4 research outputs found
Magneto-chiral nonlinear optical effect with large anisotropic response in two-dimensional halide perovskite
The chiral organic-inorganic halide perovskites (OIHPs) are vital candidates for superior nonlinear optical (NLO) effects associated with circularly polarized (CP) light. NLO in chiral materials often couples with magnetic dipole (MD) transition, as well as the conventional electric dipole (ED) transition. However, the importance of MD in NLO process of chiral OIHPs has not yet been well recognized. Here, the analysis of second harmonic generation circular dichroism (SHG-CD) provides the direct evidence that the MD contribution leads to a large anisotropic response to CP lights in chiral OIHPs, (R-/S-MBACl)2PbI4. The thin films exhibit great sensitivity to CP lights over a wide wavelength range, and the g-value reaches up to 1.57 at the wavelength where the contribution of MD is maximized. Furthermore, it is also effective as CP light generator, outputting CP-SHG with maximum g-factor of 1.76 upon the stimulation of linearly polarized light. This study deepens the understanding of the magneto-optical NLO processes in chiral systems
Color-Tunable Resonant Photoluminescence and Cavity-Mediated Multistep Energy Transfer Cascade
Color-tunable
resonant photoluminescence (PL) was attained from
polystyrene microspheres doped with a single polymorphic fluorescent
dye, boron-dipyrrin (BODIPY) <b>1</b>. The color of the resonant
PL depends on the assembling morphology of <b>1</b> in the microspheres,
which can be selectively controlled from green to red by the initial
concentration of <b>1</b> in the preparation process of the
microspheres. Studies on intersphere PL propagation with multicoupled
microspheres, prepared by micromanipulation technique, revealed that
multistep photon transfer takes place through the microspheres, accompanying
energy transfer cascade with stepwise PL color change. The intersphere
energy transfer cascade is direction selective, where energy donor-to-acceptor
down conversion direction is only allowed. Such cavity-mediated long-distance
and multistep energy transfer will be advantageous for polymer photonics
device application
π‑Electronic Co-crystal Microcavities with Selective Vibronic-Mode Light Amplification: Toward Förster Resonance Energy Transfer Lasing
Ï€-conjugated
organic microcrystals often act as optical resonators
in which the generated photons in the crystal are confined by the
reflection at the crystalline facets and interfere to gain lasing
action. Here, we fabricate microcrystals from a mixture of carbon-bridged
oligo-<i>para</i>-phenylenevinylenes (COPVs) with energy-donor
(D) and energy-acceptor (A) characters. Upon weak excitation of the
single D–A co-crystal, Förster resonance energy transfer
(FRET) takes place, exhibiting spontaneous emission from A. In contrast,
upon strong pumping, stimulated emission occurs before FRET, generating
lasing action from D. Lasing occurs with single- and dual-vibronic
levels, and the lasing wavelength can be modulated by the doping amount
of A. Time-resolved spectroscopic studies reveal that the rate constant
of lasing is more than 20 times greater than that of FRET. Furthermore,
microcrystals, vertically grown on a Ag-coated substrate, reduce the
lasing threshold by one-fourth. This study proposes possible directions
toward organic solid FRET lasers with microcrystalline resonators
π‑Electronic Co-crystal Microcavities with Selective Vibronic-Mode Light Amplification: Toward Förster Resonance Energy Transfer Lasing
Ï€-conjugated
organic microcrystals often act as optical resonators
in which the generated photons in the crystal are confined by the
reflection at the crystalline facets and interfere to gain lasing
action. Here, we fabricate microcrystals from a mixture of carbon-bridged
oligo-<i>para</i>-phenylenevinylenes (COPVs) with energy-donor
(D) and energy-acceptor (A) characters. Upon weak excitation of the
single D–A co-crystal, Förster resonance energy transfer
(FRET) takes place, exhibiting spontaneous emission from A. In contrast,
upon strong pumping, stimulated emission occurs before FRET, generating
lasing action from D. Lasing occurs with single- and dual-vibronic
levels, and the lasing wavelength can be modulated by the doping amount
of A. Time-resolved spectroscopic studies reveal that the rate constant
of lasing is more than 20 times greater than that of FRET. Furthermore,
microcrystals, vertically grown on a Ag-coated substrate, reduce the
lasing threshold by one-fourth. This study proposes possible directions
toward organic solid FRET lasers with microcrystalline resonators