Phase-sensitive total-internal-reflection sensing system for measuring vacuum pressure

Based on the principle of Chiu et al., this work proposes a phase-sensitive total-internal-reflection (TIR) sensing system for measuring vacuum pressure. In the system, linearly polarized light propagates through a specially designed phase-sensitive TIR apparatus composed of a wave-plate type phase shifter, an isosceles right-angle prism combined with a vacuum cavity, and an analyzer. Under the suitable axis azimuth of the wave plates and the analyzer, it can raise the phase difference of the s- and p- polarization states of the totally-reflected light beam from the TIR apparatus. The raised phase difference is related to the vacuum pressure; therefore the pressure is easily and accurately determinable with measuring the phase difference variation using the heterodyne phase-detection technique. The experimental results demonstrated the feasibility of this method. Measurement resolution and sensitivity levels superior to 0.4 torr and 0.02 degrees/torr were respectively attainable in measurement region of 10 ton to 760 torr.