Highly Birefringence‐Guided Microfiber Resonator for Ultra‐High Repetition Rate Ultrashort Pulse

Abstract

AbstractIn the past, most of the introduced ultrafast pulse lasers have primarily focused on shortening cavity lengths or employing harmonic mode‐locking methods to achieve megahertz and gigahertz coherent pulses. In contrast, lasers generating pulses at terahertz repetition rates seemed to have received less attention. These pulses are crucial for applications in fields such as biological imaging, quantum computing, and atmospheric earth sciences, requiring ultra‐high repetition rates and ultrafast pulses. Here, an all‐fiber laser system is presented that generates ultra‐high repetition rate pulses. It relies on the comb‐like filtering effect of a microfiber resonator and the interaction with high birefringence. This enables the production of terahertz‐class pulses with a pulse interval of ≈290 fs, achieving a remarkable maximum repetition rate of about ≈3.448 THz. To the authors’ knowledge, this stands as the highest pulse repetition rate achievable in an all‐fiber laser. By contrast experiment, the terahertz repetition rate produced by this system is related to the length of the high‐birefringence fiber; the shorter the length, the wider the filtering spacing, and the higher the achievable repetition rate. The overall system's birefringence effect can be adjusted by two polarization controllers, allowing for a wide range of tunability in pulse repetition rates.