Flat, thin and lightweight lamps providing spatially uniform and dimmable illumination from active areas as large as 400 cm2 are being developed for general illumination and specialty applications. Comprising an array of low-temperature, nonequilibrium microplasmas driven by a dielectric barrier structure and operating at pressures of typically 400-700 Torr, these lamps have a packaged thickness <4 mm and yet produce luminance values beyond 26 000 cd m-2 with a luminous efficacy approaching 30 lm W -1. Third generation lamps, presently in limited production, offer a correlated colour temperature in the 3000-4100 K interval and a colour rendering index of 80. Current lamps employ Xe2 (λ ∼ 172 nm) as the primary emitter photoexciting a mixture of phosphors, and the pressure dependence of the wavelength-integrated fluorescence from the electronically excited dimer has been investigated with a vacuum ultraviolet spectrometer. In contrast to other promising lighting technologies, the decline in luminous efficacy of microplasma lamps with increasing power delivered to the lamp is small. For a 6 × 6 inch2 (∼225 cm2) lamp, efficacy falls <16% when the radiant output (luminance) is raised from 2000 cd m-2 to > 10 000 cd m-2.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Acoustics and Ultrasonics
- Surfaces, Coatings and Films