Revisiting optical feedback: dynamic targeting for rapid and precise laser tuning

Agile and precise wavelength control in semiconductor lasers is a critical requirement for next-generation photonic systems, including high-capacity optical communications, advanced sensing, and integrated spectroscopy. Conventional tuning mechanisms, including mechanical, thermal, or electro-optic mechanisms, struggle to simultaneously deliver high speed, stability, and mode-hop–free operation within a compact, integrable architecture. In this work, we use dynamic targeting, an optical feedback based control method originally developed for stabilizing lasers under strong feedback, as an emerging solution to this challenge. By modulating the external-cavity feedback rate and phase, dynamic targeting maintains the laser on the maximum gain mode, enabling continuous linear wavelength tuning. Recent experimental demonstrations have validated the technique, achieving reproducible mode-hop–free tuning over 2.1 GHz in a free-space configuration, while numerical simulations predict scalability of the tuning range to tens of gigahertz and ultrafast scan speeds exceeding 10¹⁷ Hz/s. This technique represents a promising new direction for high-performance wavelength-agile semiconductor lasers with potential to be implemented on photonic integrated circuits.