Generation of THz frequency offset with dual-wavelength Yb:KGW laser

Dual-wavelength (DW) operation of Yb:KGW laser was demonstrated by using a 1 mm-thick birefringent filter (BRF). Based on gain balancing around a single transmission peak of the filter, DW pairs with wavelength separation far smaller than the free spectral range of the filter could be generated. A series of DW pairs with wavelength separation of around 0.5 nm (Δν≈0.14 THz) and 4 nm (Δν≈1.1 THz) within the available gain bandwidth were generated. This method can be also applied with the other lasers that have broad gain bandwidth.