A single collimating lens based dual-beam exposure system for fabricating long-period grating

Abstract A single collimating lens based dual-beam exposure system is proposed in this paper in which two interference beams share one collimating lens. Based on theoretical analysis and simulation, the interference aberration caused by the pinholes on the off-axis positions is compensated through feedback adjustment of the pinholes’ relative position. This system is more compact and stable, and can avoid the spatial position interference between two collimating lenses in traditional dual-beam exposure systems for fabricating long-period gratings. A 5 μ m period grating exposure system is constructed to verify the theoretical analysis. Using the proposed adjustment method, a spacing error of approximately 0.03 λ within the aperture of 65 mm × 65 mm is achieved.