# Actual Optical Parameters of the Main Interferometer

## Optical Parameters

### Interferometer Diagram

Note: In this figure POP is taken at the transmission of PR3, because it is easier to draw. In reality, POP will be taken at the transmission of PR2 (beam from PR3 to PR2).

### ITM=1.9km, ETM=1.9km, PRC=16.5deg, SRC=17.5deg, 16.875MHz, 45MHz

This is the parameter set chosen by the MIF group.

#### Lengths & Frequencies

 f1 16.880962MHz (3*f2/8) f2 45.015898MHz f3 56.269873MHz (10*f2/8) Larm 3000.0m Lmc 26.639m Lprc 66.591m Lsrc 66.591m Las 3.3299m Lp1 14.7615 Lp2 11.0661m Lp3 15.7638m Lmi 25m Lmx 26.6649m Lmy 23.3351m Ls1 14.7412m Ls2 11.1115m Ls3 15.7386m Folding Angle Different for different mirrors. See the CAD drawings

Folding angle is an incident angle of the beam to the folding mirrors. The angle between incoming and reflected beams is twice the folding angle.

#### Radius of Curvatures (Positive for concave)

 ITM 1900.0m ETM 1900.0m PRM 458.1285m PR2 -3.0764m PR3 24.9165m SRM 458.1285m SR2 -2.9872m SR3 24.9165m

#### Beam Spot Size (1/e^2 radius)

 ITM 35.3mm ETM 35.3mm PRM 4.457mm PR2 4.457mm PR3 36.639mm SRM 4.308mm SR2 4.328mm SR3 36.666mm

## Mirror Specs

### Test Masses

ITM

 Diameter 220mm Thickness 150mm HR Radius of Curvature 1.90(+/-0.0095)km 0.5% error AR Radius of Curvature Flat (>100km) As flat as possible AR Wedge Angle 0.025+0/-0.002deg Wedge direction: seen from the HR surface, 9 o'clock is thickest for both ITMX and ITMY. Transmission@1064nm 0.004 +0.001/-0.0 Transmission asymmetry@1064nm 2*|(T1-T2)/(T1+T2)| < 0.01 T1 and T2 are the transmission of two ITMs HR Loss@1064nm <45ppm Transmission@532nm 0.06(+0/-0.005) Transmission of ITM must be larger than ETM@532nm Transmission asymmetry@532nm No requirement HR Loss@532nm <1% AR Reflectivity@1064nm 200(+100/-0)ppm AR Reflectivity@532nm <5% As small as possible

ETM

 Diameter 220mm Thickness 150mm HR Radius of Curvature 1.9(+/-0.0095)km 0.5% error AR Radius of Curvature Flat (>100km) As flat as possible AR Wedge Angle 0.05+/-0.01deg Wedge direction: Seen from the HR surface, 3 o'clock is thickest for ETMX, 9 o'clock is thickest for ETMY. Transmission@1064nm 5ppm < T < 10ppm Transmission asymmetry@1064nm 2*|(T1-T2)/(T1+T2)| < 0.01 Best Effort HR Loss@1064nm <45ppm Transmission@532nm 0.06(+0/-0.005) Transmission of ETM must be smaller than ITM@532nm Transmission asymmetry@532nm No requirement HR Loss@532nm <1% AR Reflectivity@1064nm <50ppm AR Reflectivity@532nm <5% As small as possible

BS

 Diameter 370mm +/- 0.25mm Thickness 80mm +/- 0.5mm HR Radius of Curvature Flat (>500km) As flat as possible AR Radius of Curvature Flat (>500km) As flat as possible AR Wedge Angle 0.08+0/-0.01deg Incident Angle 44.9684deg +/-0.05deg Transmission@1064nm 50% +/-1% HR Loss@1064nm <100ppm Transmission@532nm >0.9 (99.40% for s-pol, 97.85% for p-pol designed) HR Loss@532nm <1% AR Reflectivity@1064nm <50ppm AR Reflectivity@532nm <5% As small as possible

PRM

 Diameter 250mm Thickness 100mm HR Radius of Curvature 458.1285m(+/-20)m 5% error AR Radius of Curvature Flat (>100km) As flat as possible AR Wedge Angle 1.999 deg measured Transmission@1064nm 0.1(+0.001/-0.0) measured to be 0.1035 HR Loss@1064nm <45ppm AR Reflectivity@1064nm <50ppm

PR2

 Diameter 250mm Thickness 100mm HR Radius of Curvature -3.0764(+/-0.01)m AR Radius of Curvature Flat (>100km) As flat as possible AR Wedge Angle 2.042 deg measured Transmission@1064nm 500ppm(+/-50ppm) HR Loss@1064nm <45ppm Transmission@532nm > 0.5 As large as possible (0.9 measured with witness sample at 0deg) HR Loss@532nm <10% AR Reflectivity@1064nm <1000ppm As small as possible AR Reflectivity@532nm <5% As small as possible

PR3

 Diameter 250mm Thickness 100mm HR Radius of Curvature 24.9165(+/-0.01)m AR Radius of Curvature Flat (>100km) As flat as possible AR Wedge Angle 2.019 deg measured Transmission@1064nm <50ppm As small as possible HR Loss@1064nm <45ppm Transmission@532nm < 0.1 As small as possible HR Loss@532nm <10% AR Reflectivity@1064nm <1000ppm As small as possible AR Reflectivity@532nm <5% As small as possible

SRM

 Diameter 250mm Thickness 100mm HR Radius of Curvature 458.1285m(+/-20)m 5% error AR Radius of Curvature Flat (>100km) As flat as possible AR Wedge Angle 1.997 deg measured Transmission@1064nm 0.1536(+/-0.001) HR Loss@1064nm <45ppm AR Reflectivity@1064nm <50ppm

SR2

 Diameter 250mm Thickness 100mm HR Radius of Curvature -2.9872(+/-0.01)m AR Radius of Curvature Flat (>100km) As flat as possible AR Wedge Angle 2.096 deg measured Transmission@1064nm 500ppm(+/-50ppm) HR Loss@1064nm <45ppm Transmission@532nm > 0.5 As large as possible (0.9 measured with witness sample at 0deg) HR Loss@532nm <10% AR Reflectivity@1064nm <1000ppm As small as possible AR Reflectivity@532nm <5% As small as possible

SR3

 Diameter 250mm Thickness 100mm HR Radius of Curvature 24.9165(+/-0.01)m AR Radius of Curvature Flat (>100km) As flat as possible AR Wedge Angle 2.026 deg measured Transmission@1064nm <50ppm As small as possible HR Loss@1064nm <45ppm Transmission@532nm < 0.1 As small as possible HR Loss@532nm <10% AR Reflectivity@1064nm <1000ppm As small as possible AR Reflectivity@532nm <5% As small as possible

LCGT/subgroup/ifo/MIF/OptParam (last edited 2021-12-22 14:33:51 by YoichiAso)