How to Use a Retroreflector Target for Interferometer Alignment
By Zygo | Published: 2026-10-30
Category: How-to Guides
Learn how to use a retroreflector target for precise interferometer alignment, including choosing the right version and step-by-step setup tips.
Quick Answer
Use a retroreflector target to establish a stable reference beam for interferometer alignment. Choose the version that matches your interferometer type—linear or single beam—and follow a systematic setup to avoid common misalignment pitfalls.
Why Use a Retroreflector Target?
A retroreflector target reflects light back along its incoming path, making it ideal for aligning interferometer optics. It provides a clear, consistent reference point that simplifies the alignment process and improves measurement repeatability.
Unlike flat mirrors, retroreflectors are less sensitive to angular misalignment, which makes them forgiving for initial setup. However, they are not a substitute for final alignment of the interferometer cavity; they are a tool to get you close before fine-tuning.
Choosing the Right Version
Retroreflector targets come in two versions: one for linear interferometers and one for single-beam interferometers. The linear version is designed to work with the reference and measurement beams of a linear interferometer, while the single-beam version is optimized for systems that use a single beam path.
Selecting the wrong version can lead to poor signal return and frustrating alignment attempts. Always verify your interferometer's beam configuration before purchasing or using a target.
Step-by-Step Alignment Process
- Select the correct target version: Identify whether your interferometer uses a linear or single beam configuration, and choose the matching retroreflector target. Check your interferometer's manual if unsure. Using the wrong version is a common mistake; confirm before proceeding.
- Mount the target securely: Place the retroreflector target in the optical path at the desired reference location. Ensure it is firmly mounted to prevent movement during alignment. A loose target can cause drift; tighten all mounts.
- Align the beam to the target: Adjust the interferometer's beam steering mirrors so the beam hits the center of the retroreflector target. Observe the return beam and adjust until it overlaps the outgoing beam. If the return beam is not visible, check for obstructions or misalignment.
- Fine-tune for maximum signal: Make small adjustments to the target's tilt and position to maximize the return signal strength on the interferometer's detector. Use the signal strength readout if available. Peak signal ensures optimal alignment; avoid over-tightening adjustments.
- Verify alignment stability: After achieving maximum signal, gently tap the optical table or mount to check for stability. Re-adjust if the signal drops, indicating a loose component. Stability is key for repeatable measurements.
Product Facts
- Retroreflector Target: Retroreflector target available in two versions for linear or single beam interferometers. Choosing the correct version ensures the target matches your interferometer's beam setup, preventing alignment errors and saving time.
Retroreflector Target
