Broadband Antireflection Subwavelength Structures on Fused Silica Using Lower Temperatures Normal Atmosphere Thermal Dewetted Au Nanopatterns

Abstract

The antireflection (AR) performance and far-field transmittance, depending on the morphology and parameters of subwavelength structures (SWSs), have been investigated by a 3-D finite-difference time-domain (FDTD) method. It is found that far-field transmission characteristics are dominated mainly by period of SWSs. If the period is increased above 220 nm, the far-field transmittance rapidly decreases for a short-wavelength region. An effective and inexpensive method for fabricating disordered SWSs on fused silica has been demonstrated in this paper. An Au nanoscale island mask was formed by lower temperatures thermal dewetted at normal atmosphere. Then, a disordered SWS was fabricated by reactive ion etching (RIE). The average diameter of the Au nanoscale island was easily controlled by the thickness of Au thin films and annealing temperature. The etched depth and shape of fused silica SWSs depend additionally on RIE duration, thus achieving efficient AR characteristics. The measured data and calculated results obtained by the FDTD method exhibit reasonably similar tendencies. The optimized single-side fused silica SWS that is tapered on the tips leads to a significantly high transmissivity value of 96.2%. In addition, it exhibits a broadband AR property at a wavelength range of 400–1100 nm.

Keywords

• Subwavelength structures
• low-temperature thermal dewetting
• effective medium theory
• finite-difference time domains
• optical properties