Preparation of Diamond Infrared Enhancing Filter Window
Infrared (IR) radiation is important in numerous applications. For example, IR filtering is used in medical imaging and night vision. This can also be used in energy conservation and surveillance technologies. Infrared filters, such as those based on diamond, provide efficient transmission and high throughput in the visible and near infrared (NIR) and mid-infrared (MIR) spectral regions. Diamond IR filters provide excellent transmission figures in a wide range of wavelengths and also benefit from relatively low optical absorption at high temperatures.
The aim of this study is to develop a process for the fabrication of diamond infrared enhancing filter windows. Diamond was chosen as the material for this filter window because of its low absorption, high thermal stability and low refractive index. The diamond was purified using a chemical-mechanical polishing (CMP) process. The diamond was then characterized using scanning electron microscope and energy dispersive spectroscopy (SEM-EDS), which established that the surface was homogeneous.
Following the initial purification of the diamond, an acid-etching process was used to etch the surface to remove surface impurities. The diamond samples were then subjected to a hydrogen plasma to reduce the degree of contamination.
In order to optimize the transmission characteristics, a hydrophilic coating was then applied to the diamond filter window. The hydrophilic coating was made from a mixture of polyurethane, polyether and polyolefin materials, which were then heated in order to create the coating. The coated filter window was then subjected to a second etching process in order to optimize the transmission characteristics.
Following the optimization of the transmission characteristics, the diamond filter window was then subjected to functional testing. This involved measuring the transmission, further measurements were taken under different simulated incident angles as well as in different ambient temperature environments.
In conclusion, this study has developed a process for the fabrication of diamond infrared enhancing filter windows for various applications. The results showed that the filter window had excellent transmission characteristics, with transmission figures as high as 98% in the visible and near infrared (NIR) range and 75% in the mid infrared (MIR) range. The transmission figures varied slightly with different angles of incidence and ambient temperature, but overall the filter window proved to be very effective in transmitting IR radiation in the NIR and MIR ranges.
