LCGT IFO Mirror Size
Mirror size requirements from the beam spot size
The minimum mirror sizes are calculated requiring less than 1ppm diffraction loss. This translates into the mirror sizes 2.7 times larger than the beam spot size. The situation is a bit more complicated for BS. Hiro Yamamoto calculated the loss of the light power in the PRC by the finite size of the BS using FFT simulation. BSLoss.pdf. Now we have to check what is the acceptable loss level for PRC ? 1000ppm ?
Optics |
Beam Spot Size (1/e^2 radius) |
Minimum Mirror Size (diameter) |
ITM |
3.5cm |
19cm |
ETM |
3.5cm |
19cm |
BS |
3.5cm |
7*3*sqrt(2)+2*t/sqrt(2*n^2-1), where t is the thickness and n is the refractive index. |
PR3 |
3.5cm |
19cm |
SR3 |
3.5cm |
19cm |
PR2 |
less than 1cm |
10cm is enough |
SR2 |
less than 1cm |
10cm is enough |
PRM |
less than 1cm |
10cm is enough |
SRM |
less than 1cm |
10cm is enough |