  Ultrafast optical frequency combs allow for both high spectral and temporal
resolution in molecular spectroscopy and have become a powerful tool in many
areas of chemistry and physics. Ultrafast lasers and frequency combs generated
from ultrafast mode-locked lasers often need to be converted to other
wavelengths. Commonly used wavelength conversions are optical parametric
oscillators, which require an external optical cavity, and supercontinuum
generation combined with optical parametric amplifiers. Whether commercial or
home-built, these systems are complex and costly. Here we propose an
alternative, simple, and easy-to-implement approach to tunable frequency comb
ultrafast lasers enabled by new continuous-wave laser technology. Sum-frequency
generation between a Nd:YAG continuous-wave laser and a Yb:fiber femtosecond
frequency comb in a beta-barium borate (BBO) crystal is explored. The resulting
sum-frequency beam is a pulsed frequency comb with the same repetition rate as
the Yb:fiber source. SNLO simulation software was used to simulate the results
and provide benchmarks for designing future system to achieve wavelength
conversion and tunability in difficult spectral regions.
