Fig. 1. Morphology characterizations of GDY. (a) SEM image of GDY; scale bar: 50 nm. (b) HR-TEM image of GDY; scale bar: 5 nm. Inset shows the corresponding SAED pattern. (c) Raman spectrum of the as-prepared GDY film. (d) XPS spectra of GDY film: narrow scan for element C.

Fig. 2. Schematic of the FWM in GDY-microfiber based on synchronized dual-wavelength pulses. WDM, wavelength division multiplexer; EDF, Er-doped fiber; OC, optical coupler; ILP, inline polarizer; PC, polarization controller; DWDM, dense wavelength division multiplexer; EDFA, Er-doped fiber amplifier; TF, tunable filter.

Fig. 3. Characteristics of the pump. (a) Mode-locked spectrum from the MLFL. (b) Spectrum of the dual-wavelength pump after the tunable filter. (c) Oscilloscope trace of the two pulse trains. (d) RF spectrum on a span of 100 kHz. Autocorrelation trace of (e) pump1 and (f) pump2.

Fig. 4. Optical microscope image of the GDY-microfiber device. The upward image shows the GDY-microfiber with 650 nm laser injected, where the deposition length of 860 μm could be inferred from the region of the scattered light. The downward image shows the microfiber deposited with GDY.

Fig. 5. Results of the FWM experiments. (a) FWM spectra without GDY (black line), with GDY (red line), and of the filtered first-order anti-Stokes signal (blue line). (b) FWM spectrum versus different delay between the two pump-pulses. (c) The oscilloscope trace and (d) RF spectrum of the filtered first-order anti-Stokes signal.

Fig. 6. FWM with the variation of the peak power of pump2. (a) FWM spectrum. (b) Conversion efficiency versus P2.