Fabricating multilayer antireflective coating for near complete transmittance in broadband visible light spectrum

To extract maximum performance out of the certain optical devices it is highly desirable to use completely transparent window in a broad wavelength range. In search of large-scale applicable antireflective (AR) coating for such window, herein we report the design and fabrication of multilayer coating with the aim to reduce the reflection of the window in the entire visible light range. Systematic selection of material and thickness of each layer was performed based on the criteria fulfilled by refractive index to obtain zero reflection. Low refractive index material like MgF2 is deposited by e-beam technique to obtain single-layer AR coating. While Al2O3 and ZrO2, deposited by RF-magnetron sputtering, with MgF2 are used to develop multilayer AR coating. Scanning electron microscope image along with elemental line scan obtained along the cross-section of the coating verified the thickness and composition of each layer. Deposition of four-layer AR coating (MgF2/Al2O3/ZrO2/MgF2) on both side of quartz window with optimized thickness showed considerable reduction in the reflection to 0.6% at 550 nm. The average transmittance of 99.1% was recorded in the broadband of visible spectrum in the range of 450-750 nm wavelength. With near to complete transmission, the present AR coating holds encouraging pros-pect for implementing in windows of digital display, photovoltaic module, and other optoelectronic devices.