Introduction

The SA15 laser attenuator is intended to control the transmitted power of small/medium CO2 lasers in order to assist processing.

The attenuator uses Brewster plates mounted in a ‘Vee’ configuration to eliminate lateral beam offset.
The plates may be of standard (uncoated) or enhanced type.
SA15 attenuators work only with linearly polarized laser beams.
Rotation of the plate pair about the optical axis causes the ‘unwanted’ power to be reflected and
dumped into the main body of the unit.

Available models

SA15 incorporates 2 standard Brewster plates, and transmits 11% to 100% of incident linearly
polarized radiation.
SA15-E incorporates 2 enhanced Brewster plates, and transmits <0.5% up to >98% of incident
linearly polarized radiation.
Accessory SA15-WJ external water jacket, allows use of the SA15 unit to higher power levels

Technical specifications
Dimensions : See figure 79.101.
Method of operation : Rotation of Brewster plate pair.
Calibration : Engraved T% (assumes linear pol input)
Lateral beam offset : Nil
Angular deviation : <2 arcminutes
Cooling : Air cooled (water-cooled with SA15-WJ)
Construction : Al. alloy body, black anodised, with
ZnSe Brewster plates. End bearings (2).
Connection : Via ULO Optics std. coupling rings,
52.0mm dia x 1.5mm pitch at each end.
Max power : 100W air-cooled. (250W with SA15-WJ)
Clear aperture : 15.0mm diameter.

Associated equipment
SA15 units fit directly to ULO Optics ‘OPG’ piping (data 61.1) and to lateral adjustment units
LAU25 and LAM25 (section 72).
The accessory water-cooling jacket SA15-WJ is factory-fitted if required, and cooling is via 6/4 size
fittings.
Applications note
Small/medium power lasers often have, as the only means of ‘average’ power control, a method of
changing the mark/space ratio when run in pulsed mode. This is unsatisfactory in some laser
processes.
SA15 attenuators allow control of transmitted power with cw lasers and with no change of mark/
space ratio for pulsed operation.
Quality note
Brewster-based systems can be extremely sensitive to errors of plate flatness on a scale of fractions
of one visible fringe of error.
ULO Optics 2-plate systems are tested to ensure no more than 10% beam ovality (at 10.6μm)
at 4 metres from the unit.