Improved Frequency Shifting Realization for the Delayed Self-Heterodyne Interferometric Linewidth Measurement

Abstract

A new implementation of frequency shifting for the delayed self-heterodyne interferometer (DSHI) is proposed in this paper. In order to avoid the costly and complicated acoustic-optic modulator to shift frequency in the DSHI, we propose that a phase modulator can be used instead. The alternative strategy simplifies the complexity of the DSHI setup, as well as reduces the modulation-induced noise by modulating the two arms of DSHI at the same time. Theoretical and experimental analysis show that such a strategy successfully fulfills the frequency shifting function for the DSHI and accurate measurement of a laser’s linewidth and lineshape is realized correspondingly.