Broadband and low-power light-control-light in a fiber-optic nano-optomechanical system

The coupling of optical and mechanical degrees of freedom using an optical force in nano-devices offers a novel mechanism to implement all-optical signal processing. However, the ultra-weak optical force requires the high pump optical power to realize all-optical processing. For such devices, it is still challenging to lower the pump power and, simultaneously, broaden the bandwidth of the signal light under processing. In this work, a simple and cost-effective optomechanical scheme is demonstrated capable of achieving broadband (208 nm) and micro-Watt (~624.13 μW) light-control-light driven by a relatively weak optical force (~3 pN). In the scheme, a tapered nanofiber (TNF) is evanescently coupled with a substrate, allowing the pump light guided in the TNF to generate a strong transverse optical force for the light-control-light. Additionally, thanks to the low stiffness (5.44 fN/nm) of the TNF, the light-control-light scheme also provides a simple method to measure the static weak optical force with a minimum detectable optical force down to 380.8 fN. The results established the TNF as a cost-effective scheme to break the limitation of the modulation wavelength bandwidth (MWB) at a low pump power, and show that the TNF-optic optomechanical system can be well described as a harmonic oscillator.