Abstract
A Michelson type interfermeter using two different wave-length, 10.6 μm (Co2 laser), 0.633 μm (He Ne laser), has been investigated for plasma density measurement of STP-2 apparatus. It is demonstrated that the two different beams enable to cancel effects of mechanical oscillations which appear between the optical paths. Consequently, fringe shifts due to plasma density variation up to 1/100 can be discriminated.
