Design and development of an optical beam splitter assembly and high precision colinearity measurements of laser beams

Laser beams with extremely high colinearity are often required where precision position monitoring is important. In order to achieve the said objective, a special type of Laser Beam Splitter Assembly (BSA) has been designed and fabricated in a very small volume due to space constraints. The main features and details of such a system are described here. This type of beam splitter assembly coupled with a diode laser through fibers can be remotely used for alignment or position monitoring of different medium to large size structures with a reconstruction accuracy of 10 μm. In this way, BSA generates two counter propagating laser beams from a single diode laser coupled to an optical fiber. In the present work, the colinearity between two beams within 1 mrad with the variation of 50 μrad has been achieved. The laser's power in the two arms may be controlled precisely, which is an important feature of this BSA. The BSA has been tested to work over a temperature range between −20 °C to +40 °C. It has also been exposed to 1.0 MeV neutrons at a flux of ∼5.0×10 10 n/cm 2/s and found compatible. ► BSA can produce back to back s-polarized collinear laser beams with the accuracy of less than 1 mrad. ► The BSA has a very small volume (16×24×46 mm 3) with rugged opto-mechanical structure. ► BSA can be remotely used for alignment/position monitoring purposes.