Optimal binary gratings for multi-wavelength magneto-optical traps

Burrow, Oliver S. and Fasano, Robert J. and Brand, Wesley and Wright, Michael W. and Li, Wenbo and Ludlow, Andrew D. and Riis, Erling and Griffin, Paul F. and Arnold, Aidan S. (2023) Optimal binary gratings for multi-wavelength magneto-optical traps. Optics Express, 31 (24). pp. 40871-40880. ISSN 1094-4087 (https://doi.org/10.1364/OE.498606)

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Abstract

Grating magneto-optical traps are an enabling quantum technology for portable metrological devices with ultracold atoms. However, beam diffraction efficiency and angle are affected by wavelength, creating a single-optic design challenge for laser cooling in two stages at two distinct wavelengths – as commonly used for loading, e.g., Sr or Yb atoms into optical lattice or tweezer clocks. Here, we optically characterize a wide variety of binary gratings at different wavelengths to find a simple empirical fit to experimental grating diffraction efficiency data in terms of dimensionless etch depth and period for various duty cycles. The model avoids complex 3D light-grating surface calculations, yet still yields results accurate to a few percent across a broad range of parameters. Gratings optimized for two (or more) wavelengths can now be designed in an informed manner suitable for a wide class of atomic species enabling advanced quantum technologies.

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