Single Crystal Quartz a Replacement for Diamond Optical Windows

Abstract

Diamond windows are used extensively in the field of optics due to their high transmittance and durability. However, despite their ability to withstand high pressures, diamond windows are not scratch resistant and need to be replaced when the surface is damaged. Moreover, the high cost of diamond windows necessitates extra care to protect the windows and limits the practical size of the window or lens. Thus, alternatives to the highly expensive diamond windows are needed in the optical sciences. A study of single crystal quartz has been conducted to determine if it will make a suitable replacement material. Since the transmittance of single crystal quartz is well documented and desirable for this application, only strength and surface defect experiments were conducted. Trials were run to determine the modulus of rupture of single crystal quartz samples which were also examined with an interferometer and an atomic force microscope (AFM) to correlate the surface conditions with the modulus of rupture. The results showed that even relatively numerous and large defects on the surface did resulted in single crystal quartz holding to high pressures. In addition, the measured modulus of rupture far exceeded the expected values proving that the single crystal quartz is able to withstand the pressures of vacuum. Single crystal quartz is thus found to be a viable alternative to diamond optical windows.