Toward visible ultrafast imaging with a synchronously pumped switching wave Kerr frequency comb.

The pursuit of real-time, high-resolution imaging at visible wavelength has long been hampered by the limitations of traditional laser sources. Existing visible ultrafast lasers often suffer from limited repetition rates, or complex pulse shaping requirements, hindering their applicability for advanced imaging techniques. This work introduces a novel ultrafast imaging technology using a 775 nm near visible Kerr frequency comb. Kerr frequency combs arise from the formation of stable localized dissipative structures in coherently driven Kerr resonators. Compared to conventional visible lasers, Kerr frequency combs offer unique advantages, such as adjustable spectral bandwidth, precise frequency control, and robust coherence. Particularly, Kerr frequency combs generated using a synchronously pumped scheme can offer flexible repetition rates from the order of hundreds of MHz to tens of GHz, overcoming the limited repetition rates of the existing visible imaging lasers. In this work, we realize a Kerr frequency comb source centred at 775 nm through switching wave generation and use this source in a proof-of-concept demonstration of ultrafast biological imaging. Experimentally, we are able to achieve a 500 MHz line-scan rate and demonstrate a new approach to high speed imaging of biological samples with unprecedented speed and versatility. We envisage our work will pave the way for exciting new discoveries in various fields, propelling us closer to a future where ultrafast dynamics can be visualized in real-time and with exquisite detail.