20 Nov 2003
Researchers report what they believe to be the first mode-locked ceramic laser.
A team of scientists from Japan, Bulgaria and Russia claim to have demonstrated the first mode-locked ceramic laser. Based on a ytterbium-doped yttrium oxide (Yb3+:Y2O3) crystal, the laser allegedly emits sub-picosecond pulses at 1076.5 nm. (Optics Express 11 2913)
The key to this breakthrough is the team’s nanocrystalline fabrication method, an approach which produces a range of polycrystalline ceramics doped with rare-earth ions. “Our ceramic technique is also scalable,” Ken-ichi Ueda from the Institute of Laser Science at Tokyo’s University of Electro-Communication told Optics.org. “We can develop laser-scale polycrystalline laser materials with low cost in the future.”
An 8% doped, 1.5-mm thick Yb3+:Y2O3 crystal forms the heart of the laser. The crystal sits in a z-fold cavity design and is pumped by a broad-stripe laser diode temperature-tuned to emit at 950 nm.
To mode-lock the laser, Ueda’s team introduce a saturable absorber mirror (SESAM) and a pair of prisms into the set-up, which switches the laser’s output from CW to pulsed. For a pump power of 3.3 W, the modelocked laser emitted 615 fs pulses, with an average power of 420 mW at a repetition rate of 98 MHz.
Ueda’s team is now trying to increase the laser’s output power. “A few-Watts is the target with the extension of the current setup and a few-10s of Watts will be pursued with a thin-disk geometry,” he said. “Sub-200 fs pulse generation will also be investigated by optimizing the cavity dispersion and nonlinearity. We would also like to investigate lasers based on other sesquioxide and disordered ceramics.”