High-efficiency Raman conversion in SF₆- and CF₄-filled hollow-core photonic bandgap fibers

We present a comparative experimental investigation of vibrational stimulated Raman scattering in hollow-core photonic bandgap fibers pressurized with sulfur hexafluoride (${{\rm SF}_6}$SF₆) and tetrafluoromethane (${{\rm CF}_4}$CF₄) gases. Nanosecond-duration pulses at a wavelength of 1030 nm are coupled into the gas-filled fiber, and the first and second Stokes orders are measured at the fiber output. We characterize the conversion process as a function of gas, fiber length, and input power. With a 15 m fiber filled with ${{\rm SF}_6}$SF₆, we obtain conversion efficiency to the first Stokes of 55.7% at an input peak power of 0.63 kW. In comparison, with ${{\rm CF}_4}$CF₄, we obtained a higher conversion threshold and maximum conversion efficiency of 45.4%. To the best of our knowledge, this is the first reported conversion experiment with hollow-core fibers filled with ${{\rm SF}_6}$SF₆ gas.