FORTH - Modelling Heraklion, July 2004

Issues addressed in the last 4 months SRR study: The background dielectric constant influence; the board influence Square vs non-square LHM unit cells Examination of alternative SRR systems, with aim to improve the LH peak SRR study: The electric cut-wire response (SRR vs cut-wires, and influence of SRR orientation) THz SRR structures study

Role of the dielectric constant of the board (b) 2m 1/b 20 1/b

Square vs. non-square unit cells (1) Unit cells reduced in size along E direction give higher LH peaks. Possible reasons: 1) Change of impedance through decrease of ’p (larger cut-wire (SRR) length  reduced 0  reduced ’p) E Square akxaE=5x5 mm2 Non-square (reduced) akxaE=5x3.63 mm2

Square vs. non-square unit cells (2) Unit cells reduced in size along E direction give higher LH peaks. Possible reasons: 2) Stronger interaction between SRRs? (wider <0 regimes  possibility for higher peak?) E Square akxaE=5x5 mm2 Non-square (reduced) akxaE=5x3.63 mm2

Square vs. non-square unit cells (3) k Reduction of ak does not influence the LH peak

SRRs of different dimensions We studied metamaterials of SRRs (of the conventional design) with different linear size, different rings width, different rings distance and different cuts-size with aim to improve the LH transmission, through impedance improvement. Unit cell: 5x5, 5x4.6 SRR size: 4x4 Rings width (w): 0.4 Rings distance (s): 0.2, 0.4 Gaps (g): 0.2, 0.4 No any considerable improvement compared to our experimental design

SRRs of different dimensions We studied metamaterials of double unit cell size, to see if going to lower frequencies reduces the losses in the board at the LH peak No any significant improvement compared to our experimental design

SRR vs cut-wires: Why lower 0 for the SRR? Ek EE E k + - E k - + + - - - E k + + 0

0 is in most of the cases higher in A SRR rotation and 0 0 is in most of the cases higher in A Ek EE - + A E k - - B E k + + 0

SRR rotation and 0 (FDTD) - + + - E k Bilkent FORTH E k - - + +

THz structure Unit cell: 7x7x5 m3 SRR size: 5x5 m2 All other: 1 m Board’s =2.8 (polyamide)

THz structure, FDTD & MWS, in-plane incidence k 6 uc 1 uc

THz structure, FDTD & MWS, in-plane incidence k FDTD MWS

THz structure, FDTD & MWS, in-plane incidence k E k

THz structure, vertical incidence k FDTD MWS

THz structure, inversion, in-plane incidence k

THz structure, inversion, vertical incidence k

Summarizing….. Board influences “differently” the characteristic SRR frequencies (m, 0) Unit cells reduced along the wires direction give higher LH transmission peaks 0 (SRR-FORTH) < 0 (cut-wires) < 0 (SRR-Bilkent) THz SRR structure: Magnetic response at ~6 THz Good agreement between theory and experiment Good agreement between FDTD and MWS