Near IR nonlinear absorption of an organic supermolecule [Invited]

Abstract

The photophysics of bis(terpyridyl)osmium-(porphinato)zinc- bis(terpyridyl)osmium (OsPZnOs), a D-π-A-π-D symmetric supermolecule, were investigated in the femtosecond and nanosecond regimes. The supermolecule exhibits a two-photon absorption (δ_peak ~900 GM) in the near IR (900-1300 nm) and optical pumping by two-photon absorption leads to a broad excited state absorption (σ_peak ~1.1 × 10⁻¹⁶ cm²) in the same near IR region. Since the excited state has a long lifetime, OsPZnOs exhibits a strong nanosecond nonlinear absorption in this region. That nonlinear absorption is substantially enhanced when OsPZnOs is incorporated into a multimode waveguide. When two-photon pumping is the dominant mechanism, an additional enhancement of up to ~100 × in the nonlinear absorption is observed in a microchannel waveguide. OsPZnOs is a promising material for photonic applications such as optical noise suppression and optical limiting in the near IR.