Advanced phasemeter for deep phase modulation interferometry
Thomas Schwarze, Oliver Gerberding, Felipe Guzman, Gerhard Heinzel, Karsten Danzmann
We present the development of an advanced phasemeter for the deep phase modulation interferometry technique. This technique aims for precise length measurements with a high dynamic range using little optical hardware. The advanced phasemeter uses fast ADCs and an FPGA to implement a design of multiple single-bin Fourier transforms running at high sampling rates. Non-linear noise sources in the design were analyzed and suppressed. A null measurement with an optical beatnote signal using λ = 1064 nm was conducted. It showed a sensitivity of 0.8 μrad/√Hz below 10 Hz and 13.3 μrad/√Hz above, with a large dynamic range. The shown performance could enable the measuring of optical path lengths with sensitivities down to 0.14 pm/√Hz and 2.3 pm/√Hz, respectively, over several fringes in an interferometric setup.