Two-channel, dual-beam-mode, wavelength-tunable femtosecond optical parametric oscillator

Optical vortices, which carry orbital angular momentum, offer special capabilities in a host of applications. A single-laser source with dual-beam-mode output may open up new research fields of nonlinear optics and quantum optics. We demonstrate a dual-channel scheme to generate femtosecond, dual-wavelength, and dual-beam-mode tunable signals in the near infrared wavelength range. Dual-wavelength operation is derived by stimulating two adjacent periods of a periodically poled lithium niobate crystal. Pumped by an Yb-doped fiber laser with a Gaussian (lp  =  0) beam, two tunable signal emissions with different beam modes are observed simultaneously. Although one of the emissions can be tuned from 1520 to 1613 nm with the Gaussian (ls  =  0) beam, the other is capable of producing a vortex spatial profile with different vortex orders (ls  =  0 to 2) tunable from 1490 to 1549 nm. The proposed system provides unprecedented freedom and will be an exciting platform for super-resolution imaging, nonlinear optics, multidimensional quantum entanglement, etc.