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ALS: Auxiliary Locking System?
ALS: Arm Length Stabilization?
The Spiel on Auxiliary Locking
"The task of locking the next generation of gravitational wave interferometers (GWIs) using conventional techniques will be substantially more difficult than for the present generation. Auxiliary locking techniques to assist in this process are being currently developed and tested. One promising idea involves frequency stabilizing an optical fiber system, transporting a frequency reference to the far end, phase-locking a second laser to this reference and then frequency doubling this laser using second harmonic generation to create a stable green laser that can be used to lock part of the interferometer. Skills that would be helpful, though not essential, for a SURF student involved in this project include: experience working with lasers and optics, rf electronics and software packages such as MATLAB and Simulink."
Arm Length Stabilization - some initial references
Locking
Matt Evan's thesis (2002):
http://www.ligo.caltech.edu/~mevans/lockAcq/thesis.pdf
ALS: Part 1 - Fibre Stabilization
References
- S. Foreman. Femtosecond Frequency Combs for Optical Clocks and Timing Transfer. PhD Thesis (2007) pp. 265
- Foreman et al. Remote transfer of ultrastable frequency references via fiber networks. Rev. Sci. Instrum. (2007) vol. 78 (2) pp. 021101
- Ye et al. Delivery of high-stability optical and microwave frequency standards over an optical fiber network. Journal of the Optical Society of America B (2003)
Schematic of FS part of experiment
ALS: Part 2 - Frequency Doubling
The details of the doubling (SHG) process become important to understand if we want to be able to say anything about the stability of the doubled light.
The basic idea:
- Take some 1064nm light source with some frequency and intensity noise.
Pass this light through some nonlinear crystal (http://en.wikipedia.org/wiki/Potassium_titanyl_phosphate)
Some of the 1064nm light turns into 532nm light via SHG (http://en.wikipedia.org/wiki/Second_harmonic_generation)
- Now we need to answer "how is the noise in the 532nm field related to the noise in the 1064nm field"
For 2-3, slides 14-15 of LIGO-G0900282 (in the DCC) offer a cursory explanation
Chapter (???) in Fundamentals of Photonics offers the coupled wave equation derivation