Pump-light-induced carrier modulation and multimode optical absorption in dielectric-functionalized porous In 2 O 3

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Abstract
Dynamic tuning of optical absorption remains a significant challenge for conventional plasmonic nanostructures because their optical properties are largely fixed after fabrication. Here, a physics-driven numerical investigation of a porous indium oxide (In 2 O 3 ) film fabricated on an anodic aluminum oxide substrate and functionalized with a dielectric DNA layer is presented as a dynamically tunable optical platform. Introduction of the DNA layer enhances three characteristic absorptance modes from 0.16 to 0.43, 0.20 to 0.50, and 0.21 to 0.35, respectively, owing to dielectric-environment-induced modulation of optical impedance matching and electromagnetic energy coupling. Under infrared pump-light excitation, photons with energies exceeding the deep-donor ionization threshold generate free carriers through photoionization of localized defect states, thereby modifying the complex refractive index of In 2 O 3 . As the pump-light intensity increases, the absorptance of the three modes further rises to 0.56, 0.55, and 0.44, respectively. Analysis of electromagnetic power-flow distributions reveals that absorptance enhancement is governed by the formation and confinement of characteristic localized energy-flow topologies, including bottleneck-type, vortex-type, and convergent flows, together with their spatial overlap with regions of non-zero optical loss. These findings establish a direct physical link between defect-mediated carrier dynamics, localized electromagnetic energy flow, and optical absorption in porous semiconductor structures, providing new insight into dynamically tunable optical materials and design guidelines for reconfigurable semiconductor-based photonic and sensing platforms.
Funding Information
  • Analytical Science and National Doping Test Institute, Mahidol University: (fiscal year 2026) via the New Discovery and Frontier Research Grant.

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