Regenerative amplification in feedback-controlled multi-wavelength lasers for a photonic-based THz filter

We present a compact photonic filter for THz signal processing based on optical injection into a feedback-controlled integrated multi-wavelength laser. The mechanism relies on regenerative amplification of selected spectral components, while a feedback cavity enables control of the filter response through phase tuning. We experimentally demonstrate selective filtering of optical signals emulating THz-to-optical conversion, with channels offset by 1.3 THz from the carrier. We achieve suppression ratios up to 20 dB, optical gain above 15 dB for weak input signals, and 3-dB bandwidths as narrow as 160 MHz. We further analyze the role of injection parameters on the filter characteristics and stability.