The Optics

Focusing lenses 7.5ZLF38, 7.5ZLF63, 7.5ZLF100 and 7.5ZLF127

These 3 lenses are used in the C-LN nozzle assemblies. They are all 19mm diameter and have an edge
thickness of 2.0mm. When mounted in a nozzle assembly the clear aperture will be 17.5mm. The
effective focal length (EFL), back focal length (BFL) and flange focal length (FFL) are as follows (see Fig
Fig 1: Definition of EFL, BFL and FFL
All the lenses are made from laser grade CVD ZnSe, to the optimum meniscus form for focusing
purposes and each surface is anti-reflection (AR) coated for 10.6μm.

Silicon mirrors 9.8SIS3-00 and 10SIS3-00

Made from monocrystalline mirror grade Silicon, these mirrors are fitted into the C-CM corner mirror
blocks. The mirror block will take either size, 25 or 25.4mm diameter. They are coated with ULO’s
Supermax coating, giving 99.85% reflectance at 10.6μm and 45º incidence. The mirrors also are of ‘zero
phase’ type.

Phase retarders 9.8SPR3-90 and 10SPR3-90

These differ from the above Silicon mirrors in the coating. The SPR type is designed to convert the
linearly polarised laser beam into circular polarisation by means of a 90º phase shift difference
(retardance) between the S and P components. This has processing benefits for some materials (e.g.
metals). They fit into the C-CM corner mirror blocks and C-CM-PR4 –PR2 units. The mirror block has to
be orientated with respect to the plane of polarisation as illustrated below. A retractable mount (C-RM)
may therefore be needed on the input side.Planeofpolarisation

Silicon mirror 11SIS3-00

This Supermax coated mirror is 28mm diameter (1.1”) and is used only in the C-SU shutter unit. With
the shutter closed, it reflects the beam into a water-cooled beam dump.

Beam combiner 9.8ZBS3-45-R

This optic finds use in the C-BI beam injector unit. Angled at 45° incidence, the CO2 laser beam will be
transmitted while the red visible laser strongly reflected off one surface.

Brewster windows ZBW5320MP and EZBW5320MP

Brewster windows for use in attenuators and reflection isolators are made as ‘matched pairs’. A
Brewster window works best if it has a slight wedge (1’ – 3’). However, this wedge deviates the beam
going through it. But by using an identical second window with the wedge orientated opposite to the first,
the angular beam deviation is corrected. The beam lateral displacement is also corrected because both
windows have the same thickness.
The windows are 53 x 20 x 3mm. Angled at 67.4° to the incident beam, they present a 20mm square

Beamexpander output lens 11ZLF63

For all C-BE magnifications, this is the common output lens. It is a standard lens and is used extensively
for other applications.

Beamexpander input lenses

There is a different input lens for each magnification. Each is shaped to correct the spherical aberration
of the output lens