A self-aligned assembling terahertz metasurface microfluidic sensor for liquid detection

Abstract

This paper reports a new terahertz metasurface microfluidic sensor, which is actually a kind of reflective terahertz metasurface absorber with a microfluidic-channel structure located in the strong field energy region of the absorber. The metasurface structure is made on an ultra-thin quartz substrate as the cap layer, while a two-step structure is made on a silicon substrate as the pedestal layer. In order to precisely control the thickness of the microfluidic channel, the cap layer is self-aligned assembled with the pedestal layer to form the terahertz metasurface microfluidic sensor. The obtained sensor could enhance the light–matter interaction, resulting in high sensing performance. The measured results show that the sensor has a perfect absorption peak at 2.60 THz and a high Q-factor of 62.59, which are basically consistent with the simulated results. The sensitivity and FOM calculated based on the measured results of different liquids with different refractive indices is 0.733 THz per RIU and 16.4, respectively. Compared with some recently related work, the sensitivity is increased by about 40%, the Q-factor is increased by 3–5 times, and the FOM is increased by 5 times, which make the sensor have great application potential for solution detection in the terahertz frequency band.