Superluminal space-to-time mapping in grating-assisted co-directional couplers

摘要: A superluminal space-to-time mapping process is reported and numerically validated in grating-assisted (GA) co-directional couplers, e.g. fiber/waveguide long-period gratings (LPGs). We demonstrate that under weak-coupling conditions, the amplitude phase of grating complex apodization profile a GA coupling device can be directly mapped into device’s temporal impulse response. In contrast to counter-directional this occurs with scaling factor much higher than propagation speed light vacuum. This phenomenon opens up promising new avenue overcome fundamental time-resolution limitations present in-fiber on-chip optical waveform generation (shaping) processing devices, which are intrinsically limited by achievable spatial resolution fabrication technologies. straightforward application for synthesizing customized femtosecond-regime waveforms using readily feasible fiber LPG designs, sub-centimeter resolutions.