Laboratory Demonstration of the Local Oscillator Concept for the Event Horizon Imager

Black hole imaging challenges the third-generation space VLBI, the Very Long Baseline Interferometry, to operate on a 500GHz band. The coherent integration time needed here is 450s though the available space oscillators cannot offer more than 10s. Self-calibration methods might solve this issue in an interferometer formed by three antenna/satellite systems, but the need for the third satellite increases the mission costs. A frequency transfer is of special interest to alleviate both performance and cost issues. A concept of two-way optical frequency transfer is examined to investigate its suitability to enable space-to-space interferometry, in particular, to image the "shadows" of black holes from space. The concept, promising on paper, has been demonstrated by tests. The laboratory test set-up is presented and the verification of the temporal stability using standard analysis tool as TimePod has been passed. The resulting Allan Deviation is dominated by the 1/tau phase noise trend since the frequency transfer timescale of interest is shorter than 0.2s. This trend continues into longer integration times, as proven by the longest tests spanning over a few hours. The Allan Deviation between derived 103.2GHz oscillators is 1.1x10(-14)/tau within 10ms更多