Browsing by Subject "Laser beam shaping"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item High-precision laser beam shaping and image projection(2012-05) Liang, Jinyang, 1985-; Becker, Michael F.; Heinzen, Daniel J.; Tunnell, James W.; Evans, Brian L.; Bank, Seth R.Laser beams with precisely controlled intensity profiles are essential for many areas. We developed a beam shaping system based on the digital micromirror device (DMD) for ultra-cold atom experiments and other potential applications. The binary DMD pattern was first designed by the error diffusion algorithm based on an accurate measurement of the quasi-Gaussian incident beam from a real-world laser. The DMD pattern was projected to the image plane by a bandwidth-limited 4f telescope that converted this pattern to the grayscale image. The system bandwidth determined the theoretical limit of image precision by the digitization error. In addition, it controlled the spatial shape of the point spread function (PSF) that reflected the tradeoff between image precision and spatial resolution. PSF was used as a non-orthogonal basis set for iterative pattern refinement to seek the best possible system performance. This feedback process, along with stable performance of DMD, the blue-noise spectrum of the error diffusion algorithm, and low-pass filtering, guaranteed high-precision beam shaping performance. This system was used to produce various beam profiles for different spatial frequency spectra. First, we demonstrated high-precision slowly-varying intensity beam profiles with an unprecedented high intensity accuracy. For flattop and linearly-tilted flattop beams, we achieved 0.20-0.34% root-mean-square (RMS) error over the entire measurement region. Second, two-dimensional sinusoidal-flattop beams were used to evaluate image precision versus system bandwidth. System evaluation confirmed that this system was capable of producing any spatial pattern with <3% RMS error for the most system bandwidth. This experiment extended the beam shaping to any system bandwidth and provided a reference to estimate the output image quality based on its spatial spectrum. Later experiment using a Lena-flattop beam profile demonstrated the arbitrary beam profile generation. We implemented this system for applications on the homogenous optical lattice and dynamic optical trap generation. The DMD pattern was optimized by the iterative refinement process at the image feedback arm, and projected through a two-stage imaging system to form the desired beam profile at the working plane. Experiments demonstrated a high-precision beam shaping as well as a fast and dynamic control of the generated beam profile.Item Toward applications of shaped laser fields to ultracold boson systems(2015-05) Kohn, Rudolph Nicolas, Jr.; Heinzen, Daniel J.; Becker, Michael F; Downer, Michael C; Fiete, Gregory A; Sitz, Greg OExperimental progress toward the application of laser beams with shaped intensity profiles to dipole force trapping of ultracold atoms is reported. The experiment combines a new method for beam shaping, producing beams with intensity control to the 0.3% RMS level, with an apparatus designed to produce quantum degenerate gases of ⁸⁷Rb atoms. Experiments showing the production of ultracold ⁸⁷Rb and progress toward quantum degeneracy are discussed, along with several suggestions for the advancement to Bose condensation. Novel experiments with this apparatus are proposed, which would allow the investigation of specific points in phase space which have, until now, been difficult if not impossible to access. This work could lead to high-precision measurements of phase transitions, including quantum phase transitions and quantum criticality in a Bose or Bose-Hubbard gas.