High energy-efficient UV lamps using nano-thin spectrally selective metallo-dielectric layers

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Ultraviolet wastewater treatment systems, produced by Trojan Technologies, are very effective and versatile**optical means for the deactivation of bacteria, viruses, and parasites such as giardia and cryptosporidium.**Current commercial systems prefer the utilization of medium-pressure mecury-vapour lamps since broadband**UV emission has been shown to be desirable given that it reduces photoreactivation* of bacteria. However,**medium-pressure lamps operate at relatively high temperature of 800-900 deg C thereby emitting significant**infrared radiation, and thus are energetically inefficient.**In order to mitigate this energy loss and improve lamp efficiency, an optical coating that transmits in the**UV treatment range (200-320 nm) while reflecting the infrared emission back into the lamp is required. Lamp**efficiency can be improved by using specialized metallo-dielectric coatings wherein ultra-nano-thin Ag layers**and high bandgap ceramic dielectric layers together serve to maximize reflection in the infrared and**transmission in the UV part of the spectrum.**Preliminary modelling results of such structures are quite promising, suggesting high transmission in the**UV and broadband reflection that increases with wavelength in the infrared. Accordingly, significant**enhancement in UV lamp energy-efficiency is deemed potentially viable.**The objective of this project is to experimentally demonstrate the viability of these specialized**metallo-dielectric coatings to render energy-efficient UV lamps, and hence its integration in Trojan**Technologies' product line of UV wastewater treatment systems.**_________*** Photoreactivation is the recovery from biological damage caused by UV radiation as a result of simultaneous**or subsequent treatment with light of longer wavelength.