Ultrasensitive Dispersive Fourier Transform Characterization of Nonlinear Instabilities

Noise-driven dynamics of modulation instability (MI) continue to be a source of great interest since it lies at the heart of many nonlinear optical systems. [1]. The Dispersive Fourier transform (DFT) is a well-known optical characterization technique, which was demonstrated useful to gain insight into such complex dynamics [2]–[3]. Using optoelectronic detection, single-shot spectra can be captured in the time domain, and statistical analysis of such fluctuations can be performed, as shown in Fig. 1(a). However, fast photodetectors (e.g. photodiode - PD) are limited by their detection bandwidth, which can only reach a few tens of GHz, thus limiting the equivalent spectral DFT resolution. Furthermore, their low sensitivity with poor noise figures, paired with the low dynamic range of high-speed oscilloscopes, drastically hamper real-time spectral measurements at low intensity (or for signals with over 30 dB contrast). Here, we propose an innovative variation of this technique that overcomes these limitations by using multiple single photon detectors (SPD).