It is now time for the future-generation and advanced greenhouse design practices to address a range of issues, from the energy and land use efficiency to providing plant-optimised growth techniques. In this Encyclopaedia record, we report on the practical development of spectrally selective and specialist-type advanced metal-dielectric thin-film filters that produce the optimized illumination spectrum when exposed to natural sunlight that can help maximize the biomass productivity of coated-glass greenhouse crops. Our experimental case study has been performed for the lettuce species, Lactuca sativa, L., yielding promising results.
This work is devoted to physical vapor deposition synthesis, and characterisation of 12 bismuth and lutetium-substituted ferrite-garnet thin-film materials for magneto-optic (MO) 13 applications. The properties of garnet thin films sputtered using a target of nominal composition 14 type Bi0.9Lu1.85Y0.25Fe4.0Ga1O12 are studied. By measuring the optical transmission spectra at room 15 temperature, the optical constants and the accurate film thicknesses can be evaluated using 16 Swanepoel's envelope method. The refractive index data are found to be matching very closely to 17 these derived from Cauchy's dispersion formula for the entire spectral range between 300-2500 nm. 18The optical absorption coefficient and the extinction coefficient data are studied for both the 19 as-deposited and annealed garnet thin-film samples. A new approach is applied for accurately 20 deriving the optical constants data simultaneously with the physical layer thickness, using a 21 combination approach employing custom-built spectrum-fitting software in conjunction with 22Swanepoel's envelope method. MO properties, such as specific Faraday rotation, MO figure of 23 merit and MO swing factor are also investigated for several annealed garnet-phase films. 24 25 26 1. Introduction 27 Yttrium Iron Garnet (YIG) is one of the most common and well-known iron garnet materials 28 possessing unique functional properties suitable for magneto-optic and microwave-range radio 29 frequency (RF) applications. It is chemically formulated as Y3[Fe2](Fe3)O12 where Y 3+ ions occupy the 30 dodecahedral sublattice sites, two of the Fe 3+ ions reside in the octahedral sites, and the remaining 31 three Fe 3+ ions are in tetrahedral sublattice sites. Research efforts, focusing on the refinement of 32 structure and composition of garnets through the addition of a number of elements into the garnet 33 material system, have resulted in scientific and technological benefits for various emerging 34 applications [1-12]. Many reports have demonstrated the successful synthesis of new garnet material 35 types by substituting the yttrium with either the transition-metal or rare-earth ions eg. Bi 3+ , Ce 3+ , Er 3+ , 36 Tb 3+ and others, into the dodecahedral sites, and also replacing the Fe 3+ ions by other elements (such 37 as Ga 3+ , Al 3+ , or other metals) into the tetrahedral sublattice sites [13-22]. Also several composite-type38 material systems have been explored to improve the optical and magneto-optical properties of 39 highly bismuth-substituted ferrite garnet thin-film materials [23-29]. Bismuth substitution into the 40 YIG-based garnet lattice structure enhances the Faraday rotation performance, while other added 41 components like Ga or Al contribute to the preferential dilution of iron inside the octahedral and 42 tetrahedral sites, which then reduces the net magnetization. Modified ferrite garnets, especially 43 Preprints (www.preprints.org) | NOT PEER-REVIEWED | Bi-substituted iron garnets (with compositions close to Bi3Fe5O12) have very high specific Fara...
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