Parallel Measurements of Vibrational Modes in a Few-Layer Graphene Nanomechanical Resonator Using Software-Defined Radio Dongles

Abstract

Software-defined radio dongles are small and inexpensive receivers well known to amateur radio enthusiasts. When connected to an antenna, they enable monitoring of a wide range of the radio spectrum by conditioning the input signal and transferring a downconverted version of it to a personal computer for software processing. Here, we employ a composite of two such dongles, interfaced with codes written in MATLAB and GNU Radio, as a measuring instrument to study the flexural vibrations of a few-layer graphene nanomechanical resonator. Instead of an antenna, we connect the dongles to the split output of a photodetector used to detect vibrations optically. We first perform a quantitative analysis of the dynamics of the first vibrational mode. We then measure the response of the first two vibrational modes in parallel. To illustrate our technique, we detect changes in the vibrational amplitude of both modes induced by periodic strain modulation with a delay of ≈ 1 ms between measurements. Last, we show that our software-based instrument can be employed to demodulate human voice encoded in the vibrations of our resonator. For parallel measurements of several frequency channels, and provided that the input signal is not too weak, our composite system may offer an alternative to the use of multiple lock-in amplifiers or multiple spectrum analyzers, with the distinct advantage of being cost-effective per frequency channel.

A graphene nanomechanical video receiver

“…Driving each resonator with a different video, and using a laser beam whose waist is wide enough to illuminate the entire array, it may be possible to tune in to any video with a single receiver simply by changing the center frequency of the receiver. Watching several videos at once would require splitting the output of the photodetector among several receivers [64], or using a single, wide bandwidth receiver with on-board computing capabilities. Further, our nanomechanical video demonstration reminds us of early Nipkow mechanical televisions [65].…”

A versatile, phase coherent data acquisition system based on software-defined radio for graphene nanomechanics

“…4g). Weakly modulating strain induces a weak modulation of the resonant frequency f m [55]. The effect on φ m is the same as if f m was fixed and f d was being modulated: φ m gets modulated at the frequency of strain modulation.…”