Diff for "OutputModeCleaner"

Differences between revisions 20 and 21

The Output Mode Cleaner (OMC) takes the beam coming out of the anti-symmetric (AS) port of the interferometer and cleans it of all but the fundamental (TEM00) transverse mode. This means that it strips off junk which is not Gaussian; all of the ripply junk light which comes from a constrast defect; imbalances in the wavefronts of the two arms.

Reducing this junky, useless light reduces the overall light power detected and so also reduces the shot noise.

In addition, the OMC has a narrow frequency passband (~1 MHz) and so it also reflects all the RF sidebands which are normally used to lock the interferometer.

By rejecting all the Higher Order Modes (HOMs), it is hoped that the OMC output will be stable enough to use as the gravitational wave error signal and also be used to lock the differential arm length (L-) degree of freedom.

OMC specs

http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/OMC_params.m

OMC mirror specs

Mirror	Diameter	Thickness	Side 1	Side 2	wedge	Radius of curvature	comments
M1	7.75 mm	4 mm	R > 99.9%, 0° inc	R < 0.2%	< 30 amin	1 m, CC/PL	PMC spare from P.King
M2	1”	0.25”	R > 99.97%, 0° inc	R < 0.2%	< 30 amin	Flat PL/PL	Newport HR supermirrors
M3	1”	0.25”	T ~ 1% , 45° inc, P-pol	R < 0.2%	30 amin	Flat PL/PL	LHO spare, REO part #31301
M4	1”	0.25”	T ~ 1% , 45° inc, P-pol	R < 0.2%	30 amin	Flat PL/PL	LHO spare, REO part #31301

Input and output couplers: Spares from LHO. REO part #31301 – PL/PL – 1”dia. x .250” thick; Super-polished fused silica, wedged (30 min. arc +/-15 min); Coating Wavelength: 1064 nm; Angle of incidence: 45° - “P” Polarization; Side 1: HR – T ~1% (matched as close as possible among the 3 mirrors in the order); Side 2: AR – R = 0.2%.
From: Helena Armandula; Date: Oct 19, 2005 9:51 AM; Subject: Mirrors tested at Caltech; The mirrors sent by Betsy were measured by Liyuan.; ... two 1" dia., coated at 45 degrees, P-pol, measured: T at 45 degrees P-pol is 15,500 ppm +/-200 ppm (or 1.55+-0.02%).
The 1" flat reflector is one of a pair ordered and received by Steve, broadband HR super-mirrors from Newport. Steve and Liyuan tested them. The transmission was 600 ppm, at 0 and 5degrees incidence.
the curved mirror: M1: 7.75 mm dia; 4 mm thick; side 1: R > 99.9%, 0° inc; side 2: R < 0.2% < 30 amin; ROC: 1 m, CC/PL

[http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/40mDCdetect_mirrors.pdf OMC mirror spec document]

[http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/40m-Output_MC.pdf OMC mirror spec sheet]

[http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/CALTECH2357-02.pdf REO quote for input/output coupling mirrors (and more)] This quote has nothing to do with anything we actually have. Instead we ended up just scrounging crap from whoever would crap on us. See above table.

[http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/40mDCdetect_OMC.pdf OMC design info]

-  ⇤ ← Revision 20 as of 2006-09-22 00:27:02 → 
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-Deletions are marked like this.
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-Reducing this junky, useless light reduces the overall light power detected and so also reduces the shot noise.
+Reducing this junky, useless light reduces the overall light power detected and so also reduces the shot noise. {OK}
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+----------
== OMC specs ==
<<ImageLink(http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/OMC_params.png,width=800)>><<ImageLink(http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/OMC_HOMT.png,width=500)>><<ImageLink(http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/OMC_gfac.png,width=500)>>http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/OMC_params.m
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-== OMC specs ==
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== OMC mirror specs ==
|| Mirror || Diameter || Thickness || Side 1 || Side 2 || wedge || Radius of curvature || comments ||
|| M1 || 7.75 mm || 4 mm || R > 99.9%, 0° inc || R < 0.2% || < 30 amin || 1 m, CC/PL || PMC spare from P.King ||
|| M2 || 1” || 0.25” || R  > 99.97%, 0° inc || R < 0.2% || < 30 amin || Flat PL/PL || Newport HR supermirrors ||
|| M3 || 1” || 0.25” || T ~ 1% , 45° inc, P-pol || R < 0.2% || 30 amin || Flat PL/PL || LHO spare, REO part #31301 ||
|| M4 || 1” || 0.25” || T ~ 1% , 45° inc, P-pol || R < 0.2% || 30 amin || Flat PL/PL || LHO spare, REO part #31301 ||
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-<<ImageLink(http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/OMC_params.png,width=800)>>

<<ImageLink(http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/OMC_HOMT.png,width=500)>>

<<ImageLink(http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/OMC_gfac.png,width=500)>>

http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/OMC_params.m

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== OMC mirror specs ==


|| Mirror || Diameter || Thickness || Side 1 || Side 2 || wedge || Radius of curvature || comments ||
|| M1     || 7.75 mm  || 4 mm      || R > 99.9%, 0° inc  || R < 0.2% || < 30 amin || 1 m, CC/PL || PMC spare from P.King ||
|| M2     || 1”       || 0.25”     || R  > 99.97%, 0° inc || R < 0.2% || < 30 amin || Flat PL/PL || Newport HR supermirrors ||
|| M3     || 1”       || 0.25”     || T ~ 1% , 45° inc, P-pol || R < 0.2% || 30 amin || Flat PL/PL || LHO spare, REO part #31301 ||
|| M4     || 1”       || 0.25”     || T ~ 1% , 45° inc, P-pol || R < 0.2% || 30 amin || Flat PL/PL || LHO spare, REO part #31301 ||
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-[http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/CALTECH2357-02.pdf REO quote for input/output coupling mirrors (and more)]
This quote has nothing to do with anything we actually have. Instead we ended up just scrounging crap from whoever would crap on us.
See above table.
+[http://www.ligo.caltech.edu/~cit40m/Docs/DCdetect/CALTECH2357-02.pdf REO quote for input/output coupling mirrors (and more)] This quote has nothing to do with anything we actually have. Instead we ended up just scrounging crap from whoever would crap on us. See above table. :-))