[OPTICAL REVIEW Vol. 5, No. 1 (1998) 39-42]

Mitigation of Diffraction Fringe in Quasi-Far Field Pattern Using an Edge-Shaped Plate

Noriaki NISHI, Takahisa JITSUNO and Masahiro NAKATSUKA

Institute of Laser Engineering, Osaka University, 2-6, Yamada-oka, Suita, Osaka, 565 Japan

(Received November 10, 1997; Accepted December 9, 1997)

A new concept is developed for improving the laser intensity distribution in quasi-far field using geometrical optics of a continuous phase (so-called edge-shaped plate). The diffraction fringe on a quasi-far field beam pattern of a well collimated He-Ne laser beam 5 cm in diameter is mitigated by the insertion of an edge-shaped plate with a super-Gaussian (n=40) surface profile. A diffraction code using Fresnel-Kirchhoff diffraction integration was developed to calculate diffraction patterns of aspherical optical elements. The measured beam profile is in good agreement with the calculated beam pattern.

Key words : edge-shaped plate, aspherical optics, diffraction fringe, optical phase control