Fig. 1. Schematical demonstration of the generation and tuning system of Fano-like resonance. (a) Configuration of an FBG in one arm of an MZI. The inset shows the model of graphene-coated FBG. (b) Theoretical calculations of the spectral line shapes at different phase shifts Δφad=0, π/2, π, 3π/2 (please see the detailed evolution in Visualization 1). ASE, amplified spontaneous emission; TL, tunable laser; C1/C2, coupler 1/2; FBG, fiber Bragg grating, S/MU, source/measure unit; ODL, optical delay line; PD, photodetector; OSA, optical spectrum analyzer; OSC, oscilloscope.

Fig. 2. (a) Optical microscope and (b) scanning electron microscope (SEM) images of the graphene-coated FBG with Au electrodes. (c) Transmission spectrum at the applied voltage of 10 V, showing a distinct Fano-like line shape. (d) Volt–ampere characteristic curve of the device.

Fig. 3. (a) Spectral evolution at different voltages of 0 V, 9 V, 13 V, and 17 V (please see the detailed evolution in Visualization 2). (b) Changes of the wavelength shift Δλ of the interference dip [dip A in Fig. 2(c)], FSR near 1550 nm, and calculated Fano parameter q with the square of current on the graphene layer. (c) ER and SR of Fano-like line shapes for the first evolution period with the square of current of 1–6.8  mA2.

Fig. 4. Observation of electrically induced thermo-optic switching effect. (a) Periodically modulated voltage (top) and switch of reversed Fano-like line shapes (bottom) with applied voltage. (b) Temporal response of optical switching effect.