The PLX Lateral Transfer Hollow RetroreflectorTM (LTHR): Ideal for applications where the main beam must be aligned with two or more other axis, while maintaining perfect parallelism.



  • Perfect for folding parallel light 180° degrees.
  • Ideal solution for “U” fold in a large size Michelson interferometer or back to back configurations for folding interferometers.
  • Available with sub arc second accuracy.
  • Extremely temperature stable.
  • Large choice of coatings.
  • Vacuum-compatible.
  • PLX is a registered ISO 9001 company.

Coating Specification Chart


Lateral Transfer Hollow Retroreflectors™ (LTHR) Series

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This device is virtually a segment of a perfect Hollow retroreflector, and therefore operates as an invariant.

In applications where the LTHR is vibrated, the exiting beam remains static and maintains perfect parallelism with the entrance beam. The beam deviation can be supplied to sub arc second accuracy. The LTHR provides an excellent solution for a "U" fold in a large Michelson interferometer, or in a back-to-back Retroreflector configuration for folding interferometers. The LTHR is also useful when the flat mirror is made as a 50/50 beamsplitter. This configuration enables the user to observe the view ahead while simultaneously viewing another parallel optical axis. In addition, the LTHR is extremely temperature stable because all component parts have the same coefficient of thermal expansion (CTE).

LTHR beam diagram art

For applications where the major beam must be aligned with two or more other optical axes, see PLX Specification Sheet for "Rotary Movement Devices".

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PLX Hollow Optics For Critical Alignment

When requesting a quote or placing an order, please specify your required offset. The offset is the distance from the center of one clear aperture to the other. All catalog LTHRs are custom made units to your requested offset specification.

Specification Chart
Model Clear Aperture
Mirror Surface
Exiting Beam
Max Deviation
L-10 L-10 1.0/25 λ/10 - λ/2 1.0 - 30.0
L-20 L-20 2.0/51 λ/10 - λ/2 1.0 - 30.0
Download our product datasheet