Ultra-Broadband All-Optical Graphene Modulator

In this letter, a monolayer graphene-clad microfiber device is designed to achieve ultra-broadband all-optical modulation. Based on the broadband advantage of graphene, we sufficiently discussed the priority absorption characteristic of graphene and continuous wave light saturated absorption characteristic of composite waveguide. Furthermore, superior to previous related publications which the wavelength of pump light is limited, we pioneered and verified that various wavelength light can be used as pump light to achieve all-optical modulation in the designed device. In our experiment, supercontinuum light with spectrum range (
$0.48~\mu \text{m} - 1.7~\mu \text{m}$
) is modulated by the conventional low-power continuous wave laser diode (808 nm) with pump power under 50 mW. Experimental results for the all-optical modulator achieve modulation depths of ~5.7 dB (1310 nm), ~6.8 dB (1550 nm), and ~7.3 dB (1610 nm), modulation efficiency of ~0.11 dBmW
⁻¹
(1310 nm), ~0.14 dBmW
⁻¹
(1550 nm), and ~0.15 dBmW
⁻¹
(1610 nm), respectively, crossing the O, C, and L bands. The modulation bandwidth reaches 970 nm which is obviously 20 times higher than the modulation bandwidth ~50 nm reported in related publications. This all-optical modulator based on graphene microfiber provides an easy and efficient way to modulate the ultra-broadband light with very low pump power.