- Two oscillator cavities are built around a single Ti:Sapphire crystal that is pumped by two 6.5W laser beams.
- The two cavities share focusing mirrors but have separate back mirrors and output couplers.
- All the mirrors have high reflectivity over a 150-nm bandwidth.
- Slits were placed directly in front of both back mirrors to tune the two wavelengths.
- We used a D-shaped high reflector to redirect the long-wavelength output coupler.
- The path lengths of the two colours on each side of the crystal were equalized to ensure that both beams mode lock with the same focusing conditions
- The overall round-trip time was equalized by translation of the short-wavelength back mirror on a translation stage.