TBU25 Conventional Type

IntroductionTBU Beam Splitter
Model TBU25 beamsplitter is of conventional type, with a ZnSe partially reflecting component set
at 45 degrees incidence to the laser beam. The beamsplitter component must therefore be carefully
chosen to suit the state of polarization of the incident laser beam.
(In this respect model TBU25 differs from the ‘polarization-insensitive’ beamsplitter units described
in other data sections. See data section 70.00).
The physical dimensions of model TBU25 are designed so that it may be used to replace a TM25 or
TM30 mirror block (data section 62.0). This feature allows retro-fitting of a beamsplitter or beamsampling
unit at a location within a laser system where previously a mirror was installed.
Technical specifications
Dimensions : See Figure 70.111
Construction : Aluminium, black anodised.
Connections : Via free-rotating coupling rings, 52.0 dia. x 1.5mm pitch, female thread.
Cooling : Air cooled.
Clear aperture : 24.0 mm diameter.
Optics : ZnSe 38mm dia x 3mm thick.
Max CW power : 1500W (estimated), nominal for 50:50.
Coating options
The partially reflective coating is chosen to suit the application and the state of polarization of the
incident beam.
Model TBU25 would normally be used with a linearly polarized incident beam, and so the standard
beamsplitter coating will be one of:
AR/50%, 45-deg, P-POL or AR/50%, 45-deg, S-POL,
the choice depending upon the relative azimuth of the incident linear polarization.
If used in a beam-sampling role, the user may select some suitable reflectivity to suit the application.
Example coatings might be, say:
AR/1%, 45-deg or AR/99%, 45-deg
depending upon whether the transmitted or reflected beam is to be the ‘sample’ for analysis or power
Model TBU25 is provided with external tilt-ajustment screws to enable accurate user-alignment of
the reflected beam. The transmitted beam is not affected by tilt of the beamsplitter component.
Associated equipment
TBU25 is a direct fit to OPG optical piping (data section 61.1).
It is a direct mechanical replacement for either of mirror blocks TM25 or TM30.
Align TBU25 by means of crosswire MX20 (data section 64).

TBU Beam Splitter diagram