  An experimental realization of a compact, high-power spectral beamsplitter
for nearly equal frequencies and identical polarization based on two-beam
interference in a free-space Mach-Zehnder interferometer is presented. We
demonstrate the power- and cost-efficient generation and subsequent spatial
separation of two laser tones from a single sum-frequency-generation stage
using double-sideband suppressed-carrier modulation in the infrared, and beam
splitting in the visible at high power. The interferometer spectrally splits
>98% of the incident power when accounting for bulk absorption. The
beamsplitter can be constructed identically for any power or spectral range
required for which suitable optics are available.
