The development of visible fiber
lasers toward increasing power
and variety has facilitated their usage in a rapidly growing number
of scientific and industrial applications. Until now, holes in the
visible spectral region have remained difficult or expensive to fill.
Green laser oscillation in Ho3+ active fibers has contributed
to bridging the so-called “green gap” between readily
accessible spectral ranges, which is difficult to access with conventional
semiconductor laser sources. However, green fiber lasers are limited
in power because of the lack of high-brightness pump sources. Their
wavelength tuning capability is also bottlenecked at short emission
wavelengths due to the strong signal reabsorption. In this study,
we developed a means of continuously tunable laser operation at the
true-green wavelength of 535–553 nm. In a free-running laser
operation, an output power up to 0.98 W was achieved at a center wavelength
of 543.1 nm, yielding a Gaussian-like beam. This represents the highest
power level demonstrated to date from a visible Ho3+-doped
fiber laser. The results enable a new class of broadband green tunable
fiber lasers with a power level on the order of watts and beyond,
filling in the “green gap”.