Plasmonic Nanoantenna Arrays as Efficient Etendue Reducers for 2 Optical Detection

Abstract

Optical detectors require the efficient collection of incident 10 light onto a photodetector. Refractive or reflective optics are commonly 11 used to increase the collected power. However, in the absence of losses, 12 such optics conserve etendue and therefore pose a limit on the field of view 13 and the active area of the detector. A promising method to overcome this 14 limitation is to use an intermediate layer of fluorescent material that 15 omnidirectionally absorbs the incident light and preferentially emits toward 16 the photodetector. We demonstrate here that plasmonic nanoantenna 17 phased arrays are a promising platform to improve the emission efficiency 18 of thin luminescent layers and provide an efficient method to reduce optical 19 etendue. In particular, we show an almost constant optical absorption of the 20 luminescent layer on top of the array with the angle of incidence and a 21 strong beamed emission in small solid angles in the forward direction. 22 These results pave the way for novel optical communication detectors 23 incorporating nanofabricated plasmonic materials as optical etendue reducers.