We have studied spectra and angular distribution of emission in
Fabry–Perot cavities formed by two silver mirrors separated by a layer
of poly (methyl methacrylate) polymer doped with rhodamine 6G (R6G)
dye in low (
20
g
/
l
) and high (
200
g
/
l
) concentrations. The frequency of
emission radiated to a cavity mode was larger at large outcoupling
angles—the “rainbow” effect. At the same time, the angle of the
strongest emission was also determined by the cavity size: the larger
the cavity, the larger the angle. The angular distribution of emission
is commonly dominated by two symmetrical lobes (located at the
intersection of the three-dimensional emission cone with a horizontal
plane) pointing to the left and to the right of the normal to the
sample. Despite the strong Stokes shift in R6G dye, the branch of the
cavity dispersion curve obtained in the emission experiment is
positioned above the one obtained in the reflection (extinction)
experiment. Some dye molecules are poorly coupled to cavity modes.
Their emission has very broad angular distribution with the maximum at
θ
=
0
∘
. The signatures of strong
cavity–exciton coupling were observed at high dye concentration (
200
g
/
l
) but not at low concentration (
20
g
/
l
). The evidence of the effect of
strong coupling on emission is exemplified by a strong difference in
the angular distribution of emission in two almost identical cavities,
one with and another without strong coupling. Most importantly, we
have demonstrated the possibility to control the ground state
concentration, the coupling strength, and the dye emission spectra
with Q-switched laser pulses.
Giant enhancement of photocurrents in plasmonic structures (plasmon drag effect) provides opportunities for compact electric monitoring of plasmonic effects, and thus is promising for plasmonic-based sensing applications. In the experiment, we measure photoinduced electric signals in flat and profile-modulated systems, and test their sensitivity to small changes of the local dielectric environment, such as a presence of Langmuir–Blodgett monolayers at the metal surface. We show that the addition of a stearic acid monolayer leading to a small shift in plasmon resonance conditions can be ultimately resolved with electrical measurements as the switching in the photovoltage polarity.
Plasmon-induced photocurrents in 1D profile modulated structures switch their polarity in the presence of an additional monolayer at the metal-dielectric interface. The effect presents opportunities for compact plasmonic sensors with electrical detection.
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