New frequency standard for optical telecommunications based on difference-frequency generation in PPLN waveguides

We propose a new frequency standard in the C-band at 192.0 THz (1561 nm) for optical telecommunications. This standard is based on difference-frequency generation (DFG) in a periodically-poled lithium niobate (PPLN) waveguide using a continuous-wave Nd:YAG laser at 1064.2 nm and a continuous-wave HeNe laser at 632.8 nm, allowing for a frequency standard at 1561 nm which is derived directly from two internationally-accepted primary standards. In preliminary experiments using unstabilized commercial lasers we generated tip to 0.2 μW at 1561 nm using only 24 mW at 1064.2 nm (TM₀₀ mode) and 28 μW at 632.8 nm (TM₀₁ mode). The maximum measured conversion efficiency was 4 % W^-1cm^-2. Much higher output powers and conversion efficiencies are expected with an optimized PPLN waveguide designed to allow mixing of only TM₀₀ modes, This is also, to our knowledge, the first demonstration of DFG using a HeNe laser.