LASER ALIGNMENT LAB: Laser Alignment Activity #1

Autoren: Randall Hinton

Learning Objectives for Laser Beam Alignment

Activity #1 teaches a foundational alignment method: using two adjustable mirrors to steer a laser beam through two fixed apertures that define an optical axis. The procedure is then repeated with a second mirror-and-iris pair to extend the aligned path across the breadboard.

After completing the activity, the learner should be able to:

• Establish a constant beam height parallel to the optical table.
• Use two irises as fixed references for an optical axis.
• Walk a beam through two apertures by alternating adjustments between two mirrors.
• Recover downstream alignment after intentionally disturbing the upstream mirrors.
• Recognize the roles of beam blocks, barriers, kinematic mounts, and controlled access during alignment.

How Laser Beam Alignment Using Two-Point Beam Walking Works

Two irises placed at different positions define a straight optical axis. A single mirror can place the beam on one iris, but it cannot independently control both beam position and propagation angle. A pair of tip/tilt mirrors provides the two control points needed to center the beam on both irises.

In the first section of the activity, mirror M1 primarily changes where the beam arrives at the downstream reference while mirror M2 steers the beam through the near and far apertures. The adjustments are coupled, so the learner alternates between the two mirrors until the beam remains centered at both irises A1 and A2. The same method is then applied to mirrors M3 and M4 as well as irises A3 and A4.

Edmund Optics^® Components Required for the Laser Alignment Setup

The following bill of materials supports one complete Activity #1 setup. The breadboard and screw kit are included to make the list practical for a new or dedicated training station.

How to Set Up the Four-Mirror Laser Alignment System

1. Place the breadboard in a controlled work area. Install any required barriers or perimeter guards before energizing the laser.
2. Remove watches, jewelry, dangling badges, reflective tools, and unnecessary items from the work area. Confirm that only trained and authorized participants are present. Assemble the laser, four kinematic mirror mounts, and four mounted irises on posts and post holders. Use a beam-height gauge to set the center of every optic to the same height. Ensure that the laser is securely mounted approximately parallel to the breadboard. If the laser has focus adjustment (the one in the BOM does), ensure that it is focused so that it’s approximately collimated (smallest beam diameter).
3. Arrange the components to match Figure 1. Keep each beam segment horizontal and parallel to the breadboard surface. Position M1 and M2 near the laser, followed by A1 and A2. Place M3 and M4 at the far end, followed by A3 and A4 on the return path.
4. Place the beam block after A4 so every intended beam path terminates on a rated, secured surface. During coarse setup, add temporary blocks behind the optic being adjusted to capture stray beams.
5. With the laser blocked or off, rotate each mirror mount so the planned reflections are approximately 90° and the beam will strike near the center of every mirror and iris.

Step-by-Step Laser Beam Alignment Procedure

Part A – Align Mirrors M1 and M2 Through Irises A1 and A2

1. Set A1 and A2 to the common beam height and secure their bases. These two fixed apertures define the first optical axis.
2. Position M1 so the laser strikes near the center of the mirror and reflects toward M2. Secure M1 to the breadboard.
3. Position M2 so the beam from M1 strikes near its center and is directed approximately along the axis through A1 and A2. Secure M2.
4. Close A1 to a small opening. Use the tip/tilt adjusters on M1 to center the beam on A1.
5. Open A1 and close A2. Use the tip/tilt adjusters on M2 to move the beam toward the center of A2.
6. Return to A1 and check the beam position. Alternate between M1/A1 and M2/A2, making progressively smaller adjustments, until the beam passes through the center of both irises.

Part B – Extend the Optical Axis Through Irises A3 and A4

1. Position M3 so the beam exiting A2 strikes near the center of the mirror and is redirected toward M4.
2. Position M4 so the beam is directed approximately along the axis through A3 and A4.
3. Close A3 and use M3 to center the beam on A3. Then open A3, close A4, and use M4 to center the beam on A4.
4. Alternate between M3/A3 and M4/A4 until the beam passes through the center of both irises and terminates on the beam block.

Part C - Recovering Laser Alignment After Intentional Misalignment

1. Record or mark the positions of A1 and A2. Do not disturb M3, M4, A3, or A4.
2. Intentionally misalign M1 and M2 so the beam no longer passes through A1 and A2.
3. Repeat the Part A beam-walking procedure until the beam is again centered through A1 and A2.
4. Verify that the beam has also returned through A3 and A4. Successful recovery demonstrates that two fixed control points define the beam’s downstream propagation direction, provided the downstream optics remain unchanged.

Post Laser Beam Alignment Verification and Safety Checklist

• Confirm the beam is centered through A1-A4 and fully intercepted by the beam block.
• Secure mirror locks, post holders, bases, and the beam block without changing alignment.
• Search for and terminate stray or unused reflections.
• Restore all barriers, covers, enclosures, warning controls, and interlocks required by the laboratory.
• Communicate the system status to everyone in the area before changing operating conditions.
• Leave the irises in place as alignment references or document their exact locations for repeatable reinsertion.

Laser Safety Products

Laser Safety Barriers

Red and IR Alignment Laser Diodes

More Resources

• Application Note: Simplifying Laser Alignment - A practical guidance for steering a beam with two kinematic mirrors.
• Contact Edmund Optics Application Support - Help selecting components or adapting the setup to a laboratory or classroom.

Acknowledgment

Edmund Optics gratefully acknowledges the Lawrence Livermore National Laboratory Laser Safety Office for developing the laser alignment training program, exercises, and supporting guidance that informed this application note. This document is an independent Edmund Optics adaptation and should not be interpreted as replacing LLNL training, local procedures, or Laser Safety Officer oversight.

Reference

1. Lawrence Livermore National Laboratory Laser Safety Office, Laser User Alignment and Reference Guide, Version 2, LLNL-TM-2016217, Chapter 9 and Chapter 10, Activity #1.