Diffractive optics are used to create low- and high-order Laguerre-Gaussian (LG) beams from the output of a diode laser. We examine the mode purities, conversion efficiencies, extinction ratios, and propagation characteristics. We present detailed analyses of the beam profiles for one low-order
(LG01) and one high-order
(LG12) Laguerre-Gaussian mode. Modeling the
LG12 beam as a superposition of LG modes, we find $(99.3\ifmmode\pm\else\textpm\fi{}0.9%)$ of the laser intensity in the
LG12 mode, a mode purity greater than for LG beams created by other methods external to the laser cavity. The high mode purity may be useful in making atom traps for precision measurements and for Bose-Einstein condensation.
We develop a novel technique to measure small angular and lateral displacements of structured light beams. The technique relies on using high-order Hermite-Gaussian (HG) and Laguerre-Gaussian (LG) modes, which have well-defined symmetry under inversion. We show that the displacements of such fields lead to a crosstalk with modes with opposite parity under inversion, which we measure optimally with an interferometric parity sorter. Using this technique, we achieve improvement factors of up 41 in the signal-to-noise ratio using Hermite-Gaussian modes and 21 using Laguerre-Gaussian modes with order up to 20, as compared to the fundamental Gaussian mode. Our results present a viable way of using structured light for metrology that does not demand quantum light or homodyne detection.
A spatial light modulator (SLM) has been used to create high quality Laguerre–Gaussian (LG) light beams, which have been used to study the guiding of cold rubidium atoms. The SLM allows real-time variation of the hollow guiding beam and permits direct comparison of the guided atom fluxes for different LG modes with minimal adjustment of the other optical components. It is demonstrated that, by increasing the azimuthal index l of the Laguerre–Gaussian beam, the radiation pressure pushing the trapped atoms may be reduced while maintaining the same guided flux. This is the first comparative study of hollow beam atom guiding, and further demonstrates the versatility of the SLM for studies in atom optics.