Widely Tunable High-Power Two-Color VECSELs for New Wavelength Generation

We report a collinear two-color vertical external cavity surface emitting laser (VECSEL), which with minimal changes is suitable for intracavity type I second harmonic generation (SHG), type II sum frequency generation (SFG), and type II difference frequency generation (DFG). The demonstrated two-chip cavity provides high-brightness, independently tunable two color, orthogonally polarized intracavity lasing modes. VECSEL chips with emission around 970 and 1185 nm allow the generation of a wide range of wavelengths in the visible and long-wavelength spectral range. The open cavity, collinear geometry, provided a platform for efficient SHG yellow output, SHG blue output, and SFG of green output in the same cavity while only changing the nonlinear crystals. In all cases for visible light generation, a lithium triborate nonlinear crystal is introduced in the cavity region where the fundamental beams are overlapped. Simultaneous SHG and SFG in the same cavity resulting in overlapped outputs consisting of two visible colors are also demonstrated. By using two VECSEL chips with similar gain peaks, intracavity terahertz generation by DFG is demonstrated for the first time in a T-cavity VECSEL geometry. A custom-made tilted periodically poled lithium niobate nonlinear crystal generated DFG signal around 1 THz.