Illumination module

Stabilized HeNe lasers have long been used in many application areas such as spectroscopy and interferometry. Even fiber-coupled HeNe lasers are not quite new to the market. However, in cases where the collimator is located directly behind the laser output, back reflections can significantly impair laser stabilization (both frequency and amplitude), and it can also be difficult to control polarization at the fiber output. Based on our customers' requirements, we at OptiXs have developed a module that addresses these shortcomings by integrating an optical isolator and a half-wave plate.

While the optical isolator protects the laser from back reflections, the half-wave plate allows precise control of the polarization rotation before entering the collimator. In polarization-sensitive applications, this ensures that the coupled laser beam is precisely aligned with the slow axis of the PM fiber used, maximizing the polarization extinction ratio (PER) and achieving values above 30 dB. The module has a service port that allows the user to fine-tune the rotation of the half-wave plate to compensate for any long-term changes in the polarization state. Otherwise, the optical path is covered and protected against contamination.

Despite the more complex optical path, we are able to guarantee > 75% of the laser power at the fiber output for our modules. For HeNe lasers, which typically have around 1.5 mW at their free space output, we can achieve a power over 1 mW at the end of the fiber.