Stuttgart 2012 – wissenschaftliches Programm
Q 34.5: Poster
Dienstag, 13. März 2012, 16:30–19:00, Poster.I+II
Deep phase modulation interferometry — •Thomas Schwarze, Felipe Guzman Cervantes, Oliver Gerberding, Gerhard Heinzel, and Karsten Danzmann — Albert-Einstein-Institut Hannover
We present our research plan and initial results on the development of a dedicated hardware modulation system for the Deep phase modulation interferometry technique. A sinusoidal modulation is applied through a ring piezo-electric actuator to one arm of a Mach-Zehnder interferometer in order to reach large modulation depths of the order of 10-20 rad. The interferometer phase is extracted by a complex fit to the harmonic amplitudes of the modulation frequency. A first prototype uses the first 10 harmonic amplitudes and has demonstrated length and angular measurement sensitivities at millihertz frequencies of about 20 pm/rtHz and 10 nrad/rtHz, respectively. Initial observations showed that the phase noise has a dependency on the modulation depth. Our research focus on the development of a digital modulation system based on Field Programmable Gate Arrays to perform multi-frequency single-bin discrete Fourier transforms at the required harmonic amplitudes. A dedicated floating-point microprocessor will also be included to perform the complex fit computations for the phase extraction. A digital signal synthesizer is included in the design and will use the fit output as input parameters for active control loops of, for example, the modulation depth, modulation frequency, and interferometer phase state.