The invention offers a regenerative optical amplifier enabling voltage to
be easily applied to polarizing elements such as Pockels cells, without
the need for complicated drive circuitry. An input beam of S-polarized
light is reflected by a polarizer 1 and advances to a Pockels cell 2. In
the time it takes for the input beam, having once passed through the
Pockels cell 2, to be reflected by a reflective mirror 3 and return to the
Pockels cell 2, a voltage V.sub.P1 causing a 90-degree rotation in the
polarization of transmitted light is applied to the Pockels cell 2, and
this applied voltage V.sub.P1 is maintained. The input beam is converted
by the Pockels cell 2 into a P-polarized light pulse which is transmitted
by the polarizer. Subsequently, the light pulse is converted from
P-polarized light to S-polarized light and back to P-polarized light with
each roundtrip of the Pockels cell 2, while passing each time between the
reflective mirror 3, laser crystal 4 and reflective mirror 7, so as to be
amplified in the resonator formed thereby. The amplified light pulse is
extracted by applying a voltage V.sub.P2 causing a 90-degree rotation of
the polarization of the transmitted light to the Pockels cell 6 to convert
the light pulse to S-polarized light which is then reflected out of the
resonator by the polarizer 5.
