Low random duty-cycle errors in periodically poled KTP revealed by sum-frequency generation

Low-noise quantum frequency conversion in periodically poled nonlinear crystals has proved challenging when the pump wavelength is shorter than target wavelength. This is—at least large part—a consequence of parasitic spontaneous parametric downconversion photons, whose efficiency increased by fabrication errors periodic poling. Here we characterize poling quality commercial bulk potassium titanyl phosphate (ppKTP) measuring sum-frequency generation (SFG) over a phase mismatch range from 0 to more 400 π . Over probed range, SFG behaves nearly ideally and drops normalized 10 − 6 Our results demonstrate that any background pedestal would be formed random duty-cycle ppKTP substantially reduced compared lithium niobate. The standard deviation can estimated smaller 2% domain length. From this, expect noise spectral density at 1 order magnitude current state-of-the-art single-step converters.