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

摘要

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.