We present an ultra‐low noise, near to mid infrared light source for a variety of multiphoton imaging and spectroscopy techniques. The system is based on an optical parametric oscillator (OPO) pumped by a femtosecond Ytterbium solid state oscillator with tens of megahertz repetition rate. This light source supplies three intrinsically synchronized light beams at wavelengths: 1040 nm, 1400-2000 nm (tunable) and 2200-4200 nm (tunable). Without active stabilization, the OPO preserves the shot-noise limited performance of the Yb-oscillator, along with a high long-term stability and a TEM00 beam profile. While this tuning range is already suitable for two- and three-photon microscopy, it now becomes possible to address vibrational modes and thus molecular specificity by employing further frequency conversion stages. Tailored frequency doubling provides either a narrow linewidth (0.5-1.2 nm) or a broadband (>40 nm) beam, tunable from 750-950 nm.
The fixed Stokes beam of the Yb-oscillator can directly be used as a pump source for coherent Raman scattering such as SRS or CARS spectroscopy/microscopy. To this end, we will demonstrate the capability of our system for both SRS imaging at video rate with a spectral precision of 13 cm-1 as well as SRS spectroscopy with more than 400 cm-1 bandwidth in a single shot. By further mixing the two output beams of the OPO, we are able to additionally produce mid-infrared light that is tunable from 4-16 µm. With the help of vibrational sum frequency generation, our system will allow us to cover a spectral range of 700-7000 cm-1.