We report a novel Optical Beam Steering Technique (OBST) for fiber to free-space to fiber coupling with extreme stability of the coupling efficiency and high tolerance to temperature fluctuations. The compact optical system is based near monolithic (ZERODUR) fiber couplers and relies on optical wedges and plates to perform the fine-steering of the optical beam. In our approach, we use coarsely aligned fiber couplers and then perform the fine alignment using the wedges and plates. This separation of fine and course tuning significantly reduces the manufacturing and assembly requirements of the fiber couplers. At the same time, it results in a much-reduced sensitivity to drifts increases the stability and reliability of the breadboard. OBST achieves a coupling efficiency (CE) of 94% with long-term fluctuation of 0.1% RMS at stable temperatures and 1.4% under repeated vacuum temperature cycling over a 30K range. Even under extreme mechanical stress (random vibrations of up to 8.3g) the RMS vibration of the coupling efficiency were less than 0.3% RMS. The optical breadboard technology has therefore achieved TRL5.
We present the theoretical analysis of a novel optical beam steering technique (OBST) for fiber to free-space to fiber coupling schemes on optical breadboards. This technique uses glass wedges and plates to correct misalignments in the position and angle of beams on the breadboard. It can be used in any application where stable and robust coupling of light from an input to an output fiber is required, such as laser distribution boards for cold atom experiments in space. We examine the optical performance in terms of coupling efficiency (CE) for a number of different OBST systems and compare the results. Coupling efficiencies above 95% and positional and angular resolution of smaller than 5 μm and 5 μrad can be achieved using this technology.
We present a novel optical beam steering technique (OBST) for fiber to free-space to fiber coupling schemes on optical breadboards, which uses glass wedge pairs and plates to correct for angular and translational misalignments respectively. This technique finds application in proposed missions for atom quantum experiments in space, e.g. where laser beams are used to cool and manipulate atomic clouds. The key advantage compared to the conventional beam steering is that OBST permits extremely fine adjustments whilst being far less sensitive to alignment errors and mechanical drifts. Beam steering resolutions of better than 5 μrad and 2 μm are achieved, resulting in a resolution in coupling efficiency (CE) of 0.1%. The inclusion of OBST on an optical breadboard reduces the requirements on the pointing and position precision adjustment of the fiber couplers, leading to a much-simplified design. The simpler construction of the couplers combined with the reduced sensitivity to drifts increases the stability-reliability of the breadboard and reduces the production duration and cost. We demonstrate CE of up to 90%, with a stability of 0.2% in a stable temperature environment and 2% over a temperature range from 10-40 degrees Celsius. We do not observe any change in the performance after large temperature changes.
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