Photonic time stretch has been a successful imaging and spectroscopy technique that provides single-shot and real-time performance by employing highly dispersive optical elements to slow down the modulated optical signals and overcome the speed bottleneck present at analog-to-digital conversion. Photonic time stretch has also been generalized to warped stretch with tailored chromatic dispersion profiles, enabling non-uniform (foveated) sampling. However, such tailored profiles are currently only available with fixed elements which cannot be reconfigured, lowering the robustness of such systems and limiting their applicability to static samples and environments that have relatively constant sample statistics.
To address this limitation, we demonstrate an arbitrarily programmable source of chromatic dispersion which has a 1-ns wide delay range, and inherently devoid of ghost artifacts common in spectral phase-based optical devices. Extending the concept of chromo-modal dispersion (CMD), we use an acousto-optic deflector to create a digitally synthesized and modulated angular spread of optical wavelengths, which are then coupled into the chosen waveguide mode of a multimode fiber to create the desired modal dispersion. The range and tunability enables us to on-the-fly reconfigure and correct optical dispersion. As proof-of-concept, we demonstrate real-time channel noise correction via optical feedback for warped stretch spectroscopy at 36.6 MHz.
Jacky C. K. Chan, Sebastian Karpf, and Bahram Jalali, "Dynamic chromo-angular-modal excitation of multimode waveguides via acousto-optic deflection (Conference Presentation)," Proc. SPIE 10517, Real-time Measurements, Rogue Phenomena, and Single-Shot Applications III, 105170C (Presented at SPIE LASE: January 29, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2291418.5751425876001.
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