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Laser Beam Homogenizer and Output Coupler

IP.com Disclosure Number: IPCOM000120197D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 49K

Publishing Venue

IBM

Related People

Doany, FE: AUTHOR [+2]

Abstract

Disclosed is a combination laser beam homogenizer and output coupler. A laser cavity comprising an amplification region 1, a high reflectivity element 2, and a combined laser beam homogenizer and output coupler is sketched in the figure. The homogenizer reflects back into the cavity a beam which is inverted top to bottom in the figure. This would be good for an excimer laser beam which is, in general, symmetric side to side but unsymmetrical top to bottom. The homogenizer would tend to make the top to bottom beam more symmetric and remove a linear intensity gradient. Most beam homogenizers break up the beam and overlap the parts of the beam on the target without removing a linear spatial dependence.

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Laser Beam Homogenizer and Output Coupler

      Disclosed is a combination laser beam homogenizer and output
coupler.  A laser cavity comprising an amplification region 1, a high
reflectivity element 2, and a combined laser beam homogenizer and
output coupler is sketched in the figure. The homogenizer reflects
back into the cavity a beam which is inverted top to bottom in the
figure.  This would be good for an excimer laser beam which is, in
general, symmetric side to side but unsymmetrical top to bottom.  The
homogenizer would tend to make the top to bottom beam more symmetric
and remove a linear intensity gradient.  Most beam homogenizers break
up the beam and overlap the parts of the beam on the target without
removing a linear spatial dependence.

      The device works because the beamsplitter cube 3 sends p
polarization one way, s, the other.  The light is reflected from the
high reflectivity surfaces 5.  As the light passes the g/2 plate 4,
its polarization is rotated so it passes the cube if it was reflected
on the first pass, and vice-versa.

      If the polarization plate 4 is not precisely g/2, light 6 will
be coupled out of the cavity as shown in the figure. The output
coupling can be varied by rotating the g/2 plate 4 mechan- ically or
by using a variable waveplate.

      As a retroreflector, the device is insensitive to rotations
about 2 axes.

      A corner cube reflector acts as a homogenizer (symmetric about
the center), but has...