Mitsuhashi, Shalika,

What we did:
We install HWP before mirror and observed the reflected power with respect to the degree of rotation HWP. The result was attached.
The maximized power was 3.42V and the angle was 260°.

We install all instrument before the cavity anyway. 

What we will do next:
We will try to make the cavity and install a photo detecter to catch the error signal from the cavity.