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 Frequency ν 0 Volts

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: ? 5 MHz 0 V 500 MHz

DAVLL Setup to MOT

DAVLL Lock Signal Laser output is linearly polarized Transition shifted by Zeeman effect 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 mode hops 14 hours!

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