Electrodeless lamps for lighting: a review

Abstract

Developments in semiconductor technology and changes in the standards for electromagnetic interference (EMI) have both been important in the recent exploitation of electrodeless discharges for use in lighting. There has been an active period of research on electrodeless discharges inside and outside the lighting industry and much of the basic physics and technology is now well understood. My purpose is to review and evaluate the progress. In the foreseeable future, the constraints on electronics and EM1 likely to restrict the practical general purpose light sources to the H discharge principle in which the maintenance field of the discharge is provided by magnetic induction effects. Both low-pressure (LP) and high-pressure (HP) versions have received substantial developments, judging by the extensive patent literature. The former are based on the LP mercury rare-gas principle and the latter use a variety of metal halide doses. The major target for electrodeless technology is a high efficiency, lookalike replacement for the ubiquitous incandescent lamp. Although no version is yet available on the market, recent announcements suggest that it is imminent. Meanwhile, versions of the technology meeting more specialised market needs are commercially available.

Effect of remote field electromagnetic boundary conditions on microwave-induced plasma torches

“…The latter can be found in the fields of materials processing [2][3][4], gas volume cleaning [5] and for the construction of sources of ions [6], radicals [7] and photons [8].…”

Microfabricated chip-scale rubidium plasma light source for miniature atomic clocks

“…conventional inductively coupled spherical lamps with diameters of order 1 cm use one or two external rF coils operated at frequencies typically between 75 and 300 Mhz consuming several watts of electrical power (80% for light and 20% as heat) to emit electromagnetic discharges (h-discharges) [18] driven by the changing magnetic flux of the coil [19]. although they are a good choice for compact clocks, they become highly inefficient when miniaturized to chip-scale planar lamps in terms of power requirements (tens of watts) and integration because of the external coil requirements.…”

“…The indium (100%) electrodes are deposited by placing and aligning pre-formed indium rings on top of Pyrex layers above the cavity and reflowing using a soldering iron. These external electrodes avoid electrode corrosion and might allow for lower power consumption when compared with the more traditional internal electrode designs [19]. note that in a future wafer-level production of the plasma light source, the electrodes can be directly integrated onto the Pyrex layers by evaporation or sputtering and micropatterning techniques, and could be made of a different metal or transparent metal oxide like ITo to better withstand high temperatures.…”

Low-Power chip-scale Rubidium plasma light source for miniature atomic clocks

“…The 100% Indium electrodes are deposited by placing and aligning Indium pre-form rings on top of Pyrex layers above the cavity and reflowing using a soldering iron. These external electrodes avoid electrode corrosion and might allow for lower power consumption when compared to the more traditional internal electrode designs [13]. Note that in a future waferlevel production of the plasma light source, the electrodes can be directly integrated onto the Pyrex layers used to close the cell by evaporation or sputtering and micropatterning techniques, and could be made of a suitable metal other than Indium in order to better withstand high temperatures.…”