Wideband and wide angle thermal emitters for use as lightbulb filaments

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ABSTRACT We present optimized aperiodic structures for use as broadband, broad-angle thermal emitters which are capableof drastically increasing the eciency of tungsten lightbulbs. These aperiodic multilayer structures designedwith alternating layers of tungsten and air or tungsten and silicon carbide on top of a tungsten substrate exhibitbroadband emittance peaked around the center of the visible wavelength range. We investigate the properties ofthese structures for use as lightbulb laments, and compare their performance with conventional lightbulbs. We nd that these structures greatly enhance the emittance over the visible wavelength range, while also increasingthe overall eciency of the bulb.Keywords: Optimization, Photonic Nanostructures, Thermal Emission 1. INTRODUCTION Conventional incandescent lightbulbs (ILB) are composed of a tungsten lament inside a bulb which is lledwith inert gas. These devices are less than 10 percent ecient 1,2 due to the fact that most of the applied poweris radiated as heat and not as visible light. There has been much recent work in an attempt to improve theeciency of household and commercial lighting. Compact uorescent lamps (CFLs), the curled bulbs, improveeciency slightly, but have issues with slow turn on time, higher cost, degradation of performance over CFLlifetime, and most signi cantly, these bulbs contain mercury and pose an environmental hazard if broken ordisposed in a land ll. The most ecient lighting commercially available is the light-emitting diode (LED) whichpossesses eciencies between 25 and 35 percent. LEDs, however, are extremely expensive (due to fabricationcosts) which puts them out of reach of users in emergent countries. Hence, incandescent bulbs still account forthe vast majority of home lighting in developing countries; while, in the United States, the ILB has been phasedout to be replaced with CFL or LED lighting.In this paper, we propose one-dimensional multilayer aperiodic structures for use as incandescent lightbulb laments. It has been shown that multilayer structures can tailor the emittance spectra of bulk materialsand may provide properties similar to that of more complex and harder-to-fabricate two- or three-dimensionalstructures.