1. Angular Noise in a Suspended Interferometer with DC Readout Royal Reinecke Co-Mentors: Alan Weinstein and Rana Adhikari

2. Overview Introduction to LIGO What are optical levers and how do they work? Angular noise sources –Servo-induced Noise –Electronic Noise –Laser Intensity Noise Overall Noise Budget

3. Advanced LIGO X Arm Y Arm Michelson Interferometer Fabry Perot Arm Cavities Core optics controlled by optical levers SRM OMC

4. Optical Levers Oplev Laser QPD Suspended Optic

5. Initial Jitter Seen by Oplevs X Arm of 40 mY Arm of 40 m Apparent noise floor between 10 -8 and 10 -9 radians above ~5Hz Amplitude Spectral Density

6. Servo Digital Filters Old ELP40 (blue) New ELP35 (red) Coil Drivers

7. Effects of Filter Change on Actual Mirror Motion X ArmY Arm

8. Electronic Noise Electronic Noise larger than actual mirror motion above 5 Hz Amplify QPD signal before noisy ADC stage

9. Electronic Filters Whitening Filter -20dB at 8192 Hz Falls as 1/f 2 Zero at 1Hz Poles at 10Hz, 1500Hz Low Pass Filter

10. Before and After Whitening ETMX previous ETMY previous

11. Effect of Filters ETMX Pitch Error and Out Signals (old-blue, new-red)

12. Laser Intensity Noise Apparent Mirror Motion due to Laser Intensity Fluctuations

13. Transfer Function of Input Voltage to Output Laser Power

14. Optical Lever Noise Budget

15. Acknowledgments Alan Weinstein and Rana Adhikari 40m Staff LIGO NSF Caltech SURF Program