Nickel-Copper (NiCu) Mirrors
Nickel-copper mirrors are the most widely used of all the Cu mirror types. They consist of a copper
substrate, precision-lapped to the required surface form, plated with a thin layer of nickel which is
polished and gold plated.
Copper is an attractive substrate material for mirrors in CO2 laser systems due to its high thermal
All copper used in the manufacture of these mirrors is high-specification, oxygen-free (OFHC) type.
Dimensions / tolerances
NiCu mirrors can be fabricated in sizes from 5.0mm diameter up to 250mm diameter, and in
thicknesses from 3mm upwards (to suit the mirror diameter and type of cooling required).
Metric diameters and thicknesses are treated as standard, and are available from stock or with speedy
delivery. Imperial (inch) sizes are usually made-to-order, and carry a small surcharge.
Long-radius mirrors are available, including: 1, 2, 3, 4, 5, 6, 7.5, 10, 12, 14, 15, 20, 25, 30 metres.
Diameters : +0 / -0.15mm
Thicknesses : ± 0.15mm
Parallelism : ETV within 0.05mm
Surface form accuracy : <λ/20 (10.6μm) over 90% of dia.
Surface roughness : <20Å RMS
Phase retardation : <1 (at 45° incidence)
Reflectivity : see tables 11.12, 11.13
LIDT : see below
See technical data section 11.0
NiCu mirrors are available with the following custom features:
* Rectangular or square shapes.
* Custom water-cooling fittings.
* Central or offset holes.
* Holes at 45 degrees to the surface.
* Convex radii.
* Arrays of holes.
Special shapes, including flanged mirrors, can be supplied to suit various makes of CO2 laser.
Laser Damage Thresholds
A recent series of measurements indicated a typical value of 46.7J/sq cm for 100 nsec pulses. This
translates to a pulsed LIDT value of:
4.67 megawatts/mm2 for 100 nsec pulse length.
Measured values of CW LIDT for air-cooled, unstressed, V&S NiCu mirrors are, typically:
4000W/mm +/- 12% (section 11.0 explains LIDT units)
The stated LIDT values apply to clean, unstressed components.
Tables 11.12, 11.13 give typical values for the reflectivity of a gold plated surface vs. angle-ofincidence
(for 10.6um) and vs. wavelength. The tables appear slightly to contradict each other.
This is due to the fact that table 11.12 shows computed values calculated from the known optical
properties of gold, whereas table 11.13 gives experimentally-measured values.
NB:- Actual incidence angles of 90 deg are not practically possible!