The
ability to confine and manipulate light below the diffraction
limit is a major goal of future multifunctional optoelectronic/plasmonic
systems. Here, we demonstrate the design and realization of a tunable
and localized electrical source of excitons coupled to surface plasmons
based on a polymer light-emitting field-effect transistor (LEFET).
Gold nanorods that are integrated into the channel support localized
surface plasmons and serve as nanoantennas for enhanced electroluminescence.
By precise spatial control of the near-infrared emission zone in the
LEFET via the applied voltages the near-field coupling between electrically
generated excitons and the nanorods can be turned on or off as visualized
by a change of electroluminescence intensity. Numerical calculations
and spectroscopic measurements corroborate significant local electroluminescence
enhancement due to the high local density of photonic states in the
vicinity of the gold nanorods. Importantly, the integration of plasmonic
nanostructures hardly influences the electrical performance of the
LEFETs, thus, highlighting their mutual compatibility in novel active
plasmonic devices.
Photonic crystal modes can be tailored for increasing light matter interactions and light extraction efficiencies. These PhC properties have been explored for improving the device performance of LEDs, solar cells and precision biosensors. Tuning the extended band structure of 2D PhC provides a means for increasing light extraction throughout a planar device. This requires careful design and fabrication of PhC with a desirable mode structure overlapping with the spectral region of emission. We show a method for predicting and maximizing light extraction from 2D photonic crystal slabs, exemplified by maximizing silicon photoluminescence (PL). Systematically varying the lattice constant and filling factor, we predict the increases in PL intensity from band structure calculations and confirm predictions in micro-PL experiments. With the near optimal design parameters of PhC, we demonstrate more than 500-fold increase in PL intensity, measured near band edge of silicon at room temperature, an enhancement by an order of magnitude more than what has been reported.
We experimentally demonstrate free space excitation of coupled Anderson-localized modes in photonic crystal (PhC) line-defect waveguides (W1) with polarization tailored beams. The corresponding light beam is tightly focused on a pristine W1, and out-of-plane scattering is imaged. By integrating the scattering spectra along the guide, at the W1 modal cut-off, Anderson-localized cavities are observed due to residual W1 fabrication-disorder. Their spectral lines exhibit high quality Q factors up to 2 × 105. The incident beam polarization and scattering intensities of the localized modes characterize the efficiency of free-space coupling. The coupling is studied for linearly and radially polarized input beams and for different input coupling locations along the W1 guide. The proposed coupling scheme is particularly attractive for excitation of PhC waveguide modes and Anderson-localized cavities by beam steering and scanning microscopy for sensing applications.
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