1. Cavity Locking by Piezo-Driven Mirror Botao Jia Duke University Advisor: Dr. Nanda Sirish HAPPEX Collaboration Meeting Dec 1, 2006

2. While the Prometheus Laser is away for fixing, we studied cavity locking with: Medium finesse mirrors Piezo-driven mirror (designed by Gavalya) Non tunable, low cost laser Electro optic modulator Laselock electronics

3. Transverse mode Fabry-Perot Cavity Basis Y X Z

4. Transverse mode Video

5. Fabry-Perot Cavity Basis Longitudinal mode Reflection Transmission Cavity length (nm) 266nm

6. Eorror Signal Piezo Scan Voltage Reflection Transmission Measuring Longitudinal Mode by Scanning Piezo Voltage

7. Reflection phase Transmission Characteristic signals of a Fabry-Perot Cavity Cavity length (nm) =532nm, Reflectivity=99.85%, Finesse 2000 Reflected Intensity Detuning Parameter phase

8. Measuring error signal in scan mode Reflection Error signal Transmission

9. Quasi-stable locking has been achieved by using the laselock box in a feedback loop with the piezo driven mirror. Experimental setup Feedback signal

10. Conclusion: Locking is achieved. However, not very stable. Our home-made piezo doesnt have good resolution for stable locking. 1.Laselock electronics performance in cavity locking need to be investigated further. So far we already gained lots of operating experience. 2.To try piezo with lower coefficient and higher resolution. 3.Now the Permethus laser is back. So to study and lock it to the cavity have the first priority. Thank you