of a bioactive optical fiber “in vivo”

Spaceborne sensors (1983-2000 AD): A forecast of technology

A technical review and forecast of space technology as it applies to spaceborne sensors for future NASA missions is presented. A format for categorization of sensor systems covering the entire electromagnetic spectrum, including particles and fields is developed. Major generic sensor systems are related to their subsystems, components, and to basic research and development. General supporting technologies such as cryogenics, optical design, and data processing electronics are addressed where appropriate. The dependence of many classes of instruments on common components, basic R&D and support technologies is also illustrated. A forecast of important system designs and instrument and component performance parameters is provided for the 1983-2000 AD time frame. Some insight into the scientific and applications capabilities and goals of the sensor systems is also given

直交偏光二重共鳴を有するAuメタ表面の第二高調波生成

Tohoku University石原照也課

Index to 1985 NASA Tech Briefs, volume 10, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1985 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences