Design and manufacture of a gradient-index axicon

A gradient-index axicon with its initial focus offset from the back surface was designed with the thin-lens approximation. Two samples were fabricated by means of the time-varying boundary condition diffusion method, which is based on the modified quasi-chemical diffusion model. Intensity profile me asurements were taken along the focal region of the axicons. The samples pr oduced extended line foci. From the intensity measurements, the central spo t widths and back focal lengths were determined. The peak widths matched th eoretical predictions made with the diffraction theory for the samples and showed good agreement with the predicted widths for a pseudo-Bessel beam, s howing that the axicon produced a pseudo-diffractionless beam. (C) 2000 Opt ical Society of America. OCIS codes: 110.2760, 220.3620.