Laser Locking for Long-term Magneto-Optical Trap Stability

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

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

3. 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

4. 0 Volts ν Frequency Diode Laser Frequency Stabilization • Frequency changes due to temperature and diffraction grating position • Tuned to transition frequency • Locked with a feedback circuit

5. 0 V 5 MHz 500 MHz 0 V 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: ?

6. DAVLL Setup to MOT

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

8. 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

9. 14 hours! mode hops Results

10. 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

11. 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