From nanosphere lithography to self-assembled photonic crystals

Abstract

Amongst nanolithography methods, electron-beam lithography (EBL) and nano-imprint lithography are most popular for fabrication of photonic crystal structures due to their high precision. However, cost of fabrication and yield are factored in for consideration, selfassembly methods have better potential towards commercialization; nanosphere lithography is one of the most feasible approach. Employing nanosphere lithography, we are able to pattern hexagonally close-packed arrays, and hence fabricate different kinds of photonic crystal structures. The inherent high refractive index of Gallium Nitride (GaN), which limits the light extraction efficiency of light-emitting diode (LED), in fact provides an excellent platform for the integration of photonic crystals. The light extraction problem of GaN can be solved by suppressing the guiding modes within in the LED structure. Intuitively, photonic crystal has extensively been utilized for light manipulation in different areas, and has been demonstrated as a mean of spontaneous emission control. Its periodic nature with dimensions close to the wavelength of light forbids the existence of certain optical modes, thereby achieving light confinement effects.