Laser Locking for Longterm MagnetoOptical Trap Stability Kevin

Laser Locking for Long-term Magneto-Optical Trap Stability Kevin W. Vogel Advisor: Georg Raithel Presented 07/28/04

Outline • • Magneto-Optical Trap (MOT) Laser Locking Methods Dichroic Atomic Vapor Laser Locking MOT Improvements

Magneto-Optical Trap (MOT) • Capture and cool Rubidium atoms to μK temps • 6 orthogonal pairs of circularly polarized counter propagating laser beams • Anti-Helmholtz magnetic field

Diode Laser Frequency Stabilization • Frequency changes due to temperature and diffraction grating position • Tuned to transition frequency • Locked with a feedback circuit 0 Volts Frequency ν

Laser Locking Methods • Saturated Absorption Spectroscopy – Narrow locked frequency range – Easy to lose lock – Lock time: 10 – 60 min. • Dichroic Atomic Vapor Laser Locking (DAVLL) – Difficult to lose lock – Broader locked frequency range – Lock time: ? 0 V 5 MHz 500 MHz 0 V

DAVLL Setup to MOT

DAVLL Lock Signal • Transition shifted by Zeeman effect • Laser output is linearly polarized • Each circular polarization is absorbed by a shifted transition

Improvements: • Low Noise Circuit – Produces differential absorption signal with minimal electrical noise • Temp Controlled Permanent Magnets – Permanent magnet field strength is temperature dependent – Keeps temp within ± 0. 003°C

Results 14 hours! mode hops

Other MOT Improvements • Permanent heater to clean Rubidium cell • Larger vacuum chamber cell to increase atom flow • Magnetic coils for larger cell • New laser grating and bracket

Acknowledgments • Georg Raithel, Ramon Torres-Isea, Spencer Olson, Rahul Mhaskar, Tara Cubel, Aaron Reinhard, Natalya Morrow, Rui Zhang, Brenton Knuffman, Alisa Walz-Flannigan, Jae-Hoon Choi, Eberhard Hansis, Alex Povilus • NSF • Physics Department