IFO Modeling

IFo modeling tools can be found in the svn directory https://nodus.ligo.caltech.edu:30889/svn/trunk/ifomodeling/.

Optickle

By Matt Evans.

The Optickle modeling package is part of the ISCmodeling tools. The svn contain the latest version as of Feb-02-2010.

Documented and written in a way that be read by others.

It is independent to looptickle.

40m Upgrade Optickle Model

The 40m model file is contained under the config40m directory of looptickle.

The model represents the interferometer according to this layout:

attachment:IFO_diagram.png

A dual recycled interferometer could be set in different configurations (for a discussion on the topics see: Kokeyama K. et al. Class. Quantum Grav. 25 (2008) 235013 (12pp)).

The 40m will follow the choices for Advanced LIGO.

The single sub-cavities of the model are individually set in the following ways:

• Arm Cavities: resonant for the carrier; non-resonant for the sidebands; DARM offset = 40 pm

• Michleson: resonant for the carrier; Schnupp asymmetry of 0.0307 m

• PRC: anti-resonant for the carrier; resonant for both sidebands

• SRC: resonant for the carrier; resonant for the f2 sideband; non-resonant for f1

In particular, since the model add no microscopic offset to the SRM position, the SRC is by default resonant for the carrier. That means that when the arms are locked, the carrier becomes anti-resonant and f2 resonant.

(By adding an optional microscopic offset of lambda/4 the SRC would become resonant for the carrier when the arms are locked. In that case f2 would be anti-resonant. - not desirable)

Looptickle

By Stefan Ballmer

The package adds control loops to the Optickle model.

Undocumented and written with code not easy to read.

Matlab model of optical cavities

By Alberto Stochino

It is a semi-analythical modeling package. The two building blocks of the models are a Fabry-Perot function and a Michelson function. Each function replaces either a cavity or a Michelson, with an effective compound mirror. the functions return complex reflectance and transmittance. The input parameters are the most generic. The surfaces of all mirrors are treated individually, i.e. reflectance and transmittance can be set independently for each side of a mirror.

Macroscopic length and microscopic offsets are passed to the functions as inputs.

By nesting any combination of cavities in the proper way and order, one can build up a compound mirror representing coupled cavities or the whole interferometer. then the reflectivity and transmissivity of the compound mirror will be the Bright and Dark port outputs, respectively.

All functions contain a detailed help description.