Understanding light trapping by resonant coupling to guided modes and the importance of the mode profile

Optics Express
Fiona J BeckGerasimos Konstantatos

Abstract

We present a simple conceptual model describing the absorption enhancement provided by diffraction gratings due to resonant coupling to guided modes in a multi-layered structure. In doing so, we provide insight into why certain guided modes are more strongly excited than others and demonstrate that the spatial overlap of the mode profile with the grating is important. The model is verified by comparison to optical simulations and experimental measurements. We fabricate metal nanoparticle gratings integrated as back contacts in solution-processed PbS colloidal quantum dot photodiodes. The measured photocurrent at the target wavelength is enhanced by 250%, with reference to planar devices, due to resonant coupling to guided modes with strong spatial overlap with the gratings. In comparison, resonant coupling to weakly overlapping modes results in a 25% increase at the same wavelength.

References

Jan 11, 2005·Nature Materials·Steven A McDonaldEdward H Sargent
Dec 10, 2007·Optics Express·Peter BermelJohn D Joannopoulos
Dec 5, 2009·Chemical Reviews·Dmitri V TalapinElena V Shevchenko
Jul 9, 2010·Optics Express·Vivian E FerryAlbert Polman
Sep 16, 2010·Advanced Materials·Jiang Tang, Edward H Sargent
Sep 30, 2010·Proceedings of the National Academy of Sciences of the United States of America·Zongfu YuShanhui Fan
Oct 15, 2011·Optics Express·F Pelayo García de ArquerGerasimos Konstantatos
Jul 3, 2013·Nature Communications·Ragip A PalaMark L Brongersma
Oct 15, 2013·Scientific Reports·Michael M AdachiEdward H Sargent
Oct 25, 2013·Nature Communications·Emiliano R MartinsThomas F Krauss
Nov 1, 2013·Advanced Materials·Agustín MihiGerasimos Konstantatos
Nov 28, 2013·ACS Nano·Byung-Ryool HyunFrank W Wise

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