Fig. 1. Schematic diagram of GPI device structure and preparation process. (a) Schematic diagram of GPI device structure; (b) SEM image of cross section of GO/PS composite material (inset is top-view SEM image); (c) basic process flow chart for preparing GPI device

Fig. 2. Representation diagram of GO. (a) XPS image of GO; (b) Raman spectrum of GO (inset is SEM image of GO)

Fig. 3. Electromodulation principle of GO. (a) Accumulation and depletion of electrons in GO atomic structure; (b) microscopic diagram of applied electric field affecting GPI device

Fig. 4. Schematic diagrams of optical transmission in fiber and single GO/PS local field

Fig. 5. Optical characteristic curves of GPI device. (a) Optical transmission efficiency of device varying with pump power under different driving voltages; (b) effect of different driving voltages on optical transmission efficiency of device at low pump power of 35 mW

Fig. 6. All-fiber ring mode-locked laser based on GO/PS electro-optic modulator

Fig. 7. Output power of all-fiber laser. (a) Correspondence between average output power and pump power; (b) effect of applied voltage on output power and device insertion loss at low pump power of 34.3 mW

Fig. 8. Pulse sequence diagrams under different working conditions. (a) CW signal at voltage of 0 V and QML signal at voltage of 10 V for pump power of 34.3 mW after using GO/PS structure; (b) CWML signal at voltage of 20 V for pump power of 34.3 mW after using GO/PS structure; (c) autocorrelation curve and CWML sequence plot at voltage of 20 V for pump power of 34.3 mW after using GO/PS structure; (d) autocorrelation curve and CWML sequence plot at voltage of 30 V for pump power of 44.05 mW after using GO structure

Fig. 9. Output characteristics of all fiber mode-locked laser with pump power of 34.3 mW and driving voltage of 20 V.(a) Spectrogram; (b) spectrum diagram

Fig. 10. Average output power curve of all-fiber mode-locked laser in 180 min at pump power of 34.3 mW and driving voltage of 20 V