Near-infrared antireflection coating operated with broad incident angles

We designed and demonstrated antireflection coatings that exhibit high transmittance regardless of the angle of light incidence. The suggested design is adapted from a universal impedance matching layer model and is optimized by a particle swarm optimization technique. The thin layers separated from a layer with low refractive index is known to exhibit minimal changes in dielectric constant even when incident angle changes. The simulation results obtained by finite difference time domain method showed that designed structure has transmission with more than 96% at the incidence angle of less than 71° in the range of 700–900 nm wavelength. We fabricated the designed structure and measured transmission at different incidence angles to certify simulation results. By measuring transmittance of fabricated sample while changing an incidence angle from 0° to 80° by 10°, we found out that transmittance is more than 90% within the incidence angle of 70°, and the average of transmission at the wavelength of 800 nm measured within the above incidence angle is calculated as 0.916.