We experimentally demonstrate that the photonic gauge potential could efficiently control the frequency of light. The photonic gauge potential is introduced in the optical fiber communication system with phase modulators (PMs) under dynamic modulation by a sinusoidal radiofrequency (RF) signal. The value of the gauge potential is fully determined by the initial phase of the modulation. The frequency comb in the PM can be viewed as a Bloch mode in the frequency dimension. The main effect of photonic gauge potential is to shift the band structure of the frequency comb. The propagation of the frequency comb in the PM experiences diffraction-like behavior and can be artificially controlled by tailoring the band structure. The incident frequency comb generated by a mode-locked laser will undergo red and blue shifts as the direction of gauge potential is changed. When there are two PMs applied with opposite gauge potential, the frequency comb will experience negative refraction between the PMs. The spectrum undergoes blue shift through one PM and then red shift after another. The process is similar to what happens in discrete optical waveguides but for the lateral dimension of frequency. By varying the gauge potential through changing the modulation phase, we can obtain a widely expanded frequency comb under incidence of a single-frequency laser. As two PMs are used in the system and set with opposite gauge potential, the frequency is firstly expanded and then squeezed to its origin, similar to optical imaging by a perfect lens. The results are also holds for continuous spectra. The study paves a new way to manipulating the frequency of optical communication signals.
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Presentation Title: Frequency control by photonic gauge potential
Published: 21 July 2017 by MDPI in The 7th International Multidisciplinary Conference on Optofluidics 2017 session Plasmonics and metamaterials