An acousto-optic modulator based bi-frequency interferometer for quantum technology

Abstract

Acousto-optic modulators (AOMs) have been widely used in quantum optical technology, but the non-ideal diffraction efficiency limits its application in a quantum system. Here we demonstrate a bi-frequency interferometer using AOMs as both the beam-splitter and the beam-combiner. The intensity of the input light can be as low as the single photon level, and the interferometer can work in a chopped phase locking mode. The modulation for the phase locking scheme is realized on the beam-splitting AOM driven by specially designed radio frequency signal, which avoids using extra optical modulators and makes the quantum efficiency of the system as high as $(95\pm1)\%$. By optimizing the factors that affect the mode matching, the visibility of the beating signal for the interferometer is $(99.5\pm0.2)\%$. This near prefect visibility allows the interferometer to be applied in high efficiency quantum technical schemes while leaving the diffraction efficiencies of each AOM for about $50\%$. This greatly reduced the demand for the driving of AOMs.Comment: 6 pages, 4 figure