## Abstract

In this letter we report a novel technique to measure small laser beam spot sizes. We use the open aperture z-scan technique as a tool to measure the laser beam spot size. This technique measures small spot sizes with accuracy better than 10%.

© 1999 Optical Society of America

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### Equations (6)

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(1)
$$dI(z\prime ,z)/dz\prime =-\beta I{(z\prime ,z)}^{2}$$
(2)
$$I(z)=I(z=0)/\left[1+I(z=0)\beta z\right]$$
(3)
$$T(z)={P}_{z\prime =d}(z)/{P}_{z\prime =0}(z)$$
(4)
$${P}_{z\prime =d}(z)=\underset{t}{\int}\underset{r=0}{\overset{\infty}{\int}}\underset{\theta =0}{\overset{2\pi}{\int}}\frac{I(z)\mathrm{exp}{(-(t/{\tau}_{p})}^{2}\mathrm{exp}(-2{(r/{w}_{0})}^{2})}{1+I(z)\beta d\mathrm{exp}{(-(t/{\tau}_{p})}^{2}\mathrm{exp}(-2{(r/{w}_{0})}^{2})}rdrd\theta dt.$$
(5)
$${P}_{z\prime =0}(z)=\underset{t}{\int}\underset{r=0}{\overset{\infty}{\int}}\underset{\theta =0}{\overset{2\pi}{\int}}I(z)\mathrm{exp}{(-(t/{\tau}_{p})}^{2}\mathrm{exp}(-2{(r/{w}_{o})}^{2})rdrd\theta dt.$$
(6)
$$T(z)=\frac{2}{\sqrt{\pi}I(z)\beta d{\tau}_{p}}\underset{0}{\overset{\infty}{\int}}\mathrm{ln}(1+I(z)\beta d\mathrm{exp}(-{(t/{\tau}_{p})}^{2}))dt.$$