The search for materials for nanophotonic
devices needs a way to
overcome the limitations of weak nonlinear optical response due to
reduced size. The requirement of a high-power excitation source for
inducing nonlinear effects in the active medium poses a hurdle in
realizing all-optical and integrated optoelectronic systems. Nanosized
optical materials can be embedded in photonic cavities to enhance
its optical nonlinear responses through confinement effects. This
report systematically investigates the linear and nonlinear optical
properties of polymeric 1D-photonic crystals (PhC) with a defect layer
incorporated with an imidazo-thiadiazole derivative small molecule.
The nonlinear optical studies were carried out by means of a z-scan
technique under nanosecond pulse using a Q-switched Nd:YAG laser operating
at 532 nm. The resonant excitation creates strong confinement of light
in the photonic microcavity and facilitates strong light–matter
interaction that induces nonlinear response at low input intensities.
A giant enhancement in the nonlinear absorption and optical limiting
action was observed for PhC comparing to the bare sample. The significant
enhancement in the absorptive nonlinearity is utilized for realizing
a practical, on-chip, passive, all-optical diode with a PhC/Au hybrid
structure. The asymmetrical nonlinear absorption of the hybrid structure
exhibits non-reciprocal light transmission in the nonlinear regime.
The high transmittance contrast ratio for forward/reverse bias operation
and cost-effective fabrication methods makes our system a potential
candidate toward the realization of compact photonic integrated devices.
Schematic of the optical limiting action of a novel imidazo[2,1-b][1,3,4]thiadiazole based small molecule (ThITD3), which blocks high irradiance and transmits low-intensity (less harmful) light.
Diagrammatic representation of excited state assisted two-photon absorption (2PA) behavior of a donor–acceptor type conjugated polymer (P2TPy) exhibiting an extremely low optical limiting threshold.
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