The fluorescence of chromophores embedded in a photonic crystal is inhibited by the presence of a photonic pseudo-gap. We present the influence of such an incomplete bandgap on the emission and energy transfer by studying the steady-state and time-resolved emission properties of both a donor and an acceptor fluorophore in a self-assembled photonic crystal. Our results clearly show an inhibition of the donor emission and a concomitant enhancement of the acceptor emission, indicating improved energy transfer from donor to acceptor. This is explained by the decreased number of available
photonic modes for radiative decay for the donor in a suitable engineered photonic crystal with respect to in the effective
homogeneous medium.
The fluorescence of emitters embedded in a photonic crystal is known to be inhibited by the presence of a photonic
pseudo-gap acting in their emission range. Here we present a comparative study of the influence of the pseudo-gap on
the fluorescence emission of either organic dyes or nanocrystals embedded within a photonic crystal. Our results clearly
show that the optical properties of the emitters are primarily controlled by the presence of a pseudo-gap which causes
inhibition of the emission in both cases, regardless of the differences in chemical composition. These findings are mainly
attributed to a decrease of the number of available photonic modes for radiative decay of the emitter in a photonic crystal
compared to the effective homogeneous medium. Furthermore, we show that a photonic crystal can be used to control
the fluorescence energy transfer (FRET) between donor-acceptor (D-A) pairs of dyes. Finally, we show that the
application of an external magnetic field can finely tune the emission characteristics of emitters with a permanent
magnetic moment.
Colloidal photonic crystals, even with low refractive index contrast have a significant effect on the spontaneous emission
of internal emitters. This is observed as a modification of the emitters' fluorescence spectrum and as a narrowing and
shortening of the decay rate distribution. The decay rates are observed to be nonexponential. This modification was then
put to use by fabricating a photonic superlattice, consisting of several photonic crystal slabs deposited on top of each
other. Because of the two different photonic bandgaps and effective passband is created between the two and leads to
enhancement of emission in this spectral region. These experiments indicate that the threshold for lasing can possibly be
lowered by spectrally narrowing the emission of fluorophores infiltrated in suitably engineered self-assembled photonic
crystal superlattices, and are therefore important towards the realization of efficient all-optical integrated circuits from
functionalized photonic superlattices and heterostructures.
The engineering of a well-designed passband inside the stopband of a self-assembled colloidal crystal superlattice and
its effect on the steady-state emission properties of infiltrated fluorophores is reported here. The superlattice was
constructed by convective self-assembly of slabs of silica spheres of two distinct diameters. This resulted in an effective
passband in between the two stopbands of the total photonic crystal structure as seen in transmission. Because of the
passband there is a narrow spectral range with an increased density of states for photon modes. This is seen as a decrease
in the suppression of emission (an enhancement of the emission) for the narrow spectral range where the effective
passband manifests itself. These experiments indicate that the threshold for lasing can possibly be lowered by spectrally
narrowing the emission of fluorophores infiltrated in suitably engineered self-assembled photonic crystal superlattices,
and are therefore important towards the realization of efficient all-optical integrated circuits from functionalized photonic
superlattices and heterostructures.
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