Highly tunable and versatile dual-wavelength fiber laser based on optofluidic tuning of multimode interference filters

We report a highly tunable and versatile dual-wavelength fiber laser based on optofluidically tunable multimode interference (MMI) filters. Wavelength tuning is based on an MMI fiber filter fabricated using a special fiber, known as No-Core fiber, which is a multimode fiber (MMF) without cladding. Therefore, as the MMI filter is gradually covered with liquid, the optical properties of the No-Core fiber are modified, allowing us to tune the peak wavelength response of the MMI filter with a highly linear response. The dual-wavelength laser is fabricated using two MMI filters in a standard ring cavity laser. Using this setup, we can tune the dual-wavelength emission at will, and we demonstrate wavelength tuning across the C-band under various scenarios. Given the simple, cost-effective fabrication of the MMI filters and the tuning mechanism's tunability and versatility, our system is an ideal source for several applications requiring dual-wavelength laser sources.