Laser processing method for glass substrate, diffraction grating obtained by this method, and microlens array

摘要

PROBLEM TO BE SOLVED: To form fine concavo-convex patterns such as diffraction grating on a glass substrate by a laser light. SOLUTION: When a laser light is incident on a phase mask, the plus primary diffraction light and the minus primary diffraction light are ejected. Due to the interference of the diffraction lights, the periodical strength distribution of the light is obtained near the ejection side of the phase mask. If the laser light of the incident side is a parallel light, its period is matched with that of the diffraction grating. When the glass substrate is set in an area where the periodical strength distribution is formed, the glass is evaporated or abraded corresponding to the periodical light strength, for forming the diffraction grating having the same period as the light strength on the glass substrate.