Incorporation of Colloidal PbSe Quantum Dots into 2-D Photonic Crystal Structures
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0939-O06-08
Incorporation of Colloidal PbSe Quantum Dots into 2-D Photonic Crystal Structures Yun-Ju Lee, Ganapathi Subramania, Bernadette A. Hernandez-Sanchez, Michael K. Niehaus, Timothy J. Boyle, Joseph Cesarano, and Paul G. Clem Sandia National Laboratories, Albuquerque, NM, 87185 ABSTRACT We demonstrate the functionalization of 2-D photonic crystal structures operating at ~ 1.5 µm with colloidal PbSe quantum dots and examine the modified photoluminescence from the functionalized photonic crystal. Using spin coating and airbrushing, monodisperse PbSe quantum dots were deposited from hexanes on lithographically patterned GaAs photonic crystal substrates. The effectiveness of patterning the PbSe quantum dots via standard liftoff process was examined. The near-IR photoluminescence spectra of quantum dot-functionalized photonic crystals were studied. We found that the photoluminescence peak became attenuated by approximately a factor of five and exhibited a narrow peak width (50 nm vs. 120 nm) compared to PbSe deposited on unpatterned GaAs, suggesting that there is some coupling between the quantum dots and the photonic crystal. Future work to improve the coupling and detection efficiency is proposed. INTRODUCTION Photonic crystal (PC) cavities are a subject of much recent scientific interest due to their ability to modify the propagation and speed of light in a small mode volume (~ λ3). By controlling the interaction between PC cavities and atom-like emitters like quantum dots (QDs), functionalized PC cavities have demonstrated interesting phenomena such as quantum electrodynamics,[1,2] enhanced emission,[3,4], and low-threshold lasing.[5,6] However, in most of the reports, the QDs were incorporated into PC cavities via in situ growth techniques such as molecular beam epitaxy, thus the choice of materials are limited by processing considerations. If post-processing techniques can be developed to functionalize fabricated PC cavities with QDs and other light emitters, then the list of materials that may be incorporated expands considerably. For example, colloidal QDs such as CdSe and PbSe are particularly promising materials for coupling into PC cavities due to their size-tunable photoluminescence (PL), their ability to act as single photon sources at room temperature,[7] and their ease of surface functionalization to enable applications in areas such as biological imaging and sensing.[8] Recently, Fushman et al. demonstrated coupling of PbS QDs (emission maximum at ~ 850 nm) to a 2-D PC cavity by spin coating QDs dispersed in a PMMA e-beam resist above the cavity and patterning the PMMA by e-beam lithography to remove the QDs not on the active region.[9] Using polarized PL spectroscopy with a pulsed 760 nm excitation, they demonstrated polarization-dependent PL peak narrowing and wavelength splitting depending on the excitation polarization, which matched well with calculations of the electromagnetic field intensity inside the cavity for each polarization.
In this report, we examined two different techniques for
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