Tailored optical potential for 87Rb atoms

• Main Author: Nguyen, Nghia Tin
• Other Authors: Rainer Helmut Dumke
• Format: Final Year Project
• Language: English
• Published: 2015
• Subjects: DRNTU::Science::Physics::Atomic physics::Solid state physics
• Online Access: http://hdl.handle.net/10356/63799
• Institution: Nanyang Technological University

In this nal year project, a laser system is built to create arbitrary red-detuned potentials for 87Rb atoms. The Ti:Sapphire laser optically pumped by the 532 nm Verdi 10 W laser, is used as the 850 nm laser source for the optical system. The laser beam passes through an Acousto-Optical Modulator (AOM) in double-pass con guration serving as a fast switch before being coupled into a polarization-maintaining ber for delivery to the potential forming system. The optical trap is formed using a spatial light modulator (SLM) that modulates the phase spatially across the laser beam depending on the input kinoform, and a focusing lens of f = +200 mm to create holographic image at the focal plane. The kinoform displayed on SLM screen is optimized by Iterative Fourier Transform Algorithms (IFTAs). Our system uses an improved version called Mix-Regional Amplitude Freedom (MRAF) algorithm with proper initial phase guess to create the desired patterns in the full Helmholtz regime. Further experiments have been done to measure the phase characteristic of the SLM using Sagnac and Mach-Zehnder interferometers in order to increase the accuracy of the potentials. Using a non-polarizing beam splitter, 10% of the reflected power from the SLM is used to create a potential for real-time observation with 10x objective and a CCD camera. The other 90% power passes through an astronomical telescope acting as a 4-f relay optics to reduce the beam diameter before being focused down to a spot of few tens of micrometer by a 50x objective lens for ultracold atom coupling.