Zone-boundary optimization for direct laser writing of continuous-relief diffractive optical elements

• Published in: Applied optics (2004) 2006-01, Vol.45 (1), p.53-62
• Main Authors: Korolkov, Victor P, Nasyrov, Ruslan K, Shimansky, Ruslan V
• Format: Article
• Language: English
• ISSN: 1559-128X
• DOI: 10.1364/AO.45.000053

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.