• PSL
• Intensity_Stabilization_Servo

NEW ISS

Concept

Intensity noise is one of the main laser noise sources that could potentially pollute the sensitivity. Therefore the intensity noise of the PSL must be suppressed before the beam gets into the mode cleaner. We are planning to install the combination of a photo detector and AOM to form the Intensity Stabilization System (ISS).

Equipments

Photo detector

No real photo detector has been installed yet for the ISS.

AOM

A new AOM has been installed before the PMC in the Summer of 2011. However this is AOM wasn't yet activated, so the PSL beam just goes through the AOM without any modulations.

• AOM datasheet AOMdatasheet.pdf

Electronics

OLD DAYS

The ISS measures the power fluctuations on a photodiode placed after the Mach Zender, but before the Mode_Cleaner, and tries to servo that signal to zero.

The ISS is AC-coupled, so its purpose is not to control long-term drift. In its nominal configuration, it has gain from 1-100,000 Hz. This is to suppress the intensity noise in our measurement band.

The ISS servo sits on the PSL table; its a beige box with black front and back panels. All of the hooks for doing fast loop measurements are on that box.

The ISS actuator is the Current Shunt in the MOPA box.

Schematic

• Schematic of 40m ISS servo - Beware that there are various "Revision D" ISS's floating around; this link is to the 40m version. There is a paper version of this at the 40m that is marked up with further modifications to the 40m ISS.

• Photodiode schematic - This is from Flavio's website, though the direct link from his ISS page is broken due to a misspelling.

The above links are useless. ISS servo schematic is D020241 and PD head schematic is D030452. At the time of writing this (Aug 2020), the 40m has no working ISS - the old ilog suggests there were several hacks made to D020241, but D030452 looks to represent the physical circuit pretty accurately.

In the future, the best practise is to download the PDF of schematic, add it to the attachments section of the wiki, and link it that way, instead of links to web pages.

DAQ channels