High-power Raman lasing and efficient anti-Stokes generation in mm-sized crystalline disk resonators.

We have previously experimentally observed high-power Stokes and second-order Stokes output from a mm-sized CaF2 disk using stimulated Raman scattering. A pump laser at a wavelength of 1.06 µm was coupled via a tapered fiber to the whispering gallery modes (WGM) of the disk. In this Letter, we extend this work and demonstrate the production of the first anti-Stokes sideband at power levels as high as 60 µW in near continuous-wave (CW) operation. The result is a four-component Raman comb at the output, with a wavelength range covering from 1.023 to 1.14 µm. We discuss the threshold dependence of the observed Raman lines on the crystal orientation and provide experimental validation. These advances enable the use of such mm-sized resonators as compact, efficient sources for terahertz-level frequency modulation.

Continuous-wave modulation of a femtosecond oscillator using coherent molecules.

We describe a new method to broaden the frequency spectrum of a femtosecond oscillator in the continuous-wave (CW) domain. The method relies on modulating the femtosecond laser using four-wave mixing inside a Raman-based optical modulator. We prepare the modulator by placing deuterium molecules inside a high-finesse cavity and driving their fundamental vibrational transition using intense pump and Stokes lasers that are locked to the cavity modes. With the molecules prepared, any laser within the optical region of the spectrum can pass through the system and be modulated in a single pass. This constitutes a CW optical modulator at a frequency of 90 THz with a steady-state single-pass efficiency of ∼10-6 and transient (10 µs-time-scale) single-pass efficiency of ∼10-4. Using our modulator, we broaden the initial Ti:sapphire spectrum centered at 800 nm and produce upshifted and downshifted sidebands centered at wavelengths of 650 nm and 1.04 µm, respectively.