Building a Custom Optical Isolator with Stock Components

Many laser applications are prone to having the transmitted laser beam reflect off the targeted surface and back into the laser source, causing the laser source to overheat and decrease the laser’s stability and lifetime. Although this back reflection can be eliminated by using an optical isolator, which is an optical component that emits a circularly polarized beam and allows light to transmit in only a single direction (Figure 1), pre-built optical isolators are typically expensive solutions. For price-sensitive systems, a high performance and low-cost passive optical isolator can be built using off-the-shelf optical components. Table 1 includes a part list for assembling a custom optical isolator (Figure 2). The polarizing cube beamsplitter and waveplate should be selected based on the wavelength of the laser used in the application.

Figure 1: An Optical Isolator Can be Built Using a Polarizing Cube Beamsplitter and λ/4 Waveplate

Figure 2: A Cost Effective Optical Isolator Built from Off-the-Shelf Components

Instructions for Building an Optical Isolator

1. Mount the Polarizing Cube Beamsplitter into the C-mount Cube.
2. Connect the C-Mount Double Male Rotating Barrel to the C-mount Cube at the beamsplitter’s transmitted port side.
3. Mount the waveplate into the C-Mount Thick Lens Mount.
4. Attach the mounted waveplate to the C-mount Double Male Rotating Barrel. Orient the waveplate at 45° to the transmission axis of the Polarizing Cube Beamsplitter.
5. Finalize alignment by inputting a laser beam and lock the angle position of the C-Mount Double Male Rotating Barrel once maximum beam isolation is achieved.