Doppler-effect mechanism for laser Q switching with a rotating mirror

A novel description, based on the Doppler effect, is given for laser
Q
switching by a rotating mirror. Fourier analysis yields a relation between the width of the pulse
\Deltat_{1/2}
and the angular velocity of the mirror
\dot{\theta}
. It is shown that for laser emission having a Gaussian spatial amplitude profile the temporal shape of a
Q
-switched pulse is also Gaussian. It is predicted that for different lasers
Q
switched by mirrors rotating with the same
\dot{\theta}, \Deltat_{1/2}
will depend on the wavelength of the laser. For a ruby laser, measurements are reported of
\Deltat_{1/2}
versus
\dot{\theta}
for different configurations of the cavity into which vertical and horizontal slits were introduced.