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Shape memory alloy-based tunable split ring resonators

Abhijit Bhattacharyya (University of Arkansas at Little Rock), Vasundara Varadan (University of Arkansas), Mehmet Ozturk (University of Arkansas at Little Rock), Liming Ji (University of Pennsylvania )

Prager Medal Symposium in honor of George Weng: Micromechanics, Composites and Multifunctional Materials

Mon 9:00 - 10:30

MacMillan 117

As part of a preliminary effort towards the development of SMA-based thermally tunable thin films for application in thin film solar cells and noncontact optical sensors, this paper explores the concept of tunable on-chip split ring resonators (SRRs) due to the thermally induced shape memory effect. Encouraged by recent spectroscopic ellipsometric results of a nanoindented 48.98Ni-51.02Ti(at.%) one micron-thick film where spectral shifts of the real and imaginary part of the refractive index were demonstrated (Varadan, Seal, Ozturk and Bhattacharyya, 39th IEEE PVSC meeting, June 16 -21, 2013, Tampa, FL), we examine the effect of the phase transformation in a conceptual SMA SRR (without and with memory strain). The temperature-based tunability of a Silver SRR on a Dupont substrate based solely on dimensional changes due to thermal strains was reported to be -0.00167 GHz/deg C (Varadan and Ji, IEEE Transactions on Microwave Theory and Techniques, 58(10), pp.2673-2281, 2010) whereas that for a SMA with a 1% memory strain was determined to be +0.005 GHz/deg C. The analytical design formulae of spiral and multiple SRRs (Bilotti, Toscano, Vegni, IEEE Transactions on Antennas and Propagation, 55(8), pp.2258-2267, 2007) are extended to account for the shape memory effect (without and with the memory strain) and the effect on resonant frequencies is uncovered.