Dual-comb interferometry is a multiheterodyne technique that enables spectroscopic measurements at ultra-fast rates [1]. This technique measures the complex spectral response (amplitude and phase) of a sample without using any mechanical moving parts. Dual-comb interferometry has impacted a wide range of fields, including coherent spectroscopy [1], ranging [2] or Raman microscopy [3]. Such applications used either modelocked Ti:Sa or fiber laser technology, which have repetition rates ~100 MHz. This limits the measurement refresh rate to the millisecond time scale. In contrast, electro-optic generators are an alternative comb source with significantly higher repetition rates (> 10 GHz) [4]. This opens up an outstanding opportunity for realizing dual-comb interferometry at significantly faster refresh rates albeit with a moderate number of lines. A particularly compelling application here is optical arbitrary waveform characterization (OAWC), as demonstrated in [5]. Here, we push the speed and sensitivity of such a system by working with two 25 GHz electro-optic combs in a pre-amplified balanced receiver configuration. We demonstrate OAWC at sub-microsecond speeds with a sensitivity of 25 nW (equivalent to a few photons per pulse). These results highlight the potential of electro-optic combs for realizing ultrafast dual-comb interferometry measurements at unprecedented speeds.

© 2015 IEEE

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