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Making fast cylindrical gradient-index lenses diffraction limited by using a wave front-correction element



Applied optics 37 (1998), Nr.22, S.5211-5215
ISSN: 0003-6935
ISSN: 1539-4522
ISSN: 1559-128X
Fraunhofer IOF ()
gradient-index lens; GRIN; shearing interferometer; wave-front-correction element; WFCE

A wave-front-correction element (WFCE) is produced to make a cylindrical Ag-ion-exchanged gradient-index (GRIN) lens with a high numerical aperture (0.53) diffraction limited (wave-front-error, 0.02 lambda rms). The wave-front aberrations of the cylindrical GRIN lens are measured by a phase-shifting shearing interferometer, with a conventional microscope objective used as a compensation lens. The continuous surface relief of the WFCE is produced by a lithographic process. The wave-front-corrected GRIN lens is applied to collimate the strongly divergent light (57 degree full divergent angle measured at 1/e2 of maximum intensity) emitted by a high-power diode laser. The power irradiated into full angle of 2 mrad can be enhanced by factor of 1.8 with the WFCE.