Optical vector analyzer for characterization of Fano resonance structures based on unbalanced double-sideband modulation

We report an optical vector analyzer (OVA) for characterization of Fano resonance structures based on unbalanced optical double-sideband (UB-ODSB) carrier modulation, with capability to investigate the optical structures with asymmetric and ultra-narrowband spectral responses. The ratio of UB-ODSB sidebands amplitudes is not equal to one and constant throughout the measurement process. Transmitted through the optical resonant structure UB-ODSB-radiation is sent to photodetector, that is used to convert the optical signal to electrical one. Output photodetector signal contains the beat components of the UB- ODSB-radiation sidebands and optical carrier. These components splits up by bandpass filters (BPF) for post-processing of measurement results in accordance with new mathematical model that is also presented in this paper. The proposed approach allows to measure phase and magnitude responses of the optical device under test (ODUT) with high resolution; to formulate a criterion for signal falling within the limits of the investigated spectral response; to take one-step measurements.