Ultrafast lasers must become smaller and more robust to be adopted in next-generation positioning, navigation, and timing (PNT) systems used in space. These systems previously occupied a full optical bench, but Hanna Ostapenko, a researcher at Heriot-Watt University’s Institute of Photonics and Quantum Sciences in Scotland, and colleagues saw an opportunity to use a modern bonding bench to reduce the entire femtosecond laser to a palm-sized format.
During CLEO 2022, Ostapenko presented her work to shrink the footprint of ultrafast lasers so they can one day become small enough to be incorporated into PNT systems flown on satellites orbiting the Earth.
The group built 1.5- and 2.185-GHz Kerr-lens modelocked ytterbium-doped yttria (Yb:Y2O3) ring lasers to produce femtosecond pulses directly from the cavity, and conventional, albeit small, components commonly found in most lasers: lenses, mirrors, and a gain crystal.
Their innovation is a special bonding approach—inspired by techniques already proven for aerospace applications by their industrial partner Airbus Defense and Space GmbH—to align and fix these components with respect to each other in a way that eliminates the need for optomechanics while ensuring robust, self-starting femtosecond-pulse generation.
“The coolest aspect of this work is its robustness,” says Ostapenko. “Conventional solid-state lasers are rather static—you put them in a big sealed box with lots of other scientific mounts and try not to shake it too hard in case the optomechanical mounts are disturbed. All of our laser’s mirrors are glued to a single baseplate and move with it, which means all the components shake in the same way if you throw the laser around. This solid block means that laser operation doesn’t change no matter what you do with it, which we think could make it attractive as a platform for use in space.”
Further work is needed before this laser will be appropriate for deployment on a satellite, and “the baseplate is an area we need to think about carefully,” Ostapenko says. “An all-silica design is likely to be preferred, but may present some challenges for the thermal management of heat generated within the gain crystals.”
For now, the immediate next step for Ostapenko and colleagues is to amplify the laser’s output power in a compact way, so that the entire system remains solid-state and robust. “Our eventual goal is to demonstrate a full optical frequency comb configuration suitable for atomically referenced timing and navigation applications,” she says.
RELATED READING
Y. Feng et al, Opt. Lett., 46, 21, 5429–5432 (2021); https://doi.org/10.1364/ol.439965.
