Abstract

Measurement of laser-beam diameter is essential for the estimation of beam divergence, for laser applications in optical disks, and for metrology applications that use laser sensors. Although the rectangular (Ronchi) ruling of a particular period (L) is capable of estimating the beam radius (r⁰) for r₀/L of 0.2–1.2, triangular and sinusoid gratings¹ extend the range to a much smaller radius compared to the grating period. The upper limit of beam diameter measurement has recently been improved by formulation of an aperiodic ruling² that, for a certain aperiodicity, can extend the measurement range up to an r₀/L of 10. However, because of the rectangular (discontinuous) nature of the grating, the lower values of the beam radius can not be measured. In this work, we propose a novel grating with periodic, exponential transmission characteristics that is capable of extending the range to both higher and lower values of the beam radius. Our proposed exponential periodic grating provides a linear variation of k between r₀/L of 0–1.2.

© 1990 Optical Society of America