FABRICATION OF DIFFRACTIVE OPTICAL ELEMENTS BY NEAR-FIELD OPTICAL LITHOGRAPHY

SEVERAL METHODS ARE CURRENTLY BEING DEVELOPED FOR THE PRODUCTION OF SURFACE-RELIEF DIFFRACTIVE OPTICS INCLUDING PHOTOLITHOGRAPHY, SINGLE-POINT DIAMOND TURNING, AND SINGLE-POINT LASERWRITING. ALL OF THESE METHODS ARE LIMITED IN EITHER THE ACHIEVABLE GEOMETRIES OR MINIMUM FEATURE SIZE. IN ORDER TO REALIZE THE FULL COMMERCIAL POTENTIAL OF DIFFRACTIVE OPTICS AND SUBWAVELENGTH STRUCTURED SURFACES, IT IS NECESSARY TO CREATE STRUCTURES THAT CONSIST OF SMALLER FEATURES. RESEARCHERS ARE INVESTIGATING THE USE OF NEAR-FIELD SCANNING OPTICAL LITHOGRAPHY (NSOL) FOR THE FABRICATION OF DIFFRACTIVE STRUCTURES THAT CAN BE USED AT HIGH NUMERICAL APERTURE AND SHORT WAVELENGTHS. NEAR-FIELD SCANNING CAN CREATE STRUCTURES WELL BELOW THAT PRODUCED BY CONVENTIONAL PROJECTION LITHOGRAPHY. IN ORDER TO FABRICATE USEFUL MACROSCOPIC OPTICAL DEVICES, IT IS NECESSARY TO INCREASE THROUGHPUT AND EXTEND THE MANUFACTURABLE DIMENSIONS OF NSOL. THIS CAPABILITY SERVES TO ADVANCE OPTICAL TECHNOLOGY IN THE AREAS OF UV OPTICAL SYSTEMS, OPTICAL DATA STORAGE, AND SUBWAVELENGTH STRUCTURED OPTICS. THE ABILITY TO FABRICATE NANOMETER-SIZED STRUCTURES IS ALSO USEFUL FOR APPLICATIONS IN X-RAY INSTRUMENTS AND MICROMACHINING. COMMERCIAL APPLICATIONS IN DOCUMENT SECURITY AND POLARIZATION COMPONENTS ARE IDENTIFIED.