Nonlinear frequency conversion using high quality modes in GaAs nanobeam cavities

We demonstrate the design, fabrication and characterization of nanobeam photonic crystal cavities in (111)-GaAs with multiple high quality factor modes, with large frequency separations (up to 740 nm in experiment, i.e., a factor of 1.5 and up to an octave in theory). Such structures are crucial for efficient implementation of nonlinear frequency conversion. Here, we employ them to demonstrate sum frequency generation from 1300 nm and 1950 nm to 780 nm. These wavelengths are particularly interesting for quantum frequency conversion between Si vacancy centers in diamond and the fiber optic network.