title: Zone-boundary optimization for direct laser writing of continuous-relief diffractive optical elements.
abstract: Enhancing the diffraction efficiency of continuous-relief diffractive optical elements fabricated by direct laser writing is discussed. A new method of zone-boundary optimization is proposed to correct exposure data only in narrow areas along the boundaries of diffractive zones. The optimization decreases the loss of diffraction efficiency related to convolution of a desired phase profile with a writing-beam intensity distribution. A simplified stepped transition function that describes optimized exposure data near zone boundaries can be made universal for a wide range of zone periods. The approach permits a similar increase in the diffraction efficiency as an individual-pixel optimization but with fewer computation efforts. Computer simulations demonstrated that the zone-boundary optimization for a 6 microm period grating increases the efficiency by 7% and 14.5% for 0.6 microm and 1.65 microm writing-spot diameters, respectively. The diffraction efficiency of as much as 65%-90% for 4-10 microm zone periods was obtained experimentally with this method.
authors.affiliation: Institute of Automation and Electrometry, Siberian Branch of the Russian Academy of Science, Prospekt Koptyuga 1, Novosibirsk 630090, Russia. victork@iae.nsk.su
authors.forename: Victor P
authors.initials: VP
authors.lastname: Korolkov
authors.forename: Ruslan K
authors.initials: RK
authors.lastname: Nasyrov
authors.forename: Ruslan V
authors.initials: RV
authors.lastname: Shimansky