Shaping Resonant Light Confinement and Optoelectronic Spectra Using Strain in Hierarchical Multiscale Structures

Abstract

Hierarchically structured optical materials have been a topic of intriguing research interest due to the possibility of tailoring material properties beyond the limits of bulk continuum material design. Here, an optical confinement phenomenon in a hierarchically structured waveguide platform consisting of alternating clusters of nanostructured and planar microscale domains is demonstrated. An unconventional self‐assembly‐based strain‐assisted nanomolding process is developed to fabricate these hierarchically structured multiperiodic waveguides. Further, these hierarchically patterned waveguides are used as substrates for solution‐processed photodetectors. The optical confinement occurring due to the nanoscale scattering and the wavelength‐dependent interaction between the planar and structured microdomains leads to an improved uniformity in the optoelectronic spectral response of these photodetectors. Furthermore, by tuning the multiperiodicity within the nanostructured domain structure, using a mechanical strain of 20%, an improvement of around 10% in the uniformity of the optoelectronic spectral response of the photodetectors is demonstrated. Simulations further show that these processes arise only in the presence of a hierarchical structure, due to multiscale interaction, through wavelength‐selective coupling of scattered light from nanostructured domains to the planar microdomains. In summary, hierarchical structures can address optoelectronic problems that cannot be addressed by simpler structures.

Engineering the Metal/Dielectric Interface to Unlock the Potential of Scattered Light for Boosted Photoredox Catalysis

“…Effective manipulation of light–matter interaction is desired for light-initiated chemical reactions and physical characteristics (e.g., optical absorption, transport, confinement, and scattering). − Since the optical response of metallic nanostructures is intrinsically sensitive to the dielectric environment, the specific photophysical and photochemical properties of metallic nanostructures can therefore be realized via consciously engineering the dielectric environment without altering their shape and size . Apart from the direct response of metals to incident light, metals can also absorb the scattered light of a dielectric antenna. , This is because the dielectric antenna with appropriate size and shape can trap, polarize, and scatter incident light in the form of electric and magnetic Mie resonances to alleviate the barrier for the loaded metal nanostructures to absorb photons. − Meanwhile, the near-field coupling between metal nanostructures in the form of an electric dipole and dielectric antenna in the form of Mie resonance gives rise to electric field confinement at the metal/dielectric antenna interface, and the enlarged refractive-index discrepancy between the dielectric antenna and surrounding media reinforces both electric field and light-scattering efficiency, which is advantageous to augment the optical absorption of metals for catalyzing redox reactions. ,− Based on this, tuning the optical absorption of metals by recycling the scattered light of a dielectric antenna is emerging as a promising light-manipulation-capture paradigm, which is beyond the traditional surface plasmon resonance (SPR) absorption of metals and enriches the toolbox for solar energy utilization. , …”