Design, Fabrication And Testing Of Flexible MEMS Terahertz Metamaterials Modulators And Their Applications

With the rapid development of MEMS,there are many researcher focusing on designing and developing of new terahertz metamaterials with different functions.Among them,the development of terahertz metamaterials modulator is greatly limited by its shortcomings like narrow bandwidth,small modulation magnitude,low modulation speed.Generally,terahertz metamaterials modulators are made on hard substrates.In this paper,we concentrate on the metamaterials based on flexible substrate that can be used as sensors.The main achievements are as following:Firstly,we analyzed three kinds of resonant modes of terahertz metamaterials,introduced several ways of actuating the terahertz metamaterials devices and development of terahertz metamaterials modulator.Secondly,a series of four terahertz metamaterials with two coaxial double split ring resonators are designed.The four devices are all based on MEMS techniques.The substrate used is flexible parylene-C and the thickness of the devices is only 5.2?m.With the relative angle of the splits of the two SRRs increases from 0°to 90°,the resonance frequency blue shifts,thus they can achieve dual-band tunability in the terahertz regime.At the same time,we also investigated the incident angle and polarization angle of terahertz wave for the first structure.Hence,we found that the device can be used to modulate magnitude and it is insensitive to the polarization,which is a satisfied characteristic.The devices are promising to be applied as sensors that can be used on arbitrary surface.Thirdly,we fabricated a dual-layer ultrathin terahertz metamaterial with curvature sensing.The substrate used is parylene-C with the upper layer of metal and the unit cell is an omega-shaped hollow part of both layers.The presence of the residual stress is due to the different coefficients of thermal expansion between the two materials,thus lead to the circle inside the hollow part bending upward for about??4.2°.We squeezed the device from its two sides.If the curving direction is perpendicular to the symmetry axis of the unit cell,the bent up angle of the circle does not change much.Otherwise,the curvature stress and the bent up angle are positively correlated.Then we proposed a compost structure that consists of four unit cells with each of them rotating by 90°in sequence.The curvature experiment demonstrated that the device can be utilized as an ultra sensitive sensor with only 1.3×10^-4 of strain changed leading to up to 31.1%magnitude modulation.