Laser processing of sapphire and fabrication of diffractive optical elements

Abstract

Sapphire is a high-temperature optical material with a melting temperature of over 2000ºC, high strength, good thermal conductivity, and low thermal expansion, and it exhibits chemical inertness and is optically transparent over a wavelength range of 0.15 µm to 5.5 µm. We report the detailed results of the laser processing of sapphire, fabrication of diffraction gratings, and the photon sieve, which have applications in the infrared spectrum using a nanosecond pulsed laser of 355 nm wavelength. Laser removal rates and surface roughness were studied. The fabricated gratings and photon sieve were characterized in terms of diffracted beam profile, optical diffraction efficiency, surface morphology, and depth profile.