Although recently developed bio-inspired nanostructures exhibit superior optic performance, their practical applications are limited due to cost issues. We present highly transparent glasses with grassy surface fabricated with self-masked dry etch process. Simultaneously generated nanoclusters during reactive ion etch process with simple gas mixture (i.e., CF4/O2) enables lithography-free, one-step nanostructure fabrication. The resulting grassy surfaces, composed of tapered subwavelength structures, exhibit antireflective (AR) properties in 300 to 1,800-nm wavelength ranges as well as improved hydrophilicity for antifogging. Rigorous coupled-wave analysis calculation provides design guidelines for AR surface on glass substrates.
We demonstrate GaN-based blue light-emitting diodes (GaN LEDs) with artificial compound eye structures (CESs). The GaN LEDs consist of microlens arrays (MLAs) and antireflective subwavelength structures (SWSs). The CESs, formed on the LED surface by two-step pattern transfer of reflowed photoresist micro patterns and Ag nanoparticles, play an important role in enhancing the light extraction efficiency by reducing both the Fresnel and the total internal reflection. The CES integrated GaN LEDs show an output power enhancement of 93% compared to that of conventional GaN LEDs with flat surface, without any serious degradation of electrical characteristics. Optical simulations by ray-tracing and the rigorous coupled-wave analysis method provide design guidelines for MLAs and SWSs, respectively.Index Terms-GaN-based LEDs, light extraction efficiency, microlens, subwavelength structure, compound eye structures.
We demonstrate the distinctive optical properties of disordered nanostructures on glass substrates in accordance with changes in the average size of the nanostructures. Dissimilar sizes of nanostructures were fabricated by using different thicknesses of thermally dewetted Ag nanoparticles as etch masks. Unlike a flat glass substrate, the nanostructured glasses (NSGs) show a changed optical characteristic. By increasing the size of the nanostructures, the wavelength of the peak transmittance of about 99% gradually moved from 730 to 2000 nm. To clearly discern the effect of the different sizes of nanostructures, the normalized angle-dependent transmittance spectra of the NSGs were analyzed. Only if the size becomes relatively larger than the wavelength of the incident light are the transmittance spectra more strongly affected by the incident angle as well as by the relative size, rather than by the Fresnel reflection.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.