Single-modulator, direct frequency comb spectroscopy via serrodyne modulation

Abstract

Traditional electro-optic frequency comb spectrometers rely upon the use of an acousto-optic modulator (AOM) to provide a differential frequency shift between probe and local oscillator (LO) legs of the interferometer. Here we show that these modulators can be replaced by an electro-optic phase modulator (EOM) which is driven by a sawtooth waveform to induce serrodyne modulation. This approach enables direct frequency comb spectroscopy to be performed with a single dual-drive Mach–Zehnder modulator (DD-MZM), allowing for lower differential phase noise. Further, this method allows for simpler production of integrated photonic comb spectrometers on the chip scale.