Specifications

Diamond™ GEM, G, & K, Integrator’s Guide

occur, back reflections alter the laser output and degrade the beam

quality. In other cases, the returned light may be focused on beam

delivery optics so that they are destroyed.

It is essential for GEM-series laser systems used in high beam return

(back reflection) modes, to have an optical isolator in the beam

delivery system. An isolator is a mirror with a coating that reflects

S-polarized light (light polarized normal to the plane of reflection)

and absorbs P-polarized light (light polarized parallel to the plane of

reflection).

It is essential for G & K-series systems used to cut metal, or working

over metal supports, to have an optical isolator in the beam delivery

system. An isolator is a mirror with a coating that reflects S-polar-

ized light (light polarized normal to the plane of reflection) and

absorbs P-polarized light (light polarized parallel to the plane of

reflection). This mirror is set in the beam line before an CQE module

so that the incoming beam is S-polarized. The CQE, as noted above,

converts the light to circular polarization. Any reflected light returns

to the CQE with circular polarization. The geometry is such that

when the light exits the module, it is linearly polarized at right angles

to the laser’s initial plane of polarization. This is intercepted by the

isolator as P-polarized light and is absorbed before it can do any

damage. Isolators may have to absorb substantial power, requiring

them to be water-cooled. The isolator/CQE assembly, part number

0175-990-00, (Figure 12) should be located as near the focusing lens

as possible to protect all the beam delivery optics. The CQE and

Figure 11. Installation Dimensions for Coherent CQE Module 0175-989-00