Extended Data Fig. 4: Illustration of homodyne optical interferometer.
From: A molecularly impermeable polymer from two-dimensional polyaramids
PBS: polarizing beam splitter; λ/2: half wave plate; λ/4: quarter wave plate; PD: photodetector; PID: proportional-integral-derivative controller; PAM: piezo-actuated mirror; SA: spectrum analyzer. The displacement fluctuations are measured with the spectrum analyzer connected to PD1 while PD2 is used for feedback stabilization.
