Patent ID: 7969654

Claim:
A method of producing a volume Fresnel zone plate in a solid transparent material, comprising: focusing a pulsed laser beam onto each of a set of points at a first depth within said solid transparent material so as to create a first Fresnel zone plate; and focusing said pulsed laser beam onto each of a set of points at a second depth within said solid transparent material so as to create a second Fresnel zone plate, wherein said first and second Fresnel zone plates are optically aligned with each other and include respective zones of different radii corresponding to different optical path lengths to a desired common focal point; wherein said first and second Fresnel zone plates are fabricated using femtosecond laser direct writing; and wherein said second Fresnel zone plate is at a greater depth than said first Fresnel zone plate and is created with less laser energy to maintain constant thickness of each zone plate.